Hey Rob, Just wanted to stop in and say I spent the last few slow days at work watching basically all of your videos. You've got some great talents and very innovative yet simple solutions to a lot of shop problems. So thank you for that. I also wanted to say I've been riding and have restored my dad's old 1974 Honda CB750. I know when I set up the carb slides mechanical like you have done they call that a "bench synch" which is certainly good enough to make it run acceptably. I do know, however, that a proper vacuum synch will smooth the idle significantly. Before the synch you can really hear the clutch rattling and the cam chain slapping around a bit but after it's just buttery smooth. My Honda may be more affected by the synch being that it's 4 cylinders and 4 carbs instead of 2 so maybe a moot point for you but just wanted to point that out. Anyway, thanks for all the great videos and that's a sweet old bike you've got there. Stephen Thomson (from Canada)
Stephen Thomson Hi Stephen, thanks for the feedback. I have a set of mercury columns for vacuum synching, and they are great for multis like yours. The problem with Ducati is that the rear cylinder generally runs a larger main jet to counter heat wash from the front cylinder. This tends to effect the readings I get. I gave up on using the columns years ago as it just didn't work for me. Cheers Rob
Stephen Thomson I'm not sure - I think they are the same. Would have to get out the manual to check. When you look at the carby placement on the early Ducati it's obvious that the front cylinder makes more power than the rear, having leaner jetting and much cooler air. Being a 90 degree twin it's not obvious as the primary balance is so good. Rob
I used to set up my tz 350 carb slides the same way .. 1 click . in my first year racing it, I won 3 club championships. champion of Oulton was one of them !
Nice going. The local Ducati mechanic showed me this method. Funny thing is, I have a set of mercury vacuum carby balancers and could never get a good result with them on the Ducati's. The reason being (I think) was because the front and rear cylinders had different main jet sizes and inlet manifold profiles. The rear cylinder ran a larger main jet to allow for heat wash from the front cylinder. Cheers Rob
just rebuilt my PHF carbs for my 1988 750F1, next is to tune them in, may have to do a clutch seal rebuild, if I can find it. already had to rebuild the clutch and rear break master cylinders, hoping that is all. the bikes been sitting in the garage for 20 years. have a good day and ride on the beast. James
+James Janecek Hi James, Mine was off the road for about 8 years due to some other major commitments. Apart from a new front tyre, it's ready to go. It's done about 34,000 km and the rings had gummed up standing so it blew a bit of smoke on fire up. Injected a dose of Redex in the carbs while running (Marvel Mystery oil) and all good now - easy fix. The clutch slave cylinder should only need looking at if it's leaking (caused by deteriorated grease/grot build up). Strip and clean/re-grease it and it may well be OK. Mine leaked and this fixed it. The "O" ring was replaced when I first got it - common problem. There are several sizes of "O" ring depending on the year. It's a standard metric size and should be available from a bearing supplier - but must be in a suitable compound to withstand brake fluid. Hope all goes well. Cheers Rob
Another long time bevel mechanic showed me an even simpler way. Put your left thumb at the base of the slide on the rear carb and simply watch the front slide. You’ll feel and see respectively when they are opening at the same time
Exactly what I was looking for. One of the cables om my 600 Pantah special broke so I replaced it but now the thing does not pull properly anymore at low revs and refuses to go above 115 km/h on the motorway. It's almost as if I am riding a 350! It only runs well if I tighten the new outer cable up quite far but then then it "idles" at 2500 rpm! Maybe I took away too much play by fixing down the rather lush protection rubbers. Could very well be that the tolerances I exacted there are too German for a bike that is as Prima Donna Italian as this one. :-) So thanks for the explanation. I'll run the whole procudure as you describe it and see where that gets me.
Hi Marc, Sounds like it's only firing on one cylinder. Either one ignition igniter or spark plug has died, or you have put something back together wrong on the carb. The slide can only go in one way, check that is right. I'm betting you have put the slide needle clip in the wrong position or the clip is not seated correctly. Compare it to the other carb. Usually it will be in the mid position. Cheers Rob
@@Xynudu Thanks for the tip. I've tried to be very carefull while putting everything back together again but since it was the first time it is quite possible I did something wrong. Part of the problem also is that I've bodied my bike in such a way that the front carburator is actually quite difficult to get to (see: www.brassee.com/motorcycles.html). That's what you get if you let looks go before accesibility. One additional question though: I've been wondering about the slide myself but wouldn't that mean that I would have to use excessive force to put it in the wrong way? I am sure I didn't. Or does it go in almost as easy? If so that is the most probable cause indeed.
