TOPIC:

I've been considering a few thoughts regarding the reports of low compression and also the reports of stretched camshaft chains and primary chains, so I decided to do a few calculations. I have a 1980 KZ1300 B2 and have no history on this bike other than 62000 Kilometers on the clock. Every time I hear of an issue in this site, I check my bike to see if the same reported issues are showing up on this one of mine.

The camshaft drive chain- I've seen reports of stretched chains so I decided to check mine and found that it was at it's service limit and needed to be changed. No big deal but just for giggles just exactly how does the stretch to limit actually affect the valve timing.
The service manual says that we can measure over 20 links and if the measurement is less than 128.9mm then we're ok. So let's think about that for a moment. The chain has a pitch of 6.35mm so 20 links would measure 6.35mm X 20 = 127mm. so they allowed 128.9mm - 127mm= 1.9mm of stretch over 20 links. The chain is 158 links in length so if we do the math, 1.9mm /20 X 158= 15.01 mm. Kawasaki has allowed a total of 15.01mm of stretch over the entire length of the chain.

Now, there's approximately 20 links between the 2 camshafts so that leaves about 130 odd links to be split between the exhaust cam and secondary shaft and between the intake shaft and the secondary shaft but this segment also has the chain tensioner involved so that section is slightly longer than the first. For sake of argument let's say that there's 60 links between the exhaust cam and the secondary shaft. If we assume that the chain is at it's maximum stretch then 1.9mm stretch over 20 links X 3 will give us the stretch over the drive side (60 links). 1.9mm x3= 5.7mm. if the pitch of the chain is 6.35mm then it's conceivable that the exhaust valves could be retarded as much as 8.9 degrees of crankshaft rotation.

We can take that 5.7mm and add another 1.9mm to it to determine the retard of the intake cam and get 7.9mm total stretch between the secondary shaft drive side and the driven side of the intake cam. After calculating I come up with 12 degrees of intake retard.

Retarded exhaust valves will open the valves late which is not a really bad thing and will affect performance marginally. Also note that the exhaust is not as affected by the stretch as much as the intake so the effect is not that great. also, a late closing exhaust will throw off the intake charge since it's starting later in the cycle.

Retarded intake is the real problem, especially the closing of the intake valves late. Our camshafts are somewhat to the performance side mostly due to the long stroke engine. Our intakes close at 70 degrees after bottom dead center. Now if we add another 12 degrees due to the stretch of the chain we end up with a closing of 82 degrees after bottom dead center which only allows 98 degrees of compression instead of 110 degrees of compression. The piston is almost halfway up the cylinder before the valve closes. When running at low rpm's there isn't as much velocity in the intake charge to keep it in the cylinder before the valve closes. All bad !!

Now we have to add the complication of the camshaft drive gear being on the secondary shaft. Because of this unique design any stretch in the secondary shaft drive chain (which is the primary chain) will compound the retarded timing of the camshafts. People have reported on this site having stretched primary and secondary chains so again I measured how much slop I have in my primary chain. Now I didn't measure as per the manual but did take a measurement by rotating the crankshaft back and forth and noting when the camshaft started to move in each direction. I currently have 12 degrees of crankshaft movement before the camshaft starts to move. So in my case, a worn camshaft chain retarded by 12 degrees intake and 9 degrees exhaust now becomes 24 degrees of intake retard and 21 degrees of exhaust retard. REALLY BAD !!!

So I'm in the process of sourcing out new primary and secondary chains and will be pulling the engine and replacing. I've also ordered camshaft gears from a Honda CRF 450X with the thinking that I can have the cams machined to fit these gears and then have adjustable camshafts. This is above and beyond for most people but what it does is give you an opportunity to dial in the timing of the valves irregardless of the stretch in any of the chains.

I know it's complicated to understand but the bottom line is when you have an unexplainable loss of compression and all of the tests have been done (compression and possibly a leak down test) one needs to look at the valve timing for the final explanation. Especially in our case with this particular engine which drives the cam via 2 chains.

I'd be interested in your source for primary chains as my mechanic says mine are at tolerance limits... whatever that means.

My case is split and my crank is out so I'm looking for bearings as well.

Ledkz1300 wrote: Imy mechanic says mine are at tolerance limits... whatever that means.

My case is split and my crank is out so I'm looking for bearings as well.

It means your primary chain has 21mm of slack and the secondary has 22mm of slack.
I had to machine out the big end to take a slightly larger shell then I could grind and polish the crank
As for the main shells I had no joy in finding a full set. Just the odd one that would pop up on eBay now and again.
Luckily my old ones were serviceable.

Ian

I would like to hear more about this procedure. Did you do it yourself?

everything you ever wanted to know about valve timing but were afraid to ask.
superb write up John, i understand all of that but would never have been able to put it into words, great work.
i have all mine in bits so ill stick a dial gauge on the end of the crank, then we should get some idea of how many degrees of rotation
related to the amount of slack in the chain.
Ian

Ledkz1300 wrote: I would like to hear more about this procedure. Did you do it yourself?

i didnt do the work myself i had a local engineers do it
www.applebee.co.uk/ not much good for yourself but if yer in the southeast UK
depends how bad your big end shells are, mine was shot on No5 the shells had picked up and spun so the crank needed a grind as well.