Check Your New Crank Properly

[cannondale27]

Did you read the whole post ?I only did center test till I got stand to check right way.Jay let me be clear checking the trueness/sync and balance of crank are two different things you need both to be right.All the balancing in the world will not help a out of sync or untrue crank survive.The tests I showed have been done for probably a hundred years to check sync and trueness of crank.They worked then and they work now if any crank fails the test especially the tests on trueing stand it doesnt belong in a motor.

[cdrider02]

The method pictured in the manual is the best and the most accurate,notice I did not say it was the only right way to do it other methods work but great care must be taken in holding the crankshaft so as not to distort it and get a different reading than you actually have. Holding one between centers can make it appear to be better or worse than it actually is. Sometimes when they press together, however tight they may be, the halves will not seat exactly square to the crank pin you can check this by measuring across the halves at four places around the crank I start at the pin and then every 90 deg. When this condition exists the crank appears in the truing stand, or centers, to be bent, not twisted, and can be squeezed at the wide spots or pushed apart at the narrow ones to eliminate the problem this requires a little persuasion but usually not a lot. Now imagine that, with little or no twist, that the widest measurement came from the spot 180 deg. from the pin this would make the indicator show plus or minus either at the pin or across from it depending on how it is held. Now what if you held this crank between centers? You have to apply a certain amount of pressure to just hold the slack out of the crank/centers and only a small amount of pressure will make the crank appear to be straighter than it is, nevermind what can happen if even a minute chip gets in between or if even a small amount more or less pressure is applied after it is removed and put back in, not to mention what something like a flywheel puller or a hammer (yes some people use these for removal) does to the ends of the crank. As 27 pointed out holding by the bearing journals makes the most sense, because that is the way it is designed to be held (with no pressure on the ends) and taking readings at the extreme ends of the shafts will give you the highest reading possible and the actual amount the ends are moving if you take readings halfway down the shaft it will be running out much more at the end. Anyway I could go on all night about this just my opinion you know opinions are like b---holes, everyone has one and some of them stink.

[cannondale27]

Your opinion does matter cdrider.Thats what forums are for.I have checked and synced snowmobile cranks alot but admit I am new to single cylinder 4 strokes and learning here.What qualifications do you have if you dont mind me asking?

[cdrider02]

Started riding and wrenching at 14, none of my friends or myself had any money to take our three whelers to the shop so we had to learn how to fix them ourselves and some of them had been doing it for a few years so we learned from them.I lived in Albion Pa. at the time and had my first exposure to machining in the 8th grade,worked in a machine shop through high school here, attended Texas State Technical College and until recently machined for a clothes hanger manufacturing company since 1992 where we rebuilt existing equipment, built new equipment including specialty prototype, designed and built tooling for new products and machined all of the replacement parts for the production dept. including high speed printing presses and paper folding machinery. I now work at the dealership here where I worked between T.S.T.C. and the factory and have gotten a small shop together with a friend and are doing a small amount of machining, fabrication and repair for the public. As far as the cranks go I don't know how many I have done in the past 14 years for the shop and individuals but it is well into the hundreds and have only come across one that I was unable to get straight. In doing all of these (knock on wood) I have not had a single one come back yet. Back to the riding I started on a 82 185s then a 86 trx 250r and a 84 atc 250r sold the atc and trx was stolen then a 92 quadracer 250 back problems forced sale in 95 then ran across a 86 atc 350x in 97 but then found that I had no time to ride it and sold and got the dales one last summer and one last fall. The first one is a late 02 which I have already updated and the other (wife's) is a early 02 with stars and stripes which was allegedly done by ATK but I have my doubts and she doesn't ride it hard enough to hurt so I will do the motor this winter.


Sorry I didn't catch this in the review but it is a ATV/PWC dealership where I work as a mechanic, we carry Suzuki, Polaris,Sea Doo PWC, Bombardier ATV's, Arctic Cat and service all brands.

[cannondale27]

Here are the pics from this thread.If one(pic) is yours please right click on it and save it then you can edit your post and put the picture back where it belongs for good hopefully.