Hi Marc, The slide can only go in one way as it has to mate with a brass pin which aligns with a vertical slot in the slide. Also the cutout faces the carby inlet/filter side. You would have to use considerable force to get it wrong unless you used the carby top cover screws to pull it all down. But it's unlikely it would work as it would jam solid. The accelerator lever could possible be out of alignment with the slide channel. The coil return spring should also be positioned correctly so nothing is binding. As you have fitted a new cable I would be looking at how the cable outer casing and end nipple is sitting, the needle clip position, and the clip seating. From memory it sits in a small recess. Make sure the slide needle is not bent. Nice looking machine. I can see it would be a bit tricky to work on. My F1 is snug but doable once you take the tank off. You will sort it out. Cheers Rob
@@Xynudu Hi Bob, That rules out the slide surely since it is working flawlesly. The accelerator (pump?) lever would be a better candidate then. It will after all play a role in starting, pulling away from stop and I assume also in attaining top speed. So when it does not work properly that could, I guess, also lead to the behaviour I decribed, where real power only seems to be available at high revs. When you start pulling away or are in high gear on the motorway revs tend to be relatively low. What do you mean with the lever being out of allignment? I assume it is part 43 in this drawing www.carburateurwinkel.nl/drawings/dellorto_phm_exploded_view_tekening.jpg ? I was in doubt a bit there but since everything slid in easily I thought I must have been doing it right anyway. Could I still have put that in wrong then?
Hi Marc, The plastic accelerator pump lever can be crooked in relation to the piston in the wall of the carby. I'm always extra careful to ensure it engages in the slot correctly. Sometimes you work on one thing and co-incidentally something else causes a problem. Do the cylinders both run at the same temperature at various rev ranges? Check this with the bike stationary with your hand (carefully). Also the exhaust power pulses will be different temperatures and pressure. It's really a process of elimination. One last thing that can catch you out - make sure that the brass choke piston rubber seal (disc) is not leaking. This will compress and harden over time and cause an over rich mixture. You can re-use them by prizing it out with a bag needle and turning it over. Easy to make new ones with a wad punch. As the bike is now fairly old this can be an issue, especially if they have never been looked at. Cheers Rob
Hi Rob, I thought the red bike sitting over to she side of shot in your dc motor conversion vids was a duke.. Cool.. That's an omg hold onto your hat, kinda ride. I guessed that's how you adjust twin carb cables, but your explanation was excellent. Paul Oh yeah, btw I got my 7x12" mini lathe going with a supposedly 2.5hp (maybe rates 2.5hp for 1 second,locked up with a screwdriver) rated treadmill motor and the alloy xl series synchro pulleys... Its working awesome and nothing can stall it now, even at 50rpm. Thats with the stock china made DC motor drive in it, yet to change to the KBMG-212D Hope you get your DC lathe setup back and running soon :D
djpaulk Glad your conversion worked out good. I'm having a break from metal work and am into getting my bikes road worthy. Yes, Dukes are a great way to blow away the cobwebs. The older ones especially. Cheers Rob
Hi Rob. Enjoyed your clip, very easy to follow. I have an 82 Darmah and I'm pretty novice when it comes to tuning carbs and so forth. At 3:54 you mention adjusting idle speed with motor running, having the same speed for both pots and same fuel/air mixture. Mate, how's this done...how do you know how much to adjust each slide. Hope this makes sense. cheers
Hi Matt, First you adjust the slides with the single click method outlined in the video. Then you do the mixture on each carb to get optimum smoothness. Put one hand at the exhaust outlet to feel the gas pulse, and then adjust the mixture screw until the pulses feel regular/uniform - the gas temperature will be hottest at this point. Do both cylinders this way (separately of course). Now it's a matter of adjusting the idle speed slide screws to get the minimum amount of needle flicker on the tachometer. Set the front cylinder speed first as the base reference point (1100 - 1200 RPM), then adjust the rear cylinder to match it and get smoothest running. If the engine speed is now too high, back off the front cylinder and then repeat the process. When speed seems correct, you then smooth out the motor more by checking/adjusting the exhaust pulses again until you get uniform/matching gas pulses and that loping 90 degree Ducati idle sound. You may have to repeat both the steps a few times until it's right. Cheers Rob
