High Speed Stutter

domani · Posted: April 28, 2009, 8:39 pm Post subject: High Speed Stutter

Hi everyone. I finally got my bike on the road, including a set of commando pipes from Mike's. I rejetted to Main=#147.5, Pilot=#45 and Air Jet=#127.5. The bike idles and cruises great, but stumbles a bit when I open it up over 4K rpm. I assume I have to up the mains, but before I do I am replacing the carb holders and butterfly seals. (Idle hovers a bit when the bike is hot)
y question is how big can i go on the mains on the BS34s before I screw the mid-range?

P.S. Airboxes are stock with brand new filters

kyle1911 · Posted: April 28, 2009, 9:55 pm Post subject: Re: High Speed Stutter

4k, with a slow roll on, or wide open, and falls on it's face at 4k? Makes a big difference. I would move the needle clip down one notch, (Raising the needle) and try that. I have not messed with the stock carbs on these, but the concept is universal. Free breathing exhaust will likely require more than idle mixture adjustment. Best of luck, Kyle

gordo · Posted: April 28, 2009, 10:03 pm Post subject: Re: High Speed Stutter

Kyle, the BS34 needle's are fixed. He probably need's a set of xsjohn's needle's.

kyle1911 · Posted: April 28, 2009, 10:10 pm Post subject: Re: High Speed Stutter

Ooops. My bad/lack of specific knowledge showing through. Are they shimmable? We used to cut washers from feeler gauges for some of the old Honda carbs with grooveless needles... Usually had to adjust other things, though, like drilling bigger holes in the slides, and/or cutting coils from slide springs, which sometimes became a nightmare. I'll defer to others on this one! Thought I was on the right track. (Retreats, looking for another cold beer) Kyle Smile

650skull · Support Staff Joined: Jul 19, 2007 Posts: 1186

hang on,I think i see xsjohn coming over the hill....................Won't get him tomorrow, it's thong thursday Laughing

xsjohn · Posted: April 29, 2009, 9:01 am Post subject: Re: High Speed Stutter

BS34........147.5 will surely wash the rings and cylinders fast......if not already........135 is usually right and even a 137.5 can be a bit of overkill and chance wash.........I have seen them wash with 137.5 near sea level........ better look at that one again.........

650skull ........thong thursday ah.... Laughing

....maybe Barney is there or at the fudge packers convention.........he would surely know about hogged out cylinders ........ Shocked

xsjohn

domani · Posted: April 29, 2009, 12:40 pm Post subject: Re: High Speed Stutter

xsjohn wrote:

BS34........147.5 will surely wash the rings and cylinders fast......if not already........135 is usually right and even a 137.5 can be a bit of overkill and chance wash.........I have seen them wash with 137.5 near sea level........ better look at that one again.........
xsjohn

When you say "135 is usually right" is that on a bike with stock pipes? I chose those jet sizes based on the directions from Mike's, and the fact that my mechanic told me that it was "running so lean it would blow the carbs off".

yamaman · Posted: April 29, 2009, 9:49 pm Post subject: Re: High Speed Stutter

domani, xsjohn makes custom needles that address the lean issues of BS 34's, I know he's sold heaps of them & I've never heard anyone say they weren't a great improvement.
I'd suggest you grab a set & go with Johns recommended settings for a baseline. If your interested, send John a PM 650rider.com/index.php...ile=xsjohn

Cheers

What Happened to 650rider.com?

Yamaha xs650