Belt slip - clutch modification???

[dirtdobber]

So I have taken the Hustler on several rides so far and in total have put maybe 10 hours of ride time on it since I built it. Although it runs great on dry hard ground it seems lacking in low end torque. I determined today the belt is slipping. I went through a mud hole and it wouldn't even spin the tires. Belt was slipping at the drive clutch. After 10 hours riding the belt is 1 1/8 wide. The engine compartment is dry as a bone - no oil or water on the belt. Engine is not lacking power.

Belt and drive clutch both were new (10 hours ago). The drive clutch is a Comet 780 from mfg. supply. Spring in driven clutch is presumably stock. It has no color other than metal brown. 20 horse opposed Briggs stock engine. Tires are rawhides, either 21 or 22's. Belt alignment is spot on. I think the belt should be a tad tighter but when I put all this together the driven clutch would spin slowly at engine idle (tighter would have made that worse, of course).

As I see it, the belt can only be as tight as the drive and driven clutches will bite it. will heavier weights in the drive clutch, and the famous red spring in the driven, give me more bite on the belt?

Thank you in advance for your thoughts.

[Mike]

I'm not very familiar with Hustlers but I do remember others saying that some models did not allow for any belt tensioning. Do you have a way to tighten the belt? If not, you may have to modify the engine mount so that you can adjust the belt tension. There are a few threads where members have posted photos of the way they modified their engine mounts if that would help?

[racerone3]

I'm not very familiar with Hustlers but I do remember others saying that some models did not allow for any belt tensioning. Do you have a way to tighten the belt? If not, you may have to modify the engine mount so that you can adjust the belt tension. There are a few threads where members have posted photos of the way they modified their engine mounts if that would help?

[AussieMax]

You might need heavier weights or lighter springs on the primary. If the weight is too light it will shift off early. Does it reach full speed of the trail? It sounds more like clutch setup rather than belt slip, it will feel like belt slip if the clutch downshifts too easily

[dirtdobber]

Mike - Fortunately I did build an adjustable engine mount. Unfortunately that opposed engine leaves very little clearance between it and the tub. I will replace the belt and probably tighten it a bit.

Aussie - It will run fast off the trail and on hard ground. I don't expect it to run fast in the sand/mud but it should have more torque than it does. I know the belt is slipping because I watched it yesterday. I was in some soft ground and it would not produce the torque to either pull me through or spin the tires and get me stuck. I raised the hood and watched the drive clutch slip on the belt at WOT. It wouldn't bite the belt hard enough to overcome all the resistance. Plus, the fact that I've lost 1/16 off the width of the belt in 10 hours of riding tells me it didn't just start slipping yesterday.

I shot a short video of the slip, but I haven't figured out how to load it yet.
Thanks for the input guys.

[ARGOJIM]

Perhaps someone like Raceone3 or Dan67 Could give you an approximate center to center distance so you know where to start, if the spring is brown it may well be a 2 stroke spring ( that would be weaker than a 4 stroke spring) but shouldn't cause slipping.

The driven may spin slightly at idle with proper adjustment but shouldn't push the machine with the sticks forward. Neutral would still need to be found by centering the sticks.

[Dan67]

Are you sure you have the clutches properly aligned? I set mine according to this Try a new belt after you check the alignment. Also check to see if the clutch is weighted correctly. Both Don and Raceone3 are good resources.

[dirtdobber]

20160718_211332[1].jpgThanks Dan. Those instructions are precisely what I used when I aligned the engine to the transmission. I set all this up with the frame out of the machine so I got it lined up good (pic above).

Jim I used a guide published by Quality Drive Systems for the center to center distance. I know I am a little short of that distance (by about 2 tenths of an inch if I recall) due to the lack of clearance between the engine and the back of the tub. When I replace the belt, I'm going to ease the engine back just a tad more.

Also, I'm going to talk to Roy at QDS about putting a 1 1/4 inch wide belt to compensate for the lack of correct center to center distance.

