skeeter_ca

I've burned about 5 two ounce tankfulls of fuel through my new wasp to break it in. At first it ran great but now I noticed it is starting to run poorly at full throttle. I'm using 15% nitro w/25% oil (mixed in extra castor to increase oil content). At full throttle it will start running rich, as i grasp the needle valve to adjust it it appears to go leaner and rpms increase alot. I've tried adjusting it leaner then restart but then it won't run hardly at all. If i start it then go to full throttle and hold the needle valve it runs great, but as soon as i release the needle it will slow down then stop. Is the nut on the end of the needle loose or should i look at anything else first?

jetpack

My Feedback: (1)

I have a brand new Wasp right here and I'm looking at it trying to figure out the cause.

I guess lets try and rule out the basics first. The fuel nipple is screwed in tight to the carb body and the end of it acts as the orifice for the needle also. One piece nipple and needle seat. No movement with the needle there unless it's closed down. There still could be an air passage there past the threads, and you holding the needle calms down the fuel line shake or such and changes tune.

The throttle side, there is the needle barrel for the needle, and the carb barrel with needle assembly to the carb body. Two places right there for air to find its way.

Looking at mine and testing the fit between the carb barrel and the body, there is a slight amount of wall clearance enough to feel it lightly with your fingers but not by eye. The needle however, screwed 2 1/2 turns out as recommended for starting has a huge amount of clearance between the threads and wiggles quite obviously.

I would have to say it is the needle threads causing the trouble. I guess my only suggestion and what I'll try before I run mine is seal the threads with teflon pipe tape or the other option of slicing a short section of fuel tubing and slide it over the threads to bridge the nut and the needle valve body and seal it that way - but the hex on the nut might cause problems there with the tubing, dont know. With that approach, you can more likely get rid of the ratchet that the nut holds along with the throttle arm, and it holds itself tight and air tight that way.

One more thing, is the carb base seal causing trouble. There's two set screws that can leak, and also the carb O-ring. Don't overtighten the carb screws or you will crush the carb throat. Use some RTV around that area if thats the problem.

NormF

I think Jetpack has it covered. Unless it's a collet lock on the needle (it's not) I always put a short piece of fuel line (small or med. silicone) over exposed threads. Make it 3/32 - 1/8" longer than the space. Some of the tube should climb over the needle knob (the part you turn).

- Norm

digital_trucker

Yup, my Wasp suffers from Needlus Loosenii too. Put a short piece of fuel over the whole works and it'll play nice. It'll still act a little weird while you're adjusting it, though (don't try to adjust the needle at idle, it'll probably quit).

skeeter_ca

Thanks guys,

The fuel tubing bit sounds like the trick, although i will check the other items jetpack mentioned. I'll post back if that does or does not work.

chevy43

Yup the needls are super loose! The real problem isn't the air leaking as much as it is the tip is hovering ove the hole where the fuel come out and changes all the time affecting the mixture! The fule tube helps some but doesn't solve the problem of the needle tip moving over the fule hole.... I'ts a terrible design.. The need should go INTO the fule hole IMO but that isn't they way it is desinged.

skeeter_ca

If the needle floats over the orfice opening then maybe a little teflon tape on the treads to tighten the thread sloop. I'll look into that also. I'll do each check and post the results on what improved it the most.

So far these all seems like good tips. Any other ideas the try?

treedog

Maybe a daub of rubber cement[ the stinky kind i like to sniff might work
Td