drive belt not slipping

[38racing]

Older lr121 husqvarna rider. I can't shift gears unless I stop engine. Drive belt spec has 532126520 replaced by 532419271. I'm seeing the first at 88 1/4 and the second as 88 5/8. On it I had one I measured at 88 3/4. Although I couldn't shift the transmission the transmission pulley was stopped. I figured maybe there was still some tension affecting the input shaft. I bought a new 89 belt which in hindsight I should have measured before installing. With it the transmission pulley does not even stop when clutch is full in. I'm thinking next step is to drop the engine pulley and clean the groove, then measure the 2 belts I've got and try again with the longest. Then a 90?

[38racing]

and speaking of belt sizes , isn't this helpful.

This

037X88MA Blade drive belt. Fits 42" hydro tractor. Found on Murray 1997 and newer lawn tractors with 42" LT railframe models 42509X92B and 42590X92A and Scotts 42" LT rail frame model numbers ending in XB (1997 thru 2000). Size: 1/2" W X 88-7/8" L

versus

V-Belt for Murray (1/2" X 89.5") Fits Murray 42" Hydro Tractor. *Aramid Fiber, Wrapped Belt.
Replaces:
MURRAY: 37X88
Fit Models:
MURRAY: 42509X92B, 42590X92A

[KE4AVB]

Check for bent engine pulley. I had one recently that one area was bent and it was just enough to the drive belt to move. Kinda stood out as it was shinier than the rest of the v-groove.

When it comes to belt sizes places like Stens are using +- 1/2" when they spec a belt. The last MTD replacement belt I got from Stens was 104" to replace a 103" belt. I could engage the deck and slip the pulleys which I already knew was a problem as the OEM belt was 103". I end having to put on a 102"; though, 102.5" would have been a better fit but none in the size available. I had MTD 46" cut in a row that I had to put the 102" on.

Unless you measure the v-belts you don't know if you got the right size any more. I still having problems with being on the short side even with OEM belts but at they are a lot closer to the specs. Even when you find that they sent you that wrong size they will argue with you that it is right and that the belt measurer is wrong. Stens even told me that the tool is no good for measuring the belts even though they sell the tool to customers for that purpose.

Currently I only use OEM belts because I had so much problems the last two years with belts being short most times and a few that were too long. I even was getting poly belts in place of Kevlar belts. Those literally melted in use and failed. That was Husqvarna that I had nothing but deck belts problems with. After I got my measuring tool and got the right belts on the mower the customer so far hasn't had any more problems. Doesn't mean they will not break a belt today.

[38racing]

finally got back at this . I put a 90 belt on it. Same problem. I then pulled the engine pulley and completely cleaned it up. When I was putting it back on I noticed that since deck was off I had left the deck belt guide loose. Looking closer I figured that although it went over and then down to the deck belt drive pulley that it could also guide the drive belt where it bent down. I tightened it and first test was good. I could shift now. Later test again the shift locked. Looking close at the belt on the guide I could see that the belt had ridden up to the bend was was elevated into the upper side of the drive pulley. By bending the guide inward (moving bend upward) it has kept the belt from riding up and i can shift again. I had to remove the guide and bend it back just at lower part so the deck belt doesn't rub it in the engaged position. I've managed one cut of the front lawn with no issues. It pulls ok but I'm wondering if I should go back to the 89" from 90 as it's closer to spec and see if it releases now guide pin is right.