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Please help. Eating one way bearings????

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WAOrevo

RCTalk Rookie
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RC Driving Style
  1. Bashing
  2. Racing
I am in the process of breaking in my .27 sirio, the first three tanks went fine. After i had to do a 3/4 throttle for a few seconds the truck just felt bound up. The engine was running about 225-235. I decided to check everything out and when i did i found that my OWB was completely trashed. i have the trx ez start on the engine. i cleaned the stub shaft up and all the fragments of metal and installed a new OWB. I proceeded to do 3/4 throttle bursts and the same problem, engine was lugging and would not spool up properly. Checked the OWB and once again it was trashed. What is causing this??? There is a little in and out slop and up and down slop on the stub shaft. I'm almost sure it should not be like that. Can you not run a trx ez start on the sirio? it bolted up perfect. I am certainly not a pro and i really need some help with this guys.
 
I am in no way an expert on this but it is my feeling the EZ Start can't handle that big mill or the OWB is a lot bigger than the shaft and is wobbling around and wearing itself out.
 
RC Addict said:
I am in no way an expert on this but it is my feeling the EZ Start can't handle that big mill or the OWB is a lot bigger than the shaft and is wobbling around and wearing itself out.
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I thought that as well but its not the case. A fresh bearing fits perfect. I also put a micrometer on a 3.3 stub shaft and the difference was less than 1/1000of an inch. On the other hand the big engine has so much more torque it could be killing the ez start. I DONT KNOW.
 
A lot of the BB engines bust up OWBs, especially during the break in. A little research tells you that the manufacturer recommends a pull start since the shock of an electric starter tends to crack the race. You'll also be amazed how much quicker they start, since it's not geared down.
Loosening the Glow plug is the only way around the OWB problem, for now.
 
Is there extra space in the electric starter for the hex of the shaft to push back into? I know that some engines need a spacer to hold the shaft closer to the back-plate. If the shaft is pushing into the starter, then only a portion is left inside the one-way causing it to fail. Something to check out anyways. If that doesn't cure the problem, I would go back to a pull start, they are much less damaging to the engines one-way and internals, as mentioned.
 
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Well ill just put the pull start back on. thanks for the help guys!
 
What pipe are you running? The stock blue pipe and resonator are supposedly too restrictive for the S27. Could be a reason for the restrictive running. I have seen people post that problem before.
I can't see how a bad OWB would affect 3/4 throttle, as opposed to problems starting it and on low-mid throttle as well. But someone please correct me on that if I'm wrong. It is suspicious though to have another bound up OWB at the same time.
 
LBSinGTX said:
What pipe are you running? The stock blue pipe and resonator are supposedly too restrictive for the S27. Could be a reason for the restrictive running. I have seen people post that problem before.
I can't see how a bad OWB would affect 3/4 throttle, as opposed to problems starting it and on low-mid throttle as well. But someone please correct me on that if I'm wrong. It is suspicious though to have another bound up OWB at the same time.
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I am running the blue pipe. What is a good pipe for the sirio? Low- mid throttle is awesome, sick wheelies and mad power. After half throttle it gets super sluggish.
 
That sounds more like a tuning problem, like it's too lean on the HSN.
 
Extreme RC Mods said:
Is there extra space in the electric starter for the hex of the shaft to push back into? I know that some engines need a spacer to hold the shaft closer to the back-plate. If the shaft is pushing into the starter, then only a portion is left inside the one-way causing it to fail. Something to check out anyways. If that doesn't cure the problem, I would go back to a pull start, they are much less damaging to the engines one-way and internals, as mentioned.
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That's the problem. My O.S. 21TM suffered the same problem. A slice of fuel tubing behind the OWB, inbetween it and the plastic roto backplate solved the problem. It rides off the end of the starter shaft and gets caught at roughly a 45 degree angle on the shaft. instant destruction. A 1/10th shock piston or the fuel tubing do the job. no more issues..

WAOrevo said:
I am running the blue pipe. What is a good pipe for the sirio? Low- mid throttle is awesome, sick wheelies and mad power. After half throttle it gets super sluggish.
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too lean on the HSN, too soon. wait for it to loosen up.
 
Too small of an exhaust will give you that low/medium power with no top end. I bought a single outlet rd logics big block setup for my s27 and it rocks.
 
Well i found my problem.. I dissasembled the engine to check and see if there had been any damage done. The piston still had a real good pinch and everything looked ok, except for the stub shaft.. the shaft had about .008in play up and down in the backplate bushing.. also it had back and forth play. after a lot of measuring and a long night with the lathe and mill i made a new bushing for the stub shaft to take out most of the play. it only has one half of 1000ths inch play up and down now and the same on in and out play. polished the stubshaft and put it all together. I put my pullstart on and a new fuel tank which turned out to be leaking... ran the truck for about one whole minute before my throttle servo crapped. haha it ran awesome all the way up and down. maybe it is fixed???
 

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