Alrighty, here's the situation.
I've had the bike ('82 CB650) running reliably for about 6 months up till now. This is after 3 top end rebuilds and 2 carb rebuilds (rest assured I know this engine pretty damn well, and the rebuilds were because when I fixed something something else would break, either from age or prior owner misuse... yeah, that sounds good
). With the last rebuild I had put on a new MAC 4-1 exhaust and upped the main jet size to 122s (from 118) to compensate. Turns out the compensation was too much, so I changed the mains to 120s which is stock for a CB650 Standard and Custom. However, I neglected the fact that I have a CB650 SC engine in my frame, which takes 118 mains as standard. When I let my brother in law ride my bike last week (and I got to ride his '81 BMW r100/S
) he told me he could feel a bog in the throttle on the top end, and could smell gas from my exhaust while we were riding (but not enough to smoke like the 122's had). This seemed to explain my "couldn't go faster than 95 mph" and "poor high-speed gas mileage" problem. What can I say? I like to live dangerously and expensively
This is when I made the realization that I had mistakingly put 120s instead of 118s, so this weekend I decided to remedy the situation along with a small oil leak from the camshaft cover. No serious surgery... Took off the camshaft cover and helicoiled a stripped bolt there, and took off the bowls with the carbs still on the bike to change the jets. After 4 hours of careful work (I've learned my lesson from 3 top end rebuilds
) I retuned the tappets and started her up.
It took quite a bit to get her started, and this is with gas in the bowls. And even then, #4 stayed cold for about a minute before she started firing with the others. Now I can get her to idle fine, got her off choke, but when I pull off I start to feel a "chugging" sensation and the engine runs loud and rough. I rode her around to work it out, but it didn't get better. I pulled the plugs (the old ones) and they were white. Installed fresh plugs and let it idle for a minute with a ride around the parking lot, and they are sooty black. Soooo....
The bike had been running fine, and the only modifications I made were to the main jets and re-adjusted the tappets. And as far as I know the mains don't have anything to do with a low speed pulling-into-traffic throttle position. It idles fine, and only acts up when I rev the engine or put load on the transmission. Any opinions?
Aaaand... GO!
