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Sluggish at partial throttle....

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drdoom405

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Peoria Il
RC Driving Style
  1. Bashing
So my tmaxx runs terribly at partial throttle. WOT its fine, lots of power etc, but if you pull the throttle only partway it will load up and want to die, same thing with reverse which makes sense because it only goes 70% throttle....

Common sense would say my lsn is way too rich, (its about at factory setting) so i started leaning it a 16th at a time. I did this twice and it seemed to help slightly but my temps began to shoot up quite fast. I have a hard time keeping it under 280 anyway so I quit there. Any ideas?

I'm thinking maybe an air leak somewhere. Any help is much appreciated!
 
Yeah, you're probably right. Let's see what some of the other fellas have to say before attempting to seal every crevice under the sun. Although, some guys do that day 1 anyways so it's not likeit would hurt.
 
Did you try adjusting your HSN at all? Is your air filter clean?

I'd put the LSN back and lean out the HSN a bit to see how it does.

I have a brand new 2.5R in my jato and I'm beginning to remember why I don't care for traxxas engines... tuning them sucks. Mine acts rich, but when I lean it, it heats up beyond where I feel comfortable running it (goes from 220-280 quickly), so I continually have to blip the throttle and run the idle higher than I'd like.
 
Air filter is clean and oiled, I have the HSN adjusted pretty well I think. Its making plently of power up top with lots of smoke. I could probably go leaner if it wasn't for my temp problem. Its also very responsive(the needle). A slight turn in either direction will cause a temp flucuation of around 20 degrees and a power increase (or decrease) to go with it.

I took the backplate and carb off and sealed them this afternoon. I did a leak test around the HSN and didn't see anything so I left it alone. I'll have to wait and see how it does when I get a chance to run it.
 
Ran the truck this afternoon. Throttle response is improved a little bit but I still have temp problems so I dunno. I reset the needles to factory and the truck runs great. SUPER fast, probably the way its supposed to be. Still saw blue smoke too. Unfortunatly the engine would have cooked in about 3 min. It was up to 300 in less than a minute

It will stay about 280 if i have the needle about 5 turns out or so, but its not as fast as it should be. I kind of have to adjust the needle every minute or so to keep the temps in check.

Haven't tried a new glow plug yet, old one is kinda white obviously. I'll try that tonite. I'll get new o-rings for the carb and if that doesn't fix it I'll just run the mill until it gives up and get a new one i suppose. Or sell it for an E-Maxx....
 
Have you checked the fuel tank for cracks or leaks around the o-rings?

Is this a "new to you" engine or was it brand new when you got it?

Check the cooling head bolts. Try to tighten each one to see if they have loosened on you. If they are all tight (or any are loose), take them all out, take the head off and make sure you have a head shim. Line it back up, then drop all 5 screws in the head and tighten them gently. Get them all tightened down gently, then back them all off 1 full turn. Wiggle the head a bit by hand, then gently tighten 1/4 turn at a time in a star pattern to get them to tighten flat so you don't cause more of an air leak than it sounds like you have.
 
A new glow plug solved my throttle problem but that was caused by my apparent air leak I'm sure.

Its a new to me engine. Whole truck was off ebay. Supposedly only had a quart ran through it and the truck was in a condition that seemed to support that. From what I can tell it has good compression.

I've tightend the head bolts, but not taken them out. I'll try that tommorrow. I installed all new o-rings in the carb this evening and ran it after. It made no difference. I'll keep at it though. Its gotta be an air leak.

What are some commonly available replacement engines for the tmaxx?

btw thanks everybody for the good advice, this is a pretty informative forum.
 
I have a 3.3. Problem solved though. I bought a new carb body just for the hell of it, threw it in and bam. Temps dropped 50 degrees after tuning.

Then I stripped a spur gear :( :hehe:
 

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