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Hallo everyone

I have bought a new pringle petcock from the USA and fitted to my bike yesterday 1979KZ 1300, 46000kmsince new). In the same time i allso bought a second hand ( very good condition ZX 11 cam tentioner to the bike.Few questions please

1) How will i know if the tentioner spring was in any way shortened by the 10mm as suggested on another topic elsewhere on the forum of the same tentioner , Can i run the bike as is untill someone can actually tell me what lenth the tentioner spring must be so that i can measure mine and shorten only if it was not done before (bought on ebay and have no details)unfortunately. Please help as i need to know very urgently.

2) i read on the Forum that the cam chain ZX 11 tentioner must NOT have more than 10 clicks when installed. Mine is exactly 10 . How serious can this be and should i open up to look whats happening inside?

3) I read also that the Cam chain idler gears are problematic and dont last.New ones are made somewhere in the USA for 99 dollars made of steel?

4) Now if i have to replace the cam chain and pully , i might just as well put in new pistons/ rings , valve job etc as the 13 uses lots of oil allthough has only 46000 km since new. Question is what should be done when opening

I thougt about the following:

Cam chain, Cam idler gear, pistons, rings, new gaskets , valve stem seals.Cylinder head checked and valves reseated. Obviously bore to correct size?

Lastly please confirm that with 10 clics on the tentioner as it is now i can still travel safely for a few more kms.

I stay in South africa and getting stuff here is not only expensive but takes for ages.

Regards

eddie

Hi Eddie,
I would slow down a bit hear before fitting new Pistons, Rings and Re-boring especially on a bike of that mileage, oil usage could just be down to Valve seals and hopefully a quick top overhaul should sort your problem. The reason that you are removing 10mm is to prevent the wear taking place on the tensioner plastic gear wheel.
can't advise on the length of the tensioner spring sorry, but speak to others before you go to cost of the questions you are asking

Hi Eddie in relation to spring length, I would imagine if the Tensioner came from a ZX11 it wouldn't have been shortened, we are only reducing these lengths because they weren't designed for this bike. So would think it wouldn't have been shortened, But don't take this as a guarantee from me

I'm considering switching to the ZX-11 tensioner at some point. When I do, rather than the "clip 10mm off the spring" method, I'm going to compare the spring tension between the two, and try to match the ZX tensioner up with stock. Any issues with the chain idlers (either the gear or rubber wheel) is usually due to incorrect tension on the tensioner itself- either a manual one adjusted too far, or a ZX tensioner with an unmodified spring.

Any further work is up to how deep you want to go into the engine. If you take the head off, I would agree that a valve job would be in your best interest. It's not that much for what you get, and it gives you a chance to replace the often leaky valve stem seals.

As for pistons, rings, etc.- I'd hold off. You can drop a LOT of money on that stuff really quick, for no real reason. Just as an indications, when I rebuilt my motor, I spent over $300 US on rings alone. I can't imagine what prices would be in South Africa. With mileage that low, I'd be genuinely surprised if rings were the issue. Unless it's been sitting for a long time and there's major cylinder wall damage, I wouldn't worry about it.

What are your compression numbers like? Unless they are extremely far off, I'd leave the pistons alone.

This particular "MOD" makes the hair on the back of my neck stand up on end. In the world I came from we had NICR's - Non Identical Component Replacement. and I'm sure Tyler with his background in engineering will attest to this. Before replacing components with similar designs we had to follow a process to justify that the "new " component met or exceeded the requirements of the old component. Engineers had to go to great lengths to prove that the new component met the requirements of the NICR.

Taking a ZX11 tensioner and hacking off 10mm from the spring length - YIKES!!!

Compression springs are engineered to have a force at a predetermined compression length and a compressive force at a working length. I have NO idea of the working stroke of the ZX11 tensioner as compared to the working stroke of the KZ1300 tensioner nor the spring pressures of either unit. Because of the nylon gear, the spring pressure should be by design nearly the same at both ends of the working stroke. If the ZX11 spring has too much force at the fully compressed point then it suggests to me that the spring is of a heavier gauge than the spring on the KZ1300 and as such the compressive force of the ZX11 spring will diminish quicker than the KZ1300 spring.

So here's where the hair on my neck stands up. Will there be enough compressive force acting on the tensioner when the chain is near it's service limit? Did anybody "do the math" and determine the forces on both the ZX11 spring and the KZ1300 spring over the working range of the tensioner?? I don't see anywhere in the posts on this site where that information got posted.

Just being the Devil's advocate here and trying to stimulate thought, especially to those who've gone ahead and done this "MOD"

I was actually following that same line of thought, albeit a bit less closely and in a much less academic way. Something about just cutting off a length of spring to achieve a somewhat similar amount of force to a completely different spring didn't jive with me somehow. Hence my desire to test spring pressures.

I'll admit, though, that the ball bearing design of the stock tensioner is less than ideal, and a ratchet type would, at the very least, give me more peace of mind. On the flip side, however, I see all these worn nylon idler parts, and chock them at least partially up to incorrect spring pressure.

Having never had a ZX tensioner apart, how difficult would it be to use a stock KZ1300 spring in an otherwise unmodified ZX tensioner body? Just spitballing ideas here....