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1985 ZR400B1(Z400F) engine rattle at idle speed

3438 Views 7 Replies 3 Participants Last post by  kyhick1
Bought the above and have done it up(rebuild without removing the engine). Now that it is going again, it has a very clattering, uneven engine rattle at low idle. Above 2000 there is nothing. Timing chain tensioner is on its limit, but there is still tension in the spring. 28000 miles on the clock, and, by the state of the bolt heads, nobody has ever touched it. Any ideas???? Listening with my trusty screwdriver pressed to ear, it seems to be coming from the lower gearbox. Primary chain???
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You are right, but............

Hi Heather, and many thanks. You are right about that, but, my Haynes manual states "KZ550(etc) models suffered from a cam chain tensioner fault. .... A series of modifications was tried on the Z500, the last of which was also neccesary on the 550 models, etc. ". It appears they brought out a replacement part which sorted out the problem, and I assume this is what your hubby installed. So there was a problem with the 500s and 550s, but it should not occur in the model I have.

On the other hand, with my ear for old bikes, it does make that distinctive clatter which calls to me "timing chain".
Does anyone know if you can replace a timing chain without dismantling the complete engine. It looks possible from the diagrams, but this aint no Norton..


Old Kawa cam-chains

It occurs to me that some enterprising soul could make a lot of money if he/she came up with a replacement cam chain with a master link, thus avoiding all the engine removal, stripping and rebuilding.

As a matter of no consequence at all, I have just replaced all three chains on my '58 Norton, timing, primary and main drive.
It took just over 2 hours, no engine dismantling, no messing with taking engines out of frames.

Just take off the covers and replace the chains. (OK, there is a bit more to it than that)

If the Brits could do it 40+ years ago, what's wrong with the so-called modern bike industry????
The next episode

Well. Got mad, pulled the motor, replaced camchain and various other bits, and got it going today. Camchain noise is gone, but I now have a gearbox rattle at low revs. So tonight I tried pulling plug leads off while the bike was running. Pot 1 made a minimal difference to the revs when the lead was off, and has a very weak, almost permanent spark. I am beginning to think that the fundis are correct and I should be looking at the simpler problems. I think the major ones have now been solved.

My initial plan is to get 2 new coils and HT leads, for a start. The old coils are different from each other, so something has already been replaced, and the HT leads are very hard, with old NGK plastic plugs on them.

What do the experts think?.
But it looks a lot better.

The before and after pics.
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