1986 Yamaha XT600 engine knocking
 

Folks, i have a 1986 XT600 which has been sitting unused for around two years. I have changed the oil, oil filter, air filter and spark plug, overhauled the brakes, new drive sprocket and chain, stripped and cleaned the carb and fitted new carb joints to the head. I got it running today but its very noisy and sounds like it has a knocking coming from the engine. Is this normal for these engines? Thanks for any help.

Check the valve gap and remove the cam tensioner (according to the manual) and if it's all way out, it's the cam chain.

Dont think the cam chain would make such a loud noise, it sounds more bottom end, big end type knocking?

Could easely be cam chain, check it, it only takes a minute.

What sort of knocking is it?

Is it tapping or knocking???

If it is bad knocking get a re-bore and piston - and top up your oil!!!

If it's just top end tapping just adjust your valves - 2 minute job (literally)

If you put the bike in first gear and let the clutch out with the brake on, (with the engine running) a bottom end or piston knock will get louder. If it stays the same, look at the Cam chain/Valves, ect.
My -89 is noisy at idle too, I think this is fairly common for these. I only have 6500 miles on mine.

Steve

Ok guys, I bow to your wisdom:thumbup1: I will check valve clearances and try the bike in first gear with the brake on. That's if I can get it started again? I have had the carb of it twice now and cleaned it. I am going to post another thread about that.

I have checked the valve clearances and they are spot on. Haven't got round to checking the knocking as I can't get it running again.

Hi, I had a knocking sound on a 3TB XT600e '91 with 57.000Km. This was the first defect on the bike since new. The www and the off. Yam. Dealer learned me to check the tightening of one mutter on the cranck. I did open the both cases. Rotator and cluch. Rotatot side it all felt OK. Cluch side: If I turned by hand the cranck then I saw some degrees of freedom between the first drive gear and the cranck displacement. Even with the sealing washer plate OK the mutter was'n torqued enough. (loosening by hand.)
There was some friction damage between gear and distance ring but still fine to assamble again and tighten it on torque. Now the Yam is perfect again and ready to move on!

once you've gone through all the obvious have a look at the primary drive gear woodruff key. Engine backlash is known to sheer them and once broken do make a knocking sound too as the backlash is then aggravated.

see page 27 part 1 and 2 http://www.yamaha-motor.com.mx/Manua.../3TB9_1994.pdf

(not your bike but these parts are the same) primary gear is located on top RHS of bike under the clutch cover near oil filter.

Once had strong knocking in the engine (2KF 1987 at 50.000 km) that was caused by radial play at the level of the left crankshaft bearing. Could feel it on the flywheel, could be moved up and down a little.
Had to replace crankshaft and bearing.

Regards

Guy