Listen to Harley. Bad crankseals give exactly the issue you are dealing with. If one or both are leaking, the engine looses crank compression and the engine needs to rev up to work. The most common problem with old snowmobile engines.

Very nice written and thanks for new knowledge. I didnt know that the Drifter 440 was based of the T-7. Always thought they were built in 340/440 T-1 versions like the TF. Didnt know anything about the Arctics eighter, just had a minor clue.
Cheers

When I sayd the same engine I ment the bottom. One or two carbs, oil injection or not....... Just ment that the SF, Intruder, LF and Invader use the same bottom. TF, Spitfire, Drifter use the smaller engine. Perhaps some Arctics also use the smaller bottom, but that I dont know anything about.

As Iwb140 says. The Intruder engine is the same as the Sportfire. Same bottom as Liquifire but FC. Also a better engine if you want some horsepower. I have a pretty wild ported Trailfire 440 myself. It brakes 68 hp but it feels like lottery every time I go out for a ride. If I were you I would try t...

This is what I recommend to everyone that have a TF, SF or LF. You will never get the boggi to function well with the original "kinda" shock even if its new. With very little work you can use a front shock from a 90s Polaris, Yamaha or other with similar front suspension. If you want to be...

To start with. I am Soderberg but couldnt logon with my old username. Had to create a new one. This is what happened with my Trailfire at the end. 1. I went for the LF porting. 2. As the intake looks as it does on the TF I had to make an adapter plate that connects both cylinders. Could have made th...