170 main jet with UFO StreetPro 4-2 and otherwise stock bike?

[jwood]

I moved the slide to another carb and the problem followed the slide.

The problem isn't the diaphragm--it's in sound shape, nice and flexible with no tears or holes. When I move the slide with my finger, it doesn't move smoothly--it feels like it's binding.

Loosen up the plastic screw that secures the needle into the slide and try it again...

 

[TheFleshRocket]

Loosen up the plastic screw that secures the needle into the slide and try it again...

I'll give that a shot, but.. if that helps, what's the fix? Obviously I can't leave the plastic screw loose.

 

[jwood]

I'll give that a shot, but.. if that helps, what's the fix? Obviously I can't leave the plastic screw loose.

Loosen it up just a little so the needle moves freely, put it back in the carb, check for free movement of the slide, then just lightly snug the screw up while its in place in the carb.. Check for movement of the slide again...

 

[TheFleshRocket]

Loosen it up just a little so the needle moves freely, put it back in the carb, check for free movement of the slide, then just lightly snug the screw up while its in place in the carb.. Check for movement of the slide again...

10 4, thanks.

I'm pretty sure the slider body is worn/scored, though. I'm thinking about giving it a light once-over with some very fine steel wool. I figure I can't make it any worse--or if I do, I was going to replace them anyway.

 

[jwood]

10 4, thanks.

I'm pretty sure the slider body is worn/scored, though. I'm thinking about giving it a light once-over with some very fine steel wool. I figure I can't make it any worse--or if I do, I was going to replace them anyway.

I was told, ALWAYS put the same slide back into the carb you remove it from.. Don't mix them up...

 

[TheFleshRocket]

Yeah.. I didn't keep the slides with their original carbs, but the misfire was the whole reason I took them apart in the first place. The other three slides move smoothly and snap shut with a solid thwack, so I don't think I made anything worse.

 

[Rusty McNeil]

The only time I had slides sticking was from improperly installed needles.

They MUST be able to freely wiggle around. If not they will drag on the needle jet tube thingie.

 

[Fire-medic]

I moved the slide to another carb and the problem followed the slide.

The problem isn't the diaphragm--it's in sound shape, nice and flexible with no tears or holes. When I move the slide with my finger, it doesn't move smoothly--it feels like it's binding.

They're plastic, perhaps it's warped? Any number of guys on here should be able to provide you w/a new/used replacement, hell, even if you were buying new, they aren't that-expensive. You only need one.

 

[Rusty McNeil]

Better yet. Remove the needle from the slide, reinstall the slide and see if it's dragging still.
I'd do this before dropping bucks on a new slide.

I've swapped slides around repeatedly without problems, not on purpose, but through multiple rebuilds I know it's happened many times. No problems ever arose from it.

 

[Rusty McNeil]

A 170 is a mikuni. And it's huge.

Are you saying if it's a 170 it has to be a Mikuni?

Or that the 170's you have are Mikunis?

 

[m-cman]

Bike will not run properly with air box off. Even if not correctly mounted it will not run properly.

 

[maleko89]

Are you saying if it's a 170 it has to be a Mikuni?

Or that the 170's you have are Mikunis?

Both mikuni and dj have a 170 size.

 

[maleko89]

Bike will not run properly with air box off. Even if not correctly mounted it will not run properly.

Yes, unless air correctors are installed.

 

[sdt354]

I'll give that a shot, but.. if that helps, what's the fix? Obviously I can't leave the plastic screw loose.

What I'd check is the needle to make sure it's not binding. The plastic teet on the white washer has to be in the hole. What I do is spin the needle until the little teet drops into it's hole. Then lightly seat the white screw and make sure you can wiggle the needle. Then tighten up the white screw a little more. There should still be some wiggle in the needle after final tightening of the plastic screw.
Steve

 

[TheFleshRocket]

I got another reply from Mike at UFO this morning. He recommended using some fine steel wool to clean the slide. Considering that the slides are at least $110, I'm going to give this a shot.

Definitely a big thumbs-up to Mike and UFO!

Here's what Mike had to say:

"sounds like your getting the old girl to respond a bit. as long as the slide is holding a vacuum you don't need to replace it usually. if you pull it out and take some of your WD and some 0000 steel wool and clean the varnish off the slide then clean it and make sure there's no remnants of the steel wool anywhere then lube it up again and re install it. To check to make sure your slide is holding a vacuum push the slide back and hold your thumb over the oblong hole in the top of the carb to block it off and the slide should return slow. The deal with it not taking fuel well with the cover off is if you have one slide being lazy or problematic then its not receiving the fuel in that cylinder. with the air box cover off it leans it out even more."

 

[sdt354]

Both mikuni and dj have a 170 size.

You're right, I'm wrong about that. They are way different though. Both do make them.
Steve

 

[maleko89]

You're right, I'm wrong about that. They are way different though. Both do make them.
Steve

Steve, I used to know by looking at shape. I'll take a picture and post a sticky if one doesn't exist already.

 

[sdt354]

Steve, I used to know by looking at shape. I'll take a picture and post a sticky if one doesn't exist already.

Be much appreciated Mark. As is all the info you've posted over the years. I did the stacks under my filters per your advice. My low end and mid range have never been better. It's like -hang on!
Steve

 

[one2dmax]

I think I'm currently out (though might have them). We sell the same OEM slides for $75 each new.

 

[maleko89]

Be much appreciated Mark. As is all the info you've posted over the years. I did the stacks under my filters per your advice. My low end and mid range have never been better. It's like -hang on!
Steve

Steve, glad the velocity stacks worked for you!

FYI, added new picture of the jets to an existing sticky in carbs section.