Looking for Twisted Crank info....

Hey guys, need some experienced veterans to chime in on this one. What are the symptoms of a twisted crank in a KZ1000 (My particular bike is a '79 LTD)? I'm a little paranoid and I know I've got SOME kind of issue going on. Here's the details on my setup:

-KZ1000 Engine with 25K on it.

-Bone stock bottom end (haven't even upgraded to EI yet, that is my plan for the next upgrade!)

-Wiseco 1075 Kit, 10.25 Compression version (Yes, I ALWAYS run premium)

-Very mild port/polish job done on head while off, new valve guides, new valve seals, valves lapped

-All new rollers for cam chain, no I did not replace the cam chain as I did NOT want to split the cases at the time of the 1075 kit. The kit was put on out of necessity, not want, due to a much earlier screw up by me.

-Running RS34's (LOVE these carbs, best thing ever for these bikes IMO), 4th (richer) needle position, 20 idle jets, 120 mains. Rubber boots were smoothed out to match carbs, so no fuel puddling.

-Old school 2 piece Kerker header

-No, the crank was not welded (again, stock bottom end), hence why I'm asking and paranoid.

That really about covers it. Now why I'm worried is here lately my bike just feels "off". I can't describe it exactly, but I could definitely feel it. It just didn't feel quite as quick as it did just awhile back either. So I did a quick compression check and the results aren't good: #1 = 155LBS, #2 = 150#s, #3 = 120LBS, #4 = 152LBS. I'm sure we can see the problem..... Theres no smoke whatsoever, so I know it's not the new rings haven't seated well or the gap in the rings happened to line up or anything like that. The bike doesn't feel like it's missing or anything like that either (not that missing would affect compression.)

First question is; how likely is it to twist a crank with my setup? I haven't been pulling wheelies or doing burn outs. BUT, I do get on the old girl pretty hard a fair amount, running it up through the gears. I have a buddy with an '05 GSXR750 and we're constantly at it with each other. And yes, I am guilty of running it into redline once in awhile though not considerably high into it (about 10K max). I know that's bad for it, scold me at will, but I'm just trying to be honest here.

Is there anyway to test for a twisted crank besides the rod through the piston pin holes with the head/jugs off? Is it common to have just one piston/rod out of whack with a twisted crank?

Best case scenario is that I'm hoping I need to recheck my valve shims now that I've put about 2000 miles on the bike since the top end rebuild. But I have a sinking feeling that out of adjustment shims wouldn't be enough to cause 30PSI difference in the compression.

Ok guys, let me have it.... Thanks!

Just my opinion here, you didn't twist your crank. It is said that you need to be running a slick with a wheelie bar in order to do that.

I feel that your lack of compression lies in the head. If you installed new valve guides, then the seats should have been re-cut. The seat needs to be cut concentric to the guide and I don't think that lapping could correct that.

Try running a leak-down test to see where you are loosing the compression. That will tell you all you need to know.

Yes there is a way to check for a twisted crank (even though I also do not think that is the problem). You can put a dial indicator in #1 and #4 sprk plug holes and make sure that the pistons are in fact at TDC when it shows on the timing mark.

Ive only seen one but it vibrated pretty bad

six862m6 wrote: ...Is it common to have just one piston/rod out of whack with a twisted crank? ...

I don't think there is any way for just one inner crank arm to be out of place and not affect the outer one.

Put your degree wheel on the crank, and find TDC on #1, then without moving the wheel, put the tdc tool in #4 and see if it is at TDC at the same place on the wheel. If it is twisted, it won't be.

six862m6 wrote: And yes, I am guilty of running it into redline once in awhile though not considerably high into it (about 10K max).

You may have floated and bumped/bent a valve. Do you remember missing a shift and over revving sometime? Do a leak down and find out where the leak on that low cylinder is.

I don't remember missing a shift and over revving anytime recent. It's happened before, but not recently. Still, sounds to me like the issue is definitely with the valves in that cylinder. I'd much rather it be an issue there than a twisted crank. I'm going to be away all weekend so I won't really have a chance to do a leak down test on it this weekend, but I will try to next week.

Have you checked the valve clearances? Maybe the valve on the low cylinder is hanging open a bit.

Most likely reason for lower compression in the one hole is valve lash. HOWEVER, before you rip into anything do this first. It's quck & easy

Put your vacuum gauges on the carburetors. See if the one with low compression also has a higher vacuum reading than the others. If it does, check to see if the carb synch adjuster lock bolt has come loose on that particular carburetor. I've seen that happen with RS Mikunis. It might just be that simple

Those RS synch adjusters leave a lot to be desired IMO.

Regarding the twisted crank....it's possible, but not likely. NOTE that early 79 LTD's got the small pin, small main bearing cranks while the later models got the better MKII cranks. Serial numbers can be used to identify which you [might] have. I say might because it's been a long time since 79 :lol:

testarossa wrote: Just my opinion here, you didn't twist your crank. It is said that you need to be running a slick with a wheelie bar in order to do that.

I feel that your lack of compression lies in the head. If you installed new valve guides, then the seats should have been re-cut. The seat needs to be cut concentric to the guide and I don't think that lapping could correct that.

Try running a leak-down test to see where you are loosing the compression. That will tell you all you need to know.

This is what I agree with. You cannot replace valve guides and not cut your valve seats.
If you did your compression test correctly, throttle fully open and warm engine, then the throttle linkage should not be an issue. Do your leak down test, then if you pull the top off do the head correctly.

mistake post