2008 skidoo 500ss idle adjustment

[racerxnet]

They are not air screws, they are fuel screws. Therefore turning them out adds fuel making it richer.

I suggested that you do some research and learn from Mikuhni what the screw does in this matter. I have linked the page to the tuning manual from said company. You are turning a air bleed screw. In is fatter and out is leaner. The screw meters the amount of air along with the pilot jet (fuel at a fixed rate based on hole diameter) for low speed A/f ratio.

http://www.mikunipower.com/Manuals/VM_Manual.pdf

Page 6 describes the process.

Have a nice day and ride safe.

MAK

 

[snowbuff]

We are not talking about the air screw, we are talking about the fuel screw. The carb on this sled does not even have that air scerew. So before you tell me to do research... do your own. That link is of the wrong carb.

 

[racerxnet]

snowbuff We are not talking about the air screw, we are talking about the fuel screw. The carb on this sled does not even have that air scerew. So before you tell me to do research... do your own. That link is of the wrong carb.

The Ski Doo in particular has the 40mm TM series carbs on it. Part#TM40-B352Z1 . Part number 49 is the only external adjustment to control the A/F ratio at idle. The prior link provides a good overview on how a carb is engineered and functions. Not much has changed with idle and main fuel circuits.

Link to TM series carb: http://www.sudco.com/Diagrams123/exptm.gif

If you could please enlighten me to the fuel enrichment screw vs. air screw, I would be happy to dig a bit deeper. I have 3 racks of the TM series carbs in my shop and have rebuilt many over the years. Part #49 is listed as Air Screw Pilot for a reason.

Have a nice day!

MAK

 

[snowbuff]

I'm not trying to argue with you racer, I'm just trying to help skidoo50.

The carb on this sled does not even have part #49, it does not exist on this carb. It does, however have part #56, which is the adjustable thumbwheel for the fuel screw. Some do have both but, this one should not. Manufactures specs vary on what they want or need. Just because it's a mikuhni does not mean they are all made to the same specs.

 

[racerxnet]

Hi snowbuff,

I don't argue with people. I simply supply data on various subjects I am familiar with. I agree that the Ski Doo diagram does not show a air bleed screw. It may have a air bleed jet, but without having the carb in my hand I could not positively say how the idle circuit is metered.

# 57 appears to be a slide adjustment screw, but again not positive. If I could get a picture of the carb from various angles and the horn area one can identify how the idle circuit functions. There are TM series where you can remove the air bleed jet from the horn with a small straight blade and change the A/F mixture. I this case I would probably just change the pilot jets and be done with the problem, and accept the slight additional fuel consumption. My 2000 Vmax 500 was a fuel hog and I went the other way on both mains and pilots. I got about 4 miles to a gallon. Ugh!!

Link to air jets: http://www.sudco.com/mikuni_aj.html#bs3097

I try to help as you do, and most people have the incorrect assumption regarding the air bleed screw adjustment. You are metering air into the pilot emulsion tube area. Closing the screw meters less air and fattens the idle mixture where said adjustment is available.

Though this may not apply in all cases, it is still valuable information where applicable. I hope you and I can continue helping people in the future.

As always, have a nice day..

MAK

 

[snowbuff]

In '00 or '02, doo got rid of the air bleed screw on most flat slide carbs. This did create alot of confusion, as people were used to adjusting for air. (in = richer). With the new fuel screw it's just the opposite (in = leaner). It does get confusing, you just need to know the difference. Some, poo, has both. I know what you are saying, I work on these all the time, but in this case there is no air bleed screw.

You are right about #56 being the slide stop, but rack style carbs don't have that either. The correct location for the thumbwheel in question would be part #10

 

[600etec]

I have owned 01, 02 600's with the same motor and carb set up the issues is the pilot circuit is dirty plain and simple! I have experienced the same problem...you need to take out the mixture screws and the pilot jets and put carb cleaner in and blow the passage(circuit) out with compressed air. If it is really bad you will need to soak the carbs overnight in cleaner. this will solve your problem.

As stated the pilot circuit is not allowing enough gas through which is leaning the motor out at idle. that is why burpping the gas or flipping the choke up will idle it down.

I know about carb boots and all that and it is good to check but this is the pilot circuit issue...