Smooth Bore Carbs staying open how to get them to close faster

[IronPawz]

I've a new bike with smooth bore carbs (I've never had these before). I heard the vacuum can keep them open and I've definitely noticed this happening. I'm happily flying up to a corner, close off the throttle and they half a second they stay open for I'm on that corner and doing a 5c moment slapping on the breaks.

I hear it is possible to add a spring to get them to shut off properly? If I open the throttle (bike off) and just release it, it snaps back as you would expect (this is not a sticky throttle though I will oil it to be sure).

What is the deal here? Any tips on getting it sorted? I am taking it to the mechanic tomorrow who will look at it for me and mentioned the spring but just interested in any comments generally. I also hear they are not the best street carbies (for a lot of commuting) and I've a standard set (engine is GSX1135EFG sitting in Suzuki Katana) but I seems there is a significant power gain with the smoothies so kind of like to hang onto that.

Cheers.

[Big Dog]

Sidecarbob was on about something like what you ask.
I'll see if I can find the thread.

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[jellywrestler]

I've a new bike with smooth bore carbs (I've never had these before). I heard the vacuum can keep them open and I've definitely noticed this happening. I'm happily flying up to a corner, close off the throttle and they half a second they stay open for I'm on that corner and doing a 5c moment slapping on the breaks.

I hear it is possible to add a spring to get them to shut off properly? If I open the throttle (bike off) and just release it, it snaps back as you would expect (this is not a sticky throttle though I will oil it to be sure).

What is the deal here? Any tips on getting it sorted? I am taking it to the mechanic tomorrow who will look at it for me and mentioned the spring but just interested in any comments generally. I also hear they are not the best street carbies (for a lot of commuting) and I've a standard set (engine is GSX1135EFG sitting in Suzuki Katana) but I seems there is a significant power gain with the smoothies so kind of like to hang onto that.

Cheers.

how do you know they are smoothbores and what brand and size are these alleged smoothbores?

[Big Dog]

Does this match what you want to know? http://www.kiwibiker.co.nz/forums/sh...p?p=1130992673

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[IronPawz]

Does this match what you want to know? http://www.kiwibiker.co.nz/forums/sh...p?p=1130992673

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That is my thread on the same bike. I'm lost in that conversation. I don't see anything about running on but things that might sound that way and a some concepts that I just don't really understand. Is that what is being talked about? Smoothies running on and how to prevent them?

[IronPawz]

how do you know they are smoothbores and what brand and size are these alleged smoothbores?

Fair enough I was told they are by the engineer who sold me the bike. He makes bink carbs from complete scratch. This thread on the build discusses the carbs as smooth bores.

"I have rebuilt a set of smoothbore 33mm carbs with new needle and seats, gaskets, and idle air screws etc."

http://www.thegsresources.com/_forum...ight=katanakid

I've this comment from him also re: track day (he has read some of the Kat thread so may even read this). I hope he doesn't mind it was a private email (I will ask in retro spec and remove this if so).

You may want to get a set of #130 Main jets and try them on the day. You may possibly get a bit more punch up the top end. I only managed 1 session at Puke, so never fine-tuned the Smoothies. You can drop the mains out by undoing the 17mm nut under the float bowls. Put a rag under the carbs to catch any fuel that runs out, and do not do it hot!!!

I'll go get a close up and post that.

[Big Dog]

Not enough of a mechanic to say yes or no.

My understanding was that under load the slides may not be closing effectively (In that example provided because of an air box mod) and he was speaking of using the method in the post to stretch the spring to increase the return pressure on the slide thereby overcoming the vacuum.

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[IronPawz]

how do you know they are smoothbores and what brand and size are these alleged smoothbores?

Smoother than a porn stars sniz?

[Big Dog]

Ah, so more no air box than air box mod.


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[IronPawz]

Not enough of a mechanic to say yes or no.

My understanding was that under load the slides may not be closing effectively (In that example provided because of an air box mod) and he was speaking of using the method in the post to stretch the spring to increase the return pressure on the slide thereby overcoming the vacuum.

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Right makes more sense thanks for the translation. I'll send the link to my mechanic who should understand it. He talked about it and should know or have a plan already so perhaps he will share and I'll add that back here also. I hope to over time get time to actually learn some things myself. I can at least get the idea to swap out jets etc I am sure (cold as he mentioned .

[IronPawz]

Ah, so more no air box than air box mod.

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So true, prehaps more resistant filters would help then? I think the air box room is taken up with the internal shock mounts so putting one back in is not likely (I'll go check).

[IronPawz]

Ah, so more no air box than air box mod.

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Yeah there is a very nice cross pipes welded in there for strengthening so no room for the original airbox. It is great to have the standard one to compare. Probably sell that one at some point mind.

[Big Dog]

Sounds like preloading the spring as per sidecar Bob's patented method is one option, finding a longer spring another or your mechanic may have a better answer.

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[IronPawz]

Worst case scenario at Taupo in group 4 (no stress group unless the motard hard nuts are in it again cutting everyone up in the corners) I'll just have to learn where the breaks are faster or ride more like a pussy than I do already. I'm more interested in just having a go than doing anything impressive (which is what group 4 is all about). At least I can wind it up on the straights and no one is going the other way.

Other issue is the tires have not moved in some time so as the seller said they are probably a bit stiff. If you are out in Taupo by all means stop by and have a laugh as I putter about.

[Big Dog]

So true, prehaps more resistant filters would help then? I think the air box room is taken up with the internal shock mounts so putting one back in is not likely (I'll go check).

If you are otherwise happy with three carb I'd look for a solution before I went down that road, changing your filter resistance will mess with your fuel air mix.

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