[gonomo]

I just got my new 1974 CB360 running today. It sounds like it idles nicely and it starts with only a couple kicks. After giving it gas, the engine sputters, backfires, and there are popping sounds comming out of the carbs. The engine wont rev over around 3600 RPM and after running for a couple minutes it fouled the spark plugs(they were dry with black soot). After it runs and I pull the spark plugs, I hear sizzling comming from the cylinders and a little bit of smoke comes out of the carbs when I take the air filters off. I tried playing with the little black plastic screw on the right carb while it was running and noticed nothing(is this the air/fuel mix screw?). Is the engine running too rich or lean? Is this just a matter of rebuilding the carbs?
Thanks

 

[krukster86]

Sounds to me like it is running too rich? Have you worked on the carburetors at all yourself? If not, I would take the carbs off and do a full rebuild just to be safe. Taking off all the jets and needles and clean them up. Check the float heights too while you are at it. If turning the air-mixture screw does nothing, then I think there may be something clogged? You should be able to tell really easily the difference between a half turn in either direction.

 

[frogman79]

What else has been done to the bike? Is it all stock? Modified intake and exhaust?

Is the choke on? Handle down is off.

Other wise a good cleaning and inspection sounds like is in order, if it still has factory jets and needles in it clean them and put them back as after market stuff is rarely correct especially the needles.

Sent from my SAMSUNG-SM-G891A using Tapatalk

 

[misterguitar]

Yeah gotta know if the exhaust pipes are stock and if the air boxes are stock...

 

[crazypj]

Pull the black plastic limiters off fuel screws. Won't actually make any difference, what you describe is common when cheap pods are fitted.

 

[gonomo]

I rebuilt the carbs and I'm still having a similar problem. It idles smoothly now and on both cylinders, but when I give it gas I get the same backfiring and bogging. While it was idling, I played around with the mixture screws and even when I had them as lean as they could go, it idled and backfired the same. I pulled the plugs and the right plug was carbon fowled while the left was completely fine.
My timing is on the dot but I havent done a valve adjustment since I rebuilt the top end, I didn't think that it would make a difference is how it would run but could that be a possibility?

 

[gonomo]

Also forgot to mention that everything on this bike is stock, it has 2000 miles on it. I do have an exhaust leak comming from the head to exhaust manifold connection but I'm not sure how to get rid of it.

 

[krukster86]

Also forgot to mention that everything on this bike is stock, it has 2000 miles on it. I do have an exhaust leak comming from the head to exhaust manifold connection but I'm not sure how to get rid of it.

Might need to get new copper "gasket"/crush rings.

 

[gonomo]

Solved!
It turns out that my points kept going out of time because the "rubbing block" that rubs on the cam was wearing down. I grabbed the original points (thank god I didn't throw them away) and took them apart, got them really smooth, and sanded the points. I put it back on and it ran but didn't rev very high at all. I ran it for about 15 minutes and it's running super cleanly now. It revs and idles perfectly. I took it out for its first run and had the time of my life!
Thanks for the help, I will post photos as the project unravels.

 

[crazypj]

Did you put a blob of high temp grease in the 'angle' of points heel?

 

[gonomo]

I did. Weirdly, the material is soft enough to scratch off.