Hey everyone,
First off, I just want to say thank you to the fine people who run this forum. I've been reading through the many threads on here since December, and it's really been an amazing source of information. Thank you!!! (And apologies for the wall of text. It's been an exciting day!)
And on that note, in December I purchased a 1980 Honda CB650C Custom. It was stored outside, uncovered, and frozen in snow and ice. Some haggling and $650 later (he was asking $1200), my Dad and I winched it onto a trailer and drug it home. 24 hours of thawing out in the garage later, we got it fired. Woohoo!!! It can at least run! (barely)
As we dug into the bike though, it quickly became apparent this this bike had been beaten hard, and actually laid down at some point. There was damage all along the right side; snapped cables, damaged gauges, bent handlebar, shoddy welds to hold bits on, etc. The money calculator in my brain began ticking.
Over the next few months I did a lot of parts acquisition/replacement. My bank account quivered whenever I neared Paypal. But the cool thing was, each time I fixed something or replaced a broken part, I was able to step back and go "That part's okay now. It's done. I don't have to worry about it." The peace of mind was well worth it!
The last couple of weeks have been the most dramatic and easily the most stressful. Long story short, CB650 carbs are very, very particular about their air flow! We'd gone through everything we possible could on this bike. Ignition timing, coils, spark plugs, valve adjustment, checked the spark units, cleaned the fuel petcock, and I don't know how many times cleaning those carbs. The final time they came off, we discovered that she was missing an o-ring and a washer on one of the pilot jets, which while that improved the idle a bit more, it still didn't solve the throttle issue.
Finally today I was looking at it with my Dad. I'd taken it for two rides up/down the road, and while I could very, very slowly ease the throttle up to 4500rpms, I couldn't get past 5000 no matter what. Over the last couple of days we'd come to the conclusion that it had to be fuel. It just wasn't getting enough fuel, or the mixture was wrong...something!
I said "screw it" and took the bike for one last run. We'd just had the carbs on/off again and this time while throttling, I noticed a slight "surge", like the bike was trying to get the right mixture, but for some reason just couldn't do it. I went ahead and pulled the choke cable to half. BAM!!!! Instant improvement!!!!! All of a sudden I was able to scream up to 85 like it was no sweat!
I returned home and talked it over with Dad. Obviously the choke was chaning the air/fuel mixture...but why did it help so much? I was staring once again at the bike when it suddenly hit me. We were running with the air box off. When I choked it, it closed off the carb throat. Would the air box cause a similar restriction? Only one way to find out!!!
And so out came the carbs one last time, in went the air box, and away I went. That ride was so amazing! The bike had plenty of power and pulled easy out of any gear. And no choke needed!!!!
So yeah, I love this bike. I've may have cursed it at times, begged and pleaded with it at others. But right now, all of that is forgiven!
P.S. If the Honda engineers decided you need an air box, you need an air box.
P.S.S. Picks below. The first is how she looked when I first got her in December. The second was taken just this afternoon after riding for a bit. I haven't painted the tank/side covers yet - I plan to do that this winter, since the dent will need to be pulled out of the tank first.
