jtanman

1982 XR200 smokes, low compression, but rings look good?

24 posts in this topic

On 6/15/2018 at 1:50 PM, oldspark1960 said:

Am i wrong or does the pick of the cam show that the lobe is worn down with burrs on the outside?

It does, but as he mentioned in a previous post, he plans to replace the cam. 

On 6/14/2018 at 11:20 AM, jtanman said:

I'm picking up the freshly honed cylinder later today and they'll tell me if they found the cylinder to be tapered or not. Fingers crossed! 

If they had found it to be tapered, they wouldn't have just honed it.

If they're a reputable shop that  does good business, if they found that, they would've called to tell you their findings and that it would need a fresh bore, and verify that's what you wanted done, before doing work that's more costly. Unless you told them from the start to just do what needs to be done and you'll pay for it. 

In any event, hope you get it all sorted out and ready to ride before long

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Luckily they said the cylinder was straight! No tapers found. Parts are starting to trickle in from the mail and I’m gearing up to do the work as planned. And yes, I am indeed replacing the cam. Thanks again for your insights everyone.

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Posted (edited)

Alright, I'm on the tail end of the work at this point. As far as I can tell all that's left is to assemble the pulse generator on the cam and adjust the valve clearances then pop the engine back into the frame and hope for the best. I hope to possibly get this accomplished by tonight. 

Here is what I've done:

  • Honed cylinder (machine shop confirmed no taper)
  • Replaced piston rings
  • Replaced both valves, lapped them, checked for good seal 
  • Replaced valve seals (they fit much more snugly than the old ones)
  • New gaskets (excluding the valve cover gasket that wasn't in the kit or anywhere I could find on eBay. I used high temp silicone instead.)
  • New cam shaft
  • New timing chain, guide, and tensioner

Here is a big question I have: As you may have noticed in the previous photo, the lobes of the old cam were in terrible shape. Full of flat spots, worn down considerably, and sharp burrs. Is this a natural way for the cam shaft to wear out or was there something seriously wrong? My initial impression is that it was oil deprived. Is there a way confirm that oil is flowing well into the top end? Likewise, is there a screen or something somewhere that stops up the flow that I need to check? I would hate to get the bike running only to find out that the brand new $90 cam shaft is tearing itself apart exactly like the old one.

I would also love to hear any last minute tips and tricks for adjustments, break-in stuff, etc. I'm admittedly quite nervous considering this is my very first rebuild.

Edited by jtanman

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Good news. I got the bike back together and it runs great! No weird sounds or leaks anywhere and so far it seems to start with 2-3 kicks. Thanks again for everyone's help. I've read about these bikes having a centrifugal oil screen near the clutch so I'm going to pull of the clutch cover and check that out. Anything to help ensure that the oil is flowing freely.

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