JUCD VPR

So I have not ran my FG MT in like a year, everything is awesome on the truck EXCEPT for one thing which i need a little guidance on.

So on the FG MT the shaft that goes from the spur gear through the brake and into the rear housing, that bearing that is in the rear housing keeps coming out and I have to pull the whole rear of the truck apart to push that bearing back in the housing by the rear gears, it's the bearing that is on that shaft, the bearing is fairly new and visibly there looks like nothing wrong, but once I put it back together it pops out after about 30 seconds of running the truck, this has happened to me 5 times now and it's a pain in the butt and it's getting frusterating taking the truck aprt and putting it together just to happen again. Any ideas on whats going on or how I can get that bearing to stay in there?

mradlin

Sounds like the bearing recess is a little worn(loose) You could try putting a little bit of loctite around the outside of the bearing then put it back in. Or buy a new carrier?

SAVAGEJIM

Yes, the recess in which the bearing goes into the engine mount is worn, and it must be replaced as the hole will continue to wear. Loctite or CA or even JB weld will temporarily fix this, but sooner or later, the bearing will work free again.

I assume you have the plastic carrier/engine mount. Replacing that should be pretty cheap.
Engine mount with recess for holding the bearing:
http://www.largescalerc.com/index.as...OD&ProdID=1390

If you can, I highly recommend you go with the the alum engine mounts and gear carriers:
The alum version of the left side mount (the one you are having problems with) is 66215.
Ther alum right side mount is 6485/1 http://www.largescalerc.com/index.as...OD&ProdID=1295
And also, try to get the alum gear carrier (that goes on the engine and holds the CB in): 7474.

I recommend these because the primary reason why these bearing recesses would were out is from the higher torques your engines could be producing. You might have hopped up the engine with a head kit and mod, a pipe, and.or even dropped in a much more powerful engine than the stock one. And the torques of these engines will put all sorts of torsional stresses on these parts, and plastic for what it is, flexes and gives much more easily than alum parts do.

davido666

I had the same problem. The gear that turns the diff gear is suppose to hold the bearing in. There should be a space between the bearing and the pinion gear. There should be 3 set screws that hold on the pinion gear to the shaft. Use loctite to prevent the set screw from loosening. If the pinion gear moves away from the spacer the bearing will move out. The bearings used for the shafts should be 7mm wide. When I bought my chinese clone the bearings were only 5mm wide which alowed the shaft to move and the bearing would fall out of the motor mount. You should have a couple of thousands space between the bearing and spacer. I even put a few drops of loctite on the shaft before I slide on the pinion gear. The only thing is the gear is hard to get off next time you need to take the truck apart. I use a gear puller to get the gear off when I need to work on the truck. I find blue loctite works great for this method.

SAVAGEJIM

For pulling the bearing out of the plastic carrier, I find that putting one end in a vise and applying bending torsion will strain the plastic enough to break the CA bond and even help loosen loctite, and the bearing will come out by using a tuning screw driver to reach in between the plastic and the bearing. FG plastic is rather resilient and you can put alot of torsion on it before it breaks or permanently warps to uselessness (i.e. it has a high elastic phase before it goes into a plastic phase).

If he has a modded engine or a larger displacement engine, like 28cc and above, the torque is still going to give him sproblems of warping the bearing recess. And as it warps, the bearing will begine to move, out of position of course, and even start to move in a harmonic motion up and down or side to side, depending on how the recess is bing ovaled from torsion.
Shims will keep the bearing in the recess, but the bearing moving in the ovalled recess will cause other problems. The recess will get more and more ovalled from the bearing moving inside it and weraing the recess larger. And the shaft will also put torsion that is perpendicular to the shaft moment vector (I dont know if you know what this means, I cannot describe it in words without showing a picture) on ther other bearings on the other carrier for the pinion that power the diff outer gear. All the while as the shaft is being toqued up and down or side to side, the meshe is also being thrown off, and likewise the mesh is becoming to tight and too loose depending on which way the shaft is being torqued over to.

This is why I suggest he try to upgrade to the alum alloy engine mounts and grea carriers. I find that even the stock Zen 26cc engine has enough torque to torsion the plastics. For the 23cc engines, no need to upgrade anything, the torque is not that bad at all.

JUCD VPR

THANKS, that is the answer I needed, I really appreciate the help. I have the 26cc with a DDM mid-high tuned pipe, steel gears, and a few other minor hop-ups on it. Makes sense the hole would wear out and expand under the torque. I'll try to order some new ones asap and get this baby up and running again. Thanks for the help.

SAVAGEJIM

NP, I more or less discovered this the hard way. In my 2WD, I slapped on a torque pipe onto the Zen G260 (26cc). Wheelies actually started to come with the pipe upgrade and going with off-road gearing of the 16T/48T combo, but as a result, I noticed that the plastic engine mounts were taxed and the gear carrier too was making for some "mushy" feel (that is the best I can descrie it) during full trigger accelreations once the engine's torque curve kicked in. At first I though my mesh was off, but the mesh was perfect. But my suspicions of mesh coming loose is correct especially when the platic parts bean to warp under load.

splcrazy

now im getting scared lol , im going to upgrade my fg mt engine on the weekend and now im reading this , so what i should now get is the CB carrier in alloy is that correct, does DDM sell the upgraded alloy carriers ?

SAVAGEJIM

I believe so. I bought most of my upgrades from FG Supply and LargeScale RC, and get most of my supplies (oils, grease, air filter supplies, plugs, two stroke oil, etc.) from DDM. Give DDM a try, I am sure they have it. If they are sold out, I know FG supply will have it. And I think LSRC might have some more on the way (I think it said out of stock the last time I looked, but I could be wrong, it might have been something else I was shopping for. I cannot remember, sorry).

All three of these stores are great, whichever you buy from, they will deliver and you will not be disappointed.

splcrazy

you have to pm me with those shop sites for the FG MT , i will have to eventually change those parts you mention as i know it will have to be done , just like i had to do that to both of my baja5b's when i converted the engines to horsepower beasts , it will last a while on plastic carriers then eventually they wear out and stretch . DDM doesnt carry a big supply of FG MT hopups maybe a few but nothing great , they are more focused on the 5B 5T