Cb450 bogging questions

[71cb450]

ok so my cb will run like a champ for about 20 miles then all of a sudden I will lose one cylinder at low rpm's. Help please!!

 

[Big R]

Coil overheating or maybe lack of fuel to that cylinder. What does the plug look like when it happens?

 

[71cb450]

alot darker than it should be

 

[Sonreir]

Sounds like bad compression due to a valve not sealing properly. When the engine heats up the valve in that cylinder is probably losing its seal due to heat expansion.

Do a compression test on your bike (both cylinders). After you do that, squirt a bit of oil into each of the cylinders and do the compression check again. If your numbers are about the same (and under 155 PSI), the problem is likely to be your valves.

 

[bobjohnson]

I had the same problem with the same bike, or at least the same symptoms, last year. It ended up being a microfracture in the carb housing where the mainjet seats. I spent literally about a month trying to figure it out, because the bike would run like a champ, but as soon as it was hot id lose all power in the right cylinder and plugs would foul almost instantly.


With the bike running, take the airfilters off and look down the carb mouth (be careful that its not backfiring out of the carb when you do this). Take your finger and feel around the needle seat. Is it wet? Can you see gas pooling there? If so, youve got the same problem i had.


Only solution was to buy new carbs (I tried a rebuild kit, new needles, new slides, new jets, everything). And another point of advice, locktite the choke plate screws on a new/used set of carbs. I got 5 minutes on the road out of that rebuild before it sucked a screw into the engine :-[

 

[71cb450]

alright well I really hope its the coils I got some on the way, but if its not then I'll know where to go from there.
Thanks!

 

[teazer]

Are the condensers original? If so get a new pair. When they fail, they tend to do so under load and when hot. I was stranded a few times on an old single with that problem.