Installing cams

I figured it out.My intake sprocket has a > on it ,the same as the exh.I lined this > up with the 28TH pin witch i marked but it should have been lined up with the back of the motor just like the exh.This must be an aftermarket sprocket.The bad thing is there is no referance mark for the 28th pin.Luckaly i had marked it before disasembly.I just wasnt smart enough to remember wich mark i was suposed to use.maybe it is a stock gear with the rubber removed.

Post edited by: mark1122, at: 2007/02/06 22:46

I just put my KZ back together (see sig below for details) With light springs to check valve to piston clearances.I rechecked cams and got: int opens @ 20 btdc & closes at 60* abdc. The exhaust is: op @60* bbdc , cl @20 atdc. Lobe centers = 110 , Lift = .420" The valve to piston clearance is .047" on exh @ 6* atdc. and .046" on int. @ 6* btdc.Now I have to say that the #3 and 4 intakes were bent from kissing the pistons and all 4 pistons show signes of intake valves hitting but not exhaust.This motor sat for 22 years and i ran it this summer for the first time since its last rebuild so i suspect the valve springs to be week.Also i over reved to about 11000 rpm,so these things could easily acount for the piston kissing.this clearance is obiously very close to the minimum.I have beentold that it should be .060"min int and .080" exht.If I change my lobe center to 108 will this get me there? Since there is no signs on the exhaust do i even need to wory about this if i put in new springs and a rev limiter?This is a street bike.

This is the piston. You can see where the piston hit the valve rather hard id say. Is it possible to grind out the valve pocket a bit? Isn’t .046" awfully close for a mild motor? Do you think the head may have been shaved? Maybe I should cc. it?

I would cc the head so you know how much clearance you should have with whatever piston type you have. Springs are good to 11.5 and your valves are "close". I'd use a rev limiter and or grind the pockets. It won't take much to increase that clearance. Once you bent the valve it may have hung open and then hit the piston harder. If you advance the intake to less than 110 the clearance will decrease. If you retard the ex. to less than 110 the clearance will decrease on that side. Every little bit you move the cams, you lose a fairly good amount of clearance. I think your about too close to the pistons with the clrnce you have now, but I would like a second opinion on that. I know that kz valves are heavy, and I've bent several at different times, probably at 13,000+rpm. They do bounce, and without that clearance cushion, they hit. The sprockets you have are not stock. It was smart that you marked the timing before dissasembly. It can get hard to line them up to the stock notches. The position of the bolt on your ex. cam looks to be in the same erea of the slot on the sprocket as is my ex. cam. I have 75thou clearance but my cam lift is only .407 (my lobe centers are only 1deg. different then yours 109-111). That's not enough difference to cause clearance problems, though I had forgotten that your motor has larger than stock intakes. It will be interesting to hear what clearance should be ..... Bet that thing runs good when your all done! I can't help but ask if you happened to know if the valves were bent a long time ago?

A couple things to add here. The lash you use will effect clearance as more lash on the intake side will mean the valves will open a little later keeping them farther from the piston at near tdc. On the ex. side they will start to close earlier allowing more clearance on that side. People run .008 with .410 cams and maybe that is why? Boy, the secrets people keep! We need a rev-um up crash um valve mangler to chime in here, (if we can get him out of the shop). He's probly pounding a valve out of a guide as I speak. And I just know he has something to say....

About when it happened(valves hitting pistons).I had the bigger valves installed in 1979? drove it about 150 miles parked it,got married, bought a house , had kids,bla,bla bla....Now 22 years latter I brush off the dust clean carbs and tank,turn eng over 2 times , it roars like hell,and I'm happy as a pig in shit!!Then I put 300 miles on it this summer ,felt it lacks torque and blows smoke,and take it apart.So hear we are,Having fun ,learning lots(THANKS mostly to all of you out there)

Nads.com. Can you explain to me (in simple terms)how to understand the cam advance retard theory? You said if i retard the exh i loose clearance,and advance the int I will loose clearance.I have a hard time understanding what is advance and what is retard in relation to lobe center?When i read posts sometimes it seems to be the oposite on each cam?I read that if i reduce my exh lobe cent to 108 i gain clearance(oposite to intake)and you say i will loose clearance? I find this very confusing.But allways love learning:side:

105in. would be 5deg. advanced and 115ex. would be 5deg. ad. Some engine builders advance both and get 105-105. The ex. is retarded 5deg then, So the valve opens later. It's to keep cyl. pressure in till the piston is farther down the bore and the gas pressure is fully spent. It increases torque. It decreases clearance cuz the ex. valve closes later and is closer to the piston at the END of the ex. stroke. The intake is closer to the piston when that cam is advanced, since this makes the intake valve closer to the piston at the BEGINNING of the intake stroke when it comes near the piston when it opens. In other words the piston and valve come toward each other on the intake stroke and on the exhaust stroke the piston chases the ex. valve as it's closing. Want to advance Your intake lobe center 1deg? Then it must open at 21deg btdc and close at 59deg abdc. The exhaust must be changed to open at 59deg bbdc and close at 19deg atdc. To retard it's the opposite for each. In order to get say .050 or more clearance on your ex. side, you would have to advane the lobe center to 111 or even 112. If you retarded by one deg, say 109 or 108, you would have .039 or so. these are actaully fairly close reference figures to compare with, and I know this since ive played with these changes on my own motor. That should give you a good idea of how it goes. Any questions and i'll tell you what I know and make it simple.

Post edited by: nads.com, at: 2007/02/07 13:54

Thanks that helps.So to gain intake clearance i would need to retard it to 112 or so but then i would lose torque,right?So I should halve the valve pockets cut deeper. I will also have the exhaust pockets cut to get some more breathing room.Ok ,Now the next problem.I just measured the valve to valve clearance through the plug hole .I ran dif guage wires between the valves and found the clearance to be .020". What can I do to improve this or do I need to do anything.How does lobe centers affect this?

The gasket thickness effefts clearance too. Advancing the intake and retarding the exhaust will decrease valve to valve clearance since two angeled points converge together. The intake can hit the ex. on it's way to opening. The exhaust can hit the intake on it's way to closing. I don't know the minimum clearance valve to valve though.

If it was me i'd cut the pockets myself since it's easy to do. If your bike starts popping out of second gear i'd get it fixed cuz it'll rev high when it happens. You might want to look and see if the dogs and recesses are worn. You send it in, buy new, cut it yourself like I did. It's just something that may be worth looking at. Make sure your rollers are in good shape. The stock ones will seperate from their inner liner when they get old. The cam chain rollers that is. See. I'm already in second gear.

I measured my head gaskets.The old 1 wich i'm using for this test is copper and .045".The new 1 is cometic and is .050".I dont know how much it will compress but im sure it will be close to .045".This is another good reason to have some leaway in the clearances. I hear that the clearance should be .035" minimum for valve to valve .That means I need to grind the vale diameter down .008" each.How does that sound,see any problems with that? How did you resses your valve pockets? My eng. builder said he would flycut them for $120 for 8 valves.

Post edited by: mark1122, at: 2007/02/07 20:41