help with engine problem please

[Xanth]

Greetings, we have a Losi xxxnt with the mach 15 engine.

The engine starts and runs great and will idle on my work bench with a fan on it just fine for quite awhile, when you go to drive it after about a minute if you let off the gas it will die every time.

We have tried adjusting the carb leaner/richer for hours on end but just can't figure out whats up. At first i thought it was the clutch sticking but we replaced most of the clutch parts and it still does it.

Any ideas please ???

 

[Team 17]

Have u adjusted the low speed needle?

 

[Mach.21]

I had a problem with that on my Losi XXX-nt then i found out that what happened was the little nut on the rotary carb came loose so at idle the slide didnt comeall the way closed so iturned down the idle screw so when i went to put on the brake it would close the carb air flow completely off

Just my 2 cents

 

[Xanth]

i have tried adjusting both the low and high speeds every which way you can......

 

[Team 17]

When u let it run awhile and then go have u checked the temps?

 

[Mach.21]

hAVE You checked the caR AND SEEN IF THE NUT IS LOOSE

 

[Xanth]

Yes i check the temps regularly and it doesn't appear to have anyting to do with what is happening.

Just went and checked the nut and it feels tight.

 

[Team 17]

Just went and checked the nut and it feels tight.

Did u check both? :jk:

When u attempt to take off does it bog down and cutoff? If so, it is running too rich.

 

[Rolex]

You might be trying to do too many things at once, at which point you lose track. I'm pasting my tried and true method of tuning almost any stubborn engine below. If you don't have any air leaks, this should get you up and running.

Put the nose of the truck against something firm so it can't get away from you. If you have an EZ start, keep it running while moving your LSN one way or the other till it starts to run.
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 to half 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.

By the way, the factory settings are for break in, or a starting point if you really messed things up. Once an engine is broken in, don't expect it to run right by going to those settings.

 

[Xanth]

Did exactly as Rolex said and it was runing great as usual....after a minute or so it just dies as i hit a corner and slow down. It will start right back up and run fine again after.

 

[Rolex]

Did you do the pinch test to check your LSN? If it's running good, but stalls when you slow down, the LSN and/or idle would be the problem.

 

[vbgagnon]

What about the clutch bearings did you change those? Also check to see if the carb closes all the way when you hit the breaks.

 

[Xanth]

Just replaced the clutch bearings yesterday as i thought that was the problem.
No the carb isnt closing when i hit the brakes, it dies when i let the car slow down without braking though.

I did the pinch test, the car appears to be tuned properly until i drive it a bit and then.....

I replaced all the carb O rings and the copper head gasket this morning and its still happening.

 

[vbgagnon]

Have you tried bringing up the idle? From what your saying it sounds like your low end is too rich. If sombody disagrees say so, but if you let off the throttle and it slows down and dies thats what I think.

Your best bet would be to reset to the stock carb settings and retune from there.

 

[Xanth]

right now i have the idle set to where the clutch is almost engaging.

If i lean out the low end anymore the engine gets hot.

 

[olds97_lss]

Did you change out your glow plug? I didn't see anywhere that you did.

On my xxx-nt, the little pins that hold the clutch shoes worked their way out. They actually screw into the flywheel from the rear. As they back out, they drag on the engine casing and kill the engine.

How many gallons have you ran through this engine?

 

[Xanth]

Put a new glow plug in it yesterday.
less then 2 gallons through it.
Checked the pins and they are good.

 

[Mach.21]

At this point i would call or go to your local hobby shop and pay some one to find out....That is just what i would do.......But also if the car is new team losi has a warranty on their parts.....If it is new i would call losi and talk to them and send it back and have them fix it at their expense

 

[tmaxxtx18]

either take it to lhs or check piston and sleeve
only advice i have

 

[Xanth]

I appreciate all the help folks, turns out that the carb had a hairline crack.