Advice on problem shooting my 3.3 Issue

[Kawika]

Hey guys i'm new to the forum. Recently got back into the nitro scene and have a Revo 3.3 and just purchased a used TMaxx 3.3 that has a brand new motor.

Having issues with my TMaxx and wanted some advice if any would help. I'm fairly familiar on how to tune but just can't seem to get this TMaxx to not cut out on high RPM's.

The motor has had probably 6 tanks through it with the proper break in.

Basically its getting the extremes of either too lean or too rich, even with incremental adjustments on the HSN. Basically the LSN and idle are spot on. When i get on the throttle, it accelerates like it should but right before it switches to 2nd gear it cuts out unless i get off the throttle. I've adjusted it incrementally more rich to ensure that it gets enough fuel on the top end and that didn't work even in 1/8 turn increments.

I've gone the other way and closed the HSN to lean it out and i get the same results.

I've even tried resetting all screws back to the factory settings and have gone from there, and still 1/16 - 1/8 adjustments in the HSN will either make it too lean or way too rich to where gas is literally spitting out of the exhaust.

Basically it's either too lean, or even with slight adjustments it's too rich - to where gas is really coming out of the exhaust. So much so that if i tip it over it drips out.

Could this be an O-Ring issue in the gas tank by chance? Should i try replacing the tank? I've tuned my other Revo and have had other Nitro cars before but can't seem to figure this one out and feel that it has to be another issue.

Any help would be greatly appreciated!

 

[Reddog]

Sounds like an air leak to me. Have you sealed the engine? I know there is a good post oon here about how to do it. Also, when the engine was put on were the fuel lines replaced? Just a couple things that come to mind for me. Shaun

 

[Kawika]

Thanks for the tip i'll try to research it. Not sure if it was done or not. Bought it from a friend of a friend so i'm not sure if it was done. He had the shop replace the motor, but by the looks of the lines, I'm thinking they may have not replaced the original ones. I'll look into sealing the engine. Someone had also suggested that possibly the fuel tank O-ring may be bad? I've never had to replace that due to an issue on any of my nitros. Not sure if its a common problem or not.

 

[Snook Man]

After checking that everything is working correctly with no leaks (fuel tank/lid, fuel lines, header/pipe connections, etc.) you should also make sure the pipe and pressure nipple is not restricted.
If that checks out ok and still is very sensitive to the small adjustments going from lean to rich it could be internal. I’ve seen probably a dozen 3.3 engines (most were in the early stage of break-in) that had the same symptoms. The culprit was a cracked/broken piston saddle where the con rod connects which allowed the piston to slightly rotate a couple of degrees which makes the engine un-tunable and a nice paperweight.

Hopefully it’s something simple though.

 

[Kawika]

Oh Lord.....i hope it's not that. That would really suck. Thanks guys for the advice I'll definitely check into all of that today when i get home. Hopefully i won't have to tear the motor apart and find that it's the piston saddle...urgh

 

[Kawika]

Ok apparently the guy I bought this from swore up and down it was broke in properly. NOPE. Who ever broke it in ruined it. The motor doesn't hardly have any resistance when you turn the motor over with your fingers with the flywheel as opposed to my old used Revo that has total resistance when trying to turn it over with my fingers. Took it apart and it looked squeaky clean. I don't understand how some people can ruin a brand new engine like that.

All the gas lines were fine, no air leaks, no air leaks in the tank when i pressure tested it either.

Good news is that it's basically a new block so when i rebuild it, i can at least look at it and feel like it's a new motor too LOL. Oh well.

Thanks for the help guys.

 

[chickenman242]

if the sleeve and piston aren't scored why not get them repinched ,its about 30 bucks from memory

 

[Kawika]

Thanks bud i will definitely look into that. Would you have a reccomendation of a place that does that by chance? I think new ones are only like $60 bucks or so, so i was just planning on doing that but didn't know that repinching was an option. I'll try to reasearch pros and cons on that as well

 

[chickenman242]

I got mine done at rcrenew.com ,from memory it cost me about $45 that that was including shipping to and from Australia. you could always buy a new one and get the old one done and keep it as a spare.

 

[Rolex]

You could save yourself the trouble of doing ANY tear down by looking into the Traxxas exchange program. Trade it in for a brand new one.