I got a CBR from my friend a few weeks ago and started cleaning it up. It has been sitting outside in a car port for the last year or so. I was able to start after a replacing the kerosene with fresh fuel and the choke on full. Ran ok didn't sound great and started smoking. I was hoping that it was just burning off the dust and bad fuel. I took the carbs off and cleaned them. The idle jets were on 3 of them were blocked off completely. And the vacuum diaphrams were stuck, anyway all cleaned up and back on the bike with new oil and filters. Started up and ran without smoke for a few minutes then started smoking again. I was checking the carbs by placing my hand over the openings 1, 3, and 4 really sucked my hand down but 2 can be covered without any change in the idle or suction. I did get a couple of pops out of the carbs on 2 and maybe 1 in the 10 minutes of running.

My thought at this point is to check the valves and make sure first that they are adjusted correctly. Maybe the exhaust valve on 2 isn't adjusted right. Next if that checks out or if there is a lot of play on 2 pull the head off and clean it since the valve isn't siting like it should. Or is there something else that I am missing that could be causing the smoke and lack of compression? Rings maybe?

The last set of heads I pulled off were on a '68 bug so I'm wondering how much different these are and what I should look for? How hard is it to do? The manual says you can do it with the engine in the bike. So I will give a go and see. While the head is out ( assuming the valves are adjusted right) should I do anything else to them? port and polish or clean up the casting ridges?

Another issue I noticed is the clutch won't engauge the gear until the lever is almost all the way out. The previous owner mentioned that it seemed to loosing power and I was thinking that maybe the clutch is just out of adjustment or needs replacing. It looks like it is at the end of the adjustment but since I'm not riding it yet I'm not totally sure.

Anyway thanks for any answers.

Ken

 

what color is the smoke? does it just start blowing clouds out, or is it just when you pin the throttle or let off it? does it have a smell? burning coolant is white smoke, probably more noticable after its warmed up, and will have a sweet smell. burning oil will be more of a blue color, and could be rings or valve guides. worn rings usualy smoke all the time. worn valves will smoke on deceleraction. too rich of fuel is usualy more of a grey color and will smell strongly of gas.
i have a couple acvw's, while its different design, a motor is a motor. if you can follow a maual and handy with tools i think you can work on it. might do a compression check or a leak down test to see whats happening. valve clearance check wont hurt but i dont think is the cause of the smoke.
might just need to tune up the enigne since its been sitting, and really give it a good run to burn out any deposits.
oh, and on the clutch, at the lever there is a round adjustment bolt. if its all the way out, down where the clutch cable meets the engine, there is another adjustment nut.