4040 loses power

[TFF 13]

I worked most of the day yesterday trying to figure out why my 4040 (Onan CCKA) loses power when I get to the top of my small hill. Runs fine otherwise. It's at about 3500 rpms and will sputter and start to stall at the top. I cleaned the carb and put in new gaskets, adjusted the idle jet (it has no high jet), changed/adjusted the governor springs, used a hose into a bucket to make sure the fuel pump was still working, tightened screws, changed the fuel lines and filter, adjusted the throttle cable and still it stalls. Sounds like fuel starvation but I can't figure out why. Maybe the fuel pump is just not working well? Please help.

[midnightpumpkin 83]

The high speed jet is at the bottom of the fuel bowl. Very difficult to access and almost sure to result in a burned arm from the hot exhaust!

Neat huh?

There is a top adjust carb Zenith 13793 if you can find one.

John U

[isetta 50]

Could your governed be coming into play when you get to the top and it backs off

[TFF 13]

It looks like I have a Marvel-Schebler carb, and I can't find the high speed jet - it looks like it just has a plug...

[midnightpumpkin 83]

My mistake, I was thinking CCKB carb. Can't help on CCKA.

John U

[720nut 4,225]

Thomas have you tried adjusting timing maybe even valve clearance. these engines have tendancie to allow timing to move if not tightened down tight. Just my .02

[TFF 13]

I'll try the valves and timing as see. Thanks.

[JimS 1]

How full is your tank? The pickup tube is at the front of the tank and the fuel level may drop away from the pickup when you are going uphill with a low tank.

[phillobbezoo 139]

That's a good point, my brother had a 720 that would get to a certain point and run like crap no power and so on. Ended up being the fuel lines were hooked up back ward coming from the tank

[John Mc 1]

Make sure fuel filter  is replaced every year, check wires that thy are not rubbing on anything when you are at angle- John 

[TFF 13]

Just to close this thread, after much searching, I decided to take off the carb once again and clean it.  After pondering the workings of the carb, I realized that the carb link bar was way too far out (I had adjusted it months ago) and starved the engine when under load.  Ugh.

[fishnwiz 3,290]

Glad to hear you solved your problem! 

[720nut 4,225]

Thomas glad ya got her workin. By chance do you know what length you ended up with on link bar ?

[TFF 13]

I'll measure this weekend and let you know.

[isetta 50]

I'd be interested in the length too.  Anyone else who wants to go out to the shed and measure there's we'd like to know.  Does it make sense to measure total length from end to end so we are consistent?  I recently measured mine from ball to ball and it is hard to get an accurate measurement without taking it off.  Are all those links made the same way on these Onan / Zenith carbs?

[720nut 4,225]

To cold here to think about shed. All that I have seen are just seems all are different lengths

They say up on 40's this week so maybe that will bring everyone out of hibernation.

[jlasater 287]

There are two styles of link bars that I have seen. So as long as you measure end to end on the same kind of rod, I think the measurement would be close enough that you'd never notice a difference.

[dince 276]

57 minutes ago, 720nut said:

To cold here to think about shed. All that I have seen are just seems all are different lengths

They say up on 40's this week so maybe that will bring everyone out of hibernation.

Down here, downunder, we always believed you Americans were really tough....  what, a bit of white fluffy stuff and you go woosey?

PS 110 degrees here today, howling wind, and guess who has been ordered to come inside!!!

[720nut 4,225]

Both are basicly the same just different arrangements, did you measure either of those?

I'm trying to get mine to idle now that I changed a couple of things

David, not sure I could withstand 110* either, been to Arizona a few years back and was 115* but dry heat. they were talking about -5* tomorrow morning

[jlasater 287]

If there is adjustment left in the linkage rod you have, I'd measure it as it is now for reference and then shorten it a few turns on one end until you can get it to idle. Then check to see if you still have full RPM available at full throttle. If not, you can adjust the other threaded rod with the spring on it to get power back.

[fishnwiz 3,290]

5 hours ago, dince said:

Down here, downunder, we always believed you Americans were really tough....  what, a bit of white fluffy stuff and you go woosey?

PS 110 degrees here today, howling wind, and guess who has been ordered to come inside!!!

,I would take 110 over minus 30 windchill anyday!

[tadams 989]

With your 110 heat is it dry or humid

[dince 276]

On 09/01/2017 at 3:34 AM, tadams said:

With your 110 heat is it dry or humid

Normally, it is a pretty dry heat, which I find quite bearable.  But this summer, swe had a lot of rain, so the humidity is horrendus.  Yesterday, it was close to 110 degrees and we got 76 points in about 10 minutes!  Imagine how steamy that was when the sun appeared again.  I was nearly, yes, nearly, wishing we had snow and arctic blasts!!!

[720nut 4,225]

 believe we could arrange something like that . How many feet you want ????

[dhoadley 1,747]

14 hours ago, 720nut said:

 believe we could arrange something like that . How many feet you want ????

Start him off easy; send him one foot, and then send him another foot mid-week, then another over the weekend, etc.