OH NO......NOT AGAIN !!!

I think I'm dying here...... Had a compression issue with my YZ when I got it back....Kicked like a 2 stroke but ran great. I had a sneaky suspicion that something may be wrong so I sent it back to the mechanic for a review of the upper end. I got the call this morning that the race on the intake side of the cam has been stretched due to lack of lubrication on the initial startup after rebuild. It would seem that no additional lube was coated on the cams and it took about 30 seconds for the oil pump to get oil to the top of the head after the cases had been split from the crank replacement.

The bad news is that you cannot purchase the top clamps on the cams separately, you must purchase the entire head assy $572.00.....

The good news is that MXTuner and SFO (TT Members) are very well connected and hooked me up with Mike at Engine Dynamics in California. Mike said, just package it up and send me the head, I'll fix it for under a 100 bucks. This is the kind of assistance and effort that TTer's are famous for.

I just may be back in time for the next race in the series at the end of the month.


After all this I guess I won't be selling my YZ anytime soon.....Hell it's brand new again.

Bonzai :)

If you didn't have bad luck you wouldn't have any luck at all.... :D Hope it all turns around :)

My head repair ran me $250 through E.D. a steal no matter how you look at it!!

TT to the rescue, Thats what I like aboutthis place :)

'Kaze, How exactly did the elongation of the journal affect the compression? Was it holding a valve off it's seat or not opening the valve or what? Also, you mentioned in the earlier post about having lost compression temporarily on a couple of previous occassions..?

I was trying to help a guy with a 250F at the track last year who had the same problem occur twice in two days. The first time, he just left it sit awhile and it seemed to "fix" itself... I have heard of it happening to others, as well. Do you know what causes that? :D

Real sorry to hear about your bad-luck streak, but thanks for sharing the painful learning experience with the rest of us. Boy, am I glad the small-block mechanic in me made me liberally coat everything with Red Line assembly lube when I swapped exhaust cams and reshimmed the intake!!! At the time, I wondered if I was being overly-careful and just gunking up the top end and how all that assembly lube would affect my clutch discs (not at all, it seems). Of course, I changed the oil and filter after a brief run-in.

Guess you can consider your "old friend" has a new lease on life now. :)

Glad to be of service 'Kaze.

I have noticed that when the cam journal galls it will roll a burr into the cam bucket bore and then the bucket will hang up in it without returning fully to its fully closed position. I suspect this could be the cause of the yz-f missing compression issue but there are quite a few variables to take into account.

I have seen more than one engine poop the bed because of non-oiling or insufficient start up oiling too.

I was trained when I was building big twins to make sure you visually see oil coming out of the lifter bores and the big ends of the rods before going any further.

I use an airgun to spin the crank slowly until I see oil flowing from the oil line to the top end, then I put the oil line on and make sure it is reaching the cam caps.

It takes a couple extra minutes but it is cheap insurance.

I am glad you are getting this resolved with EDCO.

Mike is a great guy and also a distibutor for KMPI.


He can do entire reconditioning and his weld ups and porting are fabulous. He has fixed a lot of my messes.

Sorry to hear about your rebuild. A light coating of oil should have been all you needed before starting a rebuilt engine. 30 seconds seems like a long time for oil to get up there. It should only take a few seconds. Is this the same bike that had the flywheel crank mount thread shear? Expensive up keep but it is still cheaper than a new bike. How is your racing season going Kaze?

SFO...You are the man...

Indy... As it was explained to me by Mxtuner/SFO and Mike at ED, When an engine is completely disassembled as mine was the oil is drained from not only the main oil galley but from every part of the engine. Sometimes it can take up to 30 seconds for the oil to reprime the pump and get enough oil to the top of the head. Appearently it took just long enough to fry just one of the cam journals. As I said in my previous post the bike ran great, If not for the two stroke kick ability I would have never suspected anything was wrong. I was lucky that the top end didn't let go during the race I guess. I just started a summer series event last Sunday (6 races - best of 5) So far so good, Just hope to have the motor back up in time for the next race scheduled for the last sunday in june.

I guess the thing that bothers me the most about this whole eppisode is that I sat there and watched the lower end going together and made a comment about a small bottle of oil being used instead of assembly lube which I offered out of my toolbox in my trailer. I was told no problem, not to worry. I'm sure this will never happen again, sometimes these lessons are very expensive. I'm not going to dog my mechanic because he is a great guy and normally pretty attention to detail oriented, as Mxtuner said....It's happened to the best of us....

Looking at the positive side....I've got a completely rebuilt 99 YZF from front to rear, so I guess I'll keep it for a couple more seasons.

Bonzai :)

I guess he really didn't slip a 450 cam in, did he.........



Dont take this the wrong way but Im just curious, you seem to know quite a bit about the in's and out's of a dirt bike engine, so why do you have a mechanic?

Like I said, Im just curious. :)

good luck yami, bout time you updated it though isn't it? it's costing more in upkeep than to update so, you know, ...!!!




I pull some pretty long hours most of the time with my regular job and my own business. I really don't have much time to spend working on the bike, When I do get some time off to race, I just want to roll it out of the trailer and onto the track..... Not that any of this is hard to do...its just a time issue. This guy is normally pretty good he just really F'd it up this time, and he's paying the bill to have it repaired. Good thing my next race isn't until the 29th of June.

Bonzai :)

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