Been in motorcycle-world the last week or so. That, and mountain biking - been doing 10 miles a day on the MTB, nearly broke the 40 minute mark today! 10.22 miles in 40:28, avg speed 15.10mph and average pace 3:58/mile. Not bad for an old fart. When I finished my ride today I headed to the shop to work on bikes.
I have a 98 Buell Defender police bike prototype that I've been playing with. They built 12 of them; my VIN is the second one built. Finally got all my accumulated parts together and got it running a week or so ago...and have been tuning it ever since. The carburetor has NOT been my friend. But on the upside...I AM really good at taking it off and apart now!
I've got a go-to jet setting I've always used on these. There's an idle jet (choices are 42, 45, 48) and a main jet (anywhere from 160 to 205, in increments of 5). Bigger number = richer jet. There's a mix screw that's usually lean from the factory at like 1.5 turns out from bottomed; I always set them for 2.5 turns, and usually run a 45/190 jet combo with a stock needle and no shims.
Well...the Defender was having none of it. Started great, idled great, cruised great...WOT it would break up BAD. So I stepped up from the 190 to a 195, and from a 45 to a 48 (this is a bone stock bike, no mods to intake or exhaust). Slightly better, but still a YUGE flat spot in the midrange and some top end breakup. So...I gave up, and read the shop manual.
Factory was a 42/200. 200!!! I've NEVER run that fat a main jet...but I popped one in, and holy CRAP does it scream up top!! 5500rpm it comes alive like boost coming on, and if you blink twice you're at 7k (redline). Woo-HOO!! But, still flat in the midrange. I'm going to step down to a 45 idle jet tomorrow and see how it does - should do just fine (the stock 42 is always lean, they always cough and fart at low throttle openings).
So I have another '98 - a Lightning - that I've had since...oh...2006(ish).
Same basic engine as the Defender...but with a full factory race kit - high flow intake, tuned length, large diameter header, a free-flow "muffler", and a recurved ignition box. I have had a 48/195 in that bike since day one and always though it ran OK, although it does have a midrange hiccup/stumble that's annoying. So...I tore into that one. Read the book (shhh...don't tell anyone I read the instructions....TWICE in one day...) and stock, it was also a 42/200. With the race kit and increased airflow....I kept the 48, but popped in a 205. I checked the needle and it was an aftermarket needle with a goofy tip on it, and three shims under the head. Tossed it, dropped in a stock needle. It is now dark out, and I learned years ago not to do shakedown runs after dark...but I had to know. So I blasted up and down my 1000' driveway and HOLY CRAP. It's a different motorcycle now. Unreal. Can't wait to do a real ride tomorrow!
So, my hands smell like fuel and my clothes smell like exhaust...but the bikes are getting some much needed attention!