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Discussion Starter · #1 ·
I was adjusting the needle (main) position on my '01 Fatboy since the top end seemed a little lean. It has a 195 jet and the stock needle. I had a small washer under the needle before, this time I removed that and just moved the "E" clip down one notch. This gives just a little more than the washer alone did. Put everything back, ran down the road and the dam thing wont bring the main circuit in!! Went back, thinking that I pinched the diaphram or something, and removed the carb. Put it back together, extremely carefully, making sure the diaphram was seated right. Went back out....same thing!! Now I am pissed. Take the carb BACK off the scoot, pull it apart again, redo the diaphram, etc. etc. This time I left the air cleaner off, and started the bike and revved it up to see if the slide was pulling up. It wasnt. Now I am stumped. I pulled the diaphram back out, it doesnt seem to have any holes in it. Is the only way to check the slide/diaphram operation to start and rev the motor?? Is there a bench test or a better way?? Maybe there is something I am missing here?? PLEASE SOMEBODY HELP BEFORE I GO CRAZY.

MO:huh:
 

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You can direct a stream of air at the oval opening at top of carb mouth opening and that will pull it open. Doesn't take a lot of air to do it either. If you do it with compressed air keep the air nozzel at least 12" away. You can also blow into same opening and it will pull up the slide too.

First thing you need to do is make sure you have the needle and spring seat installed correctly.
 

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Discussion Starter · #5 ·
Thanks for the info guys......yeah, I thought the slide was sticking too, but I had done the smoothing/polishing act on it previously, and drilled the bottom hole up one size. It worked before I did this dang needle finagling.....I revved the dam thing almost to redline sitting in the shop with no movement, I even stuck a screwdriver in there and lifted it up manually (in case of a backfire, to save the finger ends!), but the thing wouldnt budge. I have the factory manual and all it says is that the slide should move up somewhat sitting, running, with the air cleaner off, and giving it some throttle. Well, I just got back from the dealer a few minutes ago, and bought a new slide and diaphram, maybe I just THOUGHT I was getting it sealed. With a new, none stretched one, maybe that will do it.......keep yer fingers crossed!!

Mo
 

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If you can't move the slide up with a screwdriver or your finger (off the bike), you have installed something wrong. A screwed up diaphram will not keep the slide from moving if you push it up.

Also be sure you've got the vacuum line on at the back of the carb??

Also confusing cause you said you've got the stock needle and then somewhere else you talked about adjusting the E clip on the needle. It can't be both, the stock needle doesn't have any adjustable slots on it.

It almost sounds like you're mixing tuning tips for stock needle with parts from a DJ kit.
 

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0043--Licensed to Doof!
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Make sure your spring isn't cockeyed. Make sure you're not covering the vacuum hole with the white spacer.
 

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Mohead1 said:
I even stuck a screwdriver in there and lifted it up manually (in case of a backfire, to save the finger ends!), but the thing wouldnt budge.
Mo
I'm confused, are you saying you could lift it with the screwdriver or it wouldn't budge when you tried to lift it with the screwdriver? BTW, the motor doesn't need to be running when you try to lift it with your finger.
 

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Discussion Starter · #9 ·
Answers to some of the questions:

- After I put the carb together, I could move the slide up and down with ease
- With the motor running, and giving some throttle, the slide didnt move, so I took a screw driver and as I gave it gas, moved the slide manually to make sure it wasnt sticking somehow
-According to the dealer, some of the Twin Cam carbs had an adjustable main jet needle. Mine has 5 slots, it was in the middle slot, I moved the clip one down and added a 195 jet.

Update: put the NEW slide and diaphram into the carb,again being very careful to get it seated. I polished and radiused the slide first, drilled the air hole to one size below 1/8" (7/32?) and installed. Started the bike, I'll be dam, the thing works FINALLY! Apparently the previous diaphram was just too stretched and fuel warped to make the groove in the cap. All is better, I aint NEVER taken that top off again

Thanks all

Mo
 

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Mohead1 said:
Answers to some of the questions:


-According to the dealer, some of the Twin Cam carbs had an adjustable main jet needle.

