'78 KZ 650 Refreshing/Upgrade Project

Ooookay,

So this is another one of the big parts in the rebuild, which of course has all the usual attached questions. Finally tore into the engine proper, with the intention of swapping in APE valve springs and changing out the valve guide seals. The job actually went quite well, and without any major hitches, so I am more than happy with the progress on that front. However, it also lead to what seems to be the inevitable series of questions which this project has thus far come across.... That is to say, I need to swap out a couple of valve shims to get clearances right, and am curious about the condition of the combustion chamber, and what you folks out there with far more experience that I have think.

So, to start: all intake valve clearance were 0.15mm. I am more than happy with this and don't intent to mess with them at all. I may be just a hair larger than the 'perfect tune', but the point had been made a couple of time in the past (from searching old posts, and also from 650info that clearances shrink over time, they don't grow. Good enough. Exhaust valve clearance however, are a slightly different story.

Ex #1 - almost nil, less than 0.05mm (shim @260)
Ex#2 - 0.15 - more or less perfect
Ex#3 - ~0.21 (shim at 245)
Ex#4 - ~0.21 (shim at 245)

Now, using the shim size calculator, it was a reasonably easy thing to figure out what to replace the shims with. No's 3 and 4 will get swapped out to 250s to tighten up the clearance there, and #2 will remain as is, since it is pretty much spot on. Now, #1 is a bit of a guess, since my smallest feeler guage was 0.05mm, and I couldn't get it to slide in. I don't know exactly how that came to pass since I checked valve clearance less than a few thousand K's ago, and I was at least within spec at the time, but there you have it. Far too tight, and would like to remedy that. I am going to assume for the moment that there is some tiny amount of clearance, and by moving back to a 250, it should get me in the vicinity of .10 or .11 measured once reassembled. Perhaps it would be smart to pick up extra shim at 255 in case that isn't enough. This is where I am asking for advice. Those shims swaps will give all exhaust valves a (calculated) clearance of between 0.14 and 0.16, which I personally thought wasn't too bad accounting for metal expansion with heat, and wear over time. I seem to recall that the common consensus was to leave exhaust valves a little on the loose side as they get hotter, and therefore are subject to greater thermal expansion. I Just hope that I don't swap in all these new shims and wind up with clearances which are all out of keeping with what the calculations seems to suggest.

Okay. That is post #1 for the evening, and kind of technical. So, feedback is appreciated, and I will try to get out tomorrow for some new shims. We will see how that goes. Next up: the ugly. :whistle:

Jon

And again..... This time with pictures.

So, without further ado....





This is the inside of the chambers, and condition of the top of the pistons.





Okay, so all in all, there is a fair bit of carbon, but for the most part it is not hardened and impossible to remove. In fact on a couple of the piston heads, it has every appearance of being very loosely attached, and could probably be removed with a Scotch brite pad, some solvent and a little time. Now, that being said, I have had some issues with burning a little oil on cold starts in the history of this bike, which I mainly thought might be remedied with new valve seals. I am a little vague on the history of this bike, but the PO did seems to have have taken good care of it, and there is evidence that someone has been through at least part of this motor before. it may be hard to make out, but there are pretty clear marks on the cylinder walls where it appears to have been rescored, and the tiny parts on the edges of the piston heads where there isn't some carbon, the surface appears to be quite bright and shiny. Right, now I know that this isn't some sign that all is good, and leave all as is, however, I am making the big leap here and figuring that perhaps much of the fouling is due to some small amount of oil creep after long periods of standing, and perhaps old valve seals.

I would like very much not to have to pull the jugs and replace piston rings etc.... (bike is just over 30k kilometers, so I somehow don't think overall wear is the issue, but I am receptive to varying opinions!) Also, bearing in mind that compression was good (tho I failed to write down the numbers when I checked it! :pinch: )

So, as it stands, I kind of figure just a good cleaning up of the current deposits and a thorough check that all valves are sealing on reassembly is most of what is required. (On top of a very thorough check to ensure that timing is correct before starting it all up again!) I would really like some advice tho, while I am at this stage of dissasembly. I'd rather spend more time and be thorough, than slap it all back together and miss something in the process.



For what it is worth, this was the single worst valve of all of 'em. Ex #2. Strange, as it was the only one with clearance within spec.... any thoughts are appreciated.

Thanks very much in advance to all!

Jon

Jon,
The KZ650c has always been one of my favorite Kawasaki's and it looks like you have a nice one!
Have you given any thought to using a set of zr750 carbs. They are a few sets on ebay, there are jet kits
for them and they work very well. They would also be easier to find parts for.
Just an idea.

Hey 80B4,

I did realize that was an option by way of swapping out to a different model of carb entirely. I won't rule it out, but for the moment I found a set of 26mm Mikunis. If that doesn't remain a good option for whatever reason, I will take a closer look at the 750 carbs.

I am more familiar with the slide carb type, but it might not hurt to get a little review on the operation and tuning of the CV carbs as well!

