A nice modification would be an acceptable upgrade to round slide Mikuni carburetors. They perform reliably and the adjustments are spot on. I swapped from 40mm Bings to 38mm TMX flat slide Mikuni’s on my BMW R100 CS. Much better.
Sounds like the relay on the coils mod, trying to fix a non existent problem or one due to poor maintenance. Even on new Premiers I lap the bowl surface flat on a mini surface plate similar to Tornados reply. The gasket is sufficient in most cases to seal without lapping on new carbs. A lot less trouble than doing this and no problems with the idling over tens of thousands of miles. How did you check this was a problem?
I read about the gaskets leaking because the bowls weren't flat and sealing the port. I now don't think the gasket is the problem. I know the exhaust valve guide on the drive side is passing an excessive amount of oil, i believe since the rebuild. Another viewer commented about a condition caused by too much oil will disrupt the air/fuel mixture at idle. Everything i've tried has not worked leading me to take the head off and replace the valve and guide. This will be a winter project.
I assume you tried to flat the bowl on a plate of glass with some 200-600 grit paper? That is the usual process, though not heard it being needed on new carbs until someone has over tightened the bowl screws. Have never heard of air leakage past the gasket being an issue...interesting if it proves to be the fault. For the Don Pender carb "gantry" setup, I understood the chokes need to be removed...but looks like you are using them? You mentioned you need a carb balancing tool....I really like the Morgan CarbTune Pro device from the UK...very simple, uses steel rods inside clear tubes. The rods move up under vacuum and you just tweak the cable adjustments on carb tops until the rods are close to same levels. Available in 2 and four cylinder versions. Ran me about $80. Much nicer than the dial gauge type balancers.
I purchased a Digi-Sync vacuum gauge and it showed i was within 1 point from perfect. Well within limit. I do use the chokes especially in cooler weather. About 3/4 full in summer. They do help. I adjust the throttle cable up for fast idle until warm since Amal doesn't provide fast idle. Works well and i don't have to stay on the throttle. It's an easy start, one kick most times. It does puff smoke at start so there is an issue with oil leaking down into the cylinder. I'll be looking hard at it come winter. I've used 1/2 pint of oil in about 1500 miles.
If it's not a worn out carb then it's an air leak on the inlet port - either the carb connections or judging by the oil coming out of the LH side, pipe out of spec valve guides. Standard guides are useless - they bell inwards on fitment and the i.d is too big from the start. Looking and listening to the videos you still have problems - lots of oil smoke from LH cylinder on start-up - you need to strip down the top end and do it properly - send the entire top end off to a proven Norton shop.
Without boring discussion of British thread systems, the little pilot jet fitted to the Mk1 Concentric for two strokes and some Triumph models is a 1/8 inch diameter X 40 threads per inch. It is most likely in the Cycle Engineer pattern although it could be a Whitworth form. In any case a US No. 5 X 40 threads per inch would be an almost exact match. No. 6 is larger (0.1380") on the major diameter. No. 5 screws used to be popular and are still found in the bottom drawers of some old hardware stores. Big supply houses still carry them. The screws that hold the top and the float bowl on are No. 2 BA which is close enough to a US No. 10-32 to fit, albeit poorly. The BA series of screw threads is a nightmare in its own right.
Credit the original designers with some knowledge. If the idea is to compensate for warped float bowl surface flatten the surface. No need whatsoever for your modification.Better off replacing the original carbs with Amal Premiers.
@@nicksnorton2340 But you're using the Mk1's which work very well as long as there is no wear between the slide and body which, on the original design wear extremely quickly due to slide and body material being the same. Fit the Amal Premiers and you'll have no problem as long as you get the air:fuel ratio checked for your bike. P.S there is no extended tube on MK2 Amals
Great job. Even after surfacing my float bowls I had inconsistent idling with popping back. Your mod will fix it. I’m going the try the mod.
Great! i hope it works for you.
