Sos - Tmaxx 2.5 Fuel Bubbles

[wilbur]

Hello All,

I have recently installed a new fuel tank onto my 2.5 TMAXX following a little prang. The truck starts really well and idles nicely. However when I apply the throttle the RPM of the engine increases but all that happens is the fuel in the fuel tank bubbles - THE TRUCK DOES NOT MOVE AT ALL. I have checked the fuel line and pressure line and both seem air tight and are the correct way round - top of tank to exahst and bottom of tank tp carb - but I still think I have an air leak somewhere. I am losing hair by the minute - any help much appreciated.

 

[vbgagnon]

The rpm increase and the truck doesn't move? sounds like something other than a fuel system problem.

 

[Candyman]

I'd have to agree. The big problem is that the truck doesn't move when you apply the throttle. So if you floor the throttle, this truck doesn't move at all? That's a problem.

As far as the fuel bubbling, some of that is normal. It comes from the vibration of the engine. One thing you can do to help is to cushion the fuel tank. There are 4 legs where it mounts to the chassis. Cut 4 small pieces of fuel tubing about 1/8 inch long. Install those between the end of the fuel tank legs and the chassis. They'll act as dampeners for the tank. Another thing you can do is this. Taking a FULL gallon of fuel, put one (JUST ONE) spritz of Armor All (the vinyl polish) in it. No more, no less. That will keep the fuel from foaming.

 

[PiErow]

i think you might have stripped a gear

 

[ToRqUe]

could it be the clutch ¿?¿?¿?

 

[Kodama]

Check the clutch, the slipper clutch, and finally the Primary Gear drive inside of your tranny. Guaranteed it's not the fuel tank or anything, something else happened. What made you change out the fuel tank in the first place?

 

[wilbur]

I had a slight prang!

thanks for the quick reply- I am literally beginning to pull my hair out lol. The fuel line and pressure line are definitely the correct way round. The engine starts no bother idles well but the more I pull back on the throttle the more the fuel in the tank bubbles up. There sometimes is some smoke coming from the exhaust pipe. Prior to installing the tank the truck was well tuned. Do you think maybe I could have damaged something else with the crash? The first fuel tank did crack as a result of the crash. Any advice much appreciated.

Just to add....

I have had this problem previously with the tuning being offset - however this has not been a problem with this model until the crash and the new fuel tank installation - the engine is currently producing a good amount of response and power (the sound being the same as it always has) but somehow the engine output power is being delivered as back pressure through the fuel tank. As I mentioned previously the engines starts, idles and revs freely/smoothly however there seems to be a major lack of pressure to drive the wheels - this leads to extreme hair pullage - my hair!

 

[Kodama]

You better check your carb settings and make sure your carb is seated in place properly. If it idles just fine and does good at half throttle then some settings are more than likely messed up.

Rolex: Adjust your LSN and idle screw till it idles well and will run up to half throttle. (get it to running temp before you finalize any settings) When it idles properly, throttle it half way and see if it stalls or bogs down. If it stalls, it's too lean. If it bogs, it's too rich. Now go to full throttle. This is when you adjust your HSN. Same thing. If it bogs, it's too rich, stalls, it's too lean.
When it seems to be running good pinch the fuel line. It should speed up slightly and then stall within 3 - 4 seconds. If it stops quickly, your LSN is too lean. If it takes longer, the LSN is too rich.
Drive it for a while and then take a temp check to make sure it's at the proper temp.
If it's too hot, richen the HSN.
You will have to make small adjustments on the HSN almost daily to compensate for outside temperature and humidity.

As for your bubbling fuel tank, I'm not sure what the problem is, but check to make sure there is nothing in the nipple for the pressure line running from the exhaust pipe. If you have the lines all correct then it shouldn't bubble too much. How full do you fill the tank? If you fill it to the point where the fuel can easily go through the pressure line and out of the exhaust then of course it will bubble.

Did you check the clutch, slipper clutch, and gears within the tranny yet?

Later.

 

[wilbur]

I will try out all you suggest as soon as I finish work - Cheers for now..

 

[Kodama]

It sounds like your clutch might be out. Either that or you've stripped a gear.

 

[wilbur]

How could it tell (process of elimination) if my clutch was out?

 

[vbgagnon]

on the end of your engine there is a round pice with some teeth on it, this is your clutch bell. Their should be some teeth and just by looking at it you should be able to tell if it is worn down.

 

[wilbur]

right.. i have looked at the bell there is no major difference in the teeth the tmaxx is nearly new - i know thats not right...also when i increase the throttle the clutch bell goes faster but never engages with the clutch bell flywheel - even if it did turning the flywheel by hand does not even move the wheels...I think there may be a problem with the transmission...cheers for your helpful and much needed advice.

 

[vbgagnon]

I don't own a maxx. but from the sound of it there is something wrong with your tranny. Maybe the other guys can give you some more advice.

 

[Kodama]

The teeth don't matter that much... it sounds like your clutch isn't ENGAGING. Meaning the clutch shoes aren't grabbing and transfering the power from the engine to the spur and so on and so forth. Take some pliers and just hold the spur gear so it doesn't move then rev the engine, if the clutch catches it will spin the spur gear. And it will mean you have a problem with either the slipper or a gear within the tranny.

And another idea... check to see if the forward/reverse is in gear too. That could be a problem. lol I've done it once before.

I'd bet that it is the forward/reverse.

 

[wilbur]

Ya beauty....

The problem was as simple as the engine block needing re-aligned to mesh the clutch bell with the spur gear. Seems simple now but I was nearing baldiness!!....lol.... Thanks very much for your time and effort on that one....i'm hoping I can get some more of that golden knowledge...here goes...I recently installed upper and lower RPM A arms and RPM shock towers on my 2.5 TMAXX. However the suspension seems no where as good as it used to be (it seems to have lost its spring back ablility) - is this normal? Also i have tried adjusting the point at which the shocks screw to the lower A arms with no luck....Cheers....

 

[Kodama]

Either, heavier springs or lighter shock oil. It's like you trying to do the splits, the further your legs go out the harder it will be to get back up. It's just the extra distance that the A-arms add. It's not a very big problem.

 

[canadian-mgt]

did you properly adjust the pivot ball caps in the knuckles? they should be tightened down then turned back about 1/4 turn,otherwise the pivots may bind.

 

[jerry7007]

you know if u just messed with the back plate air and fuel will leak in/out and your two stroke engine will never run right

 

[guys2nv]

fuel bubbling is normal-does the armor all trick really work? start at the clutch-i would take the motor out and check the clutch-use like a 400 grit sand paper and clean the inside of the clutchbell-and if the clutch is realy worn there will a nice amount of space between where they touch. if it is the tranny its most likely the one way bearing in there-(held on by a c-clip) on the internal spur gear($20)new and make sure u spray it out w/ carb cleaner or brake clean-cause any grease on it-it will free rev still.