Throttle not returning while engine running ?

[catdna]

Hi All

Got a slight problem with the throttle on my XS1100 trike - when the engine is switched off, the cable is nice and 'snappy', but once the engine is running, it never seems to snap back .... weird

Any ideas what it could be ? Carb Diaphrams ?

Cheers
Chris

[Crazcnuk]

There is no mechanical linkage between the cable and diaphragms.

The usual cause of a hanging throttle cable is the manifold clamp screw on #3 cylinder hitting the cable eye on the carbs.

Other than that or a dirty throttle grip or dirty linkage on the carbs themselves, the last guess would be that your cable is coming apart inside the it's cover.

However, none of this should be different whether running or not.

[catdna]

There is no mechanical linkage between the cable and diaphragms.

The usual cause of a hanging throttle cable is the manifold clamp screw on #3 cylinder hitting the cable eye on the carbs.

Other than that or a dirty throttle grip or dirty linkage on the carbs themselves, the last guess would be that your cable is coming apart inside the it's cover.

However, none of this should be different whether running or not.

I did take a look at the carbs / linkage and nothing seemed to be physically stopping the throttle from returning, it's a new cable too - definitely no snags and this problem has been happening for a while - however, even if I push the throttle back down, the revs still stay high for a few seconds until returning to normal

Ta

Chris

[trbig]

even if I push the throttle back down, the revs still stay high for a few seconds until returning to normal

I was wondering about that. You need to synchronize your carbs.


Tod

[catdna]

I was wondering about that. You need to synchronize your carbs.


Tod

Hmmm.... well I did only synch them a week or so ago, but doing it again can't hurt I guess :-)

I'll post here this coming weekend and let you know how I get on.

Cheers
Chris

[catdna]

Had fun playing with my carbs - so much so that I invested in a new (well, 2nd hand set from ebay)

First off - much better performance - no more 'lumpy' running for me ! runs perfectly in low revs - haven't had a chance to get 'up to speed' yet - will still need rejetting because of the pod filters and non-standard exhausts.

However - I still have the 'slow drop to idle revs' issue which I've done a bit of searching about on here.

General consensus is that there's an air leak somewhere. Now, the carb-boots are brand new (that's not to say there might not be a leak), but a spray of WD40 in the general area didn't make a difference to the revs

This brings me to a bit of a weird question for you guys. The carb-boots have big 'funnels' in them - which I guess, are usually blocked off and only used for sync purposes on the XS11 ?

On my trike, they're connected to hoses which work the brake servo - however, these hoses aren't exactly 'tight' - could the air leak be around the hoses themselves ? any other places I should check for air leaks ?

Bare in mind, this is the second set of carbs I've had on there - the 'slow drop to idle' isn't as bad (or at least, in my 10 mins of testing, didn't seem as bad) as the old set of carbs, but it's still there

Cheers
Chris

[Shawnb]

throttle

check your throttle cable length might need to readjust your cable position on your throtlle itself .

[catdna]

check your throttle cable length might need to readjust your cable position on your throtlle itself .

Hmmmm.... well, the throttle cable length is 2.5 meters (give or take a few inches - it's got *really* long handlebars my trike) !

Which bit should I check ? should I give it a bit more free play ?

Cheers
Chris

[CatatonicBug]

This brings me to a bit of a weird question for you guys. The carb-boots have big 'funnels' in them - which I guess, are usually blocked off and only used for sync purposes on the XS11 ?

On my trike, they're connected to hoses which work the brake servo - however, these hoses aren't exactly 'tight' - could the air leak be around the hoses themselves ? any other places I should check for air leaks ?

I'm not sure what you mean by "funnels". There are vacuum ports on each carb boot (the side closest to the engine) that should be tightly plugged at all times when you're not synching the carbs. Usually, the one on Carb #2 is connected to the vacuum advance mechanism. If these ports are not properly capped, there will definitely be a problem. Is that what you were referring to?

[cywelchjr]

This brings me to a bit of a weird question for you guys. The carb-boots have big 'funnels' in them - which I guess, are usually blocked off and only used for sync purposes on the XS11 ?

On my trike, they're connected to hoses which work the brake servo - however, these hoses aren't exactly 'tight' - could the air leak be around the hoses themselves ? any other places I should check for air leaks ?

Bare in mind, this is the second set of carbs I've had on there - the 'slow drop to idle' isn't as bad (or at least, in my 10 mins of testing, didn't seem as bad) as the old set of carbs, but it's still there

If your talking about the vacuum nipples on the carb boots and if they are connected together to provide vacuum to the brake server that might be a problem. Also it their not tight that could almost certainly cause a leak and cause the problem. If your maintaining vacuum for a brake servo (I'm assuming your talking about some sort of vacuum booster?) then you should have some sort of one way vacuum valve on each line to keep them from interfering with each other as well as making sure there is NO leaking from that part of the system.

[catdna]

I'm not sure what you mean by "funnels". There are vacuum ports on each carb boot (the side closest to the engine) that should be tightly plugged at all times when you're not synching the carbs. Usually, the one on Carb #2 is connected to the vacuum advance mechanism. If these ports are not properly capped, there will definitely be a problem. Is that what you were referring to?

Sorry, yes, I meant the 'ports' (had a long day yesterday ) - I thought it was the port on carb #2 which connected to the vacuum advance, not on the boot ?

\
If your talking about the vacuum nipples on the carb boots and if they are connected together to provide vacuum to the brake server that might be a problem. Also it their not tight that could almost certainly cause a leak and cause the problem. If your maintaining vacuum for a brake servo (I'm assuming your talking about some sort of vacuum booster?) then you should have some sort of one way vacuum valve on each line to keep them from interfering with each other as well as making sure there is NO leaking from that part of the system.

I'm pretty sure there's a valve in the hoses which run to the servo (all 4 go into one hose - a photo might explain the layout a bit better) - I'll take a peak at it this evening - might also try just putting hose clips around each pipe to make sure.

If it's an issue, then I guess I'll have to remove the servo from the trike - it's never worked that well anyway

Cheers
Chris

[petejw]

yeah you are right, the vac advance is connected
to the port ON the carb of number 2.
Id also be clamping any vaccum lines, the fact that they go to a brake booster shouldnt cause any problems.
You could also check the butterfly seals to see if there leaking in air.

[catdna]

yeah you are right, the vac advance is connected
to the port ON the carb of number 2.
Id also be clamping any vaccum lines, the fact that they go to a brake booster shouldnt cause any problems.
You could also check the butterfly seals to see if there leaking in air.

ok.... (put's on novice hat ) - how would I check the butterfly seals to see if there's an air leak ?

Messing around with carbs is all a bit new to me - I know how to balance them, but the internals are all still a bit of a mystery (although reading this forum has helped a lot - this is the first time I'm come across 'checking butterfly seals' !)

Cheers
Chris

[petejw]

give the throttle shaft on each carb a spray of carb cleaner or something similar while the engine is running, if the revs increase theyre sucking air in, if no increase no air leaks, you can spray around the carb manifolds/head and any where there might be a leak. be careful tho, the stuff is highly flamable.