'84 zn 700 bottom end rattle

My '84 zn 700 with around 14k on clock has developed a rattle in the bottom end when idling. It goes away above 1500 rpm both when revved in neutral and when putting power to the ground. The rattle happens at idle both in gear and in neutral. I checked the cam spacing and it's fine, so it's not coming from up top. It's not piston slap or any other knock. It's definitely an irregular rattle rather than a rhythmic ticking or knocking. My first instinct was that it was time to retension the primary chain, but I realized that there is no primary chain tensioner to adjust. I went over my shop manual and there is NO mention of tensioning the primary chain in any way. Uh oh. Any ideas what else it could be?

sounds like the clutch basket springs.

Steve's idea is definitely worth a check.

Another place to look is the cam chain. It might just be slopping around on low idle. I would reset the cam chain adjuster and see if this cuts down the noise. It is a simple check to make. It might also be a good idea to explore if the cam chain has stetched beyond its serviceable limit.

On my '77 Kz650 with the roller-type chain (I believe yours has the Hy-Vo chain) the serviceable limit is between 160-162.5 cm. for a 20 link length. You manual should show the limit on your cam chain setup.

Keep us posted on your progress.

Cheers-Colin Firth-Ontario Canada

znrider wrote:

...rattle in the bottom end when idling....

Sometimes carb sinc and correct pilot adjustment will eliminate such rattle.

You might want to pinpoint the rattle using a mechanic's stethescope. The problem could be one of the things alrady mentioned or the primary chain as well. Shouldn't think the cam chain was rattling at 14K miles if the mileage is indeed correct, but it is possible... I think your cam chain adjuster is an automatic type... you might want to remove it from the bike and ensure it is working as it should. You could also pull your valve cover and have a look at the cam chain and see if it appears loose. Probably best to identify the source of the rattle before doing too much engine disassembly.

Sounds like a loose starter clutch. I had one rattling that drove me crazy trying to find it. Look at the other recommendations first though. You have to pull the generator cover off to check the starter clutch. You should not be able to move it chris3

Sweet. Now I have some things to check. I'll go in the order of least disassembly necessary to most. Since I have zero time to work on this right now, it might be awhile before I have some news. Thanks for all the help though. Ride hard, summer's coming to a close.

Sweet. Now I have some things to check. I'll go in the order of least disassembly necessary to most. Since I have zero time to work on this right now, it might be awhile before I have some news. Thanks for all the help though. Ride hard, summer's coming to a close.

Pull the generator cover off and you'll find the generator/alternator but you won't find the starter clutch there

The starter clutch is inside the motor between the crank and the trans on the secondary shaft.

You don't want to take the cam cover off until you remove the cam chain tensioner, the 700/750 motors have a cam chain slipper mounted on the bottom of the cam cover that pushes down on the cam chain.

I'm not going to spend the time to explain it (it's late and I'm tired), but if you remove the cam cover and then try and put it back on without removing the tensioner, you will more than likely regret it (unless you are lucky).

The noise you are hearing is probably the primary chain, sync your carbs and it will be quieter.