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One-way bearing slipping on Tmax

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Old 06-17-2003, 02:27 AM
  #1  
Doug Brindle
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Default One-way bearing slipping on Tmax

Help!
I've been flying airplanes for 17+ years. I got a Tmax in April last year... and have put maybe 8 gallons of fuel thru it. I use airplane gas and mix 50-50 with car gas. Engine runs great, but the pipe is leaking air a little bit lately - sounds like it's wheezing like an old man when it's running... I'm just too lazy to fix it.

Here's my problem. I'm on my second one-way bearing (and the shaft it slides onto) in the truck. The one-way bearing doesn't grip the starting shaft very well at all, and it slips, making it impossible to start the engine. I take the back end of the engine off, clean the bearing and shaft with a paper towel - and the thing works great - starts right up. After I put a tank of fuel thru the truck, the bearing and shaft get oily, and the bearing slips on the shaft again. Clean the shaft off again, and the truck starts up just fine. I'm just tired of cleaning the bearing every time...
Is this a common problem? Is there any good fix? I shouldn't have to buy new bearings/shafts twice a year??
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Old 06-17-2003, 02:38 AM
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Default I don't know if it's normal or not but,

I have read that many have had this problem with the oil! Maybe it needs new engine bearing?? I have read that some members of this forum have drilled holes in the E-Z start casing to let the oil drain but, I have also read that some say it will cause other problems with dirt and such! If you could drill holes and put some sort of cap on them so you could clean out the oil with some carb cleaner or nitro wash between runs?? Just a thought!
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Old 06-17-2003, 11:56 PM
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Default yep

Not a bad thought....adding a drain/cleaning hole.

I spent some time looking at the part last night. I think I figured out the problem. The brass/bronze bushing that the starting shaft rides in, is a little worn. It should have a nice tight-slip fit. It's a sloppy fit. I'm going to look for a sealed bearing to replace the bushing, and pop it in myself....or I'll just turn /jig grind a new bushing, and install it myself. I guess I could just buy a new backplate, but the Traxxas website is down, and I can't remember thier phone number, and I lost my instruction manual.

I was looking for an o-ring that I could install to help seal the oil out, but I don't think they make o-rings that'll withstand 250 degrees of heat, and rubbing at 10-12k rpm....or at least they won't be very cheap.
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Old 06-18-2003, 02:15 AM
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Default Tower has them!

http://www2.towerhobbies.com/cgi-bin...?&I=LXJL96&P=Z

And if you need a new starter shaft here it is as well!

http://www2.towerhobbies.com/cgi-bin...?&I=LXJL99&P=Z


Oh, and a back plate gasket!

http://www2.towerhobbies.com/cgi-bin...?&I=LXJL65&P=Z

P.S. it says TRX .12 on some of these but, I belive they are the same part!
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Old 06-18-2003, 04:28 AM
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Default One-way bearing slipping on Tmax

the savage uses and o ring design on the back plate. Maybe the sizes available are compatible. just a thought, i've used some traxxas parts on my savage (oh-no.. that may be a sin in savage circles...lmao)
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Old 06-18-2003, 09:11 PM
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Doug Brindle
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Default thanks.

Thanks for the heads up on Tower's prices... I never thought to look there....

Tower's prices are a little cheaper than Traxxas direct. The pictures look like the parts are OEM... shipping should be similar pricing...

-Doug
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Old 06-19-2003, 02:51 PM
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Default One-way bearing slipping on Tmax

My Tmaxxs had the same problem. The way I fixed it is by drilling a small hole on the bottom of the easy-start housing.

It turns the motor every time now. Also, do not over-prime your engine and use 3-in-1 oil.
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