Slapped in my new Wiseco pistons, and measured my deck height. Using .8mm base gasket, torqed bolts to spec in a cross pattern. Torqed to 15 lbf then to 21lbf. The Mag jug was .021 on each side of the wrist pin. The PTO jug was .013 and .024. I rotated the crank as fast as I could to center the piston. Still the same result. I can tell by looking down at the top of the piston that it is more towards the front of the block and towards the mag side. I'm thinking I have a bent rod and would like to get another opinion.

Seeing as how you are going to have to pull it apart one way or another,why not switch the pistons side to side,if the tilt goes with the piston,the wristpin was not bored right,if the problem stays with that clyinder you have rod or crank issues.Why did you replace the pistons?burn down??

Check it after both directions of crank rotation. Pistons are tapered, smaller at top than at bottom. What you might have is that the piston is "rocked" with one side parallel to the cylinder, thus leaving the top of the piston out of square. If you check it with both directions of rotation, but have the same amount of rock in the same direction, then there is something wrong with the piston (I would doubt this, as the entire piston is machined with one setup on a lathe)

If the rod was bent enough to have that much of a discrepancy the engine would not turn over. I would measure the pin height with a set of calipers and my guess the piston is defective.

Originally posted by 800MXZ@Oct 23 2003, 11:33 PM
Check it after both directions of crank rotation. Pistons are tapered, smaller at top than at bottom. What you might have is that the piston is "rocked" with one side parallel to the cylinder, thus leaving the top of the piston out of square. If you check it with both directions of rotation, but have the same amount of rock in the same direction, then there is something wrong with the piston (I would doubt this, as the entire piston is machined with one setup on a lathe)
I wouldn't be so quick to assume that the piston couldn't be bad. Yeah, you may think that the O.D. and dome are turned at the same time, but I had one of these pistons in my '02 800. The wrist pin was dead square to the O.D., but the measurement from the top of the wrist pin to the edge of the crown was off by .006" as checked on a surface plate with a height gage.

800REV pointed out that he checked above the wrist pins. That takes away any chance of piston tilt.

I think I would pull that jug, turn the piston around and see what it measures that way. (don't forget that it is in backwards) Checking it this way prevents another variable from entering the equation. (a different rod)

I will bet that the piston is bad.

Keith

I understood it that when 800REV said he measured it from the "front" that it was exhaust side vs. intake side.

Guess we need a clarification from him on that then. I read it the other way since he came up with the same on one cylinder.

Sorry.

Keith

No problem Keith, I was stating my ignorance is all LOL

I can see a couple of thou, but not much more.

Yea I took the measurement at the pin holes, side to side. I wont have any time to work on it until Sunday night.

I was going to take and swap the mag piston and put it in the pto side. This should tell me if it's the piston. I'll let ya know when I have time to work on it.

Thanks guy's

Well I switched the pistons around and I got the same result. .012 and .023 I think I'm going to take my crank back and have them check it unless you guy's know a way to do it sitting on the bench. What if I took a hammer and beat it back the other way :D

800REV,

You will need to borrow or fashion some Vee blocks. First check the runout on the crank with the bearings removed. If crank is straight, elevate the vee blocks high enough on the bench to allow the con rods to hang. Level the crank horizontally using a good level. Then check rod using a small level on the con rod's small end thrust (side) machined surface. A plumb bob will do in a pinch. If your bench is dead flat (I use a leveled table saw as a known flat surface) you can check the maximum rod drop (stroke) using gage blocks and allowing the rod to sweep at TDC (upside down). If you can't get gage blocks, use modeling clay on the bench top and allow the rod's small end to compress it then cut and measure the clay(same procedure used on automotive engines to measure valve piston clearance). If the crank pins are miss-aligned you can re-align them yourself using a brass hammer and dial indicator. !!! You cannot hammer con rods straight, as any impact on the side of the rods will damage big end bearings :cussing: .

Good luck,
T.D.

Well I took the motor to Advanced Racing to have the crank checked. Found out the rod was bent a little. They were able to straighten it to within .001 Do you guys think this will be okay?

If they were able to get it to within .001 and there are no nicks or marks on the rod, it will be just fine.....run it!!!!!!!!!!!!!!!!


Brian

Originally posted by 800REV@Oct 31 2003, 10:48 PM
Well I took the motor to Advanced Racing to have the crank checked. Found out the rod was bent a little. They were able to straighten it to within .001 Do you guys think this will be okay?
Any idea as to how it became bent in the first place. Did it submerge and ingest water or someone was over zealous with the storage oil application ?

It's hard to say. The crank was handled by three different firms. Me being one, Advanced Racing, and whoever they send it out to weld it. There are no visual marks that show it was dropped. On my end the only thing I can think of is when I took out the pin. I used a socket and extension and used the palm of my hand to smack it out. I cant belive I bent it by doing this but maybe I don't know my own strength. :D