Carburetor Pilot Screw Setting

[crazydj]

Hi guys

 

My carburettor is running too rich. I get poor mileage, a strong carbon smell and the spark plug is carbon fouled.

 

Do i screw the Pilot Screw in (right) or out (left) to make it more lean?

 

My carburettor is a MIKUNI VM22SH. In the service manual, it just stated that after i install the pilot screw, the Pilot Screw Setting is 1-1/2 turns out. So does this mean screw it all the way in and then unscrew it 1.5 turns out?

[Demon]

Hi guys

 

My carburettor is running too rich. I get poor mileage, a strong carbon smell and the spark plug is carbon fouled.

 

There could be alot of other reasons for running rich besides the air fuel mixture adjustment such as dirty air filter, wrong heat range plug, restricted muffler ...etc

 

Do i screw the Pilot Screw in (right) or out (left) to make it more lean?

 

Turn in to lean, turn out to richen

 

My carburettor is a MIKUNI VM22SH. In the service manual, it just stated that after i install the pilot screw, the Pilot Screw Setting is 1-1/2 turns out. So does this mean screw it all the way in and then unscrew it 1.5 turns out?

 

What you stated is correct.

 

Carb tuning is an art, and there is alot of trial and error. correct size needle, correct shimming, will have a big impact. If you not sure, bring it to a shop.

[crazydj]

dirty air filter, wrong heat range plug, restricted muffler

 

I just replaced my carb a few weeks back. The air filter, spark plug, muffler etc. all is the same. Never change. Before it was changed, i know my old carb was running very lean. I get a horrible 34km/L now compared to my old carb which gives me 42km/L.

 

Also, with this new carb, i have to open my throttle for the engine to turn on, whether using electric or kick start. Like how you see older bikes you need to open a throttle a little bit. Why is this so?

 

If you not sure, bring it to a shop.

 

Roughly how much will a shop charge to tune a carb? Just wondering.

[emarkie_82]

from your story above, seems like playing airscrew doesnt help much.

you may need to do rejetting on your carburetor.

 

but you can try to play with your airscrew first.

turn out anti-clockwise (open) to get the fuel mixture become leaner.

close fully and unscrew 1.5 ~ 2 turn out

[crazydj]

from your story above, seems like playing airscrew doesnt help much.

you may need to do rejetting on your carburetor.

 

but you can try to play with your airscrew first.

turn out anti-clockwise (open) to get the fuel mixture become leaner.

close fully and unscrew 1.5 ~ 2 turn out

 

I changed the magnetic coil of my bike. And suddenly my bike doesn't have that carbon smell, black plugs etc. Now i am close to getting back my original fuel efficiency.

 

Is my bike self-repairing? Haha.

[dynarolla]

Hi,

Does your bike have a TPS? Is it working? If the carb is VM22, I suppose it's the same as the carb of an X1R which has a TPS. Get the TPS set correctly first + your accelerator pump aligned before looking at other areas..

[spaiduhz]

I changed the magnetic coil of my bike. And suddenly my bike doesn't have that carbon smell, black plugs etc. Now i am close to getting back my original fuel efficiency.

 

Is my bike self-repairing? Haha.

 

Just your plug coils not getting enough juice to fire efficiently.

 

I take it your battery keeps getting drained?

[spaiduhz]

Hi guys

 

My carburettor is running too rich. I get poor mileage, a strong carbon smell and the spark plug is carbon fouled.

 

Do i screw the Pilot Screw in (right) or out (left) to make it more lean?

 

My carburettor is a MIKUNI VM22SH. In the service manual, it just stated that after i install the pilot screw, the Pilot Screw Setting is 1-1/2 turns out. So does this mean screw it all the way in and then unscrew it 1.5 turns out?

 

As far as i know, if a carb only has one adjustable screw for afr, its for air. Screw cw in, less air, richer afr. Screw ccw out, leaner afr.

 

Yours is a yamaha spark, if i recall correctly?

