2002 800 VES engine questions... need help! - Snowmobile Forum: Your #1 Snowmobile Forum

wingnut2840 · 09-09-2009, 12:51 PM

Hello everyone. I'm hoping some of you guru's out there can help me with some questions about this engine. I know very little about it, so any info would be greatly appreciated. I'm considering buying one to build a small rail buggy but not sure if it will work.

Does anyone know what clutches will work on this engine? Is it water cooled or fan cooled? Is there an electric start kit for it? Are there any specifics or problems I should be aware of? What is typical good compression for this engine? How much hp does it produce? Is it easily upgradable?

Thanks for your time and help in advance....

Squirrel

**BC_Dan** · 09-09-2009, 03:07 PM

Welcome to the forum!

Any clutch from a Liberty twin will work fine, but there are wide roller clutches and narrow roller clutches; the wide roller ones are stronger.

It's water cooled.

There is an electric start kit available. Finding one may be a problem... best bet is to look at a used snowmobile yard. One such place is Al's Snowmobile Parts Warehouse - Snowmobile Parts, Snowmobile Parts, and More Snowmobile Parts. You will also need to replace the primary with one that has the machining for a ring gear to allow the starter to turn the primary.

The biggest problem with the 800 is in the crank. There have been a lot of broken ones, especially out west in the mountain sleds. The issue is the torque the engine produces; it hammers on the crankcase and eventually wallows out the PTO end of the crankcase until it can't support the crank. Then the crank breaks. Keeping the clutch balanced helps this issue. Some guys have had good luck going to a wider PTO end bearing, it spreads the force across a greater area in the crank. Some guys replace the crank every couple years and make sure their case is line-bored to keep it exact. Adding an engine plate, torque link, and push stop are also things that can be done to keep the engine going. The VES valves are aluminum and have had issues; there is very little cooling in the cylinder area around the guillotine. The guillotine can melt, and can destroy that piston/cylinder. Going to stainless steel guillotine valves solves the melting problem. Stock HP was about 136-138, but with an SLP pipe/can and adding a few flowrites and aftermarket reeds, you can bump that easily to around 150. Compression on mine with new rings/pistons was 150 psi.

Be careful with jetting changes, there is a mid-range lean condition that was addressed in 2003, if you use the 2003 spec, you will burn the engine down. 2002 had it's own jetting chart and it's a LOT richer on the main jet than later years.

wingnut2840 · 09-09-2009, 03:40 PM

So, would a clutch set off of a 4 stroke 800 work with this engine? Aren't the rpm's much higher on a 2 stroke? Would I have to do some type of gear reduction to make this engine work with a transmission originally bolted to a 4 stroke?

**BC_Dan** · 09-09-2009, 06:21 PM

I'm not sure of a 4-stroke 800 unless you mean the Polaris Frontier. I think it was a 7something cc engine. The shaft offset for that clutch is the same on that engine as the two-stroke, but the Frontier puts out about 48 hp; the two-stroke puts out 138 hp. If I were looking for a clutch, I would try to find a wide roller clutch for an 800, anything smaller may work for a while, but will wear out a lot quicker.

Most of the clutches from the Polaris Big Block Liberty twins (97-05 700 & 800, 98-2000? BB600) are pretty much the same, all you need to do to modifiy one of those for your sled is to put the correct spring and flyweights in it for your application. Some of the Fuji triples and twins will not work because the offset on the clutch is not the same and installing those type clutches on a Liberty egine can take out the PTO seal.

LazyTiger08 · 09-10-2009, 03:34 AM

I don't think any of the manuafactuers currently make an 800 4 stroke, Polaris makes a 750 or is it 775 turbo, skidoo makes a 1200, Yamaha makes a 998 and an 1100, and arctic cat make a Z1turbo (1000). You had said that you thought 2 strokes are higher revving, ive had alot of 2 strokes and the highest revving ive seen was about 8000RPM and at that rpm being very hard on the motor, now on my apex its a different story i can hit 10-10.5 thousand RPM and still have power left, so i don't think thats true.