Finding air leaks

[Kuma]

Having my new XTM .18 in my freakin Magic Wheel, it seems to be hard to start up now (pullstart) and won't hold an idle. Factory settings are 3 turns on HSN and 5 turns on LSN and my settings are usually 3 1/4 to 2 3/4 and seems fine, but the LSN seems to be a real problem- when I accelerate it occasoinally cuts out and I know that is lean. But when I turn the LSN out continuously it still acts lean (sometimes revs up when I let it go back to idle) and I screw out the LSN so far back that it's close to falling out! There's also VERY little blue smoke coming out, I am using an O.S. #A3 plug.

THe guy at my LHS says it might be the gasket between the carburator and the intake housing. I'm having such sucky luck with everything on this truck lately.

 

[nitro dave]

Sounds like an air leak. You got to find that leak and stop it. :doc: The first and most obvious place to check is around your carb. I would also check to make sure your fuel lines are fresh. The backplate is another place where air leaks can occur. Check those places, replace your fuel lines and start with the needles back to factory and retune.

 

[NCNitro]

I hate to say it but you would be better off pulling the engine out and just sealing all the problematic areas. In the long run it will save you a ton of time, grief, and aggravation trying to find the leak, and help prevent future leaks. To seal the backplate I use Permatex ultra copper. To seal the carb, I use racers edge carb sealer. I also use some of this on the threads for my fuel filter.

To check if you have a leak in your fuel tank, remove it from the truck, put new fuel line on both the inlet and pressure line, submerge the tank in a bowl of water, block one end of the fuel line and blow in the other making sure the tank is completely submerged, if there is a leak it will bubble under water as you blow in the fuel line.

When you reinstall everything I also like to make fuel line clamps out of a small piece of fuel tubing, about 1/8 of an inch. Stretch it over the ends of the fuel line using a pair of needlenose pliers. This will also help as far as air leaks.

Good luck with it and let us know how you make out with it.

 

[Kuma]

This is crazy but the factory settings of 5 turns out on LSN was way too rich, so I surfaced the needle to flush and it worked, it can hold an idle and is very responsive. Still working on HSN but it's not as much of a problem as the LSN was, getting more thick blue smoke each time I tune it a bit. Took it to the track along with the Terra Crusher today but couldn't race either of them since the TC's starter battery died and we forgot the spare cell while mine was too unstable to race yet- so I corner marshalled all day, I still had fun.

PS- bigfish, were you there today too? Boy it was hot and some good nitro ST and buggy races.