Triumphrat

donco

Stock '04 TBS with Keihin flatslides. Found the cause of the sticking throttle -- the butt end of the hand grip was rubbing on the metal bar end. Scooted the grip inward & throttle is smooth, but . . .

in the process of checking it out, I noticed the middle carb randomly hangs part way when opening with the engine not running. I've been told the slides are hollow and can get bulged out from a backfire & stick. I thought the slides only move when the engine is running and that the throttle cable only actuates a butterfly.

I put a stethoscope on each of the carbs and cranked the throttle full stroke several times & the middle carb has a different, louder click that's not present in the other 2.

Any suggestions for checking it out further before take the carb apart?

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donco

You don't quit riding because you grow old, you grow old because you quit riding.

jimmyj900

FCR's aren't CV carbs -- the slide is manually operated so if you've got a slide sticking then there's a linkage problem at the carbs.

I'd suspect a loose stop screw on the link arm.

Jim

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rayhyland

hey Jimmy, it's not nice to suggest someone has a screw loose...




(Sorry, I just couldn't resist) :-D

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"It will always be better to be shot out of a cannon than squeezed out of a tube, and that's why God made fast motorcycles" - HST

jimmyj900

Like putting large bore FCR's on an otherwise stock bike? :-D

Jim

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MickMaguire

Or if the info is correct that a forward fire can damage the carb, then it could be internal. Have you had it forward fire on you?

Are the carbs in good shape, are they clean? Are you running them with filters? I would guess (not having touched FCRs) that dirt ingress or other foriegn bodies in the carbs could cause the slides to stick.

However, start simple, and as Jimmy suggests "suspect a loose stop screw on the link arm."

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Mick...

donco

The bike runs very nice for the most part. Some minor popping & flat spots at low-mid range when cold which I attribute to altitude (5500 ft) & jetting. It runs great when warm but hard to get it to pull redline which I'm thinking likewise is partly due to jetting/altitude, & partly due to only having 3200 miles on the bike -- it's not fully broken in yet & is still a little tight. It pulls redline alot better than it did last season.

I put a K&N filter & replaced the rubber boot that joins the airbox to the silencer with screen mesh & drilled a 1" breather hole in the right side airbox to free it up a little -- again, need to get it jetted. I'm postponing re-jetting until after I finish building the 3-1 exhaust.

I suppose I could have gotten some crud in the carb when doing the filter, but other than that, they appear spotless.

As for the sticking, I can't say it causes any issues with the way it runs. The throttle motion on the middle carb sticks slightly at about 1/3 throttle when opening, but returns from full throttle to idle position smoothly without hanging. The carbs all get full throttle simultaneously and return to idle equally well. Perhaps I could hook a syncronizer to it, which I've been meaning to do anyway. That would show if the middle one is behaving abnormally if I used a 3-channel sync. No signs of a loose throttle shaft/linkage screw.

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donco

You don't quit riding because you grow old, you grow old because you quit riding.

jimmyj900

Wait a minute.... Are you sure you've got flatslides and not the stock CVK's?

I've never heard of a setup that uses flatsides and the stock airboxes.

Jim

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donco

I'm terribly sorry, my bad. Yes, they are the CVK's. These are "constant velocity" carbs, right? That goes back to my initial premise that the slides don't move when the engine is not running. The throttle cable actuates the butterfly shafts, and only when running, does the air flow/vacuum actuate the slides, correct? So my sticking middle carb when it's not running must be related to the shaft/fittings or perhaps the butterfly, and not the slide(s), which goes back to your initial assessment that its a loose screw on the shaft. I'll check it out some more when I take the tank off to sync them.

Thanks!

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donco

You don't quit riding because you grow old, you grow old because you quit riding.

jimmyj900

No problem, but a lot more clarity! :-D

Yep, they're CVK constant velocity carbs and you're correct that the butterfly is manually actuated and that the slides are airflow actuated.

The center carb is the master carb and the butterfly controlled directly by the throttle cable, so if the center butterfly is sticking then all of the butterflies are staying open.

I'd remove the carbs and verify visually that there's sticking. If you don't find any sticking with the carbs removed then it's probably the throttle cable or grip. Lube the cable (I use synthetic engine oil), check for a kink in the cable and check the grease in the grip end.

Jim

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