Engine killing with Bully clutch

J

jacobsdad

Member
I am testing my theory here. Getting ready for this years racing season I am going through my boxes of stuff I have accumulated.
During a previous race season my son was using a Bully clutch which was working well for him. I switched gears one night to try to get his speed up, and went way too big on the rear gear. It slowed him down quite a bit, so I went back to a smaller gear which ran great for him around the track. The problem we found then, every time he tried to stop (coming off the track or if they caught a red flag during the race) his engine would kill. The track has a no restart rule, so red flags would put him out of the race. There were a few new drivers that didn't understand staying in their position on yellow flags, so every yellow flag they had to stop the race and get the new drivers back in order, so my sons engine would die. Everything on the engine checked out fine, so when I couldn't find any other reason for the engine stalling I replaced the clutch. That fixed the problem. Here is my idea on why, checking to see what everyone else thinks. I think I geared him too low and put too much drag on the clutch. This heated the clutch up and softened the springs so the clutch is not releasing. After changing the clutch with a new Bully clutch I put the old one on the shelf and have not messed with it. I looked at it a little tonight and see the friction discs look to have a lot of material left on them. The clutch didn't have a half of a season on it when I changed it out. I am guessing if it heated up enough to take the tension out of the springs it also warped discs but I am considering changing the springs so I can throw it in the trailer for a backup.
 
jacobsdad said:
I am testing my theory here. Getting ready for this years racing season I am going through my boxes of stuff I have accumulated.
During a previous race season my son was using a Bully clutch which was working well for him. I switched gears one night to try to get his speed up, and went way too big on the rear gear. It slowed him down quite a bit, so I went back to a smaller gear which ran great for him around the track. The problem we found then, every time he tried to stop (coming off the track or if they caught a red flag during the race) his engine would kill. The track has a no restart rule, so red flags would put him out of the race. There were a few new drivers that didn't understand staying in their position on yellow flags, so every yellow flag they had to stop the race and get the new drivers back in order, so my sons engine would die. Everything on the engine checked out fine, so when I couldn't find any other reason for the engine stalling I replaced the clutch. That fixed the problem. Here is my idea on why, checking to see what everyone else thinks. I think I geared him too low and put too much drag on the clutch. This heated the clutch up and softened the springs so the clutch is not releasing. After changing the clutch with a new Bully clutch I put the old one on the shelf and have not messed with it. I looked at it a little tonight and see the friction discs look to have a lot of material left on them. The clutch didn't have a half of a season on it when I changed it out. I am guessing if it heated up enough to take the tension out of the springs it also warped discs but I am considering changing the springs so I can throw it in the trailer for a backup.
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Is the bearing in the basket seizing up when it gets hot ?
 
Bearing (or bushing) seizing. Also not enough endplay for the basket will cause the engine to stall once the clutch gets hot and expands (thus locking the clutch up 1:1 with the crank.) The basket MUST have adequate endplay. This likely changed when you changed the driver. Aftermarket drivers are also different thicknesses. Set the endplay in the basket by using different thickness wafer bearings (.015" & .030") and different outside washers (.030" & .050.")

It did not soften the springs enough to engage the clutch at an idle.


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Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
29 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
Ok. I did not change the gear on the clutch, I changed the rear gear. When it started stalling on him I changed to a completely different clutch. The engine will idle fine when it is first started, and will sit and idle for 10 minutes or more on the starting grid but once it has a couple of laps then it will stall when he tried to stop the kart. I was thinking it was not dis-engaging the clutch.
I will put it back on the way I had it set up before and check the end play. I also have some new bearings I will replace the bearing. This is one I will carry along as a spare.
 
I would take it apart and check the disks for flatness. If it got real hot it can warp the disks so, check your air gap, you might try increasing the air gap to maximum. This is assuming your stall speed is where it should be and you keep the clutch clean.
 
Yep, think the problem has been found.
The gap between the discs is about .035. I took it apart and the floater looks like it has a warp in it. Out of a lack of any machine tools I laid it on a flat surface. When laid flat it has a slight rock to it. I flipped it over and it still laid a little uneven. I found another flat surface and laid it on that and it wobbles the same. It looks like it has a warp ripple in it.
I don't need it right now so I think I will set it back on the shelf for a while. Later this summer I think I will send it off to Mr. Martin to have it worked over.
 
All the way around. The high spot I found in the floater was toward the center. I have seen brake rotors with a high spot in the middle somewhere that will swell when it gets hot, this reminded me of that.
The bearing was good. I saw no burrs or flat spots on the rollers and it spins well.
 
