Engine is racing at idle

[Sandman_73]

Fires up and idles fine then after a few seconds RPMs start rising to where it will just start to take off. Sometimes it will only do it for a few seconds and other times it hangs up there until I blip the throttle a few times.


Stock 32cc MT with factory carb settings. (1.75 turns out on H, 1.5ish turns on L) Ran greate for two tanks during break-in then recently put Redcat tuned pipe on it. Just put the stock pipe back on and its still doing it. Only other thing I have done is open up the air filter housing checked filters and put back together.


If feels like an air leak to me. Any ideas?

 

[Sandman_73]

I just read the other post in regards to similar symptom and being caused by blowing head gasket on the 2-bolt motors but mine is a 4-bolt and all the bolts are snug when I just checked

http://www.redcatrampageforum.com/showthread.php?t=14791

 

[Ildy666]

Spray silicone spray around the carb and intake to check for an air leak also check ur head bolts...

 

[Sandman_73]

I'll do that. Just checked head bolts (4 of them) and they are all snug. Pulled spark plug and everything looks good.

 

[Sandman_73]

Sprayed starting fluid around the carb/intake while it was running and had no affect. Kind of ruling out air leak at this point. I'm pretty much stumped. I see there is no fuel filter on this thing. Possible something got sucked into the carb? I can't think of anything else to check. Bout ready to roll this thing off a cliff...

 

[BertR]

I had a stock carb/668 that did the same thing and the needle settings made almost no change so I put a new carb on and took care of all issues.

 

[Ice_2k]

There should be a fuel filter on the fuel line, inside the tank.

 

[Sandman_73]

So it looks like my problem was lack of venting on the fuel tank. I noticed the tank was collapsing in a couple places. Popped the cap off to let it vent and it started running right again.

Is this a common problem with the stock cap?

 

[Ice_2k]

Yes, it is. You can either go with the snappy rc tank vent kit (which some people are pleased with, personally I had nothing but problems with it and is a huge pain to install) or you can do it yourself. The setup I'm running now is a fuel line entering the tank cap (I drilled a hole in it), going up the rollcage and back down, ending with a one way valve. What this achieves is it lets air go into the tank whenever is needed but it doesn't allow fuel to come back out.

 

[Phill]

Yes, it is. You can either go with the snappy rc tank vent kit (which some people are pleased with, personally I had nothing but problems with it and is a huge pain to install) or you can do it yourself. The setup I'm running now is a fuel line entering the tank cap (I drilled a hole in it), going up the rollcage and back down, ending with a one way valve. What this achieves is it lets air go into the tank whenever is needed but it doesn't allow fuel to come back out.

I find the snappy vent great

Just make sure you get the brass fittings with it.

You'll find em on the drop down menu.

http://www.davesmotors.com/jj575.html

 

[Ice_2k]

I was also using the brass fittings. For some reason it was leaking like crazy and the guys at snappy rc confirmed that leaking is normal if filling up the tank, which I found staggering since the size of the tank in these things is one of their selling points. With the setup I'm running now, I can fill it up, roll it over, no issues. Again, since many people are fine with the snappy kit, maybe I just got a defective unit. Either way, adding to that the fact that the guys from snappy refused to help in any way because I was using their product on something else than an hpi baja was definetely dissapointing.

 

[Phill]

I was also using the brass fittings. For some reason it was leaking like crazy and the guys at snappy rc confirmed that leaking is normal if filling up the tank, which I found staggering since the size of the tank in these things is one of their selling points. With the setup I'm running now, I can fill it up, roll it over, no issues. Again, since many people are fine with the snappy kit, maybe I just got a defective unit. Either way, adding to that the fact that the guys from snappy refused to help in any way because I was using their product on something else than an hpi baja was definetely dissapointing.

Not good customer service.

Did you ever speak to DDM?

 

[Ice_2k]

No, I didn't see a reason to, DDM had no fault. I just threw it away and made my own version

 

[Phill]

No, I didn't see a reason to, DDM had no fault. I just threw it away and made my own version

I did the opposite.

Made my own and wasn't happy with it so went Snappy.

I just thought DDM might have had some advice.

 

[Ice_2k]

Engine is racing at idle

They would probably offer a refund, that's what they did when I had the faulty carb but I didn't think it would be fair, it wasn't their issue. Plus, with me being in Europe, getting stuff to and from DDM isn't all that easy/cheap.

 

[Cycletech]

No, I didn't see a reason to, DDM had no fault. I just threw it away and made my own version

Your idea is great and its what I would do!! Did you use the little check valve like the one on scooter fuel and or vent lines??

 

[Ice_2k]

I used this one: http://www.davesmotors.com/jj555checkvalve.html

 

[Cycletech]

YEP just as I thought!! Good stuff!!

 

[alfred e numan]

on dirt bikes, iremove the check valves pronto, the ones built into the gas cap- and the inline check valves. the inline check valve was put to good use on the left hand side power valve vent hose on a 01 rm 125. - blows out underneath the devol skidplate-- the dust here gets as fine as talcum powder. no tuning issues at all either.