Hi again Matt, Just to clarify a bit more - the single click method only sets the cable adjustment uniformity and end play. The actual slide and mixture idle speed is as per my previous reply. Ideally, once you have got that right, you should then redo the single click method (cables) as the slide height may have varied by a tiny amount. Cheers Rob
Hi Rob, thanks so much for that. I did the single click method today without any adjustments. Just drained the float bowls and listened for any difference in slides when I released the throttle. There doesn't appear to be any gap there. Sorry, but I need to ask a few very novice questions here....adjusting the cables, how's that done? Is there some lock nut on top to release and then screw an adjuster up or down to get cable slack? Also, correct me if I'm wrong...idle screw (clockwise to raise slide?). Mixture screw (clockwise for lean & opposite for rich?). Thanks
Hi Matt, No problem. To adjust the cables you undo the lock nut on the top cover of the carby (under the rubber boot) where the cable goes in. To adjust the freeplay you screw the centre section in or out. You should have about 3 mm free play between the cable casing and the screw in section that goes through the carby top. Yes, clockwise to raise side, clockwise to lean out the idle mixture. If the engine backfires on a trailing throttle when reved, open out the mixture screw a quarter of a turn to prevent it. Cheers Rob
Hi Matt, If the bike has been standing for a long time it's quite possible that the choke (enricheners) on the carbys may need attention as the rubber centre may be compressed and make the mixture rich due to poor sealing when closed.. These are easy to fix, just remove the choke slide (one screw) and turn the rubber centre section over and re-use. Use a needle or something similar to prize the rubber out. If they are leaking you will have no hope of adjusting the carby idle mixture. Cheers Rob
Hey Rob, Theoretically could you get a precise idle speed setting by measuring the slide gap on both carbs with a micrometer and making them equidistant of each other? Or is it not that simple?
If you had an inside micrometer it might get you close. But things aren't that simple. I have a set of vacuum tubes that theoretically should allow you to measure (and match) the exact air flow through each carby opening, but in practice it doesn't work very well on Ducati "V" twins. For starters the front and rear cylinders have different profile intake manifolds, and on some models the rear cylinder runs a different (larger) main jet to allow for heat wash from the front cylinder. What this all means is that both cylinders breath a bit differently at various throttle openings. So a slight compromise has to be made during tuning. It all comes down to the power pulses coming out of the exhaust being equal - that's the best indicator. Cheers Rob
Hey Rob, So the other day I pulled the spark plugs on my 650 Pantah and the rear was pretty sooty and the front one was actually a bit wet and sooty. I’ve been using your “1 click” method for a couple years now and I think it works best, but my question is how to know where to set the mixture screw on these engines? Should the process go in a certain order like: 1. Adjust cables first 2. Adjust idle screw 3 then mixture screw, and repeat if necessary?
Hi could you tell me.... I have an 82 MHR. I'm have issues setting the carburettor air fuel mixture. Could you give me an idea of the number of turns on the air fuel mix from tight up out
The MHR has 40 mm carbs so the idle jetting will be different to the 32's and 36's on mine. You MUST synchronise the slides before fine tuning the idle mix. Once that is done it's simply a matter of finding the mid (smoothest or fastest idle) point for each jet. Once the jets are close you can then set both idle stops to the desired idle RPM (1100). You will have to re-adjust the idle jets each time you alter the idle speed until you get both correct. Be aware that if the rubbers in the enritchener jets (choke flip levers) are worn it will be impossible to get this right, so look at those first. They will almost certainly be compressed from old age. You can usually turn them over in the brass slides to refresh the surface (once). If totally stuffed then replace them. Cheers Rob
Sorry no can do. Gowanloch Ducati will be an obvious option, but how good and how much they charge I can't comment on. The experience in SA of Ducati shops is not good from my observations and I've always done my own wrenching. The current crop are great BS artists and that's about the start and finish of it as far as I'm concerned ;) Cheers Rob
Thanks Rob, it's really hard to find anyone that is good to work on these older bikes although one would think it'd be pretty basic although fairly fiddly. Thanks again
Having owned Ducs for a similar period, your method gets you fairly near but still not as accurate as if you combine this with Gauges, your method assumes that both cylinders are performing exactly the same, it's pretty obvious that a vertical piston will need slightly more force than a horizontal one, and as both work on the same crankshaft the gauges help fine tune this. Try it and see.
