hi, when i start my 3aj after sitting for a day, firstly it starts fine,runs quiet then after 30 sec plumes of blue smoke pumps from exhaust, after 2 mins a rattle appears somewhere at the right hand side of the engine!! engine has had new side bearings,rings,valve seals camchain & carb rubbers fitted. runs fine(no smoke) when its warmed up but still rattles. anyone got an idea on this before i pull her down?? cheers T

[This message has been edited by big t (edited 19 March 2006).]

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big T

Hi Big T,

I just rebuild my engine recently, bearing, cam chain+ piston ring after 55000km
Had a bad oil leak towards what I thought was the cylinder gasket, so opened the engine again change the gasket...
The leaks remained, then I thought it was the clutch cover gasket ...
Eventually a friend came along and within 5 minutes saw that the leak was actually coming from the other side of the engine..
I forgot to put back one small screw...
If only I took the time to really check the leaks I wouldn't have waisted this time searching and fixing the wrong part...

From my view if there is smoke there is probably some oil left in the cylinder head
So I think one possibility would be that the piston ring don't do their work properly, as it can be tricky to put them back.
So I was thinking maybe you did not adjust each ring with the right angle allowing the oil to filter through.Especially if your bike has a certain mileage the cylinder get used irregularly on its surface.
For the noise I experienced also a noise after the rebuild, I found that I adjusted the timing chain correctly but then did not use the right torque and the bolts were getting lose...
The lesson I learnt is that those engine are quite basic so if something does not run properly it probably comes from one own inexperience and mistakes...

Hope my modest experience will help...

hi Gwel, the rings were lined up as the manual says, and the tensioner is fine. theres a small rubber seal between the barrel & head,im wondering could this have failed & be letting oil into the bore?? as for the rattle i,m beat!! any more help or suggestions please? T

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big T

I am actually considering a little bit of top end on mine aswell because of similar reasons.
approx. 2 out of 10 cold starts she blows smoke (not blue just solid white with a feint odour)
In talking to other mechanically minded people i think my problem, is a worn valve guide, so that when oil is up top there it can run down the valve shaft and there is a couple of ml of oil sitting on the valve waiting for me to fire it up so that this oil can enter the chamber to burn with the fuel/air. This also indicates its likely to be happening only when i stop the engine on tdc (when all the valves are shut) otherwise the oil would prob just run down over the rings.
as for noises i am playing ignorant, they clear up after a minute for me, so i just think the oil is taking a bit to get up the top.

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Yamaha XT600 1988

well took the head & barrel off today, some oil lying on top of the piston. it seems to be entering the bore at the camchain side, so maybe just a blown gasket? still can,t figure out whats making the rattling noise or why it doesn,t appear until after two minutes? gonna remove the r.h. side casing and check the big nut at the end of the crank as i seem to remember reading on another thread about this coming loose. any more ideas still welcomed thanks T

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big T

I had the same thing as mini-s-man, ie. lots of smoke every few starts and a bit of a rattley noise which goes in a few mins(on my tt600r).
Had someone more mechanically minded than me look at if after 50,000kms. He gave it a piston and rings, new camchain and tensioner and a new set of valve stem seals. Apparently the seals were v-shagged and caused most of the oil smoke and a bit of a rattle.
Did you change them?
The big nut at the end of the balance shaft is the problem one, not the crank, i think(stuck the bugger on with bearing loctite whatever). Apparently it makes a very scary noise which you will not mistake with a bit of a rattle.....

valve seals were replaced, piston rings also. this noise only appears two minutes after starting from cold, so could it be somehow heat related? will investigate deeper tmw. T

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big T