Cheers!
Jon

ARG! My desire to use a long list of expletives is only just being overwhelmed by respect for decency and forum rules.
Why? Well.....



and





Ta Daaa! :pinch:

All that despite carefully using a well adjusted torque wrench at the correct torque setting ~85 INCH pounds. Crapola. Maybe the fact I am working in a semi heated basement has something to do with it? Tho I find that sort of unlikely. Maybe the clutch cage bolts were just tightened a bit too much, once to many times? Who knows, and it doesn't much matter now. First thing: get it out. Second, try to find a new bolt/bolts to get it back together. Why is it the little jobs you don't ever think will cause a headache that really mess things up?

Adding insult to injury, the broken bit is JUST beyond the reach of my screw/bolt extractor set. Great. Off to see about finding some left handed drill bits, and hoping for the best. As always, advice is welcome.

Cheers!
Jon

Jon,
Use a lefthand bit to spin that broken bolt out. I would replace all 5 of those bolts with OEM or better .
Factory Pro tunning had a great how-to for tunning CV carbs, it is worth a look if you can find it.

Phew. Yup, the left hand damaged bolt extractor did the trick. Pulled it out neat as you please. Now, having done that, and having gotten over the worry of whether or not it will work, i can safely move on to being pissed off that I have to source and replace the bolts.

Ah well. Something like that pretty much had to happen eventually.

I would be VERY careful about drilling it out, using an "Easy-out", etc. because one slip and you'll wreck the clutch housing ($$$). Instead, check machine shops in your area to see if there is one that does ELECTRIC DISCHARGE MACHINING (EDM). If they do, they can remove that without causing any damage to the threads in the clutch housing. If you have never heard of EDM you may find the link below interesting. Ed

www.brokentap.com/services.html

Jonny wrote: Well, DoctoRot,

Thanks for the advice. Couldn't find a place locally that specialized in Motocross, but there is a custom exhaust business not too far from where I live, and they were able to pull the dent with a torch and slide hammer, or at least something like that. Pipes look great, and at least should have dealt with any potential exhaust gas flow restrictions. The exhaust system is indeed a Kerker like you had, and I was pretty happy to be able to just pay to get it fixed rather that find a new system. (I looked around at one point, and they were in the $600+ neighbourhood! :ohmy: ) While it was a little more than $60 to get this fix, it really wasn't that bad, and the manifold looks a whole lot better now. Cheers!
(As always, I will post some photos soon, I just have to get through the next most pressing thing.... the valve spring/shim swap.)

Jon

glad that worked out for you. keep up the progress.

Looks like you are doing a lovely job! Keep up the good work and keep the photos flowing!

Saw the mention about APE valve springs and will caution against this unless you are using aftermarket cams as well. The extra valve seat pressure will lead to extra wear. We always want the lowest valve seat pressure possible, without allowing valve float at high rpms.

Good luck,

Nessism wrote: Looks like you are doing a lovely job! Keep up the good work and keep the photos flowing!

Saw the mention about APE valve springs and will caution against this unless you are using aftermarket cams as well. The extra valve seat pressure will lead to extra wear. We always want the lowest valve seat pressure possible, without allowing valve float at high rpms.

Good luck,

I went with the APE springs still but instead of the normal 90 lbs Jay recommended 80 lbs since I'm only running the mild 750 cams on my 650 and will see mostly street miles.

Also since I didn't split the case I am still running the stock cam chain so wanted to be easy on that too.

Well, work on the engine at the home front will slow down a little for the moment. The head is out being a steam clean. being checked for tolerance if required, a valve seat job and levelling. Thankfully there is a machine shop nearby with guys who do great work, and who bring prices down a little if you are willing to wait. Might be a few weeks tho, and I hope I can beat the race against time, since I am off to New Zealand again for work in a little over a month. I hate the though of leaving too much work until I get back, but I'd rather have it done thoroughly and lose some riding season that just slap it all back together when i am already this far into it.

Ed: Thanks for the concern and advice. It if were a more serious situation, I would have looked around for a place that does EDM. I have never gone that route before, but I came across it on another one of your posts and did some reading. Cool stuff, and your right; when it can lead to more damage trying to remove a bolt, then it looks like a great way of doing it. Thankfully I have a very good drill press and was able to keep things nice and controlled, Just the tiniest bit of drilling into the bolt, I was able to get a good bite on it with the extractor, and spin it out by hand. No clutch baskets were harmed in the proceedure! :laugh:

Nessism/KZB2: All good advice. I had never though too much about the excess force being placed on the valve seats. However, I have to balance that against 35 year old springs and what I have read up on, in that valve float is on of the few drawbacks that these motors have at higher RPM's and wanting to mitigate that a little. I too will be mostly street miles and plan finding some 750 cams to drop in as well. I assume by 80lbs you meant spring tension? I double checked at the APE website, and it seems that the springs I have the 'entry' level upgrade, 'heavy duty' not any kind of real high performance jobbies. (Good for up to .440 lift) Are those what you went with? VS900k's. Ring bells KZB2, or perhaps I should write APE and see what I have/should swap for....

In the meantime, while waiting on the head, I figure I might as well pull the jugs and check the bores and piston tolerances. There seems to be a pretty good glaze on the bores, so as long as everything else looks good, it might just be a quick hone with a ball hone, and then reassembly one the head is finished. We shall see, Probably photos of paint projects while the engine is on temporary hold pattern.

Cheers all. The feedback and advice keeps me motivated and moving on this.

Jon