1997 1200 carburetor problems - Harley Davidson Forums: Harley Davidson Motorcycle Forum

JEBassler · 05-01-2009, 09:41 AM

Hi guys, I got a problem that is kicking my butt and wanted your expert opinions. I have a 97 1200 sportster. I rebuilt the carb due to a loss of fuel mileage and some popping through the carb on acceleration. Now it will idle fine but mid range is toast. As soon as you give it throttle it boggs down sputters and will die. Watching the vaccum slider it doesn't appear to be holding vaccum. Once throttle is advanced the slider goes up and then starts to drop off. I ordered a new slider assy, installed it and it still isn't right. I placed my hand over the intake and it continues to run at idle without trying to die. That tells me there is a vaccum leak somewhere and I am thinking it is in the manifold area where the carb attaches via the seal. Have any of you experience something similar and what fixed yours?

Thanks guys, I appreciate any help you can give. I WANNA RIDE!!! Lol!

vlade · 05-01-2009, 09:56 AM

Just roughing it I'd check your slider diaphram seal it can install outa line sometimes also your enricher valve might not be closing all the way just getting the nuts on wrong can be a problem with that. Check your rubber intake manifold to make sure you got the carb on right and it hasnt come off the intake ports creating a vacuum leak. The intake manifold may just be old an loose and need to be replaced.

JEBassler · 05-01-2009, 10:05 AM

Thanks Vlade,

Yeah the new slidder assy went on real nice, but I will check it again. I watched the enricher assy, operated it and it completely closed the hole, so I think that is working ok. Yeah, I am thinking that intake manifold is suspect. It ran good not great into the garage now it has no mid-range and I didn't mess with the manifold but I did notice something that bothered me. When installing the carb back on the bike, You have to wiggle it to get the holes to align on the front bracket. It appears to me that to do this causes the carb to sit a little cocked. I wonder if this is causing a small leak in that seal area and since there is no clamp I figure it may be causing a little air leak. I am going to spray some water in that area tonight.

Thank you for your reply.

vlade · 05-01-2009, 10:13 AM

Quote:

Originally Posted by JEBassler

Thanks Vlade,

When installing the carb back on the bike, You have to wiggle it to get the holes to align on the front bracket. It appears to me that to do this causes the carb to sit a little cocked. I wonder if this is causing a small leak in that seal area and since there is no clamp I figure it may be causing a little air leak. I am going to spray some water in that area tonight.

Thank you for your reply.

Maybe if its old new ones are generally nice and snug. some light oil not so crazy about water. Keep checkin in more ideas comin your way. I'd also have to wonder about sufficient fuel delivery at higher RPMs.

JEBassler · 05-01-2009, 11:28 AM

I agree, I will use wd-40 to spray the areas. Funny you mention higher rpm Vlade. If you get past the mid range, in the higher rpm's it seems to run ok. It's just in that mid range area. The fuel spray from the accelerator pump looks good to the naked eye or atleast to me.

**Dave63** · 05-01-2009, 12:22 PM

The slide fits in 2 ways. The airbleed hole (the one NOT in the center) needs to face the back of the carb, with the dimple visible when looking in the carb, from the aircleaner.

What needle are you running?

Stock shimmed?

Dynojet adjustable?

If it was an intake leak to bad that it effected the disphram's movement, the bike wouldn't idle at all........ That would have to be a massive air leak.

Do you have the stock diaphram spring and seat in the carb?

Are all the parts in this order?

CV Carb jet needles.

JEBassler · 05-01-2009, 01:14 PM

Thanks Dave, I believe it is a stock setup. It isn't in front of me but I am pretty sure it's stock. The slide is in with the dimple visible from the front of the carb. I looked at your pics and everything is in exactly that order. My buddy told me that with the engine running at idle, he completely plugged the intake side and the engine continued to idle normally, so it is getting air from somewhere.

**Dave63** · 05-01-2009, 02:45 PM

Check and make sure your 2 vacuum hoses are hooked up. You have one for the petcock, and one for the VOES unit.

If your petcock diaphram is ruptured, the carb will suck air, but it would be noted at idle, as well. A carb with any significant leak will not idle, if it's manifold vacuum. Venturi vacuum is another issue, with you'll find with the VOES unit.

ANY constant vacuum leak is going to be seen at idle.

I'd suspect a leak in the diaphram itself, if anything. You can take it out and hold it up to the light and look for holes.......

JEBassler · 05-01-2009, 03:07 PM

Hmmmm, then I will have three cause one line goes to the hypercharger butterfly assy on the air cleaner housing. I am having him check the petcock. What exactly does the VOES do? Is that for timing?

**Dave63** · 05-01-2009, 03:18 PM

Quote:

Originally Posted by JEBassler

Hmmmm, then I will have three cause one line goes to the hypercharger butterfly assy on the air cleaner housing. I am having him check the petcock. What exactly does the VOES do? Is that for timing?

That's another issue, because you need that venturi vacuum to open the butterfly......I don't like those things, as they do nothing for performance, and they can screw up your carb adjustments. They're bling at it's best........ The "third" line is probably "T'd" off the VOES vacuum line. There's only 2 ports on a CV carb/intake. The rubber hose on the bottom is an overflow for the carb bowl.

Secondly, having that hypercharger can cause a lean condition that you'll see in the midrange. You should consider shimming the needle jet up .050" to richen the midrange, based on the plugs and what they look like.

People think that all you need to do is add a larger pilot and main jet and that's it. Farthest thing from the truth......

What pipes are you running?

You CAN'T run a stock carb, with no rejetting, no needle shimming with aftermarket plugs and a free flow aircleaner and get good performance.

You can't NOT shim the needle with pipes and a hypercharger and expect good midrange performance, as that's exactly what the needle provides, between the idle circuit and the main jet.

The VOES is a device that retards timing on throttle use, based on Manifold vacuum. If the unit is bad, you'll have pinging issues.