hi,
need fix my hestitation problem when the engine is under load. first off, i have gas in the tank and have given my carbs the 24 hour seafoam enema.
but the hestitation continued. so today while riding i switched to the reserve tank just for laughs ( first time since i owned the bike) and WOW, no hestitation and the bike just about jumps thru its skin.
so now to my vulcan brothers & sisters, what is causing my problem with my primary feed line to the carbs &how do i fix it?

thanks & ride m safe, J

You may have a dirty screen on the primary line or a plug in the valve.

You may have a dirty screen on the primary line or a plug in the valve.


I second the dirty screen

I'd take the petcock off and open her up. You might find the problem easily. But it will give you a chance to clean things up. Might be time to rebuild the petcock too.

This may be silly, but I thought I was turning my petcock off for a long while when actually, I was putting it in reserve. On the arm of the petcock is an arrow pointing to the position it should be in. I say this because I have heard others say there is some 'lag' time to refill the reserve portion of the tank (??). If that is true, if the valve is really in the reserve position, wouldn't that cause slight hesitation? Is there any way fuel lines could be reversed?

Not knowing much about our petcock, does it have two fuel lines? If it's like the other KAW petcocks I've been around, they have one vacuum port and one fuel port. I'd think our fuel port attaches to a fuel line that T's into both carbs, but maybe I'm wrong. The valve of the petcock should have two openings that when the handle is turned it aligns the opening from either the main "ON" position tube to the fuel port, or the reserve "RES" tube position to the fuel port. The "OFF" position would close off both tube ports.

Both tube ports when routed to the fuel port on the petcock flows through an opening that is controlled by a spring loaded valve that when vacuum is applied to the vacuum port, it pulls open the spring loaded valve, opening the path to the fuel line going from the petcock to the carbs. This is why the petcock should not flow fuel when the bike is not running (no vacuum).

Someone correct me if I'm wrong about there being one fuel port and one vacuum port...


I believe on earlier models, the petcock has a prime position that flows fuel without need for vacuum.

EDIT: Looks like I was wrong about one fuel port. I found some photos where someone had two fuel filters on their bike, one on each side, so I guess it has two. Sorry!

The two fuel lines are probably feeding off the same port. The two lines you are seeing if where the fuel T's off from the petcock to the two carbs.

As far as the reserve goes it is pulling from the same place as the ON position.

The on position is like drinking out of cup with a straw that is too short. You can drink fine when it is full but eventually there is still drink in the cup that you can't reach. The reserve would be like grabbing a longer straw that reaches that last little bit of drink so you don't go thirsty before you get to the store.

Just about to respond - one vacuum port, two fuel ports. But when you guys are talking about a dirty screen, that's a screen on the petcock to one of the fuel lines? Haven't pulled apart a petcock yet (there's still time!!!), so just wondering where the build-up would be.

Actually, believe it or not I think I might have a spare one. :p I'll check at lunch while I'm home and grab it if I do. Maybe I can pull it apart and take some pictures. Then maybe I can put it back together.;)

Actually, believe it or not I think I might have a spare one. :p I'll check at lunch while I'm home and grab it if I do. Maybe I can pull it apart and take some pictures. Then maybe I can put it back together.;)

Now don't go getting my hopes up, Fergy! I'll probably pull the one on O. when I go to paint her. But pics in advance will no doubt lessen my pain. :beerchug:

Well, my old age kicked in when I went home and I forgot. Last night I looked and the one I have is from the older bikes, with Pri/On/Res and no shut off. I didn't pull it apart, but I will if someone is interested in photos of the guts. Let me know.

:( Oh, such promises unfulfilled...

Maybe I'll just have to pull the petcock on the bike I bought from Dennis this past weekend. It's not going anywhere for awhile (this coming winter's project), so, hey, why not?

Shame on you waiting for winter. That bike could be on the road in a few days if all it needs is a stator. Need help? I'll come up and help on the weekend. Gives me a reason to take a ride in a nice part of the state.

By the way I'm pulling the petcock off one of my tanks to prep it for going to the paint shop. I can post pics if wanted. Anything else anyone wants pics of I will be tearing "Priscilla" pretty much down to the bone.

