Another Tmaxx help request

[robtangie]

Ok Gents,
I've been messing with my maxx (2.5 engine converted from .15) for nearly 2/3rds of a gallon of fuel and still can't get it right.
For a bit of background... I started trying when it was still too cold here in Iowa, and then discovered an air leak in the front bearing. After a lot of trial and error I've sealed all air leaks, changed to OS plugs, still using Traxxas fuel (but that's not by choice but lack of options), and the Iowa weather is a beautiful 68 degrees today.
Nearing a good operating temp I was having problems with it not wanting to idle and after trying several times was afraid my engine was worn out. A great gent from another forum donated me a piston and sleeve with under 2 gallons on it. That installed I realized compression was not my problem. I have since got a better idle but now am having problems dogging down and dieing after a couple WOT passes, requiring full throttle to restart and then time to clear out once started again... Only to make a couple more passes before happening yet again. Engine temps have been good and HSN tuning seems to make no difference.
Today in an attempt to pinpoint my problem I started by removing both fuel filters,,, no change. Then removed the air filter (yes it has been kept clean) and as I fired the engine quickly discovered as much fuel spitting from the top of the carb as was going into the engine. This is surely the root of my doggy and dieing condition but I can't stop it... I did t one point lean the HSN until I no longer had the fuel spitting out but at that point I was WAY too lean and had a temp of 310 while just idling. I shut down and changed HSN thinking maybe someone before me (yes it was used when I got it) had turned the HSN down too far and ruined it. This did seem to be a bit better but every time I put the air filter back on it seems to go back to spitting the fuel out again.
As I mentioned I've tried the HSN and LSN all over (2/3rd a gallon worth of adjusting) with no good tune that will keep idling and run well... Dose anybody have any idea as to why I'm spitting the fuel like that? As I'm nearing the end of my patients and desperate to see this thing run right.
Regards,
Rob.

 

[Rolex]

Reset your HSN to factory specs and start the engine and let it get to temp. Lean the LSN and make a few half throttle runs to give it a chance to clear out. Hit the throttle from a full stop to see if it takes off or bogs. Lean it a LITTLE bit at a time, making half throttle passes between adjustments. Once you get a good take off, adjust your idle with the trim all the way down and the trigger in full brake position, till it sits without stalling or crawling.

Now that the LSN is set, you'll need to adjust the HSN for WOT, and if it needs tweaking for weather and outdoor temp, it's only the WOT you'll adjust.

 

[robtangie]

Rolex,
After taking a few days off and handling some other things I went out today and tried yet again...
I followed your advise to the letter and still have the fuel spitting from the carb. Although I can get it running fairly well it seems short lived as it still wants to load up on fuel and die (even without a WOT pass) on a very regular basis.
As I'm sure the fuel spitting out the carb is the root of the problem do you have any advise on what might be causing it?
Regards,
Rob.

 

[Rolex]

Turn your HSN in about a half turn. Run the engine till it warms up and punch it full throttle from a full stop. If it bogs down, lean the LSN some more. Run it in slow circles to give it a chance to clear out and punch it from a dead stop again. Do this till you get a good launch. I'm sure you'll probably need to lean the HSN some more as you start to run it with more throttle. Keep an eye on the temp.

 

[graham189]

hi mate
put ya car back to the factory settings then if that does not work then you may have to buy a new carb.... look on ebay they will be cheaper on there mate good luck.........

 

[robtangie]

Graham,
Thanks for the advise,,, I'm beginning to think that myself...

Rolex,
As I am new to these nitro engines let me ask... By a good launch am I looking for a full throttle launch or something smaller like 1/4 or 1/2 throttle when I'm looking for my launch? I tried again as you suggested and at no setting of the LSN can I get a consistent "good launch". I may get a good launch once but once I do a circle and try again it will bog on me. So again I'll make another adjustment and it may bog again right away but then after a bit of a circle get a fairly good launch only to be followed by bogging again. I've reset back to factory setting so many times that I can't count anymore...
I hate to buy a new carb if that's not the problem, but I'm at a loss... As many times as I've tried and as much fuel as I've been through I would have thought I could have at the very least stumbled on at least a close setting by now.
Regards,
Rob.