Primary chain stretch limit

Hi all,

I have just measured 30mm of sag in the primary chain of my Z650 B1, the servis limit is 27mm.

I know idealy I should replace it but they are very expensive and I really don't want to split the crank cases.

That is bound to lead to discovering other expensive work that I should do whilst i'm in there, and I'm hoping to put off a major overhaul for a couple of years / 10 000 miles. The engine has currently got 80 000 miles on it.

It has been sugested that the only problem that ignoring it will cause is the noise of it rattling at tick over.

Does anyone know of a reason why I shouldn't ignore it or how long I can ignore it for ?

Thanks

A reason you should not ignore it is pretty easy, if it breaks then major engine damage is the likely result.
As for how long it will last, that's like playing the lottery, how lucky are you?
The chain stretch is due to either the pins wearing or the holes for the pins elongating, and I personally think that pin wear is more likely (just my opinion, I have never disassembled a worn HyVo chain to see).
I just checked the sag in a GPz 750 primary chain, the motor has ~15k miles on it and the total sag (top to bottom) is 12mm.

A point to consider is that good used 650 motors with a lot less miles are generally available for $250 and maybe less.

I think the chance of a hyvo chain actually breaking is near zero. I wishI would have measured by 160,000 mile engine's to give you an idea how far they will go. I'd leave it alone.

I have to respectfully disagree about the near zero chance of a HyVo chain breaking.
(1) nothing lasts forever, so it will break sooner or later.
(2) HyVo chains are used in transfer cases and have broken many times.

I don't know how long it will last, I would guess that it's like everthing else and the lifespan would depend on the maintenance and use it has had, constant drag launches and not enough oil would shorten it's life significantly.

In your case it is already beyond the service limits, and I think that should probably be taken into consideration.

Thanks for the quick replies,

I appreciate that the correct thing to do would be to replace the chain, but Ron's responce was exactly what I had hoped to hear, and while a recognise that there is no garantee that I will not come to regret it, it seems unlikly enough to me to take that chance .

Thanks

Let us know if it does last until you rebuild the motor and the total sag at that time, that way we can point to you as an example in the future and say that you ran it for x miles with 30mm sag and had no problems.
More info to add to my mental database.

Post edited by: steell, at: 2006/03/01 07:52