Rebuild on a 1983 XC 250

that's the truth, it's like a galvanized fence post.

i had a friend who tried...we used to call him äutumn leaves as he was always falling...then we changed it to "branch" as he started falling harder...you could always see if he was in front of you due to the trail of broken husky plastics spread along the track

Reminds me of a riding friend we called "Scud", you know, the Russian guided missile, once you launched him there was no telling where he would end up!

Great looking project. I will be following your lead as I work on mine.

Down Under, is that paint or powdercoat?

Hi Arbortodd2, others,
Well in early Jan started assembly process and found that trans was locked and I could not get a gear. Bumper. project shelfed for a few months and now back into slowly. Turns out that trans lacked oil and can be very hard to shift. All good now. So build continues. We had our 4 day here with vintage as support category so I entered with two mates. That has taken all my time with my other vintage bike.
The finish is powdercoat.
The attached image is of the rebored liner and just trying to understand history of what the most desirable porting arrangement is for the Xc / CR liner cylinder combo and how they perform offroad.
regards,

mark

82 250WR cylinder has the port timing that Mike Fitgerald said was the goal of his project with the Yamaha piston. He said he could not use the 82 250WR cylinder because the volume of the ports was too low.

That bore looks pretty rough.

Did you make the nylon wear inserts for the chain guide or can they be purchased?

Hi Guys, In answer to a couple of queries:
The nylon /plastic chain inserts are made of what they call here as "stableboard" it can be purchased in various thicknesses and in sheets like ply in all respects, cut it with a jigsaw drill it etc. I have numerous thickness sheets. it is DIY and not a special part.
The bore is actually coated with oil (Castrol edge or some other car engine oil), I agree it does look pretty rough but believe me its just the oil.

I have reattached another shot showing all the ports, for discussion if need be.
The height of the ports is at 52mm from deck, I measured using a verneir (just got in there).

I read a pretty interesting test, ye old cycles think it was cycle world where they rode the 82 XC and WR back to back.
They favoured the WR as did Richard Burleson back in the day. But they still indicated the XC had plenty of power and was more suited to the desert as opposed to the woods. They also said that the port heights were 1mm difference in height and WR lacked the small transfer ports as shown above on left of screen they measure roughly 12-15mm x 12mm and two of, plus other port changes as well.
The exhaust for the XC is also the WR and have included a shot, it exits to the left and then wraps around with an extended section on bottom compared to a CR

that's about it for now.

Hi Surpriz, You mentioned about the doey power of the WR, well they recommended ditching the CR/XC liner altogether and substituting the WR....but some improvements that were already on the XC / CR see below. Thought I would attach the tech bulletin as well, which made me think twice about the liner / port configuration. Funny though... they installed the same(?) XC /CR liner in the 84 WR.
The below tech bulletin was supplied by visiteur, so thankyou, although for future reference I cannot read any of the dimensions and this would be handy for others. The change to piston just does not seem correct, it looks like they want you to raise it more but cutaway does not show increased cut.

a mate had an 83 xc 250 and i only rode it a couple of times as it was always in bits (he was a full time fixer upperer even tho nothing was wrong with it) i found it a bit pipey c/w the 84 wr but didnt have the lower end burst the wr had. they were both wierd engines to ride in hindsight. the simple fact was once you get going on them, you tend to forget about the details and just ride..till you get to "that hill"...

What's Mike's forum ID? I know him but haven't talked to him in decades. He and my other friend were always talking about the Yamaha piston mod but I never did it to my 83 250CR.