I have mercury column gauges which I never use. As the two cylinders suck differently due to manifold variations, any readings are pretty much useless as air flow changes throughout the rev range. I was shown this method by a trained Ducati mechamic. It has always worked for me. My Ducks have always run smoothly. Cheers Rob
Just to clarify the issue with tuning early air cooled ducati engines (Taglioni): - Both intake manifolds have dissimilar air flow passages, - the front cylinder breaths in cold air at speed, the rear cylinder breaths in less dense warm air as the result of heat wash from the front cylinder, - the rear cylinder on some models runs a richer/larger main jet to help cool the cylinder/compensate for heat wash. - the actual orientation of the cylinders has no bearing on engine breathing as such. The end result is that air flow, air density, and fuel mixture ratio between cylinders is not/never going to be the same (as required for vacuum gauges to be effective). Cheers Rob
Hi Rob, You've just explained to yourself why you need to use gauges to get a balanced output, both pots will run slightly differently and gauges will allow you to adjust the cables to give optimum performance, in my experience it's only a very small adjustment to get this but it will make a difference. Have you read Steven Eke's book on this? Chers Jeff
I suppose that system would work for any twin cylinder bike with a carburettors, great tip!
Hey Rob,
Just wanted to stop in and say I spent the last few slow days at work watching basically all of your videos. You've got some great talents and very innovative yet simple solutions to a lot of shop problems. So thank you for that.
I also wanted to say I've been riding and have restored my dad's old 1974 Honda CB750. I know when I set up the carb slides mechanical like you have done they call that a "bench synch" which is certainly good enough to make it run acceptably. I do know, however, that a proper vacuum synch will smooth the idle significantly. Before the synch you can really hear the clutch rattling and the cam chain slapping around a bit but after it's just buttery smooth. My Honda may be more affected by the synch being that it's 4 cylinders and 4 carbs instead of 2 so maybe a moot point for you but just wanted to point that out.
Anyway, thanks for all the great videos and that's a sweet old bike you've got there.
Stephen Thomson (from Canada)
Stephen Thomson Hi Stephen, thanks for the feedback. I have a set of mercury columns for vacuum synching, and they are great for multis like yours. The problem with Ducati is that the rear cylinder generally runs a larger main jet to counter heat wash from the front cylinder. This tends to effect the readings I get. I gave up on using the columns years ago as it just didn't work for me. Cheers Rob
I didn't think about the different jetting. Is it different pilot as well as main?
Stephen Thomson I'm not sure - I think they are the same. Would have to get out the manual to check. When you look at the carby placement on the early Ducati it's obvious that the front cylinder makes more power than the rear, having leaner jetting and much cooler air. Being a 90 degree twin it's not obvious as the primary balance is so good. Rob
I used to set up my tz 350 carb slides the same way .. 1 click . in my first year racing it, I won 3 club championships. champion of Oulton was one of them !
Nice going.
The local Ducati mechanic showed me this method.
Funny thing is, I have a set of mercury vacuum carby balancers and could never get a good result with them on the Ducati's.
The reason being (I think) was because the front and rear cylinders had different main jet sizes and inlet manifold profiles.
The rear cylinder ran a larger main jet to allow for heat wash from the front cylinder.
Cheers Rob
just rebuilt my PHF carbs for my 1988 750F1, next is to tune them in, may have to do a clutch seal rebuild, if I can find it. already had to rebuild the clutch and rear break master cylinders, hoping that is all. the bikes been sitting in the garage for 20 years. have a good day and ride on the beast. James
+James Janecek
Hi James,
Mine was off the road for about 8 years due to some other major commitments. Apart from a new front tyre, it's ready to go.
