I have done some searching and found some suggestions, but I am still not sure what to do next.

Here is my problem. I have a 2000 Scrambler 400 2x4. The piston was replaced not too long ago, maybe 10 hours of ride time?

I was riding it for a few hours when I noticed that the exhaust was looking white and it was creating a bigger cloud that it had been. I also noticed that coolant was bubbling up out of the overflow reservoir.

I suspected the head gasket, so I replaced that, torqued it to spec and checked the head for warp-age. After that work, however, the problem remains exactly as it was before.

What should I look at now? Any ideas would be appreciated.

 

I once had a catastrophic bearing failure on the counterbalance shaft. putting a hole between the crankshaft and counterbalance. It started burning coolant that had leaked past the water pump seal, that was 14 years ago I got alot smarter since then.

So check to make sure you have oil not water in the counterbalance.

 

Did you bleed the 10 mm screw on the head of any trapped air in the coolant when you first put it back together? This is something a lot of people forget to do and it can over heat and warp heads and cylinders quickly,blow head gaskets. I've had this happen a lot on carry out cylinders I've bored for people even though I've reminded them.If the damage is already done you may have to have the head and cylinder checked out and possibly mill one or the other or both down if warped.

 

I did bleed the coolant. I had the screw out until coolant came running out.

So it sounds like the head is leaking?

 

Sound like a blown head gasket if you see white smoke and can smell coolant. I'd at least have the head checked out and milled down a little if warped.Plus like mentioned check that you counter balance cavity doesn't have coolant in it also from leaking w/p seals.

 

Thank you. I will check that this week.

 

Right on OPT, plus you want to check the water pump shaft for any grooving, if so, time to replace. If your counter balancer oil is "milky", you got blow by on the seal, and the bubbling in the tank leads me to believe the pump isn't doing the job

 

Ok, so I checked the counter balance oil and it is milky white. So should I focus on the waterpump? What should I look for?

 

Seals,bearing and gasket need to be replaced along with making sure the counter balancer shaft the seals and bearing rides on isn't grooved/damaged. If it is it can be repaired. Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse http://www.ebay.com/itm/Polaris-ATV-400-350L-counter-balance-shaft-water-pump-REPAIR-balancer-/300941567648?pt=Motors_ATV_Parts_Accessories&hash=item461183e6a0&vxp=mtrA good service manual is needed on this area and helpful for all other repairs needed.http://www.ebay.com/itm/1999-2000-POLARIS-SCRAMBLER-400-500-ATVS-SERVICE-MANUAL-/171107378557?pt=Motors_Manuals_Literature&hash=item27d6cb657d&vxp=mtr