KZ650 / KZ900 cam chain tensioner assemblies

The early KZ650 cam chain tensioner assembly 12048-015 (this is the internal part with the roller that hangs down from the rear idler sprocket) is now out of stock with both Kawasaki USA and Kawasaki Japan.

The difference between the 650 and 900 version is just the size of the roller. The 650 version uses a roller that's about 5mm larger in diameter. It looks like you could substitute the 900 version 12048-001 in the 650 motor provided the tensioner itself extends far enough to put enough pressure on the tensioner assembly. The steel bracket the roller hangs from looks identical between the 650 and 900 versions.

Has anyone used a 900/1000 tensioner assembly in a kz650 motor? Does it work?

Post edited by: jeff.saunders, at: 2006/02/01 08:56

There is a distinct possibility that this may work. Going back in the archives to 2003(if you can find it), MECSCC used a 76 KZ900 manual cam chain tensioner because the push rod moves about 1/2 inch further into the engine than did the auto adjuster originaly on his 650. His problem was a sloppy 28,000 mile cam chain. The noise cleared up with the extra reach from the 900 adjuster....TwoCam also said that 1973-1978 900/1000 all use the same mechanical adjustment tensioner. 1979/80 have a different auto tensioner. The later can be verified or debunked on referencing software.

I think it should work fine - the key is knowing for sure.

The KZ900 tensioner assembly with an APE cam chain manual adjuster appears to give enough extended reach.

i put the manual tensioner on my kz650 and it bolted up perfect. has plenty of reach too. looks alot better than the stock automatic and i think its more reliable.

Jeff's question actually is asking about the part with the idler wheel on it that actually contacts the chain, not the tensioner held on the back of the block.
If the 900/1000 is only 5mm smaller, that would mean the tensioner plunger would be extended at the most 2.5mm further to bring the wheel in contact with the chain. With the manual tensioner, whether it be an Ape or stock Kawasaki, this should be no problem. With the automatic tensioner, it could get a little iffy. So in other words I don't know either, but would wager a logical guess as yes it will work.

Yes I know. Will part #12 (from a 650) be tensioned sufficiently by part #19, if 12 has a slightly smaller diameter rubber wheel (replacement part from a 900). Manual cam chain tensioners (the part that bolts onto the outer ingine case) from a 900 have a plunger #19, that extends further into the engine than the 650's, thus taking up more slack hopefully resolving the problem/question. Do I have emperical evidence?, no, just heresay and supposition, but it seems logical. Hopefully someone here has taken both 900 parts and poped them into a 650, to give us the real scoop.

Couldn't get the schematic to upload.

Post edited by: gas, at: 2006/02/01 18:56

Jeff, I looked into this a bit today, visited a guy who builds KZ900s/1000s and and compared a 650 tensioner to a 900/1000 tensioner, here's what I found:

- The shaft that holds the tensioner bracket in place (rear cam chain idler gear shaft) is the same on both tensioners (also same partno: 12052-005).

- The upper holes in the bracket are the same size. The brackets are also equally long from pivot point to wheel center meaning that the backplate where the tensioner plunger contacts the bracket is positioned right.

- The only issue I can see is that when using the 900/1000 tensioner on a 650 engine, the tensioner plunger needs to be a bit longer than previously assumed - apart from the 900/1000 wheel being smaller the bracket is equally smaller front-to-back. When aligning the front of the wheels (the side where they contact the chain) there is a 10 mm difference at the backplate as shown in the pics below. This shouldn't present a problem with a manual adjuster though, if so it shouldn't be very hard to fab a manual adjuster with a longer bolt.


Btw, while I was there the guy showed me a japanese catalogue with an interesting tensioner mod: rather than using a rubber wheel they installed a cam chain idler gear in the bracket - this can't be done with the 900/1000 bracket, the gear diameter is too large to fit in the bracket, but the idler gear is the exact same size as the 650 rubber roller and fits in the 650 bracket, might be worth looking into.

Anyway, looks like it shouldn't be a problem using a 900/1000 tensioner in a 650 engine, I'd be willing to give it a try myself.

Gordon Liska makes the tensioners with an idler sprocket rather than roller - I've a few here in stock.

Gordon says he can put the sprockets in KZ650 tensioner assemblies - so it looks promising to have some options for the future.

Yep, that's the one - hmm, I have a couple of idler sprockets lying around, maybe I should try making one of those, looks doable. Btw, note that he uses a flathead bolt to replace the rivet, there is not enough room in the cam chain cavity for a standard bolt head.

Btw, regarding the idler gear sprockets there's some additional info in this thread.

Ok, I'm in the middle of a 650 engine rebuild and the rubber wheel on the cam chain tensioner is toast, so today I dug further into fabbing a tensioner similar to the one Gordon Liska makes, turned out to be a piece of cake.

The axle that the rubber wheel sits on is nothing but a 6 mm rivet with the flat end being the rivet head. What I did was whip out my angle grinder, grind the rivetted (rounded) end of the axle down and use a 6 mm bolt to tap the rivet out so I could remove the wheel. Between the rivet and the wheel bearing there's a bushing - this bushing is the exact same size as the pivot shafts for the cam chain idler sprockets and the sprocket fits like a glove.

The bushing also doubles as a spacer for the tensioner bracket so it won't be pressed together and squeeze the sprocket when you reinstall the rivet.

All I need to do now is to either find a new 6 mm rivet or just tack weld it - there's no sideways pressure on the axle so a tack weld should hold up just fine.

Here are a few pics to show what I'm on about:

And a few more with the sprocket installed and the tensioner assy sitting in the block:






As a side note the cam chain idler sprockets for the pre-81 650s and 900/1000s are the same and can be swapped, more info in this thread

Post edited by: OnkelB, at: 2006/04/29 08:14

WOW not much left of the teeth! How many Kms were on your engine?