Stock S-25 gearing. Can the spur melt from overheating?

[MustangMan]

Hey guys...

I got home from work yesterday to find my 12 yo son running the Savy in the back yard (freshly cut short grass) without my permission. :argue:

I told him it's doing wheelies now and he wanted to see for himself. Well, after chewing him for not asking permission and also not CHECKING TEMPS I told him to shut it off and bring it back to the garage.

On the way to the front of the house I hear the engine just rev like mad. I tell him to kill it, thinking he stripped a wheel hex. :shrug:

When I get the body off I find the stock 49T spur stripped/melted.

This engine has never been out, factory "mesh", and the S-25 has about 12 tanks through it, literally, that's all...

So why did the spur go away? I'm thinking the heat. It felt pretty hot when I pulled the body off (I temped it as soon as I pulled the body and it was at 264).

I don't think the clutches are damaged since the cb seems to spin easily. Oh, and the slipper is set to stock specs.

I've got to get me another spur gear now and dreading the thought of setting the mesh. I may just pull the trans out to replace the spur like I mentioned in another post.

What do you guys think?

Thanks...

 

[1500valk]

maybe the slipper clutch was not tight enough. I know that can melt a spur gear in no time at all. Running in grass creates more drag on the drive train, and if the slipper is not tight, the spur spins faster than the transmission, and the slipper creates a ton of heat.

 

[beason]

are the teeth melted or the center?? if you rev it and the truck wont go (ie, stuck in a hole, against a wall, tring to climb,) the cb will get way hot.. then when you kill it, it will set at one place on the spur and melt the teeth, mine did that. if i woulda kept driveing it prolly would have not melted.. if its the senter then the slipper wasn't tight enough and your wheel hexes are prolly fine..

 

[rossb]

I've stripped two spurs over the course of 2 seasons. Both times this was caused by having the slipper too tight when running hard in the dirt. If the slipper is too tight excessive force in the drive train will have nowhere to go and the plastic teeth on the spur will give way. Make sure to check the brass spacer on the front of the clutch bell. If the spacer is worn the clutch bell will shift forward and back on the crankshaft. Replace the brass spacer if it shows signs of wear.

Just last night I pulled the motor to replace my 47T spur. It only takes a few minutes to set the mesh. This seems much easier to me than pulling the trans. I shine a light under the truck and eyeball the mesh through the side of the TVP. After I tighten the motor I eyeball it again and spin it to see how it feels. If it is binding the mesh is too tight. If it is noisy the mesh it is too loose. The teeth should mesh closely, but there should a slight spacing in there so that it does not bind up. Take your time, watch what you are doing, and you should not have any problems. Pulling the motor also gives you the opportunity to clean up all the grime that always makes it to the bottom of the motor and the motor mounting plate.

 

[digger]

Yeah, I could see a kid against a wall or tree trying to climb it. That would explain the engine being hotter too? (No air flow over the head.) I would check the clutch shoes too. Look at the clutchbell and see if there is plastic melted to it.
Not that hard to set the mesh. Paper in between the gears, hold the engine against the spur gear while ya snug the bolts. Then tighten. Sooner or later you will probably be changing the gearing, than you will have to set the mesh.
Most guys keep an extra spur gear. I'm not one of them. But my next rc order...

 

[beason]

mine did it when i got stuck in a ditch on some limbs, couldnt see the truck was hung up and was trying to get out.. when i walked over there i had to kill it so i could untangle the limbs and crap. once i got back to the garage my spur had a little spot on it about 3 teeth that were deformed.. its still on there though.. still going.. doenst bind or anything..

 

[MustangMan]

I'm at work so I don't have pics until tonight, but the teeth are completely gone all around the spur, it's not just in one spot. The grass is pretty short and we don't have any trees in the yard. He's pretty good with RCs (he has his own RS4 and MT2) but I think he got carried away wanting to see it wheelie...

I guess I'll pick up a couple of extras and start setting the mesh. I've got to learn some time! I'll check the brass spacer too, I read the other post about it and I haven't checked mine lately.

I've got the new HPI Bronco body on it, but I don't have a hole in the windshield, just the rear of the body open. It's usually been fine for bashing, but he might have been doing a lot of rpm in short runs to get it to wheelie and it got hot quick.

