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I did some test fitting with the HRC cylinder. I think it can be made to work with stock -86 crankshaft and 4 mm spacer under the cylinder. There was a small cap between piston skirt and intake channel when piston was at bdc. Will that cause any problems? Does -84 model have a different piston skirt shape? It is almost impossible to find a good -84 model crankshaft so I would rather build engine with stock crankshaft and spacer under the cylinder. I also have to make longer exhaust valve arm to compensate 4 mm higher cylinder.
The Shop
I'm bit worried about milling extra rare HRC cylinder head. If it goes bad I wont be able to find replacement and my HRC cylinder will be pretty much useless after that. Although the idea of 133 engine sounds still pretty good.
On the other hand it would be lot easier just build the engine with -84 crankshaft. But it turns out that it's one year model only crankshaft and its really difficult to find one in decent shape. I have one crankshaft coming from Ebay which I got really cheap but I don't know if it's salvageable and in the long run finding spare crankshafts for the bike will be real pain.
It would be nice to hear what do you think about my options?
Here is the oem cylinder head
And here is the HRC version
This is how the shock looked before I started cleaning it
After some liberal amount of brake cleaner and vigorous scrubbing
I think I have a problem here
I also cleaned the swingarm and to turned out to be in really good shape for an old bike.
first thing I did was get rid of the ATAC chamber for a Pro Circuit pipe but then it wouldn't be stock again would it.
Great find, always reminds me of Micky Dymond
I love these '86 CR125s. My buddy had the CR80 way back when. That bike looked awesome too and it ripped!
I don't have much input here, but I just wanted to suggest using Cometic Gaskets for your cylinder spacer- if you end up that route. They can make you a spacer super cheap.
I think I'm going to build the motor with 50mm stroke like it was originally intended by HRC. I'm still in process to find a good crankshaft for the motor.
This is how it looked before:
This is how it turned out after some sanding, heat gun treatment and Plastic Renew stuff. I'm still not 100% happy about the result but it's getting there
Pit Row
Have you spoken to any tuners about this ?
Heat gun works great with the sanding marks. You just have be careful not to give too much heat to one place.
I'm quite pleased how the rear fender turned out. Now I can proceed to other plastic parts.
I have already abandoned the idea of spacer under the cylinder and I'm going to use older crankshaft with shorter stroke. I have already located one crankshaft here in Finland and should be having that someday next week. I hope that will work with my cylinder and is in good enough shape to be rebuilt with new connecting rod.
Next get all that shit off your fender with gas/contact cleaner.
Now get the correct arbor to put a buffing wheel in a cordless drill. Then on low speed buff the plastic until it shines. Has to be sanded ridiculously smooth first. But you did that with the Plastic Renue already. I can't believe anyone would say that stuff is anything but sub mediocre. I'd almost rather a Craigslist Bbq black spray bomb than Plastic Renue
I'm going to ride this bike and it will have more scrathes on the plastic parts so it don't want to spent too much time polishing plastics with buffing wheel which would take forever.
They don't actually polish the plastic, they leave a thin shiny film on the plastic.
I also did some polishing with the front fender. Here is before picture:
And after polishing:
Plastic looks awesome
Good stuff all the way through.
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