I have a 1998 Polaris Scrambler 400L. My problems started about two months ago. I would go riding and my power would go mushy when I hit the throttle I would baby it for awhile then it would pick back up. That really didn't bother me as bad but then it started pinging after the power was regained. I still have both problems. I had to put new reeds in this fall after the engine sucked a petal, it didn't damage the piston at all other then one scuff mark. I have about 100psi of cranking presure at 3280ft elevation. I still have stock jetting. There is alittle oil oozing out of the flange on the exahst but not bad. I haven't noticed any oil at where the cases join so I really don't think that I have any air leaks. My plug doesn't have any Al on it so thats seems alright.. I have a 50/50 mix of water and antifreeze, I dont' know about that could be a problem the cooling system anyway. What could my problem be, all sujestions welcome. I'm sorry about the poor spelling.
Deric

 

Start at the top, pull the bowl off and check for water. The problem sounds to me like water in the fuel, but it could also be poor fuel. You can drain the tank and use 91 octane or some fuel stablizer. Also check & clean your filter. Change your spark plug. Now test. If it's still happening after this, then the next step.

Pinging on the top end power could be a couple of things. Either a piston or air leak, most likely the latter. When you do a compression test your really only checking the head gasket, you could still have a base gasket sucking in air. Here's a test I use:

Start the quad, after it's warmed up. Spray some starting fuild around the base of the jug. If the rpm vary then you have a leak. Do this around the head and intake also.

There's a method to the maddness. Like a flow chart:

Air Fuel Spark
Filter/clean Good/amount Yes/fowled

Hope this helps. Try the filter and fuel first and test. Then if this doesn't fix, then e-mail me at dmeyer@thesmsgroup.com and I try futher. I hate dealer prices...

 

Thanks for replying so quick. I have already drained the fuel and replaced the fuel filter. When I put new gas in I used 91 with alittle Heat in it. That didn't correct the problem. I will try the trick of using ether to try finding air leaks. I have used that trick tons of times on cars to find vacum leaks. I was also planning on taking the float bowl off and droping my jets and soaking them to make sure they are clean.. Thanks

 

Today I finaly had the chance to ride it around and get it warm. It was bogging very bad and didn't make much power and the pinging. I when I got back I sprayed either around the front of the motor by the base gasket and where the cases meet. A second later the engine would lose RPM and acted like it was loading up. So I take it that I have a Air leak. Is there anything else it could be.. I do have a oil around where the cases meet vertically and at the base gasket, so I'm guessing I will get to rebuild. About how much should it cost to rebuild? I'm figureing 70 for a piston, 50 for boring, 50 for gaskets what else is there and what seals would I need. Can I do this job my self, how hard is it to deal with the crack bearings and counter balancer. I have a good mechanical background so I'm not to affraid to tackle the job.. Thought another thing I've been kicking around is selling the Quad; how much would it be worth? The quad is very presentable shape. Thanks