I'll post pics tonight, and check the slipper again too.

Thanks...

 

[Carbon_Savage418]

I'm surprised my stock spur (52T) has lasted for almost 3 1/2 years (knock on wood)

 

[Tweak]

The stock spur on my RC10GT lasted about three days. Now I got a couple extra in my pit box. I just don't understand why they attach plastic parts to n extremely hot engine. I guess plastic is more forgiving and pliable than steel.

 

[jon2]

You should be able to push the car about 3 feet with a properly adjusted slipper. If it goes too far than it is too loose. If it doesn't move far then its too tight. I have burnt out too many clutches having it too tight..

 

[rossb]

You should be able to push the car about 3 feet with a properly adjusted slipper. If it goes too far than it is too loose. If it doesn't move far then its too tight. I have burnt out too many clutches having it too tight..

Are you talking about pushing the truck with the engine off? The slipper has nothing to do with how far the truck will coast with the motor off. That is related to the one-way in the transmission, the diffs, drive cups and bones, and your brake adjustment. When you push the truck forward the spur and slipper may not even spin. The one-way in first gear inside the transmission free-wheels when you coast forward. There should be nothing stopping the truck from coasting forward otherwise you will stress the clutch and drivetrain.

 

[MustangMan]

OK guys, here's some pics. Sorry for it being so late, had some deadlines at work I had to stay and finish...

I pulled the engine (as you can see) so soon I will no longer be a virgin to setting gear mesh!

Here's the stock three shoe clutch, looks fine to me with but 12 tanks on it. Clutch bell was fine, bearings and brass spacer we're fine, though I might get the Ofna shim kit before I put it back together:

Here's the spur gear from the engine side. You can see the spur and clutch bell weren't 100% touching from the factory (as far as clutch bell depth goes that is) leaving a small edge to the spur. The damage is even all around:

Finally, here's the slipper pad side. Just a bit of glaze around the center of the pad, but not burned, torn, melted, or anything out of the ordinary:

 

[RatzoRC]

I didn't read the above posts cause i'm tired.

Either your mesh is too loose, or you caught a small rock (and I mean small), in your spur gear.

I think it's a mesh problem.

 

[beason]

well you stripped your first spur.. good job.. you could also have a rock or something wedged into the axle or arm and that could strip it to.. make sure you get it tight when you put it back on.. just close enough it doesn't bind..

 

[MustangMan]

Ratzo, now that you're rested...

It was "factory" mesh, never had the engine out and all fasteners were tight (engine, trans, tvps)...

The truck rolls freely and I already checked the dogbones, outdrives, and wheels for any blockage or obstructions. Nothing to keep it from moving...

Beason, I presume you meant to say "get it right" not "get it tight" :boxing:

Thanks guys, I'm not going to be able to get to the LHS until Friday or Saturday, but I'll let you know how it performs once I get it back together.

I'll be sure to pick up an extra or two or three since this will be my first replacement! :hammer:

 

[sweetdiesel]

Here is how I set my mesh exactly the same everytime. First cut a strip of paper (I use 20lb)about 5 inches long and a little wider than the width of the spur. Double it up and stick between your spur and CB. Tighten down your 4mm engine mount screws until they are nearly snug, now back each of them out 1/2 turn. Using a metal rod, (I use a set of punches that have flat ends), lightly smack the side of the engine mount near the base and towards the screws using a hammer and the rod. Lightly tap them until the spur and cb are nice and snug against each other. Now go back and tighten the 4 engine mount screws. You should be able to roll your spur and the piece of paper will come out looking like an accordian. The spur should roll smoothly and if there is any binding check the spur gear for rough spots in the teeth.

 

[MustangMan]

Well guys, picked up another 49T spur today (two actually) and got to cleaning and repairing the Savy...

First attempt with the paper trick was too loose...

Second was too tight...

Third attempt it felt right and the engine was straight. I felt one spot where it kind of grabbed, but couldn't see anything...

Filled the tank up half way and let the Rotostart rip...

Ran the whole half tank and the spur looks like it just came out of the package still...

I guess I got it OK...

Thanks again for the tips and the "hand holding"....