crank deflection or run out or whatever you call it...

[shizzu]

so my sled mechanic take the ol 03 800 into the shop to replace the speedo cable and check the deflection on the crank and he reports that its .012 and it supposed to .002 or less. I tried searching on here regarding deflection and could not find the correct post. how much is to much and should be your trigger for a rebuild?

thx

 

[Goinboardin]

0.012" is significant. I've heard you don't want to ignore runout if its over 0.004" or so. It means the crank end is "wobbling" as it rotates, and at 8000RPM with the clutch on there that is alot of force. I know there are a few different viewpoints on this subject. One view is that you're going to snap your crank if you keep running that. The other view point is that runout is always changing, ie you land hard, crank distorts, then corrects, and its all good. I may not be explaining that second viewpoint correctly, but I read something from IndyDan about how crank runout is not always a good measure of crank health because it can vary to some degree even in a healthy motor. However, there has to be a limit where the crank will NOT return to true, and the runout will continue to grow until the crank end snaps off or the PTO rod pin breaks. I would guess 0.012" is over the limit. I would go through the motor now and get the clutch balanced. Check the case to see if it still holds a bearing tight, if not get the case machined or find a case that does provide enough clamp pressure to hold a bearing tight (but not too tight!). Unfortunately paying someone else for labor sucks...

Preventative maintenance is always cheaper and doesn't involve a tow out of the backcountry. How many miles on that motor?

Some others with more experience/knowledge will (hopefully) chime in and correct me wherever I'm wrong.

 

[markis24]

If it was measured correctly polaris say's the acceptable runout is .000-.004. .012 is alot and more then likely needs some attention. Look up Indy Dan and he will be able to get you in the right direction. The post above mine has some good info. Heres some more info on the old 800ves crank. http://www.snowestonline.com/forum/showthread.php?t=154327&highlight=indy+dan+800+ves

 

[Jay]

Goinboardin explained that really well, I'd take his advice.

 

[shizzu]

mileage is about 3k, i bought the sled used, and have run it 2 seasons, i have put somewhere between 600-800 miles on it, i wasn't sure if the wide bearing had been installed or not, apparently not. sigghhhhh..... i guess it will cost a few bucks to do if I am gona do it then.

 

[Goinboardin]

Wide bearing is not the fix. READ that thread that Markis24 posted the link to. Indy Specialty's bottom end is the way to do it for pure long term reliability, but if you're like me you'd rather squeeze a year or two more out of the Edge on the "cheap" and save for a newer chassis sled. If that's your situation, I would send the clutch to IndySpecialties to have Dan balance and shim the primary, he'll go through the clutch entirely, make it better than stock, charge $130 plus any bushings (he'll recut the sheeve faces if needed, its not overpriced for the degree of attention to detail he puts into them!). Make sure your crankcase is not beat out and still puts a little crush on the crank bearings. Get a rebuilt crank from JJ Machinery in Utah (http://jjmachineryonline.com/snowmobile/snowmobile-crankshafts/polaris?product_id=51) and some replacement pistons (they have probably collapsed some near the skirts but a caliper can confirm or refute this). Clutchman on here told me paper cylinder base gaskets tend to leak, so run the Polaris OEM cylinder base gaskets with a metal core, and ride the hell out of it. If you're running twin pipes watch out for detonation, that will wreck any motor but the stock heads on these motors make for high dynamic compression with twins and can be deto prone. Hmmm I think that's about all I know, and I'm just regurgitating what I've picked up from others.

Oh, and warm that sucker up before riding it hard! Aluminum expands faster than steel, so your case expands, loses its "grip" on the bearings, then the bearings expand and the case can "grip" them again, but you don't want to be riding it hard during that brief time of case/bearing temperature inconsistency. And of course there's the more obvious reason to warm up an engine: pistons expand faster than the cylinders, so WOT right after startup will give you a 4 corner seize, bet a guy would feel pretty stupid doing that!

I run a solid engine plate instead of the stock 2 strap mount, and an SLP push arm. Make sure your engine mounts aren't torn, that's really common with the stock engine mounting setup. I haven't torn a mount yet with that 1 piece plate though.

Don't feel too bad either, my engine is on the bench now! Lost the PTO rod bearing, MAG crank seal, MAG piston, MAG main bearing, MAG cylinder last March. Yeehaw