Do I need to replace the engine

[Jacobg45]

Ok so I got my Revo back around 2017 from a friend who sold it to me for $5 because he didn’t want it anymore and it was not in great condition. I’m not sure how old it is but it has the 2.4 ghz TQ 4 channel controller so I think it’s the 5309 2010 model. I fixed it up and ran it a lot and it ran fine but I recently have noticed that it is hard to start and it has been breaking exhaust headers (I eventually got the spring one) and has had other seemingly vibration related problems such as losing screws on the bottom of the engine mounts. I also noticed that the crankshaft seemed to wobble a little bit and I don’t know if this is normal but it didn’t seem good. I recently got a new cooling head because I had stripped it out and when I went to start the Revo it seemed hard to turn over and it was leaking a lot of fuel through the crankshaft bearings (I assume), so I went to take it apart and when I got to the backplate i noticed it had sheared itself in half (pictures below). When I tried to take out the sleeve, it wouldn’t budge even when heated with a heat gun. I eventually had to use the zip tie-exhaust port method, and it was very hard to take out even then. I eventually got it out and pulled out the piston and when I tried to take out the crankshaft it wouldn’t budge. I had to tap it out with a wrench but the inner bearing exploded and came with it, leaving the outer bearing ring stuck inside. (See picture below) I also tried the compression test and I’m not sure if it needs to be replaced. I’ll post pictures of the piston below. It also has black coloring on some parts of it which I have seen from similar posts is bad. This is my first forum post so sorry if I made any dumb mistakes.








The images aren’t showing so here’s another link: https://imgur.com/a/0yiPVZE

[corneileous]

That piston’s pretty black man, I’d either rebuild it, send it back to Traxxas as a core using the Power Up program for a new motor minus the easy start or just do like I did and opt for the OS 21TM motor.


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[corneileous]

Oh and I might add, my piston in my ten year old motor wasn’t near that color of black but it eventually got to where it wouldn’t hold compression once it warmed up and other than my old Traxxas motor just being neglected, I highly doubt it was ran as hard as that one obviously looks like it has.


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[Jacobg45]

Ok thanks corneileous that's what I was gonna do (traxxas powerup). I also read your other posts about your engine and yeah I don't think that's a good color. Also the piston was able to be pushed out of the sleeve by like .5 - 1 millimeters as seen in the picture but I don't know if it's supposed to get pushed all the way through the sleeve to be replaced or if it should already be replaced.

Also I realized that I forgot to post the pictures of the sheared in half crankcase backplate so I'll do that in a little bit when I get on my phone.

[corneileous]

Ok thanks corneileous that's what I was gonna do (traxxas powerup). I also read your other posts about your engine and yeah I don't think that's a good color. Also the piston was able to be pushed out of the sleeve by like .5 - 1 millimeters as seen in the picture but I don't know if it's supposed to get pushed all the way through the sleeve to be replaced or if it should already be replaced.

Also I realized that I forgot to post the pictures of the sheared in half crankcase backplate so I'll do that in a little bit when I get on my phone.

Yeah, it’s a good deal if you’re wanting to do everything original. I used it once already to upgrade my radio and receiver to the newer digital stuff and even got the Bluetooth Traxxas link module with it.

As far as motor rebuilding, I can’t help ya there because I haven’t ever done one but if you do end up taking advantage of the power up program, just put your motor back together with the old cooling head on it but I’m not sure if they make you reuse your old carburetor or not.... you’d have to go to the Traxxas site and make a copy of the form that you have to fill out but I wanna say you do get a new one but I can’t remember because I just went with a whole new aftermarket motor.

But I do know you’ll have to keep your original back plate- the part that bolts to the back of your motor what either the easy starter bolts to, or if you plan to use the pull starter but if you said that piece was cracked, you might as well just order you a new one and while you’re at it, I would get a new one way bearing as well being that I just found out that Traxxas actually recommends cleaning and re-oiling that bearing after you’ve gone through a half gallon of fuel so you might wanna get one of those regardless because of it ever seizes up on you, they’re a bear to replace. I had that happen to me a couple of weekends ago and it involved about an hour of my time and my dremel tool with a cutting disk just to remove the old bearing.


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[olds97_lss]

Ok thanks corneileous that's what I was gonna do (traxxas powerup). I also read your other posts about your engine and yeah I don't think that's a good color. Also the piston was able to be pushed out of the sleeve by like .5 - 1 millimeters as seen in the picture but I don't know if it's supposed to get pushed all the way through the sleeve to be replaced or if it should already be replaced.

