Will 83-86 450 Carbs drop in to an 81 450?

[Broncoman75]

I am sick of chasing the hanging idle issue on my wife's 81 450 and am thinking of getting a different set of carbs to try out. The ones I spotted on ebay are off a newer model ('86) and have the cable actuated side pull choke. Does anyone know if they will just drop in and fit up to the airbox in this 81?

 

[Guest]

Maybe.

I don't see any reason why it wouldn't work.

Up to 88 I believe the carbs overall dimensions are the same. The differences are the choke mechanism and float bowl/floats.


What have to tried?

Hanging idle is usually a lean condition.

As in you closed the throttle all the way but there is still enough air and a bit of fuel still getting through.

Or the throttle is open allot at idle and there is little fuel to mix with it.

After 88 you get into the gs500 that has a different type of carb design but still fits on the engine but not the airbox.



One thing that I've seen cause a leak in these carbs that is fixed by replacing them is the seals on each side of the carb. These seals are for the pin that the butterfly valve rotates on. They do go bad after a while and can leak allot.


I have one set of carbs I just finished dipping and rebuilding. After that I usually check for a good tight seal with the valve closed all the way. I noticed a big difference with one compared to the other. I sprayed some oil around the whole carb while it was under vacuum and when I looked inside I could see a trace coming from the where the pin goes through the side of the carb.
Then I pulled out the seal and replaced them with O-rings and that fixed the leak.

So thats one possibility that newer carbs will fix.

 

[Broncoman75]

Maybe.

I don't see any reason why it wouldn't work.

Up to 88 I believe the carbs overall dimensions are the same. The differences are the choke mechanism and float bowl/floats.


What have to tried?

Hanging idle is usually a lean condition.

As in you closed the throttle all the way but there is still enough air and a bit of fuel still getting through.

Or the throttle is open allot at idle and there is little fuel to mix with it.

After 88 you get into the gs500 that has a different type of carb design but still fits on the engine but not the airbox.



One thing that I've seen cause a leak in these carbs that is fixed by replacing them is the seals on each side of the carb. These seals are for the pin that the butterfly valve rotates on. They do go bad after a while and can leak allot.


I have one set of carbs I just finished dipping and rebuilding. After that I usually check for a good tight seal with the valve closed all the way. I noticed a big difference with one compared to the other. I sprayed some oil around the whole carb while it was under vacuum and when I looked inside I could see a trace coming from the where the pin goes through the side of the carb.
Then I pulled out the seal and replaced them with O-rings and that fixed the leak.

So thats one possibility that newer carbs will fix.

I have dipped and cleaned the carbs a few times. I have checked the boots for leaks and replaced the orings as well as the orings in the carbs. Had the head off due to exhaust bolts the po broke. Adjusted the valves at the same time to .003 ex and .0015" intake. New boots on th airbox side of the carbs as well. Have verified the throttle closed all the way. Have made sure the choke operates and disengages. Have adjusted the idle screw, and the pilot mixture screws verified zall jet passages clean. Checked float levels, New float needles and seats. Checked diagrams.
The only way I can get it to not hang once it gets hot is to back the idle screw out to where it idle so low it dies. I bench synced the carbs too, but don't have a manometer. I am at my wits end.... I guess I will looking into the shaft seals you mention but at this point I'm desperate enough to start over with some other carbs, or maybe look into sticking advance mechanism if this bike even has one as I read that can cause the same problem.

 

[Guest]

The Advance mechanism is pretty simple its only 2 springs and if they get weak it ust goes to full advance .all the time. Its an easy thing to check using a timing light.

Those seals will make the bench synch you did useless!! Found that out the hard way.

If one leaks more than the other your way off on the synch. One side running lean will drag the other one and make it rev up.