Low top speed on Max IV

[enroute]

Hi everybody. This is my first post here. About a month ago I picked up a mid-90's MaxIV. It's overall in decent shape, and I've spent the last few weeks doing general maintenance. It's got the 18hp Briggs and 26" tires. Allegedly "low hours", but doesn't have an hour meter. I've had to rebuild the carb, tension chains, replace the belt, and adjust the bands in the T-20.

Top speed on flat pavement is only 15mph. It gets up to 10 or 11mph quickly, and then takes a while to creep up the last few mph. Water is probably 2mph.

The engine revs up to about 4000 pretty easily. Actually, the engine seems to rev higher than what I would expect for just "creeping around". I don't have any other Max experience, but it feels to me like a car that's stuck in 1st gear and using more revs than necessary. It has plenty of power to go up steep hills, tow stuff, etc.... so it's not a power problem.

The drive belt never gets to the top of the drive pulley - it's always about 3/4" from the top at max speed. The driven pulley on the trans never lets the belt get more than maybe 1" down from the edge. The belt is tensioned properly.

So, I'm new to this kind of drive system and I'm not sure where to start trouble shooting. My best guess is that it's a pulley issue and not an engine issue.
What do I do next?
Thanks!!
-Chuck

[liflod]

Add spacers under the engine to make the belt tighter.

[enroute]

The belt deflection is about 1 1/4" now (1 1/4" from a straight edge across the pulleys, which would equal about 2.5" total slop). This seems to be in spec with what Dayco suggests. How tight does it need to be?

[racerone3]

go to the auto parts store and get some "lock lube" in a spray can. spray it in the holes of the engine clutch, and on the shaft of the trans clutch that the spring is wrapped around. if the driven clutch is sticking, it won't allow either of them to "ramp up".

[thebuggyman1]

The belt deflection is about 1 1/4" now (1 1/4" from a straight edge across the pulleys, which would equal about 2.5" total slop). This seems to be in spec with what Dayco suggests. How tight does it need to be?

1 1/4" should be total deflection, the other side of the belt will be tight. I'd also try 1 1/8" to see if that is any better.
ATV and Snowmobile Belts - by Dayco

[Patmax]

Factory trick on belts: grab the belt one hand each side close to the drive 'verter, put your thumbs on the belt where it goes over the pulley, wiggle side to side. More than 1/4 inch, shim to tension, or replace the belt. Check the Dayco specs to be sure it IS the right belt as well ;(.
One other possibility is a broken or popped spring in the drive unit throwout weights. Rare, but it can happen. Simply try to push the drive plate with finger pressure. If it moves more than 1/8" that's where I'd look.