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Author Topic:   KP 2bbl Question...
Dirt Forum Champ
Total posts: 1363
posted November 13, 2005 10:44 AM  
continued from before...

i got the demon 2bbl back from barry grant. they went completely through it and set it up to my engine specs. in hot laps and the heat race it ran worse than my 4412. during the main we had a lengthy caution and the engine heated up a little(the nose is closed off some). once it got up to around 210 degrees, it completely cleaned up. then after a few laps of racing the engine cooled back down to 190 and it started sputtering again, although not as bad as hot laps and the heat race. are these 2bbl engines that finicky to temperature change or did i experience a fluke? i'm thinking about putting a 210 degree thermostat in it instead of the restrictor.

please elaborate on this phenomenon, if you can...

[This message has been edited by outlawstock17 (edited November 13, 2005).]

Dirt Roller

Total posts: 18
posted November 13, 2005 03:17 PM  
1 are you running gas or alky?
2 if running alky the motor needs more heat to evaperate the fuel , remember alky is a cooling agent.
3 if running gas it may be atouch rich. we try to get ours atleast 200 gas or alky.

Dirt Forum Champ
Total posts: 1021
posted November 13, 2005 03:54 PM  
Hard to say without knowing what they did to the carb, but it does sound painfully rich with perhaps an air bleed problem as well.
I've not seen 2bbls be any more finicky with temps than any other gas motor, OR alky either for that matter, as long as it's not FAR too cold or FAR too hot. But if it's 190 or 210, under normal circumstances, one would never be able to feel the difference.

In other words, more data/specifics needed in order to answer. :-)


Dirt Forum Champ
Total posts: 1363
posted November 13, 2005 07:30 PM  
gasoline engine. the work order says they replaced the air bleeds and corrected the base gasket and that all. if they did anything else it isn't listed on the work order. this is a new oval track carb that i had to send back to them because it didn't idle correctly or respond to adjustments.

if you remember, i'm running a victor jr. intake. a guy at the track told me that with a 2bbl carb on a big open plenum intake that the carb is the restriction and maybe the engine was creating enough vacuum at WOT to cause the power valve to close creating a WOT lean condition. he said i should plug it and fatten up the jetting. i'm a little reluctant to do this. what do you think? what power valve should i be running? the engine idles at about 12 inches of vacuum.

it doesn't seem to be too rich. i noticed during the race that if i quickly and lightly pumped the throttle down the straights it would run a little better.

Dirt Freak

Total posts: 493
posted November 13, 2005 08:16 PM  
I am not KP, but everyone here who has tried a Demon, me included, have the same opinion of them.......JUNK!

The Joy of Six website

Dirt Forum Champ
Total posts: 1021
posted November 14, 2005 05:32 AM  
The PV should never be blocked, as the jetting then has to be raised so far to cover up the lack of that circuit that it is FAR too rich at idle. It "flat lines" the fuel curve and ruins the acceleration/enrichment quality that the PV circuit gives the carb.
Anyway, they may have changed air bleeds and fixed a mismatched gasket but that wasn't what was mostly wrong with the carb. There's several things we've found that fixes the Demons, whether it's the 4bbls or the newer 2bbls. All require internal "surgery".
I'm curious (and you don't have to tell if you don't want to) but how much did BG soak you for that little amount of work? :-)


Dirt Forum Champ
Total posts: 1363
posted November 14, 2005 06:16 AM  
the carb cost $383 and was defective out of the box, so BG didn't charge me anything. they even paid the shipping and gave me an extra bowl gasket to replace the one i used trying to fix their screw-up. when it ran right, the demon was clean on the throttle and off the throttle under braking. my 4412 always sounded "dirty" under decceleration. with a 750 double pumper the engine screams.

the season is over and we're having a rules meeting soon. i have a feeling we will go to 4bbls. at our fall fling there were several cars from different tracks running 4bbls so i think we will make the switch to try and accomodate them coming back. i think i just flushed $383 down the toilet.

six, i had a mighty demon on my unlimited engine and it was one of the best carburetors i've ever had...

[This message has been edited by outlawstock17 (edited November 14, 2005).]

A. Bighurry
Dirt Full Roller

Total posts: 38
posted November 15, 2005 04:13 PM  
It sounds like it's lean. Did you try jetting up to see what it would do? If it runs better when the engine is hot, and cleans up when bouncing the accelerator pump I would assume that it might be lean.

Dirt Forum Champ
Total posts: 785
posted November 15, 2005 05:53 PM  
I could be wrong but maybe a vacum leak under the intake..when it heats up its ceals it self and when it cools down it opens.. just an option.. best thing to do is get a Kp carb..I have a 2bbl he went threw for a buddy of mine and now I own it and I love it...

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