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HH100 idle down issue??


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#31 NUTNDUN OFFLINE  

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Posted April 13, 2011 - 07:26 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.


Wow, that does make it puzzling for sure. About the only way I can think of to test for a crack would be to make two plates to cap off both sides of the carb and one plate having a fitting to hook an air line to and put a couple pounds of pressure to it and spray with soapy water. Other then getting an ultrasonic test of it I have no other ideas to test for cracks.

#32 IamSherwood OFFLINE  

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Posted April 13, 2011 - 07:40 AM

You'd think that a crack that might have that much affect, would be visible, but I can't find anything.
Assuming that's the issue.

#33 NUTNDUN OFFLINE  

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Posted April 13, 2011 - 07:48 AM

When the motor is running with the demon carb, if you put your finger on the throttle lever does it stop fluctuating? I think someone else mentioned about slop in the throttle linkage could be an issue and I agree. Does the governor seem to work correctly with the throttle up higher and being put under load with the demon carb?

#34 IamSherwood OFFLINE  

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Posted April 13, 2011 - 08:01 AM

When the motor is running with the demon carb, if you put your finger on the throttle lever does it stop fluctuating? I think someone else mentioned about slop in the throttle linkage could be an issue and I agree. Does the governor seem to work correctly with the throttle up higher and being put under load with the demon carb?



That plate on top of the throttle shaft is tight. Gorvernor seems to be doing it's thing. Worked right on with the other carb. Bushing job we did is good.
I don't think there's 2 thou clearance. I had to hand sand the shaft to fit into the bushing. A bit at a time. Took about 3/4hr. I can't see getting that
any tighter.

It's that running away, as it gets hot, that is the clue.

Oh yeah, forgot to mention. Also lapped the valves back then. When I did the new head gasket recently,
the exhaust valve was white again.

#35 NUTNDUN OFFLINE  

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Posted April 13, 2011 - 09:02 AM

What about the hole in the throttle shaft lever where the cable attaches, is that worn more then the good carb?

I can't remember off the top of my head without looking at the carb, but if I remember right isn't there low and high needle adjustments? Can you try swapping the low idle jets and adjusters with the good carb and see if that makes a difference? Sounds like it is lean at idle, have you tried adjusting the low mixture a little richer to see if that helps? I am sure some of these ideas have already been covered, figured it might be good to think out loud.

#36 DH1 OFFLINE  

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Posted April 13, 2011 - 08:34 PM

The only thing I can think of is the throttle is not being held in place at idle.
Does it move on it's own off the idle set speed screw or is it held tight against it when running.
I got a bunch of carbs give me a couple of days and I'll see if I can find a good one for ya.

#37 MH81 ONLINE  

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Posted April 13, 2011 - 11:00 PM

Is there any chance this is the wrong carb? Could an over or under sized carb do this?

#38 IamSherwood OFFLINE  

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Posted April 14, 2011 - 07:25 AM

The only thing I can think of is the throttle is not being held in place at idle.
Does it move on it's own off the idle set speed screw or is it held tight against it when running.
I got a bunch of carbs give me a couple of days and I'll see if I can find a good one for ya.


Yes, that's all fine. When I throttle back, all the linkages move as they are supposed to, just like
when I had the MF12 carb on.
The throttle shaft stays tight against the stop screw, and it doesn't idle down. Then it starts to
run away. Probably as much as a 200rpm increase.
I actually didn't touch the throttle cable "Bowden wire clamp",
(there's I new one I learned by reading the manuals 38 times) as I switched the carbs back and forth.
Also didn't adjust the governor while switching carbs. Only had to richen the idle screw on the
MF12 carb, and it ran great.

Is it the right carb?? It's a LME26. The one off the MF12 is a LME27. Is there a difference?

#39 DH1 OFFLINE  

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Posted April 14, 2011 - 05:26 PM

Yes, that's all fine. When I throttle back, all the linkages move as they are supposed to, just like
when I had the MF12 carb on.
The throttle shaft stays tight against the stop screw, and it doesn't idle down. Then it starts to
run away. Probably as much as a 200rpm increase.
I actually didn't touch the throttle cable "Bowden wire clamp",
(there's I new one I learned by reading the manuals 38 times) as I switched the carbs back and forth.
Also didn't adjust the governor while switching carbs. Only had to richen the idle screw on the
MF12 carb, and it ran great.

Is it the right carb?? It's a LME26. The one off the MF12 is a LME27. Is there a difference?


LME26 LME27 if there's a difference I don't know what it is. Most of the ones I have are LME36.
If I can find a good carb for you and tested to make sure it runs right then I think it's time for that problem carb of yours to be introduced to Mr. Sledge Hammer.
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#40 IamSherwood OFFLINE  

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Posted April 14, 2011 - 05:39 PM

LME26 LME27 if there's a difference I don't know what it is. Most of the ones I have are LME36.
If I can find a good carb for you and tested to make sure it runs right then I think it's time for that problem carb of yours to be introduced to Mr. Sledge Hammer.


Hey Doug.
I agree 100%, that it's time to retire that carb.(but I won't beat it
to death. I'd really like to know what the issue is. Some day maybe)
I will gladly take you up on your offer. Just let me know.

Thanks

#41 DH1 OFFLINE  

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Posted April 22, 2011 - 07:59 PM

Hi Will you have probably already done this but maybe check again.
There a 3 small plugs, weltch plugs and 1 small vent hole, all my carbs are the same for these.
LME 12, 26, 27, 36


this one is the biggest it's in the float bowel.
LME 002.jpg


this one is either a weltch plug or a rivet.
LME 001.jpg


there are what look like 2 small ports here the top one is a plug air tight seal.
the side one is a vent goes into the float bowel.
LME 003.jpg


just thought maybe 1 of the plugs was missing or the vent plugged???
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#42 IamSherwood OFFLINE  

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Posted May 07, 2011 - 06:55 PM

VICTORY!!!
Finally.

Thanks to Doug (DH1) who very generously sent my one of his
Walbro LME carbs I've got the MF10V running like a champ.

That evil carb is still in one piece, and I'd still like to get to the bottom of
this mystery carb. When I get bored. I still think It has a crack somewhere,
and as it heats up it expands, and causes it to run lean. Just gotta figure
out how to test for that, and verify(or not) my theory.

Anyways, for now I'm damn happy to drive the girl.
Thanks Doug, and all who input to this challenge.

#43 DH1 OFFLINE  

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Posted May 07, 2011 - 07:32 PM

VICTORY!!!
Finally.

Thanks to Doug (DH1) who very generously sent my one of his
Walbro LME carbs I've got the MF10V running like a champ.

That evil carb is still in one piece, and I'd still like to get to the bottom of
this mystery carb. When I get bored. I still think It has a crack somewhere,
and as it heats up it expands, and causes it to run lean. Just gotta figure
out how to test for that, and verify(or not) my theory.

Anyways, for now I'm damn happy to drive the girl.
Thanks Doug, and all who input to this challenge.


Well it's about time. Good stuff




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