SuzukiSavage.com - where to get carb mix screw?

SugarBoogers

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where to get carb mix screw?
10/08/17 at 09:40:50

Hi all. I haven't been here in a long time (a year?) because frankly my bike doesn't give me any problems Roll Eyes

The PO buggered over my air mix screw. I have the classic backfire on shutdown, and at the same time, I have black soot on my rear brake linkage/drum.

So, I don't know if it's rich and lean at the same time Cheesy

I has a Jardine "muffler" and a K&N Lifetime air filter in the stock air box.

Poss. it could stand to be rejetted, but it seems to run fine in all aspects. I was thinking I should do first things first. A brief search shows $28 shipped on bikebandit for screw, spring, washer, and o-ring.

Where can I get that air screw most cheaply?

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Dave

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Re: where to get carb mix screw?
Reply #1 - 10/08/17 at 13:07:47

The mixture screw is a factory part - you can only get it from someone that sells Suzuki parts.

The explosion on shut down occurs because you have turned off the ignition - but as the engine is coasting to a stop it continues to pull air through carb, and pump the air/fuel mix out the engine and into the hot exhaust pipe. Once the hot header and muffler heats the unburned fuel/air mix to the ignition temperature - it explodes in the exhaust. The more open the exhaust is, the louder the bang!

Lowering the idle speed can help reduce the number of revolutions it takes for the engine to come to a stop - which can reduce the amount of air/fuel in the exhaust and therefore reduce the explosion. Just be sure to keep the idle speed above 1,100 so you have good oil pressure at idle. You can also keep the bike in gear and use the clutch to slow the engine down faster when you turn off the ignition - use the kill switch to shut off the ignition as you will need your left hand to feather the clutch.

I also wonder if opening the throttle with your right hand as you turn off the ignition would help? It sounds counter intuitive - but when the butterfly opens it reduces the vacuum at the idle circuit holes in the carb, and it may actually reduce the amount of fuel being mixed with the incoming air......Are you brave enough to try it and be the first one to experiment with this concept?

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Eegore Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 8001	Re: where to get carb mix screw? Reply #2 - 10/11/17 at 12:12:16 Dave one of my bikes sounds like a rifle when I shut it down. Coasting reduces the sound a bit, and using 1st to slow and dropping the stand, or kills-switch reduces it a significant amount. Holding the throttle open and dropping the kickstand makes it sound like a cannon. Just an FYI.
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Re: where to get carb mix screw?
Reply #3 - 10/11/17 at 12:47:24

Eegore wrote on 10/11/17 at 12:12:16:

Holding the throttle open and dropping the kickstand makes it sound like a cannon. Just an FYI.

Wrong order.....drop the kickstand to kill the ignition, then immediately open the throttle. You want the rpm as low as possible when you kill the ignition by using the key or kill switch or kick stand.

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Eegore Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 8001	Re: where to get carb mix screw? Reply #4 - 10/12/17 at 08:28:48 Ahh ok I will try it when I get back to CO. Kill bike then open throttle.
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batman Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 3806 osceola new york Gender:	Re: where to get carb mix screw? Reply #5 - 10/12/17 at 12:34:38 Or go the other way ,shift into neutral,let the motor fall to idle,and pullout the choke just before hitting the kill switch.
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Dave

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Re: where to get carb mix screw?
Reply #6 - 10/12/17 at 13:16:58

batman wrote on 10/12/17 at 12:34:38:

Or go the other way ,shift into neutral,let the motor fall to idle,and pullout the choke just before hitting the kill switch.

Seems to me that would put "more" fuel in the exhaust........not less.

Opening the throttle would cause the butterfly plate to move the flow of air away from the idle circuit port in the carb throat, and the flow of fuel would drop considerably and less would be available to fuel the explosion.

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Kris01 Serious Thumper Offline Eat, sleep, RIDE! Posts: 3767 Tennessee Gender:	Re: where to get carb mix screw? Reply #7 - 10/12/17 at 18:26:53 Why does opening the throttle after the stand goes down help to eliminate the shutdown pop?
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Re: where to get carb mix screw?
Reply #8 - 10/12/17 at 18:57:07

It is just a theory at this point....it needs to be proven.

When the throttle is closed, the butterfly has most of the carb throat blocked off, and the engine vacuum pulls air past the small holes where the small amount of fuel necessary for idle is added.

Dropping the kick stand while the transmission in gear will kill the ignition, or you can turn off the key or use the kill switch.

I believe that when the ignition is turned off and the engine is slowing down - opening the throttle will open the butterfly and the air will have the entire carb throat to flow through - so the amount of air will increase but the velocity of the air at the edge of the butterfly where the idle fuel ports are will drop dramatically.....and I believe it will not have enough velocity or vacuum to pull the fuel out of the idle circuit.

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LANCER Serious Thumper Alliance Member Offline Savage Beast Performance Parts Posts: 10589 Oklahoma Gender:	Re: where to get carb mix screw? Reply #9 - 10/14/17 at 05:22:45 Leaving the bike in gear and at idle, I let up on the clutch lever just slightly (not moving though) as I hit the kill switch. The engine just stops. No pops.
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buster6315 Senior Member Offline SuzukiSavage.com Rocks! Posts: 353	Re: anti pop Reply #10 - 10/14/17 at 19:31:12 I, for one, rather like my 'poof' at shut-off. I don't find it objectionable in the least.
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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: where to get carb mix screw? Reply #11 - 10/14/17 at 23:04:07 Have you always been a Poofter or is that a recent development?
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LANCER Serious Thumper Alliance Member Offline Savage Beast Performance Parts Posts: 10589 Oklahoma Gender:	Re: where to get carb mix screw? Reply #12 - 10/15/17 at 01:47:01 Personally, I've been known to POOF from time to time.
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Re: anti pop
Reply #13 - 10/15/17 at 03:47:34

buster6315 wrote on 10/14/17 at 19:31:12:

I, for one, rather like my 'poof' at shut-off. I don't find it objectionable in the least.

If the idle speed is a bit fast, the idle mixture is lean, and you have a free flowing muffler........the POOF can actually be a shotgun blast! Shocked

The only time my bike will make any sort of sound is if I have been running pretty fast and got the exhaust system really hot. If there is any slow riding to get to a parking space or through traffic, the exhaust cools down enough that I don't get any noise when the bike is turned off.

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Ruttly Serious Thumper Offline Thumpers Rule Posts: 4997 Manteca , CA Gender:	Re: where to get carb mix screw? Reply #14 - 10/15/17 at 15:07:05 The only time I got anything was during tuning, got a small pop when it was shutdown , I already knew it was lean by lack of giddy up n go !
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