CB350 - Lack of throttle response

sbelshe

sbelshe

Been Around the Block
For the past few weeks, there were a number of issues with the may my 72 CB350 bike was running. Suddenly sputtering at lights, reving to high RPM's when I slow down or pull in the clutch, etc/ I checked tones of things, carb clean spark, air leaks, everything seemed fine. Then I noticed wax on my ignition, turns out I had a bad ignition coil. So, I order two universals, (#SI-47 From DCC), wire em up as described here http://www.hondatwins.net/forum/viewtopic.php?f=44&t=17193 and give it a go.

Bike starts and runs great, better than it has in quite a while. But now for some reason when I hit higher RPM's or really hit the throttle, I hear the throttle response as the engine rev's, but there is lower than expected response in speed. I thought maybe it was simply an air mixture issue. I tinker with the air screw a bit (I'm running #75 Primaries and #110 Secondaries, no mufflers, 4" baffles), makes no difference.

Any ideas what may be my cause? Could my coil install be wrong or could I have a bad coil?

Thanks
 
Should mention I also added 7mm Dynatech Copper plug wires and NGK Caps during the coil install.
 
Sounds dumb, but put your bike on the main-stand and throw the wheel around. It should move freely and make it around several times. Mine usually take about 30-seconds to a minute to come to a stop. Any resistance?

If not, do the same to the front.

Otherwise, high revs and no go sounds like a clutch issue.

With the bike on, hold the front brake and rev to just about 2k rpm. Let the clutch out slowly as if trying to take off. You should be familiar with the point at which it engages, so at that point it should stall. If it doesn't stall at that point, your friction discs are worn out or the throw-out or cable is too tight.

To adjust throw-out, turn the clutch adjustment screw on the side-cover out until it moves freely. Now turn it in slowly until you feel resistance. Back it out 1/8 turn. Then adjust your clutch cable until the lever has 20mm of play before strong resistance is felt.
 
TheCoffeeGuy said:
Sounds to me like it could be cam chain tension as well.
Click to expand...

Shot, mate, that's exactly right. Adjust the chain tension (90º after T.D.C. on the compression stroke of the left cylinder) then check your valve lash!

Sure hope you ain't got one of those "automatic chain breakers", I mean "tensioner". ::)
 
Is there any reason to believe that this would have anything to do with the recent work I have done with the coils, caps and wires? Sounds unrelated and coincidental.
 
You said it was acting funny before you changed the coils. Regardless it should be checked.

Google "valve clearance". You'll need shim gauges and the bike can only be adjusted when bone-cold. Bone cold!

You should only do this adjustment after adjusting the chain tension.
 
It was acting funny, but those problems seemed to be solved by the coil change. This loss of power is new. I will check the tension regardless, thanks for the tip!
 
#75, correct. Took a tip from a local shop after telling them I wanted to run it with no mufflers and K&N pods.

http://www.dimecitycycles.com/vintage-cafe-racer-caferacer-bobber-brat-chopper-custom-motorcycle-carburetor-parts-keihin-cv-primary-main-jet-75-026-016.html
 
Check that whatever air-filters youre using, they aren't clogged with something like oil or otherwise restricting air.

Also, no mufflers? The thing will never run right below WOT...
 
stu.belshe said:
Is there any reason to believe that this would have anything to do with the recent work I have done with the coils, caps and wires? Sounds unrelated and coincidental.
Click to expand...

You may have changed the cable routing which is making clutch slip
Running without mufflers is a dumb idea and gives far worse performance than stock, same with 'pods' if you don't have carbs modified
 
I thought the same thing about the cable routing. I took the tank off and made sure cables were free to ensure that wasn't the issue. I ran muffler free for 6 months with no issues. And I've done a card sync, changed jets and adjusted the air screw to compensate for the pods. I'm not looking for tip top speed and power, just looking for a consistent ride.
 
I'd swap back to the #68 primary and change the secondaries instead. Hardly ever any reason to change primaries on the Keihin 3-jet CV carbs.
 
I re-adjusted the throw out (no clue how it got so out of wack, hadn't been that long since I set it), and I also reset the cam chain tensioner, and were back to normal. Still having other issues, but the throttle issue is definitely solved. Thanks for all the advice folks! I will try going back to the #68 as it may help with other problems I'm having. Thanks again everybody.
 
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