Cafe Racer Forum banner

1 - 20 of 44 Posts

·
Registered
Joined
·
50 Posts
Discussion Starter #1
Hi all,

I have a 1973 CB350G and I am having what i believe are some top end performance problems. My bike has great power until about 6000RPM then it just seems worthless. I can get the bike to go up to redline but even in first gear once you are past 7,000 you are better off shifting up to get more acceleration.

Here is what I have done to the bike overall. I rebuilt the engine with new OEM pistons and have great compression in both cylinders. I have checked the timing and replaced the points and gapped them to spec. Set the valve clearances to spec and have replaced the condenser. (I know new coils may be needed so if anyone could recommend a good brand I'm all ears.) The carbs have been rebuilt, brand new floats set to spec from my workshop manual. Carb jets sizes are 115 main and 78pilot (i believe thats what i put in... will double check). I have new uni-filters and have replaced the exhaust with something a little more open, but still has baffles at the back.

Battery is on the charger, will give it a go after work. But I wanted to get some opinions on what else I could do. Or perhaps to get a few performance figures from other CB350 riders as perhaps I am expecting too much.
 

·
Registered
Joined
·
50 Posts
Discussion Starter #3
No I have not just yet. I was talking to a local motorcycle mechanic who has worked on cb350's for a long time. He recommended jetting up like that to support the UNI filters. But I will do it this evening... fuel starvation?
 

·
Registered
Joined
·
2,952 Posts
115 mains are stock, I do believe. Uni's are much closer to stock vacuum compared to crap emgos, but that's oiled. Oil dries out.

Anyway, you are probably lean. Grab 120's and see if it's any better.
 

·
Registered
Joined
·
50 Posts
Discussion Starter #5
quote:Originally posted by mlinder

115 mains are stock, I do believe. Uni's are much closer to stock vacuum compared to crap emgos, but that's oiled. Oil dries out.

Anyway, you are probably lean. Grab 120's and see if it's any better.
Thanks... They are freshly oiled so they should be in good condition. Just out of curiosity could anyone take a stab at what an ideal 0-60 mph time would be. I know that its relative to how well you shift but some ball park figure would be nice.
 

·
Registered
Joined
·
2,952 Posts
With a cb350 being in perfect condition, making as much power as honda claimed in 68, about 6.5 seconds.
 

·
Registered
Joined
·
10,491 Posts
the latter 350s where slower then the early ones
 

·
Registered
Joined
·
2,952 Posts
Not sure that's true, Jag. It's true for 750's, but haven't seen enough difference in the various 350's to support that.
 

·
Registered
Joined
·
166 Posts
Is the engine just falling on its face, i.e. no power at all? If so, it sounds like what was stated before, yer running lean in the upper rpms which means you need a bigger main jet.
 

·
Registered
Joined
·
50 Posts
Discussion Starter #14
I will have to check my jet size again when i get home... I pretty much considered it would be 1 of two things... low battery which i have heard ruins your high rpm power... or fuel starvation which I think can either attribute to my petcock having poor fuel flow or incorrect jets... perhaps both
 

·
Registered
Joined
·
2,952 Posts
If you have changed your intake and exhaust, it's almost for sure jetting. 115 is stock. Again, try 120's. Adjust from there.
 

·
Registered
Joined
·
50 Posts
Discussion Starter #16
quote:Originally posted by mlinder

With a cb350 being in perfect condition, making as much power as honda claimed in 68, about 6.5 seconds.
Thanks mlinder, i was going to guess it was gonna be something like that
 

·
Registered
Joined
·
50 Posts
Discussion Starter #17
quote:Originally posted by mlinder

If you have changed your intake and exhaust, it's almost for sure jetting. 115 is stock. Again, try 120's. Adjust from there.
I will do so then report back... hopefully the roads here in va will be dry this afternoon for me to do a couple test rides.
 

·
Registered
Joined
·
1,641 Posts
I’m pretty sure stock jet was 105 main and a 70,

Are you certain the cam is aligned with the crank properly, if