[crazydj]

Just your plug coils not getting enough juice to fire efficiently.

 

I take it your battery keeps getting drained?

 

No. My battery is always good one. Never drained. Never start 2 weeks still can electric start.

 

As far as i know, if a carb only has one adjustable screw for afr, its for air. Screw cw in, less air, richer afr. Screw ccw out, leaner afr.

 

Yours is a yamaha spark, if i recall correctly?

 

 

My carb, Mikuni VM22SH has 2 visible screws accessible from the outside. One is on the right side to adjust idling and one is at the bottom which is the pilot screw.

 

And no, i ride a YBR.

[crazydj]

Just your plug coils not getting enough juice to fire efficiently.

 

I take it your battery keeps getting drained?

 

No. My battery is always good one. Never drained. Never start 2 weeks still can electric start.

 

As far as i know, if a carb only has one adjustable screw for afr, its for air. Screw cw in, less air, richer afr. Screw ccw out, leaner afr.

 

Yours is a yamaha spark, if i recall correctly?

 

 

My carb, Mikuni VM22SH has 2 visible screws accessible from the outside. One is on the right side to adjust idling and one is at the bottom which is the pilot screw.

 

And no, i ride a YBR.

[spaiduhz]

And no, i ride a YBR.

 

Ah. Ybr has a shitty magneto coil. I would have thought after so many iterations, they would have fixed it by now.

 

You might want to standby a spare magneto coil and gasket. Thems unpredictable.

 

I should be able to get ybr parts on the cheap. Let me check my workshop on monday.

[crazydj]

Ah. Ybr has a shitty magneto coil. I would have thought after so many iterations, they would have fixed it by now.

 

You might want to standby a spare magneto coil and gasket. Thems unpredictable.

 

I should be able to get ybr parts on the cheap. Let me check my workshop on monday.

 

Yeah dude. I can get the parts cheap as well. Actually, anyone can get the parts cheap.

 

You also know about the magnetic coil? Every dispatch rider and anyone who owned a ybr knows this problem haha. Anyway, do you know why i have to open full throttle when i want to start my hot engine? Here's a link to another thread i made. http://www.singaporebikes.com/forums/showthread.php/317861-Why-do-i-have-to-open-full-throttle-when-i-start-my-bike?highlight=

[spaiduhz]

Yeah dude. I can get the parts cheap as well. Actually, anyone can get the parts cheap.

 

You also know about the magnetic coil? Every dispatch rider and anyone who owned a ybr knows this problem haha. Anyway, do you know why i have to open full throttle when i want to start my hot engine? Here's a link to another thread i made. http://www.singaporebikes.com/forums/showthread.php/317861-Why-do-i-have-to-open-full-throttle-when-i-start-my-bike?highlight=

 

Your mikuni carburator, check whether the float is working. Sometimes, it is a matter of the metal hinge needing to be bent back.

 

Before you send in the bike for a service, open up the overflow nozzle when you have difficulty starting, close it back, and try again. If it fires up, voila its definately a messed up float. If it still doesnt fire up, you may want to revert back to standard carbs.

 

I hope not, since the standard carb is pretty crap.

[crazydj]

Your mikuni carburator, check whether the float is working. Sometimes, it is a matter of the metal hinge needing to be bent back.

 

Before you send in the bike for a service, open up the overflow nozzle when you have difficulty starting, close it back, and try again. If it fires up, voila its definately a messed up float. If it still doesnt fire up, you may want to revert back to standard carbs.

 

I hope not, since the standard carb is pretty crap.

 

The VM22SH is the standard carb. The choke, has almost no use at all. Ever since i got the bike. Used a different carb but same model, same thing also. Almost useless choke. Only useful on really cold rainy mornings.

 

Anyway, the issue here is not really the engine being cold. If the engine is cold, its easier to start than it being hot. In other words, starting the engine in the morning is way easier than in the hot afternoon, after a ride and coming back from buying stuff. Like if i park for like 15 mins or more, i need to open FULL throttle while hitting my electric start for the engine to come to life.

