TOPIC:

OK. Don't laugh... do the carbs have to be off the bike to check and set float mechanism?

KZErider wrote:

OK. Don't laugh... do the carbs have to be off the bike to check and set float mechanism?

Depends on what you want to check. You can check the level of the fuel in the bowl, which is a function of the needle valve and seat, float condition and float adjustment, with carbs on bike.
To check the actual condition of the needle valve and seat, the tang adjustment, responsible for float level, and the float itself, like for cracks etc., the carbs all need to come off as a complete assembly.

BTW KZERider I don't actually know anything about these bikes, but how else am I supposed to get my post count up to 987,158,458 like some folks on the forum!
Besides, if anyones answer is just dead wrong, these guys are _QUICK_ to let you know!

Post edited by: JimatMilkyWay, at: 2007/03/02 11:54

What yu want to check is the fuel level which is controlled by the float mechanism and yu can do this with the carbs on the bike. Hook up some tubing like in the pic below and open the drain screw on the bottom of the bowl. Look for a fuel level in the tube which is a couple of mm below the seam between bowl and carb body.

You might just be able to see the level in the pic.

Now float adjustment - thats a different story. There are some who say you can take off the bowls with the carbs on the bike but I could never do it. I always found it easier to take the carbs off the bike first. If you do have to make adjustments to the float mechanism try to hook up something so that you can adjust, replace the bowl, and check the level without having to take the carbs on and off the bike repeatedly.

This bit can be a PITA but when it's done it's done.

Good Luck

Concur with JR.

Here's how:

adjust float level

Thanks, Jim, JR and Patton. That's quite a long thread so a bookmarked it to soak it in tomorrow. Never thought to search under dropping a cylinder before posting a new topic. Seems like all we need to find out is there if we know how to find it. And when we don't, you guys are tremendous at helping out.

To avoid possible confusion about the clear plastic tube method for determining fuel level in the float bowl --

Fuel from the float bowl into the clear tubing must come from the float bowl DRAIN hole (NOT from the overflow hole or overflow nipple).

When fuel comes from the float bowl overflow, the level is already too high. You are not testing the overflow level. You are testing the service fuel level as determined by the float.

Mikuni float bowls with side drain hole screws are easier to access with the clear tubing (just ignore the overflow nipples on bottoms of float bowls).

Mikuni smoothbores do not have an overflow, just a bottom screw for both drain and quick access to the main jet. So just fab up a connection for the clear tube.

A little leakage at connection of clear tube and drain hole is okay during testing because fuel is entering the bowl faster than leaking out and will not affect the reading.

Keihin carbs apparently have the drain hole on the bottom of the float bowl where it might be confused with the overflow.

Regardless of carb type, be sure to attach the clear tubing to the float bowl DRAIN -- not the overflow.

JR wrote:

What yu want to check is the fuel level which is controlled by the float mechanism and yu can do this with the carbs on the bike. Hook up some tubing like in the pic below and open the drain screw on the bottom of the bowl. Look for a fuel level in the tube which is a couple of mm below the seam between bowl and carb body.

You might just be able to see the level in the pic.

Now float adjustment - thats a different story. There are some who say you can take off the bowls with the carbs on the bike but I could never do it. I always found it easier to take the carbs off the bike first. If you do have to make adjustments to the float mechanism try to hook up something so that you can adjust, replace the bowl, and check the level without having to take the carbs on and off the bike repeatedly.

This bit can be a PITA but when it's done it's done.

Good Luck

I _shore_ did look long and hard, locally, to find a 6mm X 0.75 (I think 0.75 is correct) pitch nipple or something, to screw into the drain hole which I could then attach my float-level tube to.
If someone could tell me where to get one I would buy 'em some cool ade or sumpin.
As it is, I have a piece of appropriate size silicone tube "threaded" into the hole. It ain't satisfactory, but then maybe I just shouldn't be such a sissy when it comes to using my shop vac to suck up 25 gal of gasoline off the garage floor.

Patton wrote:

Keihin carbs apparently have the drain hole on the bottom of the float bowl where it might be confused with the overflow.

KZErider and I have the same bike and the same Keihin CV34 carbs just like the one shown in the photo.

On this carb the drain hole and the overflow are one and the same thing. It's the brass nipple on the very bottom of the float bowl. Open the drain screw and gas comes out the overflow. The nice thing about this is that you just have to get the tubing to fit over the nipple and if you have clear overflow tubes they can double as fuel level indicators if you just hold em up and open the drain screw

I think even the Keihins on the 400s have separate drain and overflow holes and as Patton describes the Mikunis all seem to have separate drain and overflow holes. In these situations you have to find something or some way to screw the tubing into a hole.

Us 750/4 people are a bit odball

JR wrote:

...KZErider and I have the same bike and the same Keihin CV34 carbs just like the one shown in the photo. On this carb the drain hole and the overflow are one and the same thing. It's the brass nipple on the very bottom of the float bowl. Open the drain screw and gas comes out the overflow. The nice thing about this is that you just have to get the tubing to fit over the nipple and if you have clear overflow tubes they can double as fuel level indicators if you just hold em up and open the drain screw.

I think even the Keihins on the 400s have separate drain and overflow holes and as Patton describes the Mikunis all seem to have separate drain and overflow holes. In these situations you have to find something or some way to screw the tubing into a hole....

Many thanks, JR, for clearing that up about Keihin carbs on 750 models using the same bowl outlet nipple for both drain and overflow.

Patton wrote:

Many thanks, JR, for clearing that up about Keihin carbs on 750 models using the same bowl outlet nipple for both drain and overflow.

Are we all sure about that? By definition, I can't see a overflow tube connecting to a drain hole?
Does someone have a diaphragm,, err, I mean a diagram?

JimatMilkyWay wrote:

Patton wrote:

Many thanks, JR, for clearing that up about Keihin carbs on 750 models using the same bowl outlet nipple for both drain and overflow.

Are we all sure about that? By definition, I can't see a overflow tube connecting to a drain hole? ....

Mikuni overflow design allows excess fuel a direct escape path through the under-bowl nipple leaving normal non-excess fuel in the bowl. Loosening Mikuni drain screw allows bowl to completely empty through the drain screw hole.

Suspect Keihin overflow design is similar in allowing excess fuel a direct escape path through the nipple leaving normal non-excess fuel in the bowl. But with this design Keihin, am learning that loosening the drain screw allows bowl to completely empty through the same nipple used for overflow (instead of emptying though the drain screw hole).

JimatMilkyWay wrote:

I _shore_ did look long and hard, locally, to find a 6mm X 0.75 (I think 0.75 is correct) pitch nipple or something, to screw into the drain hole which I could then attach my float-level tube to.
If someone could tell me where to get one I would buy 'em some cool ade or sumpin.

I wonder if something like this would work:

???????



Post edited by: Skyman, at: 2007/03/04 00:13

Post edited by: steell, at: 2007/03/04 14:13