What kind of top speed are you getting? Sure the sled isn't just running out of steam?
If not, how does the engine sound, misfiring like bad ignition, deep and throaty like it's overgeared, quiet and boggy like it hasn't got enough fuel?

 

Well,

I never checked the top speed but i would say no more than 40 mph, (this machine did do about 80 mph before i got it) it revs up and jumps to speed quick but then tops out at that speed, kind of a plateau. I know a guy had told me that someone switched the gears once in it, so this weekend I am going to check what gears are on them. I think stock is 20/35 or 39 so i will check to see if that is maybe a problem. I am also going to do a clutch cleanup, alignment and stuff like that other than putting a whole kit in right now. That can be a summer project. Fuel seems to be fine.

 

I think you better do some seriouse checking because there is not a chance in hell a 1988 fan cooled 340 ever in it's wildest dreams did even close to 80mph. I would bet it had a hard time even thinking about 60mph..
Do you have a 440 liquid cooled sled?
I would check your clutches and carbs for starters then move on from there.

 

me never heard of a stock 88 340 doing 80 either. the most I ever got out of mine was 60 on the speedo in ideal condition s most of the time it is maxed out at 55
and even then you want to be on something smooth.
as far as bogging at the hi end im going to guess fuel or compression.

 

Sounds like you are on the right track, don't overlook something as simple as the belt as well.
Curious, does the sled have a tach and if so what are you getting for RPM?

 

my 03 370 will hit 62, but you have to be on a nice hard packed road and weigh 100 lbs. As for 80, well yeah, when its on the trailer behind the truck,,, but thats the only way.
40 does seem low though,,, I would look into clutching before gearing if it rode faster before changing the coil. Especially if you never changed the gearing yourself.

 

The 80 mph was told to me by guy that owned it last, i thought it was a bit high, but im gullable too. I intend to do a compression check to make sure engine is fine, i dont have a tach on this machine so not sure what rpm is running at, my buddy things my engagment for mid and high clutch is not right and is going to help adjust it.

Thanks gang,

P.S. I don't really need the max speed, but knowing what the machine can do would be nice too

 

in good conditions, I can see 60 on the speedo (little less with track spin figured in),,, tell the guy before you that he never saw 80 on the speedo though,,,

 

I forgot to mention spark plugs simple cheap fix if that is what it is You usually don;t have much trouble with the 340 engine they are very durable.
You do have to keep the carbs clean if you don't run it much the fuel will gum up the lines and starve oil to the cylinder and blow out a pistion. had that happen on my 93 but not the 88.

 

I know what your problem is I had the same sled for ten years. Its your compression rings do a test if its down even 10 pounds thats what it will do, and those litte sled are good for 55 mph when working properly and everything is greased good and no woren bearings.

 

Great stuff gang,

I will get the compression tested and see whats up there. Maybe a ring job this summer, maybe some bearings, i don't know but not much time left and want to use it all up before its gone