Also I realized that I forgot to post the pictures of the sheared in half crankcase backplate so I'll do that in a little bit when I get on my phone.

It shouldn't come out the top of the sleeve at all really. If it does, it means it's very worn and when the engine heats up, it will be even worse.

These were some I had that I had repinched:


They would have constant flame outs for no reason and had weak compression.

This was after having them repinched:


Considering the wear and damage to yours, I'd definitely just replace the entire engine.

[Jacobg45]

Ok thanks! this information helps a lot. I'm going to eventually drive to hobbytown and get a new one through power up. Olds97 lss Is that as far as you could get the piston to go with your hands? I pushed mine as much as I could get it with my hands and I got like .5 mm over the top if that. I'm going to replace it anyway I just want to know for reference.

[olds97_lss]

Yep. With a bit of ARO on the piston, I was able to push them up through the top without a lot of effort. The "after" photo's was similar.

The difference with the 3 I had done was that the con-rods had zero slop, the engines still looked/felt like new inside and they all had alloy carbs that worked well. So spending the $25 a piece to get the sleeves pinched got us another 4-5 gallons out of those engines. Two of them were mine, one was a buddies at the time. We mostly ran in grass and at skate parks, so the engines saw very little dirt running, if any.

[Jacobg45]

Here are the pictures of the crankcase backplate:



If you can't see the images then these might work:



Since the images are not working at least for me here are the links:
https://www.dropbox.com/s/d6lnazj288...P0002.JPG?dl=0
https://www.dropbox.com/s/vlg348fknv...P0006.JPG?dl=0

[olds97_lss]

Here are the pictures of the crankcase backplate:



If you can't see the images then these might work:



Since the images are not working at least for me here are the links:
https://www.dropbox.com/s/d6lnazj288...P0002.JPG?dl=0
https://www.dropbox.com/s/vlg348fknv...P0006.JPG?dl=0

Replace dl=0 with raw=1 from the dropbox url's, then they will post as images.



Yep, that's busted alright!

[Jacobg45]

Replace dl=0 with raw=1 from the dropbox url's, then they will post as images.

Ok thanks! Will traxxas take a broken engine head and/or piston for their exchange program? I asked them about the backplate and they said it was fine I didn't need to replace it.

[olds97_lss]

Ok thanks! Will traxxas take a broken engine head and/or piston for their exchange program? I asked them about the backplate and they said it was fine I didn't need to replace it.

I don't know. I never used the service.

[grizzly03]

Ok thanks! Will traxxas take a broken engine head and/or piston for their exchange program? I asked them about the backplate and they said it was fine I didn't need to replace it.

I don't see why they wouldn't.

Here is what the say "Make sure the engine(s) being exchanged is complete. Exchange engines MUST be complete with crankcase, crankshaft, piston, sleeve, connecting rod, cylinder head, backplate, and carburetor. Be sure to KEEP your EZ-Start assembly, header, clutch assembly, flywheel and engine mount; these items are not supplied with new engines."

It would be no different if you had a really bad crash and broke the engine in half against a tree. As long as the parts are there broken or not, it's still complete.

[Jacobg45]

I don't see why they wouldn't.

Here is what the say "Make sure the engine(s) being exchanged is complete. Exchange engines MUST be complete with crankcase, crankshaft, piston, sleeve, connecting rod, cylinder head, backplate, and carburetor. Be sure to KEEP your EZ-Start assembly, header, clutch assembly, flywheel and engine mount; these items are not supplied with new engines."

It would be no different if you had a really bad crash and broke the engine in half against a tree. As long as the parts are there broken or not, it's still complete.

Ok good lol cuz mine has a couple broken parts

[Jacobg45]

Ok update my local hobby shop accepted it I'm all good now this is just so readers know it worked.

[Siq6six]

That piston’s pretty black man, I’d either rebuild it, send it back to Traxxas as a core using the Power Up program for a new motor minus the easy start or just do like I did and opt for the OS 21TM motor.

Ok update my local hobby shop accepted it I'm all good now this is just so readers know it worked.

First I've heard of this Power Up program, looks like a good deal! I've got an old Revo from ohhhh '06/07 that I had upgraded with the 3.3. Refreshed it around the end of 2018 but the engine wouldn't hold an idle. I may be hitting up my LHS in a couple days here.