It's done about 34,000 km and the rings had gummed up standing so it blew a bit of smoke on fire up. Injected a dose of Redex in the carbs while running (Marvel Mystery oil) and all good now - easy fix.
The clutch slave cylinder should only need looking at if it's leaking (caused by deteriorated grease/grot build up). Strip and clean/re-grease it and it may well be OK. Mine leaked and this fixed it. The "O" ring was replaced when I first got it - common problem.
There are several sizes of "O" ring depending on the year. It's a standard metric size and should be available from a bearing supplier - but must be in a suitable compound to withstand brake fluid.
Hope all goes well.
Cheers Rob
Another long time bevel mechanic showed me an even simpler way. Put your left thumb at the base of the slide on the rear carb and simply watch the front slide. You’ll feel and see respectively when they are opening at the same time
Exactly what I was looking for. One of the cables om my 600 Pantah special broke so I replaced it but now the thing does not pull properly anymore at low revs and refuses to go above 115 km/h on the motorway. It's almost as if I am riding a 350! It only runs well if I tighten the new outer cable up quite far but then then it "idles" at 2500 rpm! Maybe I took away too much play by fixing down the rather lush protection rubbers. Could very well be that the tolerances I exacted there are too German for a bike that is as Prima Donna Italian as this one. :-) So thanks for the explanation. I'll run the whole procudure as you describe it and see where that gets me.
Hi Marc, Sounds like it's only firing on one cylinder. Either one ignition igniter or spark plug has died, or you have put something back together wrong on the carb. The slide can only go in one way, check that is right. I'm betting you have put the slide needle clip in the wrong position or the clip is not seated correctly. Compare it to the other carb. Usually it will be in the mid position. Cheers Rob
@@Xynudu Thanks for the tip. I've tried to be very carefull while putting everything back together again but since it was the first time it is quite possible I did something wrong. Part of the problem also is that I've bodied my bike in such a way that the front carburator is actually quite difficult to get to (see: www.brassee.com/motorcycles.html). That's what you get if you let looks go before accesibility. One additional question though: I've been wondering about the slide myself but wouldn't that mean that I would have to use excessive force to put it in the wrong way? I am sure I didn't. Or does it go in almost as easy? If so that is the most probable cause indeed.
Hi Marc, The slide can only go in one way as it has to mate with a brass pin which aligns with a vertical slot in the slide. Also the cutout faces the carby inlet/filter side. You would have to use considerable force to get it wrong unless you used the carby top cover screws to pull it all down. But it's unlikely it would work as it would jam solid. The accelerator lever could possible be out of alignment with the slide channel. The coil return spring should also be positioned correctly so nothing is binding. As you have fitted a new cable I would be looking at how the cable outer casing and end nipple is sitting, the needle clip position, and the clip seating. From memory it sits in a small recess. Make sure the slide needle is not bent. Nice looking machine. I can see it would be a bit tricky to work on. My F1 is snug but doable once you take the tank off. You will sort it out. Cheers Rob
@@Xynudu Hi Bob, That rules out the slide surely since it is working flawlesly. The accelerator (pump?) lever would be a better candidate then. It will after all play a role in starting, pulling away from stop and I assume also in attaining top speed. So when it does not work properly that could, I guess, also lead to the behaviour I decribed, where real power only seems to be available at high revs. When you start pulling away or are in high gear on the motorway revs tend to be relatively low. What do you mean with the lever being out of allignment? I assume it is part 43 in this drawing www.carburateurwinkel.nl/drawings/dellorto_phm_exploded_view_tekening.jpg ? I was in doubt a bit there but since everything slid in easily I thought I must have been doing it right anyway. Could I still have put that in wrong then?
Hi Marc,
The plastic accelerator pump lever can be crooked in relation to the piston in the wall of the carby. I'm always extra careful to ensure it engages in the slot correctly. Sometimes you work on one thing and co-incidentally something else causes a problem. Do the cylinders both run at the same temperature at various rev ranges? Check this with the bike stationary with your hand (carefully). Also the exhaust power pulses will be different temperatures and pressure. It's really a process of elimination.
