Motorcycle Repair: Honda High Speed Sputtering, honda vt 500, air fuel mixture

Question
Hello.  I just purchased a 1984 Honda VT-500 Ascot that runs great except at high crusing speed.  It can rev quickly up through gears if really accelerating, but once I smooth out my speed and coast, any slight increase in throttle will cause the bike to stumble dramatically.  We have rebuilt both carbs extensively and even enriched the mix by raising the needle a bit as a dyno test indicated it was running lean at high speed cruise.  We are now looking into a wiring defect perhaps.  Any ideas?  Thanks for any advice!

Answer
Hi Mark,

Keep tuning the air-fuel mixture. Read the spark plugs to know if the A/F mix is rich or lean.

Use throttle opening positions when tuning carburetors. Carb circuit ranges are tuned in relation to the areas of throttle opening they control. Ask what throttle opneing positions does the sputtering began and end, and tune those circuits.

Make signle tuning changes at a time to know what effect each change has made. Otherwise, you'll be wasting time redoing the work.

Tell me your environment elevation, average temperature, and current jet sizes. I'll do the math and reply with the corrected jet sizes.

I return tech files by email. There was no email address with this question as requested.

Respectfully,
Mark Shively