YZ450 Crankshaft and Bearing Specs

Sorry if this topic has already been discussed, but could not find the answers I need. A friend is in the process of replacing the crankshaft on his 2004 YZ450. He purchased a complete brand new Wiseco kit from the states. The crankshaft and new bearings were taken to a local engineering shop to have the bearings installed onto the crankshaft. However, the engineering shop notified him shortly after with the news that the right-hand side bearing had approximately one thou clearance between the bearings inner race and the mating surface of the crankshaft. (The left-hand side bearing was installed with no issues - don't know what sort of interference it had though). In a nutshell, want to know if both the crankshaft bearings should have some amount of interference onto the crankshaft, and if so how much? Also, if interference is required, can we get away with loctite on this application or will the shaft require metal spraying etc. Unfortunately he has had no help or replies to his questions from the supplier. Any information would be greatly appreciated.

Edited by Stauno

Both bearings should be a light to moderate pressed fit, normally requiring a puller to draw the crank into a cold bearing. If the bearing fits loose, the crank is defective, and should not be used under any circumstance.

If you check, you will probably find the crank to be misaligned, also. The Wiseco cranks are built in China, and unfortunately, there have been a number of cases in which the quality did not meet the same standards to which their pistons are made. If it were me, I'd get a refund and use an OEM crank, or at the least, a Hot Rods.

Alot of people think that wiseco just means better, just aint the case these days.

Would be nice if wiseco changed factorys, got out of their 20% AOK Defective quality control standards. Too bad they don't give a united states factory work and get them to make a part that exceeds OEM quality and charge another 100$ for it.

Alot of people like using aftermarket parts, it's just too bad that they are supposed to be better when in fact the most important ones are not.

Please contact Wiseco directly if you have any questions. You can reach Wiseco customer service at 800 321-1364.

Thanks very much for your replies, much appreciated. Decided today to talk to one of the mechanics at a local motorbike shop. Unfortunately he had not worked on a YZ450 crank but did tell me that a lot of the newer bikes such as the CRF's etc have a slide fit with the bearing onto the crankshaft. So now I am even more confused, as one side of the new crankshaft was a press fit and the other has one thou clearance. He said the best thing to do is remove the old bearings from the old crankshaft and measure the mating surfaces. Will keep you posted on what I find.

This has nothing to do with your bearing clearance issue - although your friend should definitely be contacting Wiseco directly at teh number that was given to you above.

What I found strange is the procedure you explained for installing the bearings/crank and I hope that the way you explained it is NOT the way it was/will be done...

The crankshaft and new bearings were taken to a local engineering shop to have the bearings installed onto the crankshaft.

Your bearings need to be installed into the case halves and the bearing retainers need to be installed BEFORE you ever think of installing the crank into the bearings - these retaining clips are vital since they hold the bearings in the cases, bearings that are not held down can travel and cause a binding issue with the crank down the road...and the way you described the procedure - there would be absolutely no way for anyone to install the clips since you would be pulling the crank (with bearings installed) into the case halves as you assemble the full bottom end.

Just mentioning this for your buddy's sake - hope the way you explained it is NOT the way it is being done.

Thanks for your reply matt4x4. You are dead right, in what you said about the bearings going into the case halves first. The quote I stated unfortunately is exactly what happened. For some reason my friend thought the bearings had to go onto the crankshaft first (don't know why), and said to the shop to put them onto the crankshaft. I am guessing the shop was doing what he wanted and didn't question it. Unfortunately I knew nothing of his actions and was only aware when he asked for my help after he picked up his crankshaft from the engineering shop (I did inform him that the bearings had to go into the case halves first). Sorry if my original post caused any confusion in relation to the order of the bearing installation, and appreciate your good observations and feedback. As stated, intent of thread was to find out what fit the bearings should have on the crankshaft. Will let you know what Wiseco say about the crankshaft and what dimensions the old one is.

Any update on this I am having the same exact issue

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