You could add a .010 shim to open the clearance up. Then you would have .045 air gap . That might suffice until you send it in.
The shim goes under the pressure plate , pull the five center Allen head bolts pop it apart and reinstall. Seeing how you already had the floater out should be easy.
 
A few weeks ago I picked up a kart and a bunch of parts. I have not looked through the boxes of parts until today. I found a box of clutch parts. There are shims, snap rings, bearings and a couple of new friction discs and floater discs among a handful of other Bully clutch parts. I am going to try to talk to the guy we got it all from tomorrow, I will see if these are new parts or parts he took out of something he rebuilt. It might be a good plan to put it together with the new parts and shim it to set the air gap a little wider.
 
.035 is the optimal air gap for a Bully. I wouldnt pre-set anything past that

Id have to have the clutch in my hands to see, but some of the biggest problems I find in rebuilding clutches is that the pressure plate (where the springs attach) cannot slide easily up and down the spline of the drive hub, or the levers tend to be rusted/bent, and do not open properly and evenly.

Also, pull the basket off and check the drive hub shaft....a lot of times, they will get a hairline crack from end to end. If this is the case, then thats junk
 
I forgot to add to my post, when I pulled the allen screws out of the clutch to take it apart, it would not come apart. I am not sure of the names of the parts, but I had the basket off, pulled the allen screws and it should have pulled apart. I had to work it back and forth while I was pulling hard on it and it finally slowly worked apart. One of the shafts had a burr on the end that wouldn't let things slide apart. I polished it with emery cloth until it worked back and forth smoothly. The shafts I am talking about would be on the drive hub, it didn't want to come apart or go back together with either the pressure plate or activator plate. Not sure of the names of each part.
Also, I haven't had the clutch on an engine since early last race season so I cant check for sure, but I suspect the clearance between the clutch and engine were not correct. I had a spacer that went between the clutch and the engine, but reading what has been posted here prompted me to do some research, and I believe the clutch may have been tight against that spacer.
I believe I may be in over my head, time to go ahead and send it off to someone that has the knowledge and equipment to rebuild this thing the right way. I wont need the clutch right away, I have a couple of others I can carry with us for spares, I just don't like having parts laying around that are not in working condition.
 
Looking a t a friends of mines clutch. It doesn't say Bully on it so I don't know what kind it is. His grandson just started racing. He had a box stock predator on the rookie class. I believe he had the engagement speed all wrong. The clutch has very strong springs on it to start with. When the kid would gas it it would rev way up then grab. The clutch got very hot and would lock up. He ran it three races. I asked him if after the first raced he cleaned and greased the bearing and he said he didn't. He didn't know to. I got the clutch yesterday and was go to take it apart and take a look. I pulled the snap ring off and the drum must be galded to the hub.. it looked like it had a hairline split to me. I tried tapping it out with a brass hammer and did bust the hub. Should I be able to send it off and have it repaired. I can't get it apart. I used to use martinbuilt years ago. I just wonder if it got that hot is it worth fooling with.
 
Thats a yes and no answer .
Rebuild is say 75 dollars new hub 65$ then whatever else shipping both ways
Plus labour . A hillard might be a better choice or stnger .
Buy a used one use that for parts .
 
.035 is recommended air gap on the bully, pretty sure anything more than .050-.055 is when it's time for new disc's or to change the the floater to a thicker one to close up that air gap, I always put a pinch of grease on the thrust bearing and end play washers to avoid them overheating and keeping the clutch from disengaging....never have had a clutch problem that would end up pulling the motor rpms down when tooling around the track under yellow doing it this way...
 
bullerman said:
Looking a t a friends of mines clutch. It doesn't say Bully on it so I don't know what kind it is. His grandson just started racing. He had a box stock predator on the rookie class. I believe he had the engagement speed all wrong. The clutch has very strong springs on it to start with. When the kid would gas it it would rev way up then grab. The clutch got very hot and would lock up. He ran it three races. I asked him if after the first raced he cleaned and greased the bearing and he said he didn't. He didn't know to. I got the clutch yesterday and was go to take it apart and take a look. I pulled the snap ring off and the drum must be galded to the hub.. it looked like it had a hairline split to me. I tried tapping it out with a brass hammer and did bust the hub. Should I be able to send it off and have it repaired. I can't get it apart. I used to use martinbuilt years ago. I just wonder if it got that hot is it worth fooling with.
Click to expand...
You can cut the bearing race off and use a removable bearing race from SMC, or you can replace the hub, although new hubs are hard to get now.
 
He went with a different clutch but was just wondering about getting this one fixed. I didn't know if he cod send it off and get a new hub installed qith whatever we r else it takes to fix it.
 
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