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new chapter in motor teardown...

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T-maxxJared

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I opted to put the new piston and sleeve in my stock 2.5, so no problem, take the motor all the way down, clean it off perfectly, put it all back together triple checking everything was where it should be. Go to start it up, and pow bam clang whack thump. Yes, thats exactly how it went. I took the motor all the way back apart and checked for damage and everything seems to be ok, the motor only turned over a couple times and I stopped. The only thing I can figure and I think it's a pretty good guess is that the aluminum connecting rod has stretched a little bit. Oh well, I am going to have to get a new one of those too. I have learned my lesson this time, but on the next go around there will definitely be a whole new motor that is not a .15 going in.
 
Does it look like the piston hit the head or glowplug? Is there any visible damage at all?

I am wondering if it's a very tight piston and sleeve - try heating it up with a hair dryer for a minute or two before you run it and see if it runs.

If you opt for the new rod try e-bay there are guys that tear down brand new trucks and part them out. Usually it's a lot cheaper then buying new.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=44028&item=5978943308&rd=1&ssPageName=WDVW

The last one this guy sold went for $8.50.
 
Did it make those noises really loudly? Maybe you forgot a circlip in the piston or it or the pin is scraping the ports... been there, done that...
 
No visable damage, but see 2 paragraphs below for what I did see. The noise was definitely loud, or at least noticable, if you hear it you know instantly it's a sound that shouldn't normally be made out of this engine, and that's the first thing I checked was to see if the jesus clip was still in the piston to hold in the wrist pin, I have had that mishap on a motor I built for my mud jeep once. It was still in there properly, and the bearings were fine, I cleaned and re-oiled them when I re-built it the first time this afternoon but I checked them again anyway.

Should there be any play at all in the hole in the connecting rod that the wrist pin goes through? It's not visible, but you can feel it just a little bit when you push and pull the piston/connecting rod in opposite directions. I don't think it is that big of a deal, but I don't know, at 35,000 rpm or whatever these things turn, maybe it's the kiss of death.

I took a closer look when the head is off and the new piston/sleeve is so tight that when you rotate the motor by hand with the head off, at the very top of the stroke when the piston is about 3/16" or so from the top of the sleeve, the sleeve will lift out of the crank case with the piston for about 1/16-3/32" and go back down. I think that I may try to put the motor back together and somehow warm it before I fire it for the initial break in so maybe these parts will contract enough to break in properly and hopefully be ok from there. When the motor made the loud noise, I had my hand on top of the head and you could feel a vibration that wasn't normal, which kind of makes me think that the connecting rod could be fine, and the piston/sleeve fit is where I need to be giving more attention. The motor has only had about 2 gallons run through it, so I am just a little surprised that the connecting rod would be stretched to the point of being un-usable this soon.

Any more input would be great, I really appreciate the insight of those who have done this more than once unlike myself, thank you again
Jared Williamson
 
Last edited:
Please refrain from starting another thread to get help. Simply wait for a response.It will come as there are many who are knowledgeable of this motor.

Now this is a used motor but you put in a new Piston and sleeve? ARe you certain that everything was re-assembled properly?
 
I'm sorry about that other post, it won't happen again. I followed the how-to guide on the traxxas website for rebuilding the 2.5 and just to make sure, I took the motor apart and re-assembled it twice after the first time and I got the same result.
And yes, this is my used motor that has had about 2 gallons of fuel run through it that I am trying to put a brand new piston/sleeve to revive.
 
well I have seen that rebuilkd done but with the Siro piston and sleeve and it was a screamer! Not sure if you did stretch the con rod. Never took mi old maxx mill apart that far. I would take it to the LHS to ask a mechanic if you can't figure it out. Better to stop running it till you know
 
Jared you can NOT be NEAR ME any more....My bad Mojo rubbed off on you....run while you still can....LOL.....seriously..... :JK: but for real no stay
 
If you have ever eaten at that mexican joint Celito Lindo's on the corner of 6th street and Dixie, it has the same effect. I think their food contains ingredients to make a bomb, because thats what you get about an hour or 2 later.
yeah, I was sitting @ my desk last night around 3:30 and the fx wasn't doing much, so I couldn't take it anymore, had to try to fix the truck since the parts were in front of me. Still interested in the sleeve pincher guy though.
 
I didn't go to the track tonight and I didn't hear from him so he's probably still in Jupiter.....he said he'd have my mill done for saturday......before I go pick it up I'll see if I can't pick up your P/S........and I eat Celito Lindo's all the time love that spicy stuff......And when I pick it up I can take a look at your mill and see what's up if you didn't go to the hobby shop before then......did it stop when it made the load noise or did you stsop it?
is/was it locked?
check the button under the head (the part where the plug screws into) and see if there is ANY scars....all that metal should be smoother than ya baby sisters ass cheek....look at teh edges of the piston head for ANY nicks even the tinniest little peice can make hell noise...
lines / grooves in the sleeve or on the side of the piston head?
does the conrod have an oil port to the bushing?
is the port facing the right way?
the crank turn smooth when everything is out?
push on the rear main bearing w/ a little pressure and feel the race...is it like glass or are there rough spots?
If all that checks out I'd fire it up again.........
 
did you dry the parts out when it was dissasemled and then not oil it all before reassembling it?
 
Plaidfish said:
did you dry the parts out when it was dissasemled and then not oil it all before reassembling it?
Click to expand...

You beat me to it...I was about to ask if he oiled the parts before reassembling it.
 
-I made a point to wash everything in alcohol and blow it all dry and used after-run oil on all bearings and when I reassembled all parts with metal to metal contact. I took out the bearings and took the seals off, cleaned, and re-oiled them. The crank turns smooth as a babys bottom when the rod/piston is not hooked to it.

-there is an oil port in the side of the connecting rod, and I have it facing the big counter weight of the crankshaft, this is what the traxxas web site said to do.

-no nicks or dings in the piston, and the sleeve has a little bit of wear marks where the piston gets really tight at the top, but they are uniform and progressive, they don't look out of the ordinary.

-The motor starts and runs making the noise it was before, and I shut it off, it didn't shut itself off. I think I am going to take a heat gun and heat it up for a little first, and then fire it up and see if it makes the noise.
 
have you ever had one of your motors or heard of anyone else besides mine make an ackward sound like this on the first start-up after you had it pinched or re-sleeved?
 
Did you remember to put the shim under the head? I have never had one of mine do this but that doesn't mean anything. I would double check everything and try it again. Preheat if you have to.
 
The shim is there, and in fact I just replaced it with a new one when I rebuilt everything, and made sure it was the same thickness as the stock one. I am going to try to preheat it on the first couple tanks of break-in, and hopefully by then everything will be mated and worn in together and this will be over with...
 

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