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Discussion Starter · #1 ·
I just bought a 79 KZ650 SR and I took all the plugs out to do a compression test. Now, 3 of the plugs go in fine, but one of the inner plugs turns about 3/4-1 turn and then hangs up. I feel like if I go any further than hand tightening, the plug will strip the hole, so I am holding back. What should I do to get this thing going in the right thread? I looked into the head and the thread is fine for almost the whole depth, but it is a little hosed in the first thread or so apparently. Is it possible to buy a 14mm x 1.25 tap and just chase the thread? Is this the best way to do it? I know the problem is not bad enough to warrant the use of a Helicoil. :?:
 

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Hmmmmm you COULD POSSIBLY run some metal shavings into the cylinder ... which may or maynot harm

I'd be willing with the head off the bike. Maybe be really gentle until you feel some real resistance and then stop. Remove head and then go at it.
 

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Your choice

I had the same prob on my car.....but I fu*ked the threads a bit. I ripped it apart took head off and got a tap. My mechanic buddy laughed at me. He said he would have just turned the motor over by hand until the piston was at the top, tapped the hole, used a shop vac or something with some good suck and that would be fine. Especially if it is just a little bit crossed there should be very little filings to worry about. It is up to you. I still am happy I took the precautions but it was a lot of extra work especially on the car, bike would not be quite as hard.
 

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Discussion Starter · #4 ·
Well, I finally managed to get the plug in without using the tap much at all. I just finessed it until I felt like I was catching the original threads and applied just a litttle torque with a socket wrench and it evenually got easier to turn once I got past the tweaked top thread. I figure it would be "do or die" and if I messed up a couple more threads I would have to take the **** head anyway, but it worked out and the plug threaded in fine. Now, unfortunately, I have a new problem. I can get the bike to start, but it dies after a few seconds. After repeating this process a few times, the headers on cylinders 1 and 2 are ice cold and 3 and 4 are warm. I have checked and I have spark on all cylinders though. Any ideas?
 
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