Mo
I find that very, very hard to believe. Glad to hear you got your problem solved though.
 

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Highly Seasoned Rider!
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Mohead1 said:
Answers to some of the questions:

- After I put the carb together, I could move the slide up and down with ease
- With the motor running, and giving some throttle, the slide didnt move, so I took a screw driver and as I gave it gas, moved the slide manually to make sure it wasnt sticking somehow
-According to the dealer, some of the Twin Cam carbs had an adjustable main jet needle. Mine has 5 slots, it was in the middle slot, I moved the clip one down and added a 195 jet.

Update: put the NEW slide and diaphram into the carb,again being very careful to get it seated. I polished and radiused the slide first, drilled the air hole to one size below 1/8" (7/32?) and installed. Started the bike, I'll be dam, the thing works FINALLY! Apparently the previous diaphram was just too stretched and fuel warped to make the groove in the cap. All is better, I aint NEVER taken that top off again

Thanks all

Mo
I'm curious now.....why is it that you drilled the hole out in the slide? I've heard about this but never could understand it. I run a stock CV on my shovelhead and it runs great and has for ten years. Is it a speed thing?

.
 

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I'm gonna powder his nose
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Drilling the equalizer hole in the slide to a larger drill number will increase the slide speed thus giving you better low end throttle response. This only works in combination with a shorter less tensile slide spring.

The slide speed test can be done on a dyno, it's something we do when chosing springs to making a jet kit.

Why do all this?

The EPA makes all machines pass a static emission test, that test is done at low RPM. The manufacturers found that a small slide equalizer hole, stiff slide spring and lean slow speed circuit will pass the EPA test, among "other" thricks thay do.
 

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ohiomotoxer said:
Drilling the equalizer hole in the slide to a larger drill number will increase the slide speed thus giving you better low end throttle response. This only works in combination with a shorter less tensile slide spring.

The slide speed test can be done on a dyno, it's something we do when chosing springs to making a jet kit.

Why do all this?

The EPA makes all machines pass a static emission test, that test is done at low RPM. The manufacturers found that a small slide equalizer hole, stiff slide spring and lean slow speed circuit will pass the EPA test, among "other" thricks thay do.
I guess it's in the mind of the beholder. My 1993 FLHS with CV had excellent low speed throttle response. So does my present 1982 FXS. I can't see why raising the slide faster (giving more air than originally designed) would increase low speed throttle response. To show you that I put my money where my mouth is, I bought an entire bucket full of CV carbs and parts at a swap meet a few years back. There were about 5 complete carbs. and ten separate slides of which five or six had been drilled out to various sizes. I guess they couldn't make up their minds. They all went in the can along with the varous length cutoff springs and the two butchered carb. bodies tnat someone had attempted to drill out. I did get some good stuff, though.

I just run the stock carbs. What do I know. :)
 

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Pestilence
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Ultra you have a point.
Can't just drill the slide for the sake of faster throttle.
Drilling the slide goes hand in hand with spring rate, needle taper and emulsion tube design. Works well, only as a "package".
 

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I'm gonna powder his nose
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newultraclassic said:
I guess it's in the mind of the beholder. My 1993 FLHS with CV had excellent low speed throttle response. So does my present 1982 FXS. I can't see why raising the slide faster (giving more air than originally designed) would increase low speed throttle response. To show you that I put my money where my mouth is, I bought an entire bucket full of CV carbs and parts at a swap meet a few years back. There were about 5 complete carbs. and ten separate slides of which five or six had been drilled out to various sizes. I guess they couldn't make up their minds. They all went in the can along with the varous length cutoff springs and the two butchered carb. bodies tnat someone had attempted to drill out. I did get some good stuff, though.

I just run the stock carbs. What do I know. :)

***I don't know how I could have explained slide speed theory, the reason for modification or EPA emission standards any better, sorry.
 
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