QuestionHi Mark, I recently picked up this 1983 Honda Shadow 500cc from a friend. Four years ago he replaced the CDI box because the bike would heat-up quickly(@ 20 minutes)and shut down. After replacing the CDI box the problem went away. He got @ 300 miles on it, then it started running very poorly on a ride. He made it home, parked it and it sat (he says untouched) until recently when he gave it to me to try and repair. It starts easily, but it has very
poor throttle response and won't run good at high rpm. If I give it gas quickly(to
full throttle and hold it there) it accerlerates to @4000 rpm then immediately "bogs"(down to @1500rpm) and then revs back and forth between 1500+2000 rpms. When fully choked the engine runs
better under ALL conditions (hot or cold), the proceedure I just mentioned is the same with full
choke...except initially it jumps to 4500 rpm, and
then revs back and forth between 2000+2500 rpm's.
It also idles higher and runs smoother with full choke (hot or cold). If I slowly increase the rpm's I can only get about 3500 rpm (before it "breaks-up", starts running like junk,etc). If I apply FULL CHOKE (yes, hot or cool)and slowly increase the gas I can get it up to 4000 rpm's. The gas tank was emptied and
filled with fresh gas. I installed a clear gas line to see if it is getting enough gas, it looks
good, no air at all in the line! You should know at some point somebody removed the pilot screw plugs. I have no idea when they were removed, and probably adjusted! Could you tell me the proper setting for them? So...I'm wondering if the timing
is "off"? Is the timing adjustable on this? (my Arctic Cat snowmobile is NOT adjustable!) is the coil weak? is the CDI box going bad? Or did somebody mess with those pilot jets (I have doubts
about the number of miles it was driven after the CDI box was installed)? I have never driven this bike, so everything I mentioned happened in neutral(as you probably guessed). Well, I'm stumped and I don't want to spend a lot of time and money guessing. I would be greatful for any information you have! Thanks, Mike S.
AnswerHi Mike,
The symptoms you've described are consistant with carburetor varnishing. That's when gas in the carbs goes bad and changes to a gel like substance over time.
Get this fixed and then you may begin investigating the problem your friend had that caused him to park it.
If you want repair information files, send me an email adress as requested in my question posting directions. I'll return files on repairing the problem.
Respectfully,
Mark Shively
