EVO carb issues

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Dec 26, 2015 | 02:05 PM

das56170

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Joined: Oct 2008

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From: Southern California

EVO carb issues

I have a 1990 FXSTS with about 20k miles on it. It's all stock (air cleaner, exhaust, etc)

I've only ridden it 3 times since i got it (busy with work). All trips were only a few miles, around town. It would idle and run fine, but had a slight hesitation under hard acceleration.

After doing some looking around online, I replaced the velocity needle (with a slightly shorter needle) and slide spring with new ones from CV performance. I also drilled out vacuum slide with a 7/64th drill bit (as was advised on several websites). After that the bike will start right up (actually a little easier than before) but as soon as I give it some throttle, it dies, no matter how much I adjust the mixture screw.

So, I put back the original slide spring and velocity needle, and it didn't fix anything. The only thing I can't undo, it the larger hole in the vacuum slide. Would that be the reason it dies under even the slightest amount of throttle. Do I need to get a new vacuum slide, or am I overlooking something.

On a side note: Everything i read online said to adjust the mixture screw with the bike warmed up and running, but it's not possible to access the screw with the stock air cleaner assembly (even with the EZ-just mixture screw from CV performance). Should I just be making adjustments with air cleaner assembly removed and the bike still running?

Thanks in advance.

Dec 26, 2015 | 02:13 PM

Dan89FLSTC

Seasoned HDF Member

Joined: May 2008

Posts: 21,143

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From: South Carolina

Make sure the needle jet is not installed upside down (it`s the part that protrudes up into the lower part of the carburetor throat).

Don`t ask me how I know this...

Dec 26, 2015 | 02:29 PM

Owtlaw

Road Warrior

Joined: Oct 2011

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From: Round Rock, TX

Drilling the slide to 7/64 won't in and of itself keep the bike from running. Did you do a full rebuild while you had it apart, including float adjustment?

Dec 26, 2015 | 07:52 PM

das56170

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Joined: Oct 2008

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From: Southern California

Quote:

Originally Posted by Dan89FLSTC

Make sure the needle jet is not installed upside down (it`s the part that protrudes up into the lower part of the carburetor throat).

Don`t ask me how I know this...

I used the rebuild kit from CV Performance. I checked the float and it didn't need to be adjusted.

Here's a dumb question. When you remove the main jet and needle jet holder, is the needle jet supposed fall right out with the holder. If so, that's my problem. I went back to check after you posted your suggestion, and I didn't see the needle jet, unless it stays up in the carb (which I'm assuming it doesn't). So when I took everything apart last weekend, I probably dropped the needle jet somewhere in the garage without realizing it. This is my first time messing with a carb, and it's all trial and error at this point. I guess I'll be ordering a new needle jet online, unless the local dealership has them in stock.

Thanks for the suggestion. I would have never figured this out by myself.

Last edited by das56170; Dec 26, 2015 at 07:57 PM.

Dec 26, 2015 | 09:48 PM

das56170

Thread Starter

Cruiser

Joined: Oct 2008

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From: Southern California

Ok, just went back and double checked. The needle jet is in there and is installed the right way. But, since this was my first time taking apart a carb, I didn't realize I put the damn thing back together wrong. After going back through, I realized that I put the spring seat in first and then the velocity needle/jet needle. Dumb mistake, but live and learn, I guess. I'm pretty sure that will fix the problem. I'll start it up tomorrow and see how it runs.

Last edited by das56170; Dec 27, 2015 at 09:16 AM.

Dec 26, 2015 | 11:15 PM

langwilliams

Elite HDF Member

Joined: Jul 2010

Posts: 3,830

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From: Lorain Ohio

I made a mistake on the needle/slide when putting my old 94 back together...I try to have a manual right in front of me from then on or at least re an reread the steps on my digital manual.