AP diaphram/jetting/merge racing adj leak pump?

Hello...Im a newbie...2nd post. Couple quick ?'s...sorry if this has been way over talked about. Riding a 06 kx450f stock, bought new last year...40ish hrs, and started running bad (lean probs...throttle bog, popping on decel). Figured clogged jetting, dirty carb, so I pulled it a few days ago to clean, (also bought r&d adj fuel/air screw...figured it would be a good time to install). As Im pulling the ap cover and float bowl, i notice small rubber pieces, only to see that my ap diaphram looks like a small dog chewed on it??? This bike has been maintained, running premium pump gas,and has never sat for more then 3 weeks...How does this happen, and any suggestion for future?? Also, my first post was about ap o-ring mod, or just adjusting ap screw...got lots a great feedback, so i have merge adj leak pump on order right now. Was wondering how hard to tune in with air screw simultaneously, and possible recommended settings for sea level to 1800 ft. Any input would be much appritiated. Thanks agian.

The AP diaphragm probably did not like the ethanol fuel.

You could drain the carb after each session but that would require float bowl pulling.

Since you are thinking about installinthe ALJ, I suggest you pony up and get the stiffer Merge AP can sprinmg too, eliminate the chance of a failed oring.

BTW, it is a fuel screw, not an air screw on a FCR.

Fuel Screw/Pilot Jet

Fuel screw settings in the 'book' are recommended starting points. Every bike is different, as is the temp and altitude. Set the screw according to this method.

Gently turn the screw all the way in. Now back it out two turns. Start the bike and fully warm it up, go for a 10 minute ride. Set the idle to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly). Once warmed, slow the idle to the lowest possible speed.

*** When turning the fuel screw, keep an accurate 'count' of the amount you are turning it and record it in case you have to reset it for some reason. Makes life easier when you can just set it from notes Vs. going through the procedure again.***

Turn the screw in until the idle becomes rough or the bike stalls.

if it stalled, open the screw about 1/4 more turn. Restart it and slowly screw it in till you can just perceive a change.

If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet.

Now very slowly, open the fuel screw till the idle is smooth. Blip the throttle, let the bike return to an idle, wait say ten seconds. Confirm it is the same smooth idle.

If the screw has to be opened more than 3 turns to get a smooth idle, you need to go up a size in pilot jet.

If you find it does not stall with the larger jet but has to be open more than three turns with the smaller pilot jet, put the larger one in and set the fuel screw at 1/2 turn.

If the idle speed increased, adjust the idle speed knob to return the bike to a real slow idle speed. You must then re-visit the fuel screw. Keep doing this till the fuel screw is opened just enough to provide a nice steady idle at the lowest possible RPM. Once this is done, increase the idle speed to the normal one for your bike, typically about 1,800 rpm, but go by the spec in your manual.

I would post this in the Kawi forum too, it will get specific exsposure.

Sorry William, I wouldn't have posted if I had seen your post. Great info.

Thanks for the info...ill post on kawi forum. My mistake on the air screw (coming off 2 strokes) so much is new for me.

Actually, the best place for this post would of been the jetting forum....

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now