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drm, I was hasty on my last post to this thread and also mis-read your measurement of the rear and wanted to clarify. The dirty little secret is, std OEM pistons are small, generally 3.4965 (+) or (-) .0002 so the rear is already borderline but possibly usable as it stands. I may have missed some posts but I assume you are at least planning on using a ball flex hone and new rings? (please say yes) and don't re-use any removed wrist pin locks, period.
Your measurements for the front are typical of a virgin cylinder but especially after seeing the replacement studs, someone has been in there before. Maybe warranty work when the bike was young considering the older rocker lower gaskets or who knows... they likely pulled the front with piston remaining and since you have to push the piston back into the bore to get the rear out of the frame (do -able but tedious going back together), they probably pulled it and had to hone it for rings. My point at the moment was, if the cylinders, especially your rear, are chucked in a lathe there's a better than even chance they'll be marred to a point that honing it out will get you to a size that won't seal well. Maybe some guys have done it, but everyone I ever knew who trued or milled bases on a lathe went to an oversize piston.
A lapping plate works great cleaning up the bases with a little patience. I use a bottom torque plate with 220 grit, 6" d/a sand paper (hole cut out of the middle) and WD40. They turn out just like the last photo on the link that bagger posted.
Have a general machine shop cut a piece of 1" thick x 6" (round or square) plate with a 3 - 11/16" hole in the middle, milled smooth on one side, and use the sandpaper trick if you want the cheap way out for lapping the bases true.
You've gotten some excellent info and advice from others on here and if I may add one general thing - don't EVER try to get a machinist (or mechanic) to do it "your" way if they offer any resistance. You'll most often end up with a very bad result. The guy saying the "studs pull" was actually telling you, in his own way, he doesn't want to do it!
Thanks! I was curious as to why you said that I would need to over bore the cylinders and use oversized pistons after having had the bases trued, so thanks for clearing that up!
Yes, I planning on new rings, and thanks for the warning about re-using the wrist pin retainers. I'll be sure to get new ones.
I wish I could find someone to hone cylinders and lap the bases instead of me having to buy/fabricate the tools I need, although I'm guessing this won't be the last time I tackle engine work like this because, to be honest, I enjoy this much more than my regular job!
Changing subjects slightly, will I hurt the cylinders, heads and valves if a media blast them with crushed walnut shells? I've tried Sea Foam and CRC Valve cleaner, but neither makes much of an impact. I'm not worried about the exterior of the parts, since much of the black paint is wearing/flaking off.
Thanks! I was curious as to why you said that I would need to over bore the cylinders and use oversized pistons after having had the bases trued, so thanks for clearing that up!
Yes, I planning on new rings, and thanks for the warning about re-using the wrist pin retainers. I'll be sure to get new ones.
I wish I could find someone to hone cylinders and lap the bases instead of me having to buy/fabricate the tools I need, although I'm guessing this won't be the last time I tackle engine work like this because, to be honest, I enjoy this much more than my regular job!
Changing subjects slightly, will I hurt the cylinders, heads and valves if a media blast them with crushed walnut shells? I've tried Sea Foam and CRC Valve cleaner, but neither makes much of an impact. I'm not worried about the exterior of the parts, since much of the black paint is wearing/flaking off.
I put my jugs and the heads in a shallow metal pan and bathed them in "strip eze". By morning, after hosing them down, they were buck naked. It melted away all paint, all gasket material and the carbon ring at the top of the jug.
Pour the pint of strip eze over the parts and with a fat parts cleaner brush work it into the nooks and cranny's. Wear rubber gloves and either googles or a clear face shield. After the initial soak work it into the crevices a few more times after an hours wait.
When and if you do a head job, make sure the non metal valve end keepers are replaced. The cometic gasket kit I received had new ones.
Last edited by almostakeeper; Jan 15, 2020 at 08:19 PM.
I put my jugs and the heads in a shallow metal pan and bathed them in "strip eze". By morning, after hosing them down, they were buck naked. It melted away all paint, all gasket material and the carbon ring at the top of the jug.
Pour the pint of strip eze over the parts and with a fat parts cleaner brush work it into the nooks and cranny's. Wear rubber gloves and either googles or a clear face shield. After the initial soak work it into the crevices a few more times after an hours wait.
When and if you do a head job, make sure the non metal valve end keepers are replaced. The cometic gasket kit I received had new ones.
I don't know strip eze but acetone will also do the same trick, and old takeaway chopsticks, sharpened flat at the end will be a good tool to scrape residue away.
Originally Posted by drm1978
compression ratio of 8.5:1 ... increase the compression ratio by maybe 2%?
Firstly, 8.5:1 was the 'design' compression rate. I'll bet you $100 it's not that high in real life. Machining (and matching the cylinders, they'll also likely be a little unequal) isn't going to get you an appreciateable compression difference, but will improve the squish effect and turbulence and, hence, performance/burn.
Neither will skimming the heads. You've got to add a lot of material to the heads, as per Branchm or use use high comp pistons.
Last edited by harley peter; Jan 17, 2020 at 09:12 PM.
I had a friend fabricate this plate for me. My plan is to put adhesive backed sandpaper on it and use it "freshen up" the gasket mating surface prior to re-assembly. My question is, what grit would you recommend?
I had a friend fabricate this plate for me. My plan is to put adhesive backed sandpaper on it and use it "freshen up" the gasket mating surface prior to re-assembly. My question is, what grit would you recommend?
-Dave
Actually, Bagger answered my question in an earlier post...220 grit paper. Thanks!
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and don't re-use any removed wrist pin locks, period.
