VintageVmax.com

i have a 1984 540 v-max and it runs great up until abot 6500 rpms then it has no power and won't go over 60, How fast do these sleds usually go? I have put 2 brand new pistons in it and it still did not help the problem.

With the correct clutching, my '83 will turn about 8200 rpm on top end and with enough room in a field I can be over 100 mph without even thinking about it. 60 mph is what mine runs at about 1/2 throttle and about 6500 rpm.

Check your clutching, check your carbs, check for restrictions in the airbox and exhaust. Mine love our sleds.

Donnie

Scribe a line from top to bottom on your primary and secondary with a sharpie, do a WOT run and then check to see how far the belt goes up in the primary and down in the secondary.

ARe your carburetors nice and clean the jets plug up over time especially when sitting for the off season and is the fuel getting to the carb if not could be a fuel pump issue. Is your spark lightning blue in colour if not could indicate a fouling plug, bad wires, bad coil, bad stator coil, all these specs. are in the article index weak yellowish spark is an indicator. Compression has to be good too, mines around 120 125 psi or so. A really worn clutch will mess with your engagement and top rpm. Also there is the crankshaft bearings they will slow your engine down when they wear out, i was geting 6200 rpm after my mag side pump drive bearing scattered, if you roll the clutch by hand you will feel rough spots or grinding noises on the crank bearings. 2 stroke engines can be a pain and arent made to last a long time so preventative maintenance, good oil and proper storage will help to make these babies last. If the mileage is between 5000 to 10000 and the engine hasnt been rebuilt in my opinion its just a matter of time, I,ve been down this road too many times!

motor was just rebuilt with maybe 20 miles on it. the last snow i took it out and tried to go wot throttle and i held it there for about 10 seconds and it would't rev over 6500 rpm and then the motor sounded like the rod chucked out of it and it shut down and locked up. i let it sit for about 5 seconds and it unfroze and started rith up and ran great until you get about 6500 rpm and it will do it again but it will always start right back up after it sits for a few seconds. as long as you keep it under 6500 it will run fine and won't try to seize up? what would be causing this?

If your engine is locking up i,d be looking at the crankshaft cause it sounds like it to me!!

i just don;t understand why it starts up again and runs fine as long as you keep it under 6500rpm?

On my engine the bearing thats in the gearcase messed up. It loaded the engine down because all the ballbearings were on the bottom half of the bearing causing a drag on the crankshaft. Also theres bearings in the pump drive itself and if they are wore out or non exsistent then it will load the crankshaft down as well and could lock up your engine when the gears bind up. I wouldnt try this but you can stall a snowmobile by simply rubbing your hand on the spinning primary clutch, same idea as when your belt is too short and the engine wont idle properly. Something is slowing up the motor, if the clutch is toast it will play hell with the engine as well. From my experience with the Vmax engine is that it is a rock solid engine, better than most. They last along time because the bearings and the connecting rods are bigger than most engines out there. My buddie is a crankshaft specialist and from what i seen over the years this is a heavy duty 2 stroke engine. My engine ran after it locked up, i rotated the clutch back and forth and it unlocked itself and it started up but would only do 6200 rpm, i got lucky in my opinion because it didnt leave me stuck in the bush.