Is XR 400 top end rebuild difficult?, Couple of worries?

[Syris the Indomitable]

I have done a few two stroke top end rebuilds which I guess are a little easier.

Will I need to break a link in the timing chain?
Also I am not too clued up about bushes as opposed to small end bearing and cam bearings or bushes as the case may be.
How can I tell if the bushes are worn?

I am hoping to get away with a piston kit change because the compression is low and it's struggling to idle in cold weather, however after a long journey (When oil gets hot), I acquire a top end metallic taping.
It's not the clearances which is why I am thinking about weather or not it could be what ever is used in place of the small end bearing- The small end bush?????

Thanks!
Any advice would be helpful.
https://img577.imageshack.us/img577/8011/oie914114vh3flkwa.png

https://www.xrstuff.co.uk/partsXR400List.htm
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In Greek mythology Ichor is what immortals have in the place of blood
Those that mind, don't matter...Those that matter, don't mind. Do you agree with this?

[craigT19]

No you dont need to break the timing chain, once you remove the chain tensioner and guides the chain will be loose enough to remove the cam/cams.

Dont worry about the small end bush, get it on a press and just push it out, then press the new bush in. Your see wear on the old one as it will have a shinier surface were its been "polished".
If your gunna go to the trouble of stripping the lump worn or not i would change it anyways, probably isnt much more than a few quid and your kick yourself if it starts to give grief and you gotta strip the engine again

Personally i always use a socket thats about the right size as a drift to press on the outside of the bush
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Bikes owned :- 2001 nsr125, 1999 zx6r, 2006 yzf-r1, 2009 xmax 250, 2012 yzf-r1, 2015 MT-07
Current bike : - 2016 MT-10
BCF member pops. sadly missed 1945-2003

[Syris the Indomitable]

[craigT19]

[Jamie S]

I'd be inclinded to fit new valve stem seals, and lap the valves in aswell considering the top end is coming apart any way.
Jamie

[Syris the Indomitable]

Ok, thanks craig. will do.

I will buy new valve stem seals too but what does "Lap the valves mean"?
Thanks!
____________________
In Greek mythology Ichor is what immortals have in the place of blood
Those that mind, don't matter...Those that matter, don't mind. Do you agree with this?

[Jamie S]

[Syris the Indomitable]

Cheers, I will look into that.
I might as well do a good a good job of it.
____________________
In Greek mythology Ichor is what immortals have in the place of blood
Those that mind, don't matter...Those that matter, don't mind. Do you agree with this?