One last thing that can catch you out - make sure that the brass choke piston rubber seal (disc) is not leaking. This will compress and harden over time and cause an over rich mixture. You can re-use them by prizing it out with a bag needle and turning it over. Easy to make new ones with a wad punch. As the bike is now fairly old this can be an issue, especially if they have never been looked at.
Cheers Rob
dead simple and very well explained.............thanks
thornwarbler Yes, almost too simple to believable. But it works well. Rob
Hi Rob, I thought the red bike sitting over to she side of shot in your dc motor conversion vids was a duke.. Cool.. That's an omg hold onto your hat, kinda ride.
I guessed that's how you adjust twin carb cables, but your explanation was excellent. Paul
Oh yeah, btw I got my 7x12" mini lathe going with a supposedly 2.5hp (maybe rates 2.5hp for 1 second,locked up with a screwdriver) rated treadmill motor and the alloy xl series synchro pulleys... Its working awesome and nothing can stall it now, even at 50rpm. Thats with the stock china made DC motor drive in it, yet to change to the KBMG-212D
Hope you get your DC lathe setup back and running soon :D
djpaulk Glad your conversion worked out good. I'm having a break from metal work and am into getting my bikes road worthy. Yes, Dukes are a great way to blow away the cobwebs. The older ones especially. Cheers Rob
Hi Rob. Enjoyed your clip, very easy to follow. I have an 82 Darmah and I'm pretty novice when it comes to tuning carbs and so forth. At 3:54 you mention adjusting idle speed with motor running, having the same speed for both pots and same fuel/air mixture. Mate, how's this done...how do you know how much to adjust each slide. Hope this makes sense. cheers
Hi Matt,
First you adjust the slides with the single click method outlined in the video.
Then you do the mixture on each carb to get optimum smoothness.
Put one hand at the exhaust outlet to feel the gas pulse, and then adjust the mixture screw until the pulses feel regular/uniform - the gas temperature will be hottest at this point.
Do both cylinders this way (separately of course).
Now it's a matter of adjusting the idle speed slide screws to get the minimum amount of needle flicker on the tachometer. Set the front cylinder speed first as the base reference point (1100 - 1200 RPM), then adjust the rear cylinder to match it and get smoothest running.
If the engine speed is now too high, back off the front cylinder and then repeat the process.
When speed seems correct, you then smooth out the motor more by checking/adjusting the exhaust pulses again until you get uniform/matching gas pulses and that loping 90 degree Ducati idle sound.
You may have to repeat both the steps a few times until it's right.
Cheers Rob
Hi again Matt,
Just to clarify a bit more - the single click method only sets the cable adjustment uniformity and end play.
The actual slide and mixture idle speed is as per my previous reply.
Ideally, once you have got that right, you should then redo the single click method (cables) as the slide height may have varied by a tiny amount.
Cheers Rob
Hi Rob, thanks so much for that. I did the single click method today without any adjustments. Just drained the float bowls and listened for any difference in slides when I released the throttle. There doesn't appear to be any gap there. Sorry, but I need to ask a few very novice questions here....adjusting the cables, how's that done? Is there some lock nut on top to release and then screw an adjuster up or down to get cable slack? Also, correct me if I'm wrong...idle screw (clockwise to raise slide?). Mixture screw (clockwise for lean & opposite for rich?). Thanks
Hi Matt,
No problem.
To adjust the cables you undo the lock nut on the top cover of the carby (under the rubber boot) where the cable goes in. To adjust the freeplay you screw the centre section in or out.
You should have about 3 mm free play between the cable casing and the screw in section that goes through the carby top.
Yes, clockwise to raise side, clockwise to lean out the idle mixture.
If the engine backfires on a trailing throttle when reved, open out the mixture screw a quarter of a turn to prevent it.
Cheers Rob
Hi Matt,
If the bike has been standing for a long time it's quite possible that the choke (enricheners) on the carbys may need attention as the rubber centre may be compressed and make the mixture rich due to poor sealing when closed..
These are easy to fix, just remove the choke slide (one screw) and turn the rubber centre section over and re-use.
Use a needle or something similar to prize the rubber out.
If they are leaking you will have no hope of adjusting the carby idle mixture.
