Topic: Why is it running weak/sounds different on one cylinder? (cb450)

[Carver]

The right cylinder is running fantastic/ revving great and sounds great.

The left cylinder, however, is running, but a little bit weaker and it sounds like its kind of "popping" if that makes sense and has less pressure coming out of the exhaust. I took a video but I'm not sure it translates well. Just rebuilt the engine.

any ideas guys?

http://youtu.be/mO7W1Imxxo4

First revving is the right cylinder, second is the left cylinder.

[Carver]

I should add not popping like backfiring or loud pops, its just the only way i can think to describe it. you can kind of hear it when the bike was idling in the video too.

[fendersrule]

Did you make sure to line up the marks on the cam when you installed the timing chain?

Is your valve lash set properly at TDC?

Is your timing set correctly? It takes skill and time to get these perfect, easy to mess up. What's your gap at the end?

Did you perform the straw test on your carbs to see if the slides are moving freely?

The video is hard to make out because I'm not sure if I'm listing to your exhaust, or just the sound quality of the video…

btw, what was the issue before, throttle cable?

[Carver]

it was routed wrong. Cam timing and ignition timing is perfect, valves adjusted. carbs professionally rebuilt. It should be running right which is why this is bothering me so much.

you can hear it most prominently in the video when its idling, but during the second set you can hear how its more "poppy" than the first set of revvs.

[fendersrule]

"puffing" sounds via the exhaust are due to improper timing. Something is off. Did you static time it? That's the only way to do a CB450 IMO. Follow the timing procedure EXACTLY by the book. if your point gap on either side is outside the range of .012-.016 at the very end of the process, the bike will "miss" or "puff" when the timing isn't right. Also, use a strobe when you are finished, rev the bike to 4,000 RPM (having a large fan helps keep the bike cool) and make sure the advancer is within the lines. I had to modify my advancer on my K7 because it was 1/2" past the lines as the RPM exceeded 3,500 (this sentence isn't your issue, but PLEASE check).

"popping" sounds (not a backfire) made at the carbs can be due to many things, but for me it was having too much slack in my timing chain (my father didn't tension it correctly). Make sure your tensioner is set via the static method. If you take off your front valve cover, you can poke the chain. I was getting way too much movement which was throwing my timing off, even though it was set spot on.

[Carver]

hmmmmmmmmm come to think of it I didn't gap the points, I just did the static timing. I'll have to check that, kind of an oversight, whoops. Cam chain is nice and tight, brand new, and my tensioner is in pretty nice condition and does work, made sure while it was out.

Thats why I post these threads, sometimes I get too ahead of myself.

Any other suggestions are still welcome just in case!

[fendersrule]

email me at nashDOTStantonATgmailDOTcom and I will give you a kick ass timing guide made by the master Bill lane.

Make sure you release the plunger onto the chain at the proper setting of the rotor….not just "anywhere" will work...

[strynboen]

just set gab 0,40 milimeters..and set multimeter to beeb. one vire to frame..other to breaker platin( remove coil vire up at coils). turn anti clockvise.vhen it stop beeb the marks must pass overfor ft or f.(.it is static timing).. test both cyll ..firing point