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WA-55 Carb Adjustment

 
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Don Kruse



Joined: 16 May 2007
Posts: 437
Location: Albuquerque

PostPosted: Mon Jun 30, 2008 10:51 am    Post subject: WA-55 Carb Adjustment Reply with quote

Tom Krause posted this on 4cycle.

The WA55 is a tiny carb on a big motor, which means the adjustments actually work, and work a bit too well. An 1/8 turn or less in the wrong direction and you're out to lunch, especially on the Hi needle.

I start the 55 with at 2 turns on the Lo, 5/8 on the high, assuming the pop-off is something over 15lbs. From there, the Lo will go up to a 1/4 turn either direction, the Hi almost always ends up between 1/2 and 5/8.

You can get the Lo close on the stand. Pulling the motor up against the clutch richen it until the motor is crisp, yet 4 cycles just slightly the first time you pull the throttle, the 2nd pull should be clean. Play with it a bit and you'll get it close. Be aware of clutch heat while doing this.
Also the clutch should be engaging somewhere in the 8-8300 rpm range, if it's too low or too high fix that first, then go back to the carb.
Through the race night, you can tweak the Lo when you start the motor on the grid. Listen when the driver first hits the throttle, if the motor falls flat it's a bit lean, if it 4 cycles it's too rich. You want a very slight 4 cycle as it leaves the grid.

The Hi is tough, if you can, get a practice session where you can listen to the motor on the track. Richen in very small increments till it 4 cycles, then lean it slightly. As I've said, the Hi will almost always end up between 1/2 and 5/8, so you don't have alot of wiggle room.

IMO, unless you have a very advanced Jr driver, they have no business trying to adjust the carb on the track, they need to be paying attention to driving. That said, IF you feel the driver can handle it, and the motor is 4 cycling badly at the end of the straights, show them how to tweak the Hi just slightly leaner.

Ideally, if you have a driver who can't, won't or shouldn't(I've had all 3) adjust the carb on the track, get a recording gauge with EGT. Download the data from each race on a laptop. Study up on tuning EGT and you can do a really good job of tuning based on the recorded data.
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TDKmotor(Tom Krause)



Joined: 10 May 2007
Posts: 5

PostPosted: Sun Jul 27, 2008 6:05 pm    Post subject: Reply with quote

I guess I'd better watch what I'm posting, the eyes are watching Shocked
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