Where to source oversize piston/rings?

jbeebe

Been Around the Block
Hey everyone,

I'm working on a '75 Honda XL100 dual sport. Looks like the cylinder will need a rebore...

The standard bore is 50.5mm

Can be rebored if <52.6mm

Mine is measuring in at 51.3mm

I've never had anything rebored before. Will the machine shop source oversize piston and rings for it or will I need to take them in for them? I can't seem to find anything online for this thing. The FSM states they made oversize kits all the way up to +1mm, but other than a couple examples on ebay that are coming from Indonesia, I can't seem to find anything.

Any help and guidance would be greatly appreciated!
 
For my 360, and the current 550, i’ve sourced from a company in Japan and been very happy with the service and quality.

cruzinimage.net

steve
 
For my 360, and the current 550, i’ve sourced from a company in Japan and been very happy with the service and quality.

cruzinimage.net

steve
Unfortunately they don't make any for the 100, but i'll keep the site in my back pocket for other bikes. Thanks for the tip!
 
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From my limited experience, I'd take the list of oversizes and the cylinder to the machine shop and let them decide. They may want the piston before they bore it, and will need to know the piston-to-wall clearance, which should be in the FSM or available from the piston manufacturer.

For aftermarket, did you try Wiseco? David Silver may have a Honda kit if you don't want to buy off eBay.
 
From my limited experience, I'd take the list of oversizes and the cylinder to the machine shop and let them decide. They may want the piston before they bore it, and will need to know the piston-to-wall clearance, which should be in the FSM or available from the piston manufacturer.

For aftermarket, did you try Wiseco? David Silver may have a Honda kit if you don't want to buy off eBay.
bingo! davidsilverspares has a piston and rings in each of the available + sizes. I've ordered from them before rebuilding a cx500, I can't believe I forgot about them. Thanks!
 
yeah david silver always got what you need for a honda good service too ive ordered a bit of him and never had a issue
 
For my 360, and the current 550, i’ve sourced from a company in Japan and been very happy with the service and quality.

cruzinimage.net

steve
i also have these pistons in my 350 alough i havent started it yet i ordered them as they seemed a bargain seeing that your pleased with yours gives me a bit of confidence in them they also have a good range of bore sizes for the 350 twins
 
Hey everyone,

I'm working on a '75 Honda XL100 dual sport. Looks like the cylinder will need a rebore...

The standard bore is 50.5mm

Can be rebored if <52.6mm

Mine is measuring in at 51.3mm

I've never had anything rebored before. Will the machine shop source oversize piston and rings for it or will I need to take them in for them? I can't seem to find anything online for this thing. The FSM states they made oversize kits all the way up to +1mm, but other than a couple examples on ebay that are coming from Indonesia, I can't seem to find anything.

Any help and guidance would be greatly appreciated!
im pretty sure a cg 125 or 150 cylinder will fit on the xl engine ? sure theyre almost identical engines? the cylinders ans pistons for cg125 are avalible for literally peanuts from the chinese suppliers i would check the stroke and see if itd the same as the cg i would bet that just the bore dia is different
 
im pretty sure a cg 125 or 150 cylinder will fit on the xl engine ? sure theyre almost identical engines? the cylinders ans pistons for cg125 are avalible for literally peanuts from the chinese suppliers i would check the stroke and see if itd the same as the cg i would bet that just the bore dia is different

good to know! if david silver doesn't work out with the 1mm over piston i'll check it out.
 
A reputable machine shop (check with the vintage racer community in your area) will take your piston and cylinder and bore to match and to factory specs. For a multi-cylinder bike they match each piston to a hole and mark the pistons so you put them in the right cylinder, as there are variances from piston to piston.

Should be about $50 per hole for a bore and hone.
 
ok, turns out my cylinder was already bored to 1 over! The problem is that Honda didn't make anything bigger, and nobody makes any aftermarket pistons for these little thumpers. It was burning a little oil in the cylinder before (some white smoke) and the piston skirt measured in below allowable tolerance, so I ordered a new Honda +1 piston and rings from david silver.

short of re-sleeving back to stock bore (LA Sleeve quoted me $375), I believe this is my best bet. As long as it doesn't noticeably smoke a bunch, i'm not worried about it being perfect. These little 100's aren't worth very much.
 
You could also just replace the cylinder. A few years ago, I bought a used standard-bore cylinder for my XL100 on eBay. It was $30 including shipping.
 
I haven't messed with XL100 since the 80's and just can't remember what we did with them.
. CG clone won't work, being a push-rod motor BUT, you can shrink out the liner, fit it to 100 cylinder (will need some major boring but aluminium cuts very easy) and have a 125 instead (56mm bore)
I'm way more familiar with boring 125's to take modified CB750 pistons to get a 145cc motor. I think CB500 pistons can also be modified to fit, just don't remember all the dumb stuff I did back in the day (heck, I started doing 'big bore' small engines around 1975)
 
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