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HH100 idle down issue??


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#16 IamSherwood OFFLINE  

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Posted April 06, 2011 - 04:39 PM

Sound like you going about it the only way you can, eliminate all the possibility's till it's right.
Could always try another carb of a HH100 or 120 that you know has a good idle.


Put the carb off the 12 onto the 10 (the one that's been giving me trouble)

The idle down issue went away, so obviously there is something not right
with the mf10 carb. Not sure what, whether it's self induced or ???
At least the problem has been narrowed down to the carb.

#17 DH1 OFFLINE  

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Posted April 06, 2011 - 04:41 PM

Put the carb off the 12 onto the 10 (the one that's been giving me trouble)

The idle down issue went away, so obviously there is something not right
with the mf10 carb. Not sure what, whether it's self induced or ???
At least the problem has been narrowed down to the carb.


That's good news cause it tells you the rest of the motor is good only the carb has problems.

#18 IamSherwood OFFLINE  

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Posted April 06, 2011 - 04:47 PM

Yes, that is good news.
So, now my queston is, if I had set the float level to low,
could it cause that idle down issue?

#19 DH1 OFFLINE  

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Posted April 06, 2011 - 05:05 PM

All you can do is pull the carb apart again and do whatever you can to set everything the way it's suppose to be, float level they say is 1/8" set with the carb upside down gap between casting rim and float.
Check for things like vacuum leaks, throttle bushing, any where that air can get in where it's not suppose to.
Plus ???
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#20 NUTNDUN OFFLINE  

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Posted April 06, 2011 - 05:13 PM

Wasn't the carb off the 10 the one that you said had a little play in the throttle shaft? I would start there first, it isn't going to take much un-metered air to cause idle issues.

#21 IamSherwood OFFLINE  

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Posted April 07, 2011 - 07:09 AM

Wasn't the carb off the 10 the one that you said had a little play in the throttle shaft? I would start there first, it isn't going to take much un-metered air to cause idle issues.


Yeah, there is about 10-15 thou play there. I guess I'll get brother to turn up a bushing.
Thanks

#22 NUTNDUN OFFLINE  

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Posted April 07, 2011 - 07:24 AM

Yeah, there is about 10-15 thou play there. I guess I'll get brother to turn up a bushing.
Thanks


If you replaced the main nozzle with a known good service nozzle whether it was bought or made and there is nothing wrong with the butterfly plate, and your float height is set right the slop in the throttle shaft is about the only other thing that could be causing it.
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#23 DH1 OFFLINE  

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Posted April 07, 2011 - 04:12 PM

If you replaced the main nozzle with a known good service nozzle whether it was bought or made and there is nothing wrong with the butterfly plate, and your float height is set right the slop in the throttle shaft is about the only other thing that could be causing it.


I agree but there is also the passage ways in the carb for the idle circuit, maybe there plugged or partially plugged up???
Soak the carb in carb cleaner and try to blow out the passages with compressed air???
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#24 NUTNDUN OFFLINE  

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Posted April 07, 2011 - 04:36 PM

I agree but there is also the passage ways in the carb for the idle circuit, maybe there plugged or partially plugged up???
Soak the carb in carb cleaner and try to blow out the passages with compressed air???


Very true, I was going under the assumption that he already cleaned the carb really good.

#25 IamSherwood OFFLINE  

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Posted April 07, 2011 - 05:02 PM

Oh yeah, that carb has been cleaned, and recleaned several times now.
All the passages have been reamed with small pipe cleaners (paint gun cleaning
kit stuff).
Today, I found a bowl gasket that that actually fit, so I reset the float, because
I had a feeling I had set it too low. Reason for that was, because the bowl gasket
out of the after market kit didn't fit right, and I couldn't get the bowl to stop
leaking.

Same stuff going on still. After high rpm's for 30 seconds, if I throttle back, it
won't idle down.
Today, I tried something. As it sat there rev'g away when it shouldn't, I put my
hand within 1" of the carb air intake (no air filter on), and it immediatley went
to idle.

#26 NUTNDUN OFFLINE  

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Posted April 07, 2011 - 07:50 PM

Is there slop in the linkage for the throttle plate? It sounds like it is still lean on the low side. I am still putting my money on the throttle plate shaft though.

#27 DH1 OFFLINE  

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Posted April 07, 2011 - 07:57 PM

Some thing to try with the engine running full speed put your hand over the inlet end of the carb, make an air tight seal till the motor stalls out, won't take long, this puts a high vacuum in the carb, sucks the gas though all the jets and passages cleaning out all the loose crap that's in there.
Done this lots of times on carbs that have non adjustable or limited idle jets and it works for cleaning them out.

#28 broken2 OFFLINE  

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Posted April 07, 2011 - 08:25 PM

I bought a mf12 that wouldn't idle or run rite. It was like it had a mind of it's own. The problem turned out to be the piece at the top of the throttle shaft that the cable hooks to was a little loose on the shaft. If you held the throttle shaft still you could turn the top of it about an 1/8 turn. It must have driven the PO nuts. I fixed it by putting a big drop of solder on it, tightened it up nice. When the engine is at the mystery high idle is the throttle actually open a little bit? Hope you find the problem soon and I'm very interested to hear the culprit. If you take the throttle shaft out I suggest using some tread locker on the screws for the butterfly. Those little buggers like to work loose and raise hell. Good luck.

#29 jscam OFFLINE  

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Posted April 12, 2011 - 06:51 AM

Although I dont have any Tecumseh experience (yet), I do know my Kohler is VERY picky when it comes to setting up the governor. Maybe worth looking at? Just a thought.

#30 IamSherwood OFFLINE  

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Posted April 13, 2011 - 07:18 AM

Back to this. I let it sit for a bit, because as you know, sometimes
it's better to just walk away for a while. A light bulb might go on.

No light bulbs here.

Here is what I've done recently.
re modified the main nozzle. Thought that maybe the groove wasn't deep/wide
enough. no change.
New head gasket, and level sanded head.New gasket between block and heat shield. no change.
Recleaned all pasages in carb.
New main nozzle and main jet. Set float as per instructions in new seal kit.
New low speed jet. no change.
Bushed the throttle shaft. no chage.
So then, because I started second guessing myself, I took the carb off the 12
again. With some adjusting the 10 runs like a clock. Perfect in my mind.
Put the 10 carb on the 12. Created the same no idle down situation.
One thing I noticed, is that as the engine gets hotter, the problem gets worse.
That's using that cursed carb on either the 10 or 12.
As it sits there rev'g and not idling down as it's supposed to, it will start
racing faster as it heats up.
Now I'm thinking-crack in the carb? as the metal heats and expands it
sucks more air. Make sense? How can that be verified?
I really want to know what's wrong with this carb before I cremate it.




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