 

If i wait about 12 hours, the whole day and turn on the engine again the next morning, no problems whatsoever. Weird huh?

[spaiduhz]

The VM22SH is the standard carb. The choke, has almost no use at all. Ever since i got the bike. Used a different carb but same model, same thing also. Almost useless choke. Only useful on really cold rainy mornings.

 

Anyway, the issue here is not really the engine being cold. If the engine is cold, its easier to start than it being hot. In other words, starting the engine in the morning is way easier than in the hot afternoon, after a ride and coming back from buying stuff. Like if i park for like 15 mins or more, i need to open FULL throttle while hitting my electric start for the engine to come to life.

 

If i wait about 12 hours, the whole day and turn on the engine again the next morning, no problems whatsoever. Weird huh?

 

Standard carb can adjust idle speed already?

[crazydj]

Standard carb can adjust idle speed already?

 

My idling when engine is hot is at 2k. When it is warm, its at 1.5k. Anything lower and the bike will just keep dying in the morning.

[Stylo]

The way u tune the carb is correct. Fully tighten 1 1/2 out ( +/- 0.5 turn to get the best result you need to try it yourself).

Idle is quite high. Try to lower a bit not less than 1.2krpm (lower engine will off).

Since you already clean the carb. Clean the air filter or change if damage).

Good luck.

[crazydj]

The way u tune the carb is correct. Fully tighten 1 1/2 out ( +/- 0.5 turn to get the best result you need to try it yourself).

Idle is quite high. Try to lower a bit not less than 1.2krpm (lower engine will off).

Since you already clean the carb. Clean the air filter or change if damage).

Good luck.

 

New carb and air filter bro... How like that? Old carb, also same thing.

[Stylo]

New carb and air filter bro... How like that? Old carb, also same thing.

 

For most bike carb best tuning is between 1~ 2 full turn.

You have to try to fine tune like I said +/- half turn. Each time 1/8~1/4 turn. And try to ride it for at least 20km. Before can feel the result. If not try again

eg, from u current setting

-0.5 turn test, then -0.25 turn test, +0.25 turn test and +0.5 turn test. Compare the result( write down on paper to compare result or not later mess out after few try).

Carb tune screw and idle screw is different hope you don't mistaken. After you get the best result in fuel to air mix( that carb tune screw). Then try to reduce the idle rpm.

[spaiduhz]

For most bike carb best tuning is between 1~ 2 full turn.

You have to try to fine tune like I said +/- half turn. Each time 1/8~1/4 turn. And try to ride it for at least 20km. Before can feel the result. If not try again

eg, from u current setting

-0.5 turn test, then -0.25 turn test, +0.25 turn test and +0.5 turn test. Compare the result( write down on paper to compare result or not later mess out after few try).

Carb tune screw and idle screw is different hope you don't mistaken. After you get the best result in fuel to air mix( that carb tune screw). Then try to reduce the idle rpm.

 

Or you could pull the plugs, and make adjustments by colour. If very dark, turn ccw 1/2. If very light, turn cw 1/2. If a little bit dark or light, 1/4 turn in the correct direction.

 

You should wait untill an oil change between turning the carb mixture screw to let it change colour.

[robokp]

For most bike carb best tuning is between 1~ 2 full turn.

You have to try to fine tune like I said +/- half turn. Each time 1/8~1/4 turn. And try to ride it for at least 20km. Before can feel the result. If not try again

eg, from u current setting

-0.5 turn test, then -0.25 turn test, +0.25 turn test and +0.5 turn test. Compare the result( write down on paper to compare result or not later mess out after few try).

Carb tune screw and idle screw is different hope you don't mistaken. After you get the best result in fuel to air mix( that carb tune screw). Then try to reduce the idle rpm.

 

for those who are looking for a pic, http://www.team-bhp.com/forum/iipcache/85465.jpg

i found this pic when i needed a visual