My pride and joy

Alright, got the head pulled off today.

Head work by mmsmithgall , on Flickr

There was A LOT more carbon on the piston tops and combustion chambers than I thought there would be. I use to run a strong dose of Seafoam through every 1,000 miles or so

Head work by mmsmithgall , on Flickr

Head work by mmsmithgall , on Flickr

Head work by mmsmithgall , on Flickr

Head work by mmsmithgall , on Flickr

I also noticed something funky on the cam bearings:

Head work by mmsmithgall , on Flickr

Head work by mmsmithgall , on Flickr

Have a few questions... This is a low budget get on the road as cheap as possible rebuild. The 1105 will come later.

I was not planning on removing the block, just pulling the head to replace valve guides and seals; however, considering the amount of carbon build up on piston domes, I'm thinking I should pull the block and pistons to gently wirebrush the carbon off the domes and get a new set of rings and hone the bores.

This might not be a bad idea, as who ever does the head will clean it up, and there was some oil seepage from the head gasket down on the block and this would be a great opportunity to clean up the block as well.

Regarding the wear pattern on the cam bearings, it looks as though it's a material issue, not really a wear pattern. There is no sign of anything wrong on the cam journals.

I've had this bike since it had 14k miles on it and have never removed the cams, they are likely the original bearings Should they be replaced as well?

Manual cam tensioner... A good idea or not? I've heard conflicting results.

While the head is off, I'm also thinking of replacing the stock 6mm exhaust studs with APE 8mm studs to hopefully eliminate any problems for myself down the line. Yay or nay?

Lastly, thinking about a replacement set of APE cylinder head nuts.

Thanks!!!

mtbspeedfreek, if you are planing on going with a 1105 kit later I wouldn't bother with taking the block off right now. Unless your compression numbers were low to begin with. New rings, honing and bottom gasket would add at least $150-$200 to the cost. I'm sure some of that carbon you see may actually be burnt oil from the leaky valve seals. I wonder if you can clean your piston domes while they are still in the block. But not with a wire brush. Maybe with a scotchbrite pad soaked in some WD40. Being carfull not to touch the cylinder walls. In my case, I had the block off when i cleaned my pistons and used a sctochbrite on 3m roloc (HF knockoff) attached to a drill with WD40. The pistons were not taken off their connecting rods. If I had to do it again, I may try it with the block on.

Either way, be sure to check the front cam chain guide located within the block on the exhaust side (front) of the block about half way down the block. It is only a $19.00 part from Z1E and should be inspected and replaced if worn.

Not to sure what to say about the patterns on your camshaft lower half bushings. Like you said, doesn't look like wear markings.

Your cam chain tensioner is a manual tensioner. Just make sure that the plunger can freely move back and forth when the side locking bolt is loose. You can always take it apart and clean if you want to be thorough.

I also noticed something funky on the cam bearings:

Head work by mmsmithgall , on Flickr

Head work by mmsmithgall , on Flickr

I have seen that before, misalignment of the bearing cap causes it. one side of the bearing wears clean, the other shows spotting from surface corrosion. Put your cams in and plastiguage several spots, that will tell the story.

Thanks for the input guys, turns out we were all close... it's from water/moisture contamination in the oil causing the babit in the bearing to erode or pit. Boat engines have this problem often.

Anyhow, my OCD won't be able to stand it... I'm going to pull the jugs to better clean the pistons.

What are my options for raising the compression ratio? Stock is 1:8.5... how can I get it in the range of 1:9/9.25 without new pistons? Deck the head? No base gasket? Anything else?

The 1105 is a completely separate engine from this 903, and frankly, it'll be at least 6 months before I have enough saved up to go through and replace things in the 1105. So I gotta rebuild the 903 the right way.

Just purchased new valve guides, seals, and cam bearings! The head has been off this bike since October and I haven't ridden it in over a year! Pretty excited to get back in the saddle!

congratulations on parts procurement sir!

leon

I'm making progress, ever soooo slowly... Yesterday I dropped the head off to a local and recommended machine shop to have the valve guides and seals, and cam bearings replaced. I should get it back next week at the latest.

Gotta buy a few gaskets and o-rings, purchase a new battery, and clean my smoothbores! Any idea what sort of jetting to start with? It has pods and a Kerker?

Hopefully I'm back on the road in a month!

mtbspeedfreak wrote: Thanks for the input guys, turns out we were all close... it's from water/moisture contamination in the oil causing the babit in the bearing to erode or pit. Boat engines have this problem often.

Anyhow, my OCD won't be able to stand it... I'm going to pull the jugs to better clean the pistons.

What are my options for raising the compression ratio? Stock is 1:8.5... how can I get it in the range of 1:9/9.25 without new pistons? Deck the head? No base gasket? Anything else?

The 1105 is a completely separate engine from this 903, and frankly, it'll be at least 6 months before I have enough saved up to go through and replace things in the 1105. So I gotta rebuild the 903 the right way.

Saw your update and just got caught up on this thread...

Just wanted to let you know that I just fired up my rebuild with no base gasket. Seems to be working great so far, but I only have some idling and about 20 miles on her in test rides and a run to the dmv.

Figures after working on this for a year, it would rain for a solid week after it passed inspection!

Anyway, no oil leaks, runs great. Puts you at about 9.25-9.5:1 compression ratio with stock pistons.

Check out the FrankenEngine thread in the engines section if you are want to see the specifics. If you have any questions let me know here or there! :laugh:

tachrev wrote: Saw your update and just got caught up on this thread...

Just wanted to let you know that I just fired up my rebuild with no base gasket. Seems to be working great so far, but I only have some idling and about 20 miles on her in test rides and a run to the dmv.

Figures after working on this for a year, it would rain for a solid week after it passed inspection!

Anyway, no oil leaks, runs great. Puts you at about 9.25-9.5:1 compression ratio with stock pistons.

Check out the FrankenEngine thread in the engines section if you are want to see the specifics. If you have any questions let me know here or there! :laugh:

Sweet, thanks man! I'm just going with the cheapest, fastest way possible to get my KZ back on the road right now. No performance work unfortunately, I'm hoping to get it on the road in a month or less!

Got the head back from the machine shop on Friday. One of the exhaust valves was bent and I had a little difficulty finding another one with square keepers. I had them put in new Kibblewhite valve springs while the were in there - I wasn't planning on it, but I figured why not.

So new cam bearings, new valve guides and seals, new valve springs, and a valve job.

I had them order a nice Cometic MLS head gasket but it was for 73mm bores (1100s) not 69mm bores (900s) so I'm exchanging it for just a plain old copper one as I'm still running 8.5:1 compression.

Got my valve shim kit in, so hopefully this weekend I can get the head bolted on and get the valves adjusted to button up the top end.

Gotta get my 29mm smoothbores cleaned, any suggestions there?