crankshaft woes

[2stroke]

I am in the middle of building my '93 KX250. I replaced the main bearings, and I got a Pro series rod kit. I sent the rod kit, and the crank to a shop, to have them install the rod. This is one of those things I just cant do, because I dont have the press or the jigs to do it, although I HATE having any one else working on my stuff!

I got the new bearings in the cases, and then installed the newly rebuilt crank. Then, I figured Id spin the crank around to feel how nice the new bearings felt. BOTH ends of the crank have some SERIOUS wobble!!! Also, looking down onto the crank as it is in the case, there is a gap between each crank half, and the case half walls. These gaps also vary, as I spin the shaft. I am COMPLETELY pissed!

It assembled very nicely, I did the whole freezer/oven thing, and I had to use very little effort to assemble everything. Theres no way I did this to the crank upon installation. (the worst thing I did was use a rubber mallet to tap around the last case half as I lowered it on.) I put a call into the guy who did the crank, but as it is Sunday, no answer. Im gonna call him tommorrow and see what the hell his problem is. This kills me.

This guy was telling me when I took the crank in ( regarding balance), that it would be no problem, that he has some sort of jigs to assemble the halfs,so I wouldnt have to worry about him "knocking " on the crank with a hammer. Well,I can see jigs, or guides being able to make sure that the halfs spin on a common center, but besides that, the crank halves can also be either "pinched" or "spread", which is what I think is wrong with mine. My thinking is seriously outdated, but it used to be put a couple of run out gauges on the crank halves, and then hit them with a brass hammer to get them on a common center, and then put the gauges on the shaft ends, and adjust the thing until there was no runout. IF this guy just pressed the thing together in a jig, how is that enough?

any comments would be appreciated.
Neil

 

[DEA]

If both ends have a"'wobble" , that you can see visually then it is VERY out of round ( or bent) The gap in the middle is lower rod clearance , measured either by side to side or by the total width of the crank(webb to webb width) The usual run out is .001" on most:uh:
I hope this isn't to depressing

 

[jmics19067]

If you ask me time to take it back out ! Get it measured! You are correct in that a crank<except honda tin cranks> can be trued up using v blocks or a truing stand and knocking it back into shape with a brass hammer. takes time and effort and patience so the jig is the fastest way to assemble them for a guy that makes his money off of it. But it doesnt sound like to me that he double checked it. I beleive everything you say can and could happen as you explain it .

 

[2stroke]

thanks.
Originally, the big end of the rod had seized on the crank, thats why I had to get it rebuilt. Both ends are wobbling, but I dont see how anything was bent, so I guess its out of round. Looking at it in my hand, I cant tell anything is wrong. Even tried measuring it with a ruler. But mounted in the cases its obvious. Its noticeable simply by looking at the shaft, either end, while spinning. The bearings are seated all the way in the cases as well.

Im going to see if the guy I had build it can do anyhting with it. Im not really sure about his operation, he was recommended by a friend, who took it over and picked it up for me as well, because he was getting some work done as well. I am going to visit this guy personally tommorrow if I can, and see what kind of equipment he really has.
(I have removed the crank already.)

I guess, worst case, Ill take it into another shop, and just have them "balance" it. I gonna call "cycle world" tommorrow and see how much that would run me. Cycle world is one of the larger shops in the Baltimore area, and I called them originally about rebuilding the crank, but their price was REALLY high. ($200) The guy on the phone at CW told me the reason it was so high was of the time taken in balancing it, and how important that was.

This guy I had do it was half their price. I HOPE this doesnt turn into a case of you get what you pay for, but I dont think I am unreasonable to exepct that if I pay someone $100 to balance a crank, that it should spin true. So Im gonna give this guy a chance to make it right, unless CW can balance it for cheap.

 

[jmics19067]

well it could be very easily possible to bend the left side of the crank trying to remove a stubborn flywheel. I have ruined the threaded section on two different cranks on two differnt bikes even while using the proper puller ,lots of penetrating oil , little bit of heat ,then a fire extinguisher and a lot of cursing!!:scream: . I do not rebuild cranks for a living but I do my own and my buddies if they need it so i am far from truly being experienced with a vast knowledge. But what I have done has held up to the point that the rest of the bike became worthless before I had to do the crank again. Except for one bike that I did twice and that was the bike that caught on fire . oh how I can go on about that devil of a machine!

 

[DEA]

Why spend your money twice??The shop that first did it should take care of it,ask him if he trued the crank or just pressed it together. For 200$ you can buy a new one?? Many moons ago when I worked in shops we charged 40.00 to rebuild & true a single cyl. crank
Try this, if you have the crank out & don't have v blocks & dial indicator.Use a feeler gauge (the thickest one) or small straight edge lay it(on the edge) ascross the the crank halves in several places all the way around the crank. It should lay flat,with no gaps on either side." THIS IS NOT A REPLACEMENT FOR USING DIAL INDICATOR'S".
IF it cost 100.00$ to do a crank today then, I'm thinking about getting back into it!!

 

[2stroke]

I went over this afternoon, and he agreed to take it apart and build it again. It would not fit on his jig, an indicator that it was not true. He said that it was pinched, wondered if someone dropped it or if I put the cases together with a hammer.
I then watched as he tried to press the pin back out, and it wouldnt budge at all. He got it to move about 5 mm but that was it. used a torch, no efffect. THen he explained there was another way to separate the crank, using some kind of plates in between the halves, but it may damage the spacer blocks. He had another KX crank lying around, and he was gonna try to get that one apart by pressing the pin out, so he could use the blocks from that one if the ones on mine got beat up. I left it there, and I will call on it tommorrow.
I dont know.
I saw the jig he used, and more or less the halves will NOT go together without the halves being perfectly aligned (very nice setup). As far as the pinching or spreading, I dont know how that works. As to why the pin wont come out now, I havent a clue. A 50 ton press, and it was BENDING the steel bars the crank was resting on! What a trip.
Just par for my course. Everything seems to drag out. But, at least he is trying to remedy the situation.
So, if $100 sounds high, then I dont mind if he does it twice. heh.
Thanks, and Ill keep you all posted.

 

[jmics19067]

the connecting rod pin is probably galled into the crank halves now. The best way I can describe galling is the shearing of metal from one side and it welding itself together of the other side ie.. the metal from the pin itself is shearing off in little bits and then those fragments attach themselves to the crank halves . Probably not the best way to describe it but if you know what I mean it does its job good luck!!!!

 

[georgieboy]

2stroke, i was doing a search on cranks and came onto this one.
pls what happened with yr crank in the end????
everything fine now?

 

[DEANSFASTWAY]

He probably never TRUED it . I have a $750 jig but I always have to check them afterwards for runout and almost always have to do some adjusting.This is very important or your bike will shake like a heroin junkie on withdrawal.