Weird engine behavior

Ice_2k

Senior Member
Messages
1,391
Hey guys,

I'm having some really strange behavior with my 32cc DuneRunner. Basically, it's gotten more & more difficult to start it and after it does start, after about a minute or two the idle revs start going up. It starts up very nicely at 3500-4000rpm and then it goes as high as 8000rpm. The tank is vented, I checked. Sometimes just giving a squirt on the throttle and then letting it go and the revs refuse to come back down. Carb butterfly is moving ok. The really weird thing is this: I thought "what the hell, maybe the LSN got screwed up and it's running very lean?" and I tried playing with it a bit. When the car was idling at ~7000rpm, I turned the LSN clockwise (so, giving it even less fuel) and it choked on itself, the way it does when you give it a lot of fuel on the LSN. I'm confused, anybody got any ideas?

Not sure if it matter but this is my setup:
Stock 32cc
Walbro WT1107
JetPro exhaust
JetPro silencer
 

Ice_2k

Senior Member
Messages
1,391
Hey guys, good to be back, I'm impressed you remember me :) I had a lot of things going on in my life during the past year and really didn't have the necessary time to hang out on forums anymore. But now I'm back :p I think the DuneRunner actually spent more than a year tucked away in its storage place. This revs issue is probably its way of punishing me :))

Getting back to the issue at hand, I will try to swap the WT1107 with the stock carb and see if that changes anything. I was thinking if there's a simpler test I can do before taking the car apart. Is there an easy way to check for an air leak?
 

designed2survive

Senior Member
Messages
1,005
Location
MA
Hey guys, good to be back, I'm impressed you remember me :) I had a lot of things going on in my life during the past year and really didn't have the necessary time to hang out on forums anymore. But now I'm back :p I think the DuneRunner actually spent more than a year tucked away in its storage place. This revs issue is probably its way of punishing me :))

Getting back to the issue at hand, I will try to swap the WT1107 with the stock carb and see if that changes anything. I was thinking if there's a simpler test I can do before taking the car apart. Is there an easy way to check for an air leak?
@Ice_2k

Glad to have you back and hope all is ok.

To detect air leak, spray WD40 around the carb while it's running. If RPM goes down, you have a leak.
 

Ice_2k

Senior Member
Messages
1,391
there it is! I remembered something about spraying something but couldn't put my finger on the details :D Thanks a lot, I'll try it in the weekend and report back.
 

macandnews

Junior Member
Messages
30
Location
France
Hey guys,

I'm having some really strange behavior with my 32cc DuneRunner. Basically, it's gotten more & more difficult to start it and after it does start, after about a minute or two the idle revs start going up. It starts up very nicely at 3500-4000rpm and then it goes as high as 8000rpm. The tank is vented, I checked. Sometimes just giving a squirt on the throttle and then letting it go and the revs refuse to come back down. Carb butterfly is moving ok. The really weird thing is this: I thought "what the hell, maybe the LSN got screwed up and it's running very lean?" and I tried playing with it a bit. When the car was idling at ~7000rpm, I turned the LSN clockwise (so, giving it even less fuel) and it choked on itself, the way it does when you give it a lot of fuel on the LSN. I'm confused, anybody got any ideas?

Not sure if it matter but this is my setup:
Stock 32cc
Walbro WT1107
JetPro exhaust
JetPro silencer
Hello,
I think you need this:
http://www.davesmotors.com/walbro-wt-499-wt-603-wt-668-carb-rebuild-kit-k20-wat.html
 

Ice_2k

Senior Member
Messages
1,391
Thanks, if it turns out to be the carb, I'll definitely get that. Or maybe finally pull the trigger on an OBR engine :p
 

bravo71

Member
Messages
5
everytime i have an issue the quick fix is a new plug. the amount of playing with the fuel mixture reminds me of a nitro car. shouldnt be like that. small turns real sensitive
 

Ice_2k

Senior Member
Messages
1,391
already tried a few plugs, that's not it. I actually didn't play with the screws at all since the first tuning it, just tried it now since this issue appeared.
 

G-Man

Junior Member
Messages
871
Location
Pittsburgh,PA

BertR

Senior Member
Messages
1,687
Location
Shoshone,Idaho
Hey guys,

I'm having some really strange behavior with my 32cc DuneRunner. Basically, it's gotten more & more difficult to start it and after it does start, after about a minute or two the idle revs start going up. It starts up very nicely at 3500-4000rpm and then it goes as high as 8000rpm. The tank is vented, I checked. Sometimes just giving a squirt on the throttle and then letting it go and the revs refuse to come back down. Carb butterfly is moving ok. The really weird thing is this: I thought "what the hell, maybe the LSN got screwed up and it's running very lean?" and I tried playing with it a bit. When the car was idling at ~7000rpm, I turned the LSN clockwise (so, giving it even less fuel) and it choked on itself, the way it does when you give it a lot of fuel on the LSN. I'm confused, anybody got any ideas?

Not sure if it matter but this is my setup:
Stock 32cc
Walbro WT1107
JetPro exhaust
JetPro silencer
It's been a while since I have been on and this is a fairly old thread but I was wondering if you have put new crank seals in. I had one of my OBR engines do this and ended up being the seals were shot.
 

Ice_2k

Senior Member
Messages
1,391
So, since I last wrote here the problem actually got slightly worse. I've been quite busy between kids and work and only get to use the DR once every few months but now the issue is bad enough that I need to make a decision. Either get to the bottom of it or get a new engine because it's getting frustrating.
Basically, it's running fine for the first couple of minutes until it warms up. Then, it's revving fine, it pulls great, good top speed, all that. However, if I let it idle for a few seconds it runs very irregular and seems to just choke. I sprayed the carb all over with WD-40 and got no difference so I don't think it's an air leak.

 

Ice_2k

Senior Member
Messages
1,391
Is there an easy way to diagnose a potential head gasket issue? Ideally without taking the engine out of the car :)
 

Ice_2k

Senior Member
Messages
1,391
I'm guessing it can't be something too obvious since the engine is running fine except for idling, right?
 

V8srfun

Active Member
Messages
29
Mine ran fine above idle think of the head gasket as a intake manifold gasket it serves the same purpose for n the sense that the crank case needs to be sealed for a proper air fuel mixture.

The big problem with a bad head or intake gasket is if ignored will cause a lean condition and the engine will run to hot and take to much damage.

The weird part with mine was it would idle for a couple seconds before stalling but only when the engine was wam. When cold it would not idle at all
 

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