A nice modification would be an acceptable upgrade to round slide Mikuni carburetors. They perform reliably and the adjustments are spot on. I swapped from 40mm Bings to 38mm TMX flat slide Mikuni’s on my BMW R100 CS. Much better.
What a stylish act with a steady pace , Nick. Regards from Malaysia.
Thank you! I appreciate that.
Sounds like the relay on the coils mod, trying to fix a non existent problem or one due to poor maintenance. Even on new Premiers I lap the bowl surface flat on a mini surface plate similar to Tornados reply. The gasket is sufficient in most cases to seal without lapping on new carbs.
A lot less trouble than doing this and no problems with the idling over tens of thousands of miles.
How did you check this was a problem?
I read about the gaskets leaking because the bowls weren't flat and sealing the port. I now don't think the gasket is the problem. I know the exhaust valve guide on the drive side is passing an excessive amount of oil, i believe since the rebuild. Another viewer commented about a condition caused by too much oil will disrupt the air/fuel mixture at idle. Everything i've tried has not worked leading me to take the head off and replace the valve and guide. This will be a winter project.
I assume you tried to flat the bowl on a plate of glass with some 200-600 grit paper? That is the usual process, though not heard it being needed on new carbs until someone has over tightened the bowl screws. Have never heard of air leakage past the gasket being an issue...interesting if it proves to be the fault.
For the Don Pender carb "gantry" setup, I understood the chokes need to be removed...but looks like you are using them?
You mentioned you need a carb balancing tool....I really like the Morgan CarbTune Pro device from the UK...very simple, uses steel rods inside clear tubes. The rods move up under vacuum and you just tweak the cable adjustments on carb tops until the rods are close to same levels. Available in 2 and four cylinder versions. Ran me about $80. Much nicer than the dial gauge type balancers.
I naturally assumed (incorrectly) the bowls were flat because they were new.
I purchased a Digi-Sync vacuum gauge and it showed i was within 1 point from perfect. Well within limit. I do use the chokes especially in cooler weather. About 3/4 full in summer. They do help. I adjust the throttle cable up for fast idle until warm since Amal doesn't provide fast idle. Works well and i don't have to stay on the throttle. It's an easy start, one kick most times. It does puff smoke at start so there is an issue with oil leaking down into the cylinder. I'll be looking hard at it come winter. I've used 1/2 pint of oil in about 1500 miles.
If it's not a worn out carb then it's an air leak on the inlet port - either the carb connections or judging by the oil coming out of the LH side, pipe out of spec valve guides. Standard guides are useless - they bell inwards on fitment and the i.d is too big from the start. Looking and listening to the videos you still have problems - lots of oil smoke from LH cylinder on start-up - you need to strip down the top end and do it properly - send the entire top end off to a proven Norton shop.
My norton is the same color :-)
what is the name of the color? i have forgotten.
1/8 tube with a 6/32 thread it looks bigger than that ???
Without boring discussion of British thread systems, the little pilot jet fitted to the Mk1 Concentric for two strokes and some Triumph models is a 1/8 inch diameter X 40 threads per inch. It is most likely in the Cycle Engineer pattern although it could be a Whitworth form. In any case a US No. 5 X 40 threads per inch would be an almost exact match. No. 6 is larger (0.1380") on the major diameter. No. 5 screws used to be popular and are still found in the bottom drawers of some old hardware stores. Big supply houses still carry them.
The screws that hold the top and the float bowl on are No. 2 BA which is close enough to a US No. 10-32 to fit, albeit poorly. The BA series of screw threads is a nightmare in its own right.
Credit the original designers with some knowledge. If the idea is to compensate for warped float bowl surface flatten the surface. No need whatsoever for your modification.Better off replacing the original carbs with Amal Premiers.
If you know anything about the Amal MKII, they did just that.
@@nicksnorton2340 But you're using the Mk1's which work very well as long as there is no wear between the slide and body which, on the original design wear extremely quickly due to slide and body material being the same. Fit the Amal Premiers and you'll have no problem as long as you get the air:fuel ratio checked for your bike. P.S there is no extended tube on MK2 Amals