Timing Issue?

facefirst35

facefirst35

Coast to Coast
I've noticed that on my '72 CB350 that when I hit about 5000 RPM in any gear that the bike starts to sputter and just won't go. It's especially noticeable if I accelerate quickly. If I slowly accelerate it seems that it isn't as bad. I read that one thing to try is when it's sputtering to put the choke on a little and see if it gets better, which would indicate that it might be running lean. I have big UNI filters and run a 2-1 exhaust so I thought maybe that would be an issue. But before the 201 I was running a 2-2 and still had the issue. The bike came with UNI filters so I have no clue if the original air filters made a difference or not.

I recently picked up an electronic ignition that I have yet to install. At any rate, does my problem sound like the timing might be off?
 
I had the same issue after replacing some fuel line. Ended up that it was a tad too long and there was an ever so slight kink. Not enough gas was getting to the carb when getting past 5g on the tach. Especially if it was a quick acceleration. Shortened it....no kink...no problem.
 
Ya know, I did replace the fuel line that runs under the spine from one side to the other. I purposely cut it a bit longer so it was easier to hook back up. I'll give that a look.
 
Did you check your advancer? Its hidden under the points. When rpm rises, the weights are spun outwards and they activatexthe timing to be a little sooner. 9 of 10 times itd rusted shut or the springs have snapped.
 
timing being slightly off wont make it sputter that said it is pretty easy to set the timing and if you are asking about it ,it probably needs to be set
that along with properly set points and fresh sparkplugs
check the advancer like said
if you are chasing running issues you need to eliminate the easy fixes first
 
Installed an electronic ignition and replaced the plugs. It's definitely running better but every now and then around 5-6k if I gun it it will big down a little. The timing is set correctly. Maybe a jetting issue?
 
Anyone have any ideas? took it for a long ride and any time I gun it in 3-5 gear, when it hits 5-6K RPM it bogs down.
 
I'm gonna soak my carbs in Berryman carb cleaner. Maybe something is gummed up. I guess I should rule that out before I worry about rejecting.
 
wow 5-6 k is not even in the power yet either
you should be between 6-9k all the time
keep at it good luck
 
While you have the carbs apart for cleaning be sure to check the diaphragms as well. Inspect them well to see if there are any pinholes or tears.

Also, how is the compression?
 
How would I go about testing the compression on it? Would any compression tester work? I ran into a problem when I bought a carb sync tool and there's no taps to actually hook it up on a 350. I didn't know if that will be a problem with a compression tester too (I know it's not hooked to the carbs, just saying.)
 
Compression is tested via the spark plug holes, the tester is threaded into the hole just like a spark plug. What your referring to about the carb taps is for syncing the carbs.
 
Would this be ok to use?
http://www.autozone.com/autozone/accessories/Actron-Professional-compression-tester/_/N-25j0?itemIdentifier=347021_0_0_
 
yes rhat is fine
test on a warmed up engine
be sure and have both sparkplugs out so the engine spins as freely as possoble and hold the throttles wide open
crank it quite a few times until the guage quites rising
 
So I checked the compression and I'm getting right about 170 PSI for each side.

After right about 50 miles, here's the left plug
xEeQ


Here's the right plug
xEeY
 
That's good compression so no worries there. I'm no expert on plugs so hopefully someone else can chime in. Were these new plugs put in for this test?
 
Check your float height. If it's off the carb bowls may not be filling fast enough. Definitely sounds like a fuel starvation issue. Also be sure your carbs are synced and that your petcock is free of debris. I recently had a similar issue and when I checked the petcock the screen in the bowl was gummed up. She rips now. OK, rips for a 350 that is. ;)
 
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