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Fire Axe Man
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Discussion Starter #1
pulled my carbs apart and found i couldn't easily move the small diaphram, didn't move at all... should it move in and out easily? everything else in carbs now moves great and works properly... just can't idle bike and starts real hard, (ether) re-jeting tomorrow to compensate for ear shave, but wanna make sure about this small diaphram while carbs are out tommorow as well...
 

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pulled my carbs apart and found i couldn't easily move the small diaphram, didn't move at all... should it move in and out easily? everything else in carbs now moves great and works properly... just can't idle bike and starts real hard, (ether) re-jeting tomorrow to compensate for ear shave, but wanna make sure about this small diaphram while carbs are out tommorow as well...
that is the air cut valve it should have a rather stiff spring behind it,it may be the brass part is stuck to the aluminum of the carb body if you are talking about the one on the side of the carb.Don't ask me what it does but it would be working at a high vacuum situation such as at idle or when you close the throttle fast.

and I am by no means a carb guru or anything else as far as that goes.but they should move.
 

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Fire Axe Man
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Discussion Starter #3
beautiful so shouldn't have anything to do with my isuue... but may cause backfiring upon deceleration... im a car guru NOT a bike wizz...
 

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@ Denny The manuals call that thing the coasting enricher, not that I mean to correct you. I think it supplies extra fuel when engine braking, since the idle circuit doesn't provide enough fuel at higher rpm's. With the butterfly valve closed, the slide drops and the main jet doesn't let out any fuel.

@Mike That air cutoff/coasting enricher would cause decel backfiring if it doesn't function and leaves you with a lean coasting mixture. Remember that it works against the spring, so you want to pull on it. As I recall that thing is a little tricky to grab and pull. Have you played with the one on the other carb for comparison?

I wouldn't pin the backfiring during decel on that diaphragm quite yet. It could be responsible, but if you have done an ear shave without re-jetting, you will be running lean. If the plugs covering the mixture screws are still in the carbs, drill them out while it's easy. The bike is tuned lean when stock and MawKaw doesn't want you to mess with the mixture. Bigger jets will compensate, but you still might need a little help from the mixture screws.
 

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When I pulled my carbs, I tore them down and went through them. The coasting enricher diaphrams could be stuck in the carbs, or just sticky. I used a metal dental pick with an angled tip to gently get under the edge of the diaphram, and pull it up to get a hold of it with my fingers. When you get them out, check to see if they are stiff. They should be fairly soft and flexible, not too stiff. If they snap or are too stiff, it's time to replace them.
I took some 2000 grit sand paper, and GENTLY sanded them to clean the brass up, and they work great now, slide in and out like they should.
 

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Fire Axe Man
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Discussion Starter #6
they didn't move at all... and don't still, but as for riding lean i have no cables for throttle yet so not riding just operating by hand to try to get it to run,... today i hit the starter button it back fired so loud i thought it blew thew pipes off the bike, then fired up and runs like a dream, starts every time now and idles great, no smoke, no backfires, just purs beautiful... jets come in tomorrow to re-jet and will mess with the fuel mixture screws and try to get these coasting enrichers to work properly again... this one is a tough one trying to work out 100 problems at once from the bike sitting for 7 years... it will be an interesting first ride next weekend maybe, all cables and ordered parts come in friday 4-29-11 or 5-1-11 cant hardly wait!!! few new pics in my profile for those interested in how the project is coming...

P.S. what setting do you have the fuel pet-cock at to ride, On or Pri? seems to run out of fuel "On" pet-cock is very clean and screens all in good shape... havn't tried reserve... pri seems to pour fuel in...
 

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Linkmeister Supreme
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P.S. what setting do you have the fuel pet-cock at to ride, On or Pri? seems to run out of fuel "On" pet-cock is very clean and screens all in good shape... havn't tried reserve... pri seems to pour fuel in...
PRIme will pour fuel in without any vacuum applied to the center nipple on the petcock. That function on yours is working properly.

ON and REServe settings require vacuum applied to the middle nipple to move a diaphram for the fuel to flow.
The PRIme position is only found on models from 1985 to `88 or `89.
Later models have OFF, ON and REServe.
 

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Air cut diaphragm and coasting enrichment diaphragm are different words for the same part; depends on where you look in the manual and parts diagrams as to what it's called. The brass plunger prolly has varnish buildup/gum on it; clean up as RakerBill said above, or use 0000 steel wool, and flush out the opening it goes into with carb cleaner.

The petcock issue has me puzzled, unless the vacuum hose isn't hooked up to the nipple on the left carb, or the petcock is gummed up, too. The vacuum port on it may be clogged.
 

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Fire Axe Man
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61 Posts
Discussion Starter #9
i have the vaccume line hooked up from the left carb to tank and right vaccume on carb is caped off, but the center to lines are vaccume as well? or breathers? earshave said put a filter on these but if there vaccume that would be a " vaccume leak" to simply put a filter on them... this problem seemed to start after ear shave i believe...
 

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i have the vaccume line hooked up from the left carb to tank and right vaccume on carb is caped off, but the center to lines are vaccume as well? or breathers? earshave said put a filter on these but if there vaccume that would be a " vaccume leak" to simply put a filter on them... this problem seemed to start after ear shave i believe...
The two upper hoses that tee into one are the float chamber vents; the one hose usually goes to the right ear, or on older bikes to the nipple on the cover for the tank sending unit. In the earshave, it gets a filter to keep bugs and dirt out; it's not a vacuum hose.

If it was running well before you started on the earshave, it's doubtful the petcock is a problem.

Until you've got near the right jets, both main and pilot, in the carbs, and your throttle cables hooked up, you're kinda pissin' in the wind. However, it should still idle. Check that the idle adjustment is turned in enuff that the throttle butterflies are just starting to open; should be around a turn and a half after the end of the adjuster touches the arm. There's a newer thread that shows that part futher up the list here. (Never mind; I see where you posted there)

Jim
 

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Air cut diaphragm and coasting enrichment diaphragm are different words for the same part; depends on where you look in the manual and parts diagrams as to what it's called. The brass plunger prolly has varnish buildup/gum on it; clean up as RakerBill said above, or use 0000 steel wool, and flush out the opening it goes into with carb cleaner.

The petcock issue has me puzzled, unless the vacuum hose isn't hooked up to the nipple on the left carb, or the petcock is gummed up, too. The vacuum port on it may be clogged.
Thanks J.D. I was just calling it what LANCE told me it was and if it has PRI on the petcock ,gas should flow freely in this position,that's normal ,however if this petcock won't let it run in any other position you do have some sort of vacuum problem.

try a syringe on the petcock and pull a vacuum with in run and reserve position to see if it is working properly.use the hose that goes on the carb and if it doesn't work try a known clean hose to eliminate the hose as a problem.
 

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Fire Axe Man
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61 Posts
Discussion Starter #12
ok got the new jets in, washer shims on needle new vaccum hose and put it all back together, filled the tank, hit the button with no choke and fired up instantly ideling great revs instantly no lag, no delay runs and revs perfect, the old vaccum hose was hard and cracked on the back side, and the jets were way wrong before... thanks for all your help guys!!!!! I put a lawn and garden fuel filter on the top vent hoses, and car breather in the crank breather in front of the engine...
 
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