Cheers Rob
Hey Rob,
Theoretically could you get a precise idle speed setting by measuring the slide gap on both carbs with a micrometer and making them equidistant of each other? Or is it not that simple?
If you had an inside micrometer it might get you close. But things aren't that simple.
I have a set of vacuum tubes that theoretically should allow you to measure (and match) the exact air flow through each carby opening, but in practice it doesn't work very well on Ducati "V" twins.
For starters the front and rear cylinders have different profile intake manifolds, and on some models the rear cylinder runs a different (larger) main jet to allow for heat wash from the front cylinder.
What this all means is that both cylinders breath a bit differently at various throttle openings.
So a slight compromise has to be made during tuning. It all comes down to the power pulses coming out of the exhaust being equal - that's the best indicator.
Cheers Rob
xynudu Cheers! Thanks for the response and the wisdom Rob :)
Hey Rob,
So the other day I pulled the spark plugs on my 650 Pantah and the rear was pretty sooty and the front one was actually a bit wet and sooty. I’ve been using your “1 click” method for a couple years now and I think it works best, but my question is how to know where to set the mixture screw on these engines? Should the process go in a certain order like:
1. Adjust cables first
2. Adjust idle screw
3 then mixture screw, and repeat if necessary?
Hi could you tell me.... I have an 82 MHR. I'm have issues setting the carburettor air fuel mixture. Could you give me an idea of the number of turns on the air fuel mix from tight up out
The MHR has 40 mm carbs so the idle jetting will be different to the 32's and 36's on mine. You MUST synchronise the slides before fine tuning the idle mix. Once that is done it's simply a matter of finding the mid (smoothest or fastest idle) point for each jet. Once the jets are close you can then set both idle stops to the desired idle RPM (1100). You will have to re-adjust the idle jets each time you alter the idle speed until you get both correct.
Be aware that if the rubbers in the enritchener jets (choke flip levers) are worn it will be impossible to get this right, so look at those first. They will almost certainly be compressed from old age. You can usually turn them over in the brass slides to refresh the surface (once). If totally stuffed then replace them. Cheers Rob
Cheers Rob, I'm looking for someone to help me out in NSW Australia, anyone you can recommend?
Sorry no can do. Gowanloch Ducati will be an obvious option, but how good and how much they charge I can't comment on.
The experience in SA of Ducati shops is not good from my observations and I've always done my own wrenching. The current crop are great BS artists and that's about the start and finish of it as far as I'm concerned ;) Cheers Rob
Thanks Rob, it's really hard to find anyone that is good to work on these older bikes although one would think it'd be pretty basic although fairly fiddly.
Thanks again
I've currently sinced the slides and have the air fuel mix screw 1 turn out
Having owned Ducs for a similar period, your method gets you fairly near but still not as accurate as if you combine this with Gauges, your method assumes that both cylinders are performing exactly the same, it's pretty obvious that a vertical piston will need slightly more force than a horizontal one, and as both work on the same crankshaft the gauges help fine tune this. Try it and see.
I have mercury column gauges which I never use. As the two cylinders suck differently due to manifold variations, any readings are pretty much useless as air flow changes throughout the rev range. I was shown this method by a trained Ducati mechamic. It has always worked for me. My Ducks have always run smoothly.
Cheers Rob
We'll have to agree to disagree on this one!
Just to clarify the issue with tuning early air cooled ducati engines (Taglioni):
- Both intake manifolds have dissimilar air flow passages,
- the front cylinder breaths in cold air at speed, the rear cylinder breaths in less dense warm air as the result of heat wash from the front cylinder,
- the rear cylinder on some models runs a richer/larger main jet to help cool the cylinder/compensate for heat wash.
- the actual orientation of the cylinders has no bearing on engine breathing as such.
The end result is that air flow, air density, and fuel mixture ratio between cylinders is not/never going to be the same (as required for vacuum gauges to be effective).
Cheers Rob
Hi Rob,
You've just explained to yourself why you need to use gauges to get a balanced output, both pots will run slightly differently and gauges will allow you to adjust the cables to give optimum performance, in my experience it's only a very small adjustment to get this but it will make a difference. Have you read Steven Eke's book on this?
Chers
Jeff