Shame on you waiting for winter. That bike could be on the road in a few days if all it needs is a stator. Need help? I'll come up and help on the weekend. Gives me a reason to take a ride in a nice part of the state.

I may indeed need some help at engine-pull time. I'd like to get Orleans mostly back together before I start on....whatever I'll call Dennis' bike. But that could be soon. You did an engine pull on Angel, right?

I may indeed need some help at engine-pull time. I'd like to get Orleans mostly back together before I start on....whatever I'll call Dennis' bike. But that could be soon. You did an engine pull on Angel, right?

Yes I did. And I had a friend who is a shade tree mechanic there to help. It CAN be done on your own, however I wouldn't recommend it. Give me a few days notice anytime you need help. Like I said gives me a good reason to head up your way. Next time I'm bringing a fishing pole, it's been a while since I fished at Harpers Ferry.

I've just installed a pair of inline fuel filters on my fuel lines, so I've been thinking of removing the fine screen in the bottom of the fuel tap assembly entirely to save any future problems with this getting clogged. (see pic)

I cleaned the screen as best I could during the rebuild of the bike, but it still had a few tiny black specks around the bottom of it that I couldn't remove without damaging the screen. Considering that I had a problem getting the bike running properly due to dirty carbs and a sticky float for the front cylinder, I was thinking that ditching the screen in the tap and just using the inline filters, would make it a lot easier to check for fuel flow problems in the future.
Good or bad idea??

I would leave it in place. If you remove the screen, any dirt, rust, debris, etc in the tank will plug your fuel valve.

That's kind of what I was thinking, although, if the tank is rust free, seems like it would be hard to get any debris in there large enough to clog the valve, but it is something to consider.

here is an update to my hesitation problem. went out today and it started to hesitate on hard acceleration. decided to add a little choke & the engine smoothed out and acceleration rate increased? now my question is what is the problem with my fule system if to correct it i have to give it a little choke so it runs good? thanks, john

here is an update to my hesitation problem. went out today and it started to hesitate on hard acceleration. decided to add a little choke & the engine smoothed out and acceleration rate increased? now my question is what is the problem with my fule system if to correct it i have to give it a little choke so it runs good? thanks, john

Since it appears to be running lean you could check the float levels to make sure they are right.

If the bike is not stock on the intake side (other than maybe K&N filters), you may want to richen up the carbs a bit. When does the hesitiation kick in? Certain rpm, part throttle, full throttle, ??

Jon

it happens on full throttle. how do i richen the fuel mixture on thes carbs? thanks john

it happens on full throttle. how do i richen the fuel mixture on thes carbs? thanks john

First, is your bike stock? If not, what changes have been made, only care about the intake side.

Jon

intake is pure stock. just an FYI have V/H cruisers on the other end

With a pure stock intake system, you should be fine on stock jetting. You might want to check the float levels in the carbs, if too low, it will starve for gas in high demand.

Have you already done the Seafoam treatment?

Jon

doing it as we text. do i have to remove the carbs to adjust the float level? thanks john

doing it as we text. do i have to remove the carbs to adjust the float level? thanks john

Actually you have to have them installed to do the measurement, they need to be removed if they have to be adjusted.

Do you have a Clymer's or Kaw seervice manual? If not, perhaps I can send you the pages referenced to due the float level measurement.

Jon

Choking the carbs cuts off some of the air getting to the combustion chamber, resulting in a richer mix. If adding choke eliminates your hesitation, then it sounds like your hesitation is caused by a lean mix, or too much air (or not enough gas) getting to the combustion chamber.

The first thing I think of when dealing with a lean condition is vacuum leaks. That's because there are so many areas that can leak vacuum, i.e. pinholes in vacuum hoses, cracked and old rubber manifolds (carb mounts), even rubber vacuum port caps get old and cracked and leaky. Also, if your air cleaners have holes torn in the foam, it will change the air pressure coming through and will effect your performance.

If it is caused by not enough fuel, then your fuel delivery system is suspect, petcock, screens, fuel hoses, carb floats, float valves, etc.

Sorry Jon! I just realized I posted this without seeing all your responses above. I'm not sure how I did that, but I'm on some really strong pain meds since yesterday and I guess I can blame them! Looks like you have this one well under control.

Fegry you points about vacuum leaks are worth checking before anything else. Good ideas there.

Jon