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01 top end rebuild advise???

By skagroovy,
in XR250R & XR400R

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skagroovy

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just bought a 2001 xr400... very excited... fired it up and ran good but started smoking white smoke ...and it had a loud knocking noise....so i torn it down.. needed new cam chain but the piston was stock but looked in really good shape and rings looked good ... valve seats are good ... so i was planning on a honing the cylinder.. new wiesco 11 to 1 std bore... and new valve seals and lapping the valves.. and a new cam chain.... does this sound like a decent top end rebuild ...am i missing anything? also planning of a carp update and already did the usd fork conversion....

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Grand Master

boomman

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I did a top end on my XR400 and did everything - piston, re-bore, rings, valves and seats and valve seals - everything but the valve guides because the shop said I didn't need them done. After all was put back together, the bike still smokes a bit on start up after a few days of sitting. Only thing I can think of is that the valve guides are letting a little bit of oil get past them when it sets in the garage for a day or two. I wish I had spent a few more bucks on new guides when it would of been easy to install.

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Alex 400

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I did a top end on my XR400 and did everything - piston, re-bore, rings, valves and seats and valve seals - everything but the valve guides because the shop said I didn't need them done. After all was put back together, the bike still smokes a bit on start up after a few days of sitting. Only thing I can think of is that the valve guides are letting a little bit of oil get past them when it sets in the garage for a day or two. I wish I had spent a few more bucks on new guides when it would of been easy to install.

both my dad's and my bike leak smoke a bit on start up, his more than mine but they both do it after sitting for a while. the valve seals are mostly like the culprit. My dad has his cylinder head cleaned up (sticky valve) and they looked at it and said that all of the parts looked to be in great conditions so they just cleaned them up and replaced the seals. if you decide to tear it apart again i would say definitely change the valve seals.

Rule of thumb on any project, you never want to visit an area twice, so check everything and if you have any doubt about the condition of a part after checking, replace and be done with it. peace of mind is key in projects, especially engine work.

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Alex 400

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i mic'ed the valve stems and they were in spec

???? why the valve guides, valve seat looked great too...

i am trying to avoid the machine shop....

even though the valve stems are within spec, the valve guides could be worn and out of spec allowing more space between valve and the guide that can let the seal weep a little bit.

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Grand Master

boomman

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both my dad's and my bike leak smoke a bit on start up, his more than mine but they both do it after sitting for a while. the valve seals are mostly like the culprit. My dad has his cylinder head cleaned up (sticky valve) and they looked at it and said that all of the parts looked to be in great conditions so they just cleaned them up and replaced the seals. if you decide to tear it apart again i would say definitely change the valve seals.

Rule of thumb on any project, you never want to visit an area twice, so check everything and if you have any doubt about the condition of a part after checking, replace and be done with it. peace of mind is key in projects, especially engine work.

I did replace the valve seals.

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ATJ_Number_1

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just bought a 2001 xr400... very excited... fired it up and ran good but started smoking white smoke ...and it had a loud knocking noise....so i torn it down.. needed new cam chain but the piston was stock but looked in really good shape and rings looked good ... valve seats are good ... so i was planning on a honing the cylinder.. new wiesco 11 to 1 std bore... and new valve seals and lapping the valves.. and a new cam chain.... does this sound like a decent top end rebuild ...am i missing anything? also planning of a carp update and already did the usd fork conversion....

I'd still get the cylinder mic'd to be sure if a std piston is the way to go.

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