GT 3100 Engine/PTO alignment?? Front PTO belt comes off.

Joelk · #1 09-14-2014, 09:09 PM

I recently bought a 2005 GT 3100. It seems to be in pretty good shape/works well except for an issue with the front PTO belts.

The prior owner told me there was an issue before I bought it. Said it would usually mow short grass without, but PTO belt would come off if it got into tall grass.

The PO had replaced the vacuum actuator and PTO Idler Pully(Old one came with the tractor and did not seem to be bad), but said the problem continued even after replacing the parts. I looked at the alignment before operating it and it appeared to be pretty good and nothing appeared to be bent or loose.

I mowed for about 1/2 hour and it seemed to be working fine, then the front belt came off the idler pulley and started getting chewed up. I pulled the hood/muffler etc. off the front of the tractor and could see a very slight misalignment of the Idler pulley(used straight edges to check) vs. the engine. It does not look like it would be far enough out of alignment to cause the belt to come off, but apparently it is.

I pulled the engine out of the tractor to do some other work and have the engine installed with the bolts in, but not tightened. I tried twisting the engine and it seemed to move a fair amount(I saw no wear in the engine or frame mount holes/bolts) and am wondering it there is recommended procedure for aligning the engine. If there is not, I will probably try twisting it to the position that provides best alignment of the belts on the PTO actuator pulley.

Any other suggestions on how to improve the alignment?

With belts costing about $50 for a pair, I would like to get it fixed on the first attempt.

Thanks, Joel

J-Mech · #2 09-14-2014, 09:52 PM

Check to see if the idler lever is bent, bearings out of any of the idler mechanism. Check the front lower (PTO) shaft and make sure the bearings are good in it. May also be a problem with the vac diaphragm losing vacuum under a high load (wot) situation. I wouldn't move the motor around, as you will throw off the driveshaft alignment.

Joelk · #3 09-14-2014, 10:33 PM

The idler bracket does not appear to be bent. The bearings/bushings all turn smooth and free. The PTO(runs through front axle) turns free and smooth.

If the vacuum actuator were to leak, wouldnt't that just make it disengage?

I don't understand why that would make the belt come off of the idler pulley. If it would/might, please explain how/why?

As far as engine alignment goes, I am just using the bolts and bolt holes that came from the factory. Due to clearance between the holes and bolts the engine can be moved slightly forward, slightly rearward, slightly to the right or left, or slightly rotated, clockwise, or counter clockwise. Should I try to find the "most neutral" position for the engine or how should it be aligned.

I read a thread where a guy had R&Id his engine and then had issues with the PTO Belts. This makes me think there is a right way and a wrong way to position the engine. I want to do it the right way, but not sure what the right way is.

J-Mech · #4 09-14-2014, 10:43 PM

If the belt goes slack (because of the PTO losing vacuum) it can "kick" itself off. Haven't you ever seen a belt running that wasn't tight enough? They can really move around.

As far as the motor position goes, try it. Seems reasonable, but I really don't know that it moves enough to make a difference. If it does, great, if not, then keep looking. No, I looked through the manual and there is no "procedure" for aligning the motor and the front drive.

Oak · #5 09-15-2014, 09:22 AM

I have pulled my 3165 engine and just bolted it back in place with no problems, I didn't recheck the alignment but it works fine. How tight is your belt when the actuator is engaged? I used a clean tube and sucked on it to engage the pto to check tension of the belt with the motor turned off. Can you post any pictures of your set up. Maybe that will help also.

Joelk · #6 09-15-2014, 07:19 PM

I bolted the engine back in and twisted it the way I thought helped the alignment the most. As I got the bolts close to tight it took out just about all of the slack so I doubt that twisting it had any significant effect. The manual probably does not discuss aligning it because it really only "goes where it goes".

There seems to be good tension on the belt when the actuator is engaged.

I may be able to get some photos in a few days, but I would really be surprised if anyone could see the issue with it in photos.