kinda confused here

so as i stated in a previous thread i just bought a 09 sm from a dealer. dealer didnt know much about the bike as the guy faulted his loan and they stole it back from him. now this bike has a RS-4 yoshi exhaust and a somewhat 3x3 mod....the PO did put a 3x3 square hole in the airbox on top but then he put a plastic cover over that and a hole in the middle id say about 2 inches in diameter ( so bascily i have a 2 in diameter mod lol). now the bike seems to run pretty damn good, no hesitations pulls from top to bottom (maybe a little flat up top, but im coming from a 1000cc inline four)

i just took apart the carb today and it looks like its been untouched. the problem im having is that i think the bike is running lean because it pops like a bastard when decelerating, but on the other hand when i start it cold it doesnt need any choke to start, actually if i use full choke it wont start at all and if i use half choke it has a hard time starting but itll finally catch and run (itll idle at a higher RPM of course) and also if at neutral i hold it about 1/8-1/4 throttle itll rev and i can hear it backfire a bit. so the decelerating pops makes me think its running lean, but the cold starts and neutral rev pops makes it seem like its running rich..what gives. the fuel mixture screw still has its brass plug in it so that hasnt been touched yet.

 

i tried pulling the airbox cover off and running it like that (havent actually rode it, just got owned by the cops but thats another story and to make it short i cant put it on the road for a while) and it doesnt seem to change the backfiring at all.

 

im going to order some jets from suzuki and try messing around with a 25 pilot and 155-160 main but im just curious to others opinions on why its running the way it is 

If they put on an aftermarket exhaust and cut out a 3x3 hole in the airbox, they should have rejetted the carb.  Either way, best to find out exactly what's inside (MJ.PJ, etc...).  Also while you have the carb out, drill out the brass plug for the fuel mixture screw.  You could also get an extended fuel screw so it'll be easier (slightly :devil: ) to adjust.

 

If you think it's running lean, then leave the airbox door ON and instead tape off the cut/drilled hole in the airbox.  That will simulate a slightly richer mixture.  Once you get access to the fuel screw, then you can experiment with making adjustments to achieve the fastest/smoothest idle, reduce decel pop and good off-idle response.  However, even with a properly tuned carb you'll get some decel pop with an aftermarket exhaust (nature of the beast, open exhaust lets more noise out).

You are going to hear a lot of popping in the exhaust with an RS4.  Probably just normal.  Also you can't tell much running it in the driveway.  Have to get out and ride it to evaluate.

so as i stated in a previous thread i just bought a 09 sm from a dealer. dealer didnt know much about the bike as the guy faulted his loan and they stole it back from him. now this bike has a RS-4 yoshi exhaust and a somewhat 3x3 mod....the PO did put a 3x3 square hole in the airbox on top but then he put a plastic cover over that and a hole in the middle id say about 2 inches in diameter ( so bascily i have a 2 in diameter mod lol). now the bike seems to run pretty damn good, no hesitations pulls from top to bottom (maybe a little flat up top, but im coming from a 1000cc inline four)

i just took apart the carb today and it looks like its been untouched. the problem im having is that i think the bike is running lean because it pops like a bastard when decelerating, but on the other hand when i start it cold it doesnt need any choke to start, actually if i use full choke it wont start at all and if i use half choke it has a hard time starting but itll finally catch and run (itll idle at a higher RPM of course) and also if at neutral i hold it about 1/8-1/4 throttle itll rev and i can hear it backfire a bit. so the decelerating pops makes me think its running lean, but the cold starts and neutral rev pops makes it seem like its running rich..what gives. the fuel mixture screw still has its brass plug in it so that hasnt been touched yet.

 

i tried pulling the airbox cover off and running it like that (havent actually rode it, just got owned by the cops but thats another story and to make it short i cant put it on the road for a while) and it doesnt seem to change the backfiring at all.

 

im going to order some jets from suzuki and try messing around with a 25 pilot and 155-160 main but im just curious to others opinions on why its running the way it is 

I think I would start by removing the plastic 2x2 cover and purchase a JD needle and jet  kit.

Not needing choke to start cold would indicate a rich pilot circuit, probably not helped by the 2x2 plastic cover.

Install a JD jet kit and revise the intake hole back to 3x3....

The adjustable needle can not be purchased separately..your wasting your time changing out the main jet and not replacing the needle....

first thanks for the replys.

was doing some research on jets to see if i can find the ID dimensions on specific jets, i was going to measure the ones i pulled out at work tomorrow but i found an even easier solution. the jets have their size stamped right on them haha. so yeah like i thought i have the stock main jet (142.5) and pilot (22.5) in there

just very weird that it starts with no choke....ill look into the air jets tomorrow to make sure they are stock sizes and are not clogged.

 

Install a JD jet kit and revise the intake hole back to 3x3....

The adjustable needle can not be purchased separately..your wasting your time changing out the main jet and not replacing the needle....

yeah, i was trying to avoid spending the 80 bucks because i plan on going with the fcr carb in the near future and i thought i could get away with bigger P&M jets...guess not haha

first thanks for the replys.

was doing some research on jets to see if i can find the ID dimensions on specific jets, i was going to measure the ones i pulled out at work tomorrow but i found an even easier solution. the jets have their size stamped right on them haha. so yeah like i thought i have the stock main jet (142.5) and pilot (22.5) in there

just very weird that it starts with no choke....ill look into the air jets tomorrow to make sure they are stock sizes and are not clogged.

 

yeah, i was trying to avoid spending the 80 bucks because i plan on going with the fcr carb in the near future and i thought i could get away with bigger P&M jets...guess not haha

 

You can shim the stock needle to richen the fuel mix, but does not fix the profile of the needle to obtain the correct fuel curve

another Connecticut rider... Welcome aboard. get a JD jet kit it has everything you need and superior taper on the needle. Where in CT are you? Is this an SM or do you ride dirt?

Is this an SM or do you ride dirt?

With a RS4 id very surprised if its a dirt bike.

another Connecticut rider... Welcome aboard. get a JD jet kit it has everything you need and superior taper on the needle. Where in CT are you? Is this an SM or do you ride dirt?

 

im riding and sm from manchester. just ordered the JD kit

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