Setting Piston Ring Gaps for my Honda CB750 Cafe Racer Project Bike + Painting Engine Barrels | 17
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- Опубликовано: 19 мар 2023
- Setting Piston Ring Gaps for my Honda CB750 Cafe Racer Project Bike + Painting Engine Barrels | 17
Although excited to find that I had a set of Yoshimura pistons for my Honda CB750 Cafe Racer project, I had the problem of finding a different set of barrels and getting them rebored and I also needed new piston rings. It took quite a time, sourcing a barrel having it machined. But I found a better supplier for the piston rings than I ever expected.
Now I have the barrels back I need to get the pistons ready to fit to the engine.
What I used:
IMD Piston and Ring shop: ebay.us/HmdH7r
BLACK E-Tech 400ML Extremely High Temperature Paint: ebay.us/DrPPSA
I got the piston rings from a company called IMD in Cheshire. They supply lots of pistons and rings for all sorts of vehicles. It turned out that they had bought a job lot of NOS pistons, rings and other things from Yoshimura R&D inc back in the eighties. This included piston rings for the 823cc size pistons. I had a great chat with one of the guys from IMD about all of the stuff they had bought, apparently it all came loaded in an old American car which they had shipped to the UK.
Although the pistons are a little larger than the originals, but 3.5mm I don’t think the end gaps would be very different. My research lead me to believe that the pistons were made in the same factory that made the original Honda pistons, and they were made out of the same material. Although they are Yoshimura, these are cast pistons, not exotic forged ones like you might have thought.
When I came to set the end gaps most were just above the minimum clearance, or just needed a little adjusting. You adjust the end gaps with a file, taking a little of each side until you get them to be just above the minimum gap specified. When the engine is running the rings will expand slightly, if the gap is too small they could bind and seize the engine. If the gap is too large the engine will lose compression. And if the gap is way too large the ends of the rings will scratch the bores like mine did.
I did notice that my file was looking a little past its best. In my defence all of my better files are at the other garage where we are working on the E30. I only had to take a little off the rings that needed adjusting, most were just fine.
Mechanically the barrels are fine, and I have already spent a fair amount of time cleaning off the corrosion and old paint. Now I needed to give them a final clean and paint them. I had previously used paint stripper, degreaser and even soda blasted them, but they have been to a machine shop and back so I expect they will have a bit of muck and grease here or there.
I gave them a good wire brushing to scuff up the surface then I used brake cleaner to remove any grease, before masking them up for spraying. I use Xtreme Heat Paint to coat the barrels. When I was happy with the coverage I baked them for an hour in an oven at 160c. This cures the paint properly and should give it a much longer life on the bike.
Overall I am very pleased with the barrels, pistons and rings. Now I just need to get the engine together. I can’t wait.
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#cb750 #hondacaferacer #cb750caferacer 
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![Which Barrels & Head Combo For My Honda CB750 Cafe Racer Engine Build? [300 vs 410 Barrels] 17](http://i.ytimg.com/vi/JziM5jJ9dy0/mqdefault.jpg)
![Which Barrels & Head Combo For My Honda CB750 Cafe Racer Engine Build? [300 vs 410 Barrels] 17](/img/tr.png)
Thanks for showing how you do it. Another great video. One step closer!!
It's getting exciting now. Soon have eht engine together :)
Great series thanks
Glad you enjoyed it
I’m glad you stuck with the big bore kit, I saw that you used SEP for the rebore,top job mate,keep them coming
Thanks, I can't wait to get this engine together. But there are a couple of more hurdles to get over.
@@SPANNERRASH a few oil leaks, then the fun starts finding out what else is wrong
I have a '76 Honda CB750 K6, Its got a 4-1 exhaust, and the tank and side panels are gloss back. I was going to sell it, but you have rekindled my interest in it. fitted new ignition coils and ultrasonically cleaned the carbs, fitted new jets etc, apart from noisey primary chains, sounds and runs o.k. so thanks!
That's great. I'm really pleased to hear of your rekindled enthusiasm. There is a video about measuring the deflection of the primary chain tensioner to help judge how worn the chains are, it can be done with the engine in the bike, at least then you would know how worried to be. It's an engine out job to replace though.
Good work as always 👍
Thank you, Mark! Cheers!
Great job Les. Always enjoy seeing you work on an engine 👍
Glad you enjoyed it, it's the best part :)
Thx for the video les enjoyed it very much
Glad you enjoyed it
Nice work minding the gaps (sorry) 👍👍
Thanks, Doc. It was funny how the two outer cylinders didn't need any adjustment, but the two centre needed a bit. Maybe I am over thinking it, I hope.
Put 2 piston pins in the piston, turn the piston over and push the ring down until the pins hit the deck. Square in the bore in 3 seconds
I like the way you think.
Master job. Question: Is the end gap position of the oil ring really that important as with the other two rings when putting the cylinder on?
The main wisdom seems to be, ring gaps not lining up (120 degrees apart if possible) and not on one of the thrust faces. I am not sure if the oil ring is treated differently, I am researching this at the moment to make sure I am right before I put the barrels on. Any advice is welcome, as per usual there is a lot of conflicting information on the 'net. I have always stuck to my first sentence with previous engines but thought I would put a little more thought into it this time. There is also the issue that the rings are said to move around the piston as it is running, so what does that do to the spacing?