Daily Warmup Transitional Stutter

Wheelman-111 · Post by **Wheelman-111** » Wed Feb 25, 2009 9:44 am

Greetings:

As Flash is running so well in general, I thought I'd ask about its one remaining glitch. Starts great, especially in cooler weather. I barely have time to release the button. Usually I let it idle on the Bystarter just long enough to fasten helmet and gloves. Won't take kindly to throttle before at least 30 seconds on the bystarter anyway.

As I ride off and down the block - it's about an eighth mile to the stop sign - it gives just a few seconds of "stumble"; the power cuts out or is reduced considerably for a few hundred feet @ 25-30 MPH. It happens in almost the same geographic spot every morning, too. I was thinking BAeromuda Triangle. Then it runs like a Champ all day!

I'm guessing there's still an issue with imprefect transitional carburetion - the point at which the Bystarter closes fully and "hands off" carburetion duties to the midrange circuits. At this point the temp gauge is usually around 200. Setup is PA 04 W carb, common to AF 05 and AF 16 engines alike (?). Main jet currently is a 96.5 inhaling through big K&N, feeding Polini 65 through 0.5mm Carbon reeds and exhausting through LeoVinci SP3 pipe.

Anyone else notice this with their stock carb? Comments welcome.

Post by **noiseguy** » Wed Feb 25, 2009 11:27 am

My stock Spree does this too. Only when cold; seems like a warm-up issue.

Kenny_McCormic · Post by **Kenny_McCormic** » Wed Feb 25, 2009 4:11 pm

Just warming up.

dgsoles · Post by **dgsoles** » Wed Feb 25, 2009 4:52 pm

My '86 also does this.....I let it warm up on stand, take it to ride, stutters a little for about 100 feet or so, then runs like a champ. I agree, just warming up, it is probably still running a little rich...

Kenny_McCormic · Post by **Kenny_McCormic** » Wed Feb 25, 2009 5:41 pm

dgsoles wrote:My '86 also does this.....I let it warm up on stand, take it to ride, stutters a little for about 100 feet or so, then runs like a champ. I agree, just warming up, it is probably still running a little rich...

Cold engines need MORE fuel therefore when cold it is running lean.

SprEE*MP* · Post by SprEE*MP* » Wed Feb 25, 2009 7:58 pm

Let your scoot warm up longer!

Kenny_McCormic · Post by **Kenny_McCormic** » Wed Feb 25, 2009 8:16 pm

I rev mine on the stand, warms it up nicely.

CaptDan · Post by **CaptDan** » Sun Mar 01, 2009 11:59 am

noiseguy wrote:My stock Spree does this too. Only when cold; seems like a warm-up issue.

Same here. For me, the problem is worse because I cruise down a steep hill which, in turn, causes the engine to take longer to warm up.

Soon as I hit the first level road, and WOT it, the little bugger spits 'n snaps for a few moments - like it's clearing its throat - then BubOOm. Clean and mean. I still have to 'nurse' the throttle a bit, but things settle down rather quickly.

CaptDan>

SayTen · Post by **SayTen** » Sun Mar 01, 2009 1:29 pm

Kenny_McCormic wrote:I rev mine on the stand, warms it up nicely.

What he said.

chevyguyjay · Post by **chevyguyjay** » Sun Mar 01, 2009 2:41 pm

my aero the same. i let it warm up on the stand. then ill rev it a few times to burn off all the oil that drips into the crankcase. looks like a smoke bomb went off after doin that. once the heavy smoke stops, its warmed up, and off i go.