Do I need to rejet my Carb? By cirnobyl (Read 3,632 times)

[cirnobyl]

So while I'm doing other fixes on my bike, I decided to see if I could eke more performance out of my bike. Well first thing I looked at was the airbox. After doing some experimenting I came up with this number:



Of course it didn't run with that. The slightest twist of the throttle would make it bog and die. So that has me thinking the pilot jet. I haven't been able to test it yet but I was hoping that backing the pilot jet screw all the way off may offer enough fuel. Or am I misunderstanding what that screw adjustment does? I know a guy who can get carb jets for me if necessary.

Also, when you do a mod to the intake you should do somethng to the exhaust too, ya know? So what are you guys opinions in that area? Just drill the stock exhaust (or partly debaffle it) or is there a aftermarket solution? My bike is a 244 CFmoto type btw.

[Alleyoop]

Taking the pilot jet out will probably be to much fuel. Have you tried Adjusting the Air/Fuel mixture, turn the out at least 2 1/2 turns and see if it gets better maybe even more turns. But be carefull to many turns out and it may vibrate out and you will loose it. If you get it to run with it out then put some silicone on it to keep it from vibrateing out. The Pilot jet is good up to about 15mph then the needle comes to play up to about 3/4 then the main jet to wot.
You may have to also go up on the Main Jet, but you won't know until you get the idle and midrange working.
Alleyoop

[cirnobyl]

Its hard to do fine tuning on those screws since with the carb tightened in you can't access them. What little bit I did yesterday pretty much involved taking the carb off, messing with the screw, putting the carb back on, starting it, listen, repeat.

oh btw which screw is a/f? So far the only 2 I've seen is the pilot and the one on the bottom I assume is for the float.

Update:

OK did some more adjustments on the pilot screw. I tightened it all the way in, backed it out 2 1/2 turns, ran it, then another turn, ran it, and then my battery went dead lol. With 3 1/2 turns out it'd still bog but wouldn't die upon adding throttle. Thus I was able to get it mid rpm and WOT. It was awfully rough at mid throttle but really picked up closer to WOT and got a kind GROOOMM sound to it. I liked that, now to make it sound like that through the whole powerband.

My stupid jet Needle doesn't have any notches for adjustment so I made a spacer out of alu foil and I will test it tommorow.

[scootaway]

Cirnobyl Alleyoop is right you can never take the idle jet out as it will never idle. The idle jet must be in tight ,however you can alter the value (a little number like #38 or #40 will be stamped on it) The reason why it is bogging down is because the original air intake point (the two little holes) is gone and the engine is now getting a lot of air but still the same amount of fuel. You will have to alter the idle jet, the jet needle (here I suggest buy another one with grooves but of the same value as it too has a value) and the main jet. I have a #38 idle, 118 main, same needle just on the 2nd groove from top. A word of warning though. Once you alter the air etc you have set yourself on a road of great frustration unless you lucky and get it right first time. It is however fun and you can teach yourself a lot. Do one thing at a time as that way you can control and undo what you did last.

[Alleyoop]

Scootaway is right on, you need to go up on your pilot jet and main jet. After you put in a bigger pilot jet you will have to re-adjust your Air/Fuel mixture screw to Lean it out. If you have to turn the Air/Fuel Mixture out over 3 turns that means you need a larger Pilot Jet. You want the Air/Fuel Mixture to be out the most 2 1/2 turns so that you have possible adjustments Left for Rich or Lean for Cold and Warm weather running.
Alleyoop

[cirnobyl]

Hey guys, thanks for the advice. I know a local guy who is a expert on motorcycle mechanics. He has access to all the jets I need and I will probably get with him sometime later this week. But for now! I have a treat for you...

My aluminum foil spacer worked...in fact probably too well as you will see..



The pop at the end wasn't so bad. A oil line that went into the valve cover popped out and sprayed oil all over the place. I got pics...





EDIT: The oil looked watery too me so I took a sniff and it has a bit of a gasoline smell. Since changing the stator will cause all my oil to come out I will just let her sit till it comes time to do the big job. Second, somehow the a/f tightened itself all the way down magically. The test you see done here was with the A/F screw all the way in. A second test after i fixed all the hoses got the fast idle down by simply adjusting the idle screw. I will invest in a adjustable needle jet later. I think my spacer is allowing the needle jet to supply some fuel during idle :S. When I get the oil changed out and can run it for awhile I'll run her and see if the plug comes out gunky.

[Alleyoop]

Cirnobyl,
If your Air/Fuel mixture is loose and won't hold its position, you can either take it out and stretch the Spring a little so it puts tension and holds it in position or you can put a little dab of silicone on the screw so it does not move once you get it set.
Alleyoop

[cirnobyl]

Ok I don't want to open a new thread so I'll ask this here. Since I've gotten into this performance improvement mode I went on and bought some parts from scrappy dogs. Most of it worked fine but the 32mm carburetor didn't have the same connections for the choke that my old one did.

So here is a pic of my old choke, my new not yet installed stator and a blurry example of how they relate.



The blue circle is showing where the line from the choke (enrichment circuit) hooks up to one of the yellow AC connections from the stator. My new stator has an extra plug just for this.

The red one shows the connector that goes onto the temp gauge in my thermostat. The new carb doesn't have a connection for the temp sensor. So then my temp gauge is pegged at hot on a cold start. So...

My old choke, does it rely on info from the temp sensor to variate how open or closed it is? Should I install my old choke into my new carb?