speed problem

[Pazazzz74]

So I have a 70's Swamp Fox and it doesn't want to go over about 7 mph. The belt looks alittle loose so couldn't that be the issue or does it sound like a bad torque converter? Any help would be greatly appreciated! Forward and reverse work fine so I am hoping the trans is fine.

[Toys4Me]

Belt tension has a lot to do with speed slow and fast.

[allwheeldrive]

The larger the belt the less the pulleys can make use of their full range to get into "high" gear. Same if the belt is too tight. Do you have factory engine location and trans?

[Pazazzz74]

The original engine had been taken out and an article cat 340 was put in. Problem is they welded the engine mount so I have to cut it free and put tensioners on. Belt is fairly loose

[Toys4Me]

You could try finding a smaller belt.

[allwheeldrive]

Finding a new belt size isn’t impossible you may be in luck and one could exist close to what you need.
https://www.mcmaster.com/#v-belts/=1a93g0w just some examples there are many more (you’ll pay more for odd sizes)

What I did was take out the old belt, measure its length with a cloth tape. Than make a belt from cardboard layered to the same thickness and cut to the same width. I wrapped that around the clutches as if it was the real belt and snipped it to the correct length. The only problem was the cardboard method will usually give a too perfect fit and you want some slack so add an inch or so to be safe. Then compare to the original belt the two shouldn’t be a huge amount off.

[tbone9]

If you look up Ultimax belts ( which I highly recommend) they have all the dimensions on their website and should be able to find the right width and length.

[hydromike]

Here's a good place to start once you get your measurements down...

[ARGOJIM]

From your hard to see picture it looks like you have a 1-7/16 belt on there now, the driven would have had either 1-3/16 or 1-1/4 stock, also the driven probably has a green spring in from the four stroke. The drive is also probably set up for a larger diameter driven.
Sounds like lots of issues going on there, personally I'd 4 stroke it so you can use it. However now you probably can't tell if there is a band issue going on either ( hopefully it's fine like you hope).

Is the engine spinning up over 5000 rpms and not going fast or lugging and 7 is all it will pull at low rpm's?
Post a better pic for people to chime in on, your belt deflection should be 1"-1-1/2".