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Old 04-02-2013, 05:29 AM   #16
Plaka
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Originally Posted by gvganser View Post
Thanks for the Info. So I guess I did tune them. As I stated earlier I set the mixture and idle stop screws and gave the amounts.
Those are your nominal settings. it's where you start so it'll run enough to tune them. Those are not your final settings. You always start your tune with those settings, you don't finish with them.
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Old 04-02-2013, 05:38 AM   #17
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Yes. I understand that. I didn't expect to not have to make adjustments. But as I said this is my first time. When the RPMs were sitting that high I thought it best to ask those that know before I started fiddling with anything and potentially making it worse.
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Old 04-02-2013, 05:48 AM   #18
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Originally Posted by gvganser View Post
Yes. I understand that. I didn't expect to not have to make adjustments. But as I said this is my first time. When the RPMs were sitting that high I thought it best to ask those that know before I started fiddling with anything and potentially making it worse.
Nah. Just do your tune and balance. That finishes the job. THEN if you have a problem with high RPM, Ask the gurus (I think there's one over there--->)

No worries about making it worse, just go back to your nominal settings and begin again.

If the problem isn't the carbs, that's different. But do the carbs first.
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Old 04-02-2013, 07:21 AM   #19
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Originally Posted by gvganser View Post
... I did o-rings, enricher gasket, needles, needle jets, floats, springs and diaphragms. It is a 1988 R100GS and the diaphragms are the type with the 4 screws to remove the top piece, not the press on kind. ...
You didn't say if you removed the butterflies to replace the o-rings on the throttle rod. If you did remove them, then the problem may well be you didn't get the butterflies reinstalled properly and they're hanging up in the carb body. If you didn't remove them and the idle was operating properly prior to the rebuild, then I don't suspect the butterflies.

The diaphrams have small tabs both on the inside and outside edges. These tabs fit into depressions on both the slide and the carb body. If these aren't set correctly, you could either have a poor diaphram seal or the slide may not be installed the correct direction.

Being an '88, I assume the carbs have the large return spring around the slide and under the diaphram. I believe this spring wasn't in earlier carbs.

Put your finger down the throat of the carb and verify that the slide moves up and down with no drag and that it seats fully down with no hang up.

An irregular idle usually means an air leak on the output side of the carb. As suggested, verify that both clamps are tight and the carb doesn't move when you try to rotate it.

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Old 04-02-2013, 02:07 PM   #20
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Dave.

No. I didn't do the butterfly o-ring. I did verify the tabs on the diaphragms when putting them together and I believe there are the wholes in the bottom of the slide that are on the output side.

I did check the resistance if the slides and they seemed smooth. Won't say that I didn't mess something up. Ill start with the idle stops and go from there.
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Old 04-02-2013, 02:19 PM   #21
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As per 109e's comments.... The idle stop screws are the first and simplest place to start while synching and fine tuning the carbs. I have had high and hanging idle before when everything was in good shape but the idle stops were set just a fraction too high. More than once. (I try to keep my idle at about 1000 rpm for better cam oiling at idle.)

+1 on at least a 10 mile warmup - more if you are in cold temps.
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Old 04-03-2013, 02:09 AM   #22
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As per 109e's comments.... The idle stop screws are the first and simplest place to start while synching and fine tuning the carbs. I have had high and hanging idle before when everything was in good shape but the idle stops were set just a fraction too high. More than once. (I try to keep my idle at about 1000 rpm for better cam oiling at idle.)

+1 on at least a 10 mile warmup - more if you are in cold temps.
Actually your start your tune with the idle mixture. if that is off it affects the mixture well into the needle jet range. having that off and trying to make up for it with the idle stop screws is a mistake.
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Old 04-05-2013, 12:22 PM   #23
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Ok. So the idle stop was definitely the main ingredient to the secret sauce. Turned those back and what a difference it made. I still have to finish the sync. I understand the concepts here and the info you have given has helped with that.... My execution seems to be piss poor even though I thought I had proper preparation.

There is a MD airhead tech barn in a couple weeks. My goal was going to be just go and meet some of the Airheads I hadn't met before but I think I will see if I can have somebody walk me through... I'm having a hard listening and finding sweet spots.

Thanks again for all of your advice ad information.
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Old 04-05-2013, 03:51 PM   #24
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Found this..................
I wonder what the experts say about it

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Old 04-05-2013, 04:33 PM   #25
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Found this..................
I wonder what the experts say about it
Somebody got it completely screwed up.

Sigh, it's so simple but seems so out of reach for too many...
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Old 04-05-2013, 05:16 PM   #26
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Originally Posted by Plaka View Post
Somebody got it completely screwed up.

Sigh, it's so simple but seems so out of reach for too many...

Okie Dokie, sorry for posting that , not sure where I found it.......

No worries, I'll toss it out for the dogs.

But now I'm for sure taking notes.
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Old 04-05-2013, 05:30 PM   #27
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Okie Dokie, sorry for posting that , not sure where I found it.......

No worries, I'll toss it out for the dogs.

But now I'm for sure taking notes.
You could keep some of it, unscramble some of it and correct the numbers for some of it.

I've written this up from memory a couple times. I suppose when I have a min I'll do a page on it. I still have my quickly scribbled notes from when I was taught to do it a whole lot of years ago.


If somebody in the longmont/ boulder/denver area has video gear we could film it.
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Old 04-05-2013, 05:35 PM   #28
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I don't see what Plaka's problem is with the balancing method presented. That is basically how I do it. What am I doing wrong?

I will admit that my carbs will not maintain a nice idle. I have to blip the throttle to keep the engine rpms out of the basement. But if I set them up any I end up with a 1500 rpm idle.
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Old 04-05-2013, 05:51 PM   #29
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I don't see what Plaka's problem is with the balancing method presented. That is basically how I do it. What am I doing wrong?

I will admit that my carbs will not maintain a nice idle. I have to blip the throttle to keep the engine rpms out of the basement. But if I set them up any I end up with a 1500 rpm idle.
I'll get to that. Do it right and the idle is no problem.

You set idle mixture first, idle speed second, cruising rpm third and go back and touch up the idle speed again last---usually on your test ride.

This one gets step 1 and 2 backwards and misses the cruising RPM and final idle speed altogether. And while you will get it by ear quickly enough, you do look at the tach (provided it works). You have the cables max slack for idle and very slight slack only for the high rpm balance. You ensure the chokes are closed at all times.

It does pick up the slip of paper trick. I'm getting tired of that and I'll dedicate a feeler gauge I never use and count turns to zero the screw.

I've done this so many times since I learned it it isn't funny (50+?). It comes out really well every time.

My latest setup will short all four plugs which will be new. I used to do my dual plug engines with the bottom plugs shorted and left that way. My toolkit sticks still work that way. The new sticks kill all four.

I was making a rig to short through plugs for the last Nth...blew it off.
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Old 04-06-2013, 10:17 AM   #30
lkchris
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There has to be slack in the throttle cables. This can go away with heat.

I had an Airhead once that idled at 2K rpm and the cause was no compression in one cylinder.
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