Bearing dilemma!!

[Bkyd Basher]

well i went through my second set of bearings, well just the inner actually. Ball bearings came right out of the race and went out the exhaust i assume. What could be causing this?

 

[2revo1maxx]

Lean tuning.

 

[Bkyd Basher]

well if so i can't understand why, wasn't idleing high, wasn't ever cutting out like it would if to lean and the temps never got over 250-260 since i put the new bearings in. And if it was to lean it would look like u beat the top of the piston up?

 

[joshman1204]

well if so i can't understand why, wasn't idleing high, wasn't ever cutting out like it would if to lean and the temps never got over 250-260 since i put the new bearings in. And if it was to lean it would look like u beat the top of the piston up?

What fuel are you running? If you are running a very low oil content then too lean can actually be a very small window and you may not even know you are too lean until it is too late.

I run VP 30% fuel with 9% oil and if I follow robins tuning guide to get it just right it is only running about 230-240 on a near 100 day. So depending on fuel you could still be way lean at 260. Granted its very unlikely but I just wanted to point out that temps should only be used as a second opinion when tuning and should not be the sole basis for a tune.

If you havent already read the guide on robins site and learn it like the back of your hand. Once you get it down you wont even need the temp gun anymore.

 

[Bkyd Basher]

we r running S&W 30% fuel. And i know what ur saying about tuning to temps. I try and tune from ear and performance and second check with the temp just to see what its running with those settings. But like i said i never heard or noticed anything weird in the way it ran. Anyone know where i can find a pic of what pre-detonation looks like on a piston?

 

[joshman1204]

I dont know about the pic but what plug are you running with the 30%?

I read a good thread by robin somewhere that explained how the temp ranges of the plugs affected the timing of the engine. A hot plug essentially advances the timing and a colder plug will retard the timing. If you are running a hot plug with the 30% fuel you run a good chance of causing problems due to the higher fuel content and the timing advance caused by the hot plug. Make sure if you are running a high content fuel that you run a good medium plug such as a MC-8.

I very well may have misinterpreted robins post but I think I got it right.

 

[Bkyd Basher]

i am running a traxxas medium plug

 

[Zdragon71]

Try running a cold plug with the 30% also get a good set of boca bearings. As far as plugs go you need a medium or hot plug with 24% or less to burn off the higher methanol content and a cold plug for 25% or more nitro.

 

[joshman1204]

I run a medium plug with 30% in all of my rigs with no problems. It honestly sounds like you may have just had some bad luck with bearings. I would just get a new cheap set and make sure you get the shields facing the right direction. I honestly wouldnt spend the coin on boca bearings in your situation even though they are badass bearings.

If it was me I would get a new crankcase off of ebay with bearing already in it for about $20 just incase there is something stupid wrong with the crankcase.

 

[2revo1maxx]

Only the most extreme all-out racing engine will need a cold plug.
What engine is it anyway?

 

[Bkyd Basher]

just a 3.3. Which way should the sheilds be facing? both of mine have came out in pieces.I mean the top of my piston looks lkie someone put a little screw in there and ran it. So i would assume that something went in there or its like pre detonation or something. Should i get a pic for yall to look at and maybe be able to tell better?

 

[Punisher]

Detonation will leave marks such as you have described.

If you are using 30% you should have a .40mm head shim . . .

http://www.ebay.com.au/itm/Traxxas-...Control_Parts_Accessories&hash=item35bf7ed468

 

[2revo1maxx]

How bad were the bearings last time they failed? Did you get a new block?
A lot of people don't realize this, but the fit between the crank scoop and block is critical. It works like a rotary valve and if the bearings are allowed to get too loose the block will get worn as a result.

 

[Bkyd Basher]

Well the first set locked up the motror. When i took the crank out the bearing fell out in pieces. Inner race and all the ball bearings. The outside case of the bearing was still in tact and was tight to get out till i heated it up. 2nd set also went in snug, and the same exact thing happened. And i really flushed the block out and blew it out good with compressed air. I am gonna get a pic of the piston in a few minutes for ya to see. Not real worried about it cause i just recieved a new one in the mail but i dont want it to happen to this motor if its something I'm doing, but maybe it was a fluke.

 

[Bkyd Basher]

Not a great pic and it wasn't that bad till this second time

 

[nitroroosta]

what kinda pipe are ya running? Do ta have good back flow pressure with it?

 

[2revo1maxx]

That does not look good! It is hard to tell because the bad bearing could've done most of that damage, but I think it was run too lean.

 

[Bkyd Basher]

i was just running the stock resonator, but just purchased an aftermarket pipe and header so i dont have to mess with those stupid rubber couplers. Well as i said i got my new motor in and about half way broke in. I will make sure shes running rich enough this time.

 

[Bkyd Basher]

So as i was swithcing over everything to the new motor, i noticed a crack in the motor mount. So i went and bought the whole assembly. I powder coated that and the new braces that mount the engine mount to the chassi. As i was switching them out i found that one of the brackets i just descibed was broke also. Question is,is could that maybe have put more stress on the crank bearings causing them to fail?

 

[2revo1maxx]

Nope.....