As far as the spring in the driven, I don't know what the original engine was. I appreciate any input on the weight/spring issue.

Thanks guys.

[wfo]

use the green spring

[dirtdobber]

I hope this works. Here's the video of the belt slip. Notice that the slip is at the drive pulley. See the puff of smoke at the very end. WFO, does the green spring make it more difficult to open the sheave on the driven pulley, thus keeping a lower ratio between the drive and driven for torque purposes? If so, I don't see how a heavier spring would have changed the situation in the video (I'm not arguing with you, I'm just learning!). I don't doubt I would benefit from a heavier spring, but since I've got to pull the tranny to do this I want to make sure I'm doing the best thing possible.

I tore down an old drive clutch this afternoon and now I understand how it works. It seems a lighter set of springs would make the drive clutch bite the belt harder, and of course the driven pulley would have to have a stronger spring to offset the new strength of the drive pulley; otherwise, it would go straight to high gear, so to speak.

[wfo]

green spring will hold it in lower gear longer and let the drive clutch pull the vehicle, i think what is happening is that its upshifting too soon and smoking the belt.
i had a similar issue with the invance set up. went back to the 1190 and 780. works great or MADE IT GREAT AGAIN. hahahaha

[Dan67]

I watched the video several times and as you revved the throttle I did not see the drive clutch start to close up as the rpms increased. I am betting it came with weights and springs set for a higher engagement then what we use. Also did not see the driven clutch open as it was spinning to slow to open. It looks like the smoke from the belt at the end is because the belt was slipping on the driven too from being too loose.

[dirtdobber]

Dan,

The drive clutch was trying to close but it wasn't closing with enough force to bite the belt hard enough to fully engage it - thus the slip and puff of smoke. in a no load situation the drive and driven work together and move as they should.

I pulled the cover off my drive clutch this morning and found that it has yellow springs with blue rollers and green side cones. According to the QDS engagement chart this arrangement should engage at 1400 rpm's. What engagement RPM do you guys typically use?

It's entirely possible the slipping condition in the video is driver error. I was stopped in a high torque situation, and to go forward i engaged the laterals and then got into the throttle. Perhaps no arrangement of springs and weights will work when the driven pulley won't spin. I could have engaged the clutches with the laterals in the neutral position and then called for forward motion. I don't drive it like that to avoid undue stress on the chains and bands. ALTHOUGH, I stopped in a high torque situation because it wasn't giving me the torque to get through it in the first place. I was easing across a silted in ditch, slowly.

I am awaiting a return call from Roy at QDS. I'll share what I learn from him with everyone else. Green spring may be all I need.....and a new belt with a little more tension.

[dirtdobber]

For what it's worth here's the clutch working under a no load situation. When you see the belt stop turning it's because I bumped it into gear.

[dirtdobber]

I talked to Roy today and here's what he thinks. From what I described to him, he thinks I have a 3 fold problem. First, excessive heat can lead to glazing and belt failure. This may or may not be a contributing factor since I don't know what the temp is in my engine compartment. Second, since my belt is running a little loose it could contribute to heat buildup not to mention a loss in torque ( i knew that part because of the larger effective radius it creates). Third, the further the drive clutch closes the "weaker" the bite on the belt. This has to do with the angle of contact between the roller arms and the metal dome of the clutch as it travels from open to closed. So, because my belt is a little loose I'm losing some of the "bite strength" available when the clutch first begins to close.

So, I've ordered a new belt (the old one will be a good spare) and I'll squeeze the engine back a little more for belt tension (I'm currently at 2 inches of deflection when I should be at 1). I'll roughen the pulley surfaces, and then give it a try and see how it does. ALTHOUGH.....I"m really interested in what the green spring will do.

I wish I had a baseline against which to measure my machine's performance. I just might have to make the long journey to Busco so I can see how other machines perform!