Are my crank bearings shot?

[stealth50]

I just replaced my crank seals a couple of engine hrs ago and they are shot again.(I think) I replaced them the first time because of a bad bog/miss when on the throttle. I had tried jetting and it seamed to do nothing so I replaced the crank seals and it was fine for a while but now has started to do it again. The symptoms are will not accept throttle smoothly,(1/2 to full)Hesitates before powerband,Lost its snappyness.

I tore it down again and really inspected the crank beaings. They seam fine (no pits,spin great) but they have play in them side to side. Is this normal? Where do I take it to get them replaced? Should I just replace the crank? Trying to get out of this cheap and quick cause I have a trip on memorial day weekend.

Thanks

[FireHead]

Have you check the seal surfaces of the crank with a micrometer to see if they are worn? What is the run-out you were experiencing that caused you to replace the crank bearing in the first place?

[stealth50]

Have you check the seal surfaces of the crank with a micrometer to see if they are worn? What is the run-out you were experiencing that caused you to replace the crank bearing in the first place?

I will have to check the seal surfaces. I only replaced the seals the first time it was apart. I only got about 5 hrs out of the new seals.

[blowit]

I will have to check the seal surfaces. I only replaced the seals the first time it was apart. I only got about 5 hrs out of the new seals.

 

 

Some axial play is normal since a radial ball bearing is designed for primarily radial loading. It will be very hard to detect or measure radial clearance without proper gear. I would say that if you pull up and down on the crank ends and can actually get verticle movement, you have a problem. I would sure think something is out of balance if that is the case. You would reall want to check those cases too for an oversized bearing bore. If the center bearings are in question, the crank needs taken apart and trueing and welding should follow. Like fire guy said, if there are any grooves in the crank shafts, you may have an issue there. The LH side can sure be testing with flammable gas around the sealing area while running to test for air leakage. Of course the safest method is the leakdown tester.

 

Brandon

[FireHead]

Of course the safest method is the leakdown tester.

 

Brandon

That's all I probably should have said is that he ought to perform a leak down test before he throws parts at the problem. I sort of get the feeling that seals and crank bearings never were the problem here. :ermm:

[stealth50]

I probably should have mentioned that for the first couple of minutes of riding it seems fine and then starts to act up. When ever we stop so my buddy can have a smoke the first couple of minutes after we start riding again it is fine and then starts acting up.

[blowit]

I probably should have mentioned that for the first couple of minutes of riding it seems fine and then starts to act up. When ever we stop so my buddy can have a smoke the first couple of minutes after we start riding again it is fine and then starts acting up.

 

 

Um, you are aiming right at an electrical CDI or stator coil issue. Try a quick swap with someone on the CDI and give it a try. electrical goodies love to fail when they get warm.

 

Brandon

[FireHead]

Um, you are aiming right at an electrical CDI or stator coil issue. Try a quick swap with someone on the CDI and give it a try. electrical goodies love to fail when they get warm.

 

Brandon

That sounds alot more likely than crank bearings and seals. :thumbsup: