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Please help I am ready to give up on my XR400!!

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Alright guys I am a problem with my bike and I cannot seem to get the problem fixed. Maybe I am just missing something or you could point me in the right direction. I posted on here a few times about problems I was having with my 2001 XR400 (http://www.thumpertalk.com/forum/sho...d.php?t=747633)

I have not yet tried to kick start my bike yet because I am manually cranking over my bike and there is compression there but like I said I can hear a hissing noise and I cannot find were it came from. I am affraid to put the whole thing back together and then have to tear it apart again. Is this hissing noise normal? I honestly cannot remember it hissing before when I would manually turn the bike over (with a wrench on the crank bolt). I have tried turning the bike over with the kick lever but I remember there being more compression or harder to kick over. One other thing I was just thinking about is could the hissing be coming from the crank case breather?

Here is what I have done to the bike since my problem has started. I had all four valves replaced and head work done to make sure the valves are seating properly. I also replaced the springs and valve stem caps. Basically everthing in the head except for the valve guides (I was told they were good). I also but a whole new gasket kit and have replaced all the gaskets on my bike.

When I had my bike apart the cylinder wall did not look scared or any damage to it. The wall still had all the crosshares from the honing that was done to it. The XR400 415 kit I have in there can't have more then 300-500 miles on it. I can't image the rings going bad. They did not look bad and wouldn't they damage the cylinder wall if there were bad.

I have not had a chance to do a compression test yet because I cannot seem to find the right adaptor for the sparkplug hole. I have all the other sizes except this one.

Do I need to pour some oil down into the cylinder? Do I need to finish putting everthing back together and try to kick the bike over and see what it does? Any thoughts or ideas would be great. I really don't want to get rid of this bike but it is testing my nerves and I am very mechanical and have worked on many engines but this has got me stumped.

Thanks guys and please help out if you can.

:):banghead: :banghead:

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you are probably going to get some hissing because you are kicking it so slow that you are hearing the air rush around the valves. I would say start it and if it runs bad, then you have problem, if not, then ride, ride, ride. :)

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You will hear some hissing when cranking it slow. It is compression leaking past the valves and rings. All engines will do that when cranked over slowly in a quiet shop. I'd put it together, and give it a try. As long as you don't have a big "clunk", give 'er a try.

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If everything is back together and the valves are adjusted properly, you shouldnt have any problems.

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thanks for the input guys. I will finish and let you know. Is there obvious signs to tell if the piston rings are bad other than doing a compression check.

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thanks for the input guys. I will finish and let you know. Is there obvious signs to tell if the piston rings are bad other than doing a compression check.

well if it smokes a ton or it has no compression. You can feel a hard spot in the kick stroke right? that would mean you have compression. I think you are fine.

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that is just it the hard spot is not as hard as it used to be. I used to have to hit the decompression lever to get the piston to tdc. Now I can kick it over.

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that is what I don't understand. also this all happened after I took the sparkplug out and kicked over a few times because I thought I flooded the bike. ever since then I have had this problem and that is what led me to doing a complete top end rebuild

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Your new rings may not be seated in yet. Also, cranking it over slowly won't get a good splash of oil up to the rings to help them seal. Dry rings will surely leak.

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As others have said, it sounds like you're probably fine, and the hissing is normal when you're turning an engine over slowly. The link you posted is dead so I'm not sure of what you or others said in the original thread, but you need to just start it up and ride it!!!

How far is it pulled apart right now? If you're doing engine work, I assume the carb is off and the rear subframe bolt is out...one evening and you can have it back together and running. Put it together, adjust the valves, and take off.

Who did the valves? Someone you trust? These engines really are pretty simple and bulletproof - I had a bent valve (stuck open about 15 seconds after I started it, for some reason that will forever be unknown), and all I did was replaced that one valve (lapped all four to be sure they sealed reasonably well), installed new rings (because mine were out of spec), and put it back together with new OEM gaskets, and it started right up. I ride it to work almost every day.

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I am about to put the head back on my xr400 after boring out to a 406. When reinstalling the cam, the manual talks about lingin it up to install first allen screw then turing crank to tdc to install second. How does TDC relate to the piston. Should the piston be at the peak of its rotation. everything i have used to relate to tdc to this point has to do with the valves being all closed. It's possible to screw up the timing and i am tring to avoid this. It would seem that getting the timing correct begins now with piston position and moves on to proper valve position. BTW nothing was changed or rotated after initial removal of components. I know some folks recommend rotating the piston by hand with the crank to help with break-in. If i did this, the above stated questions become much more important.

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Remember, when the engine is actually running (with combustion in the cylinder and all that stuff), the increased pressure in the cylinder causes the rings to seal *much better* than when the engine is cranked by hand. Just make sure the valves are adjusted properly and the oil is clean and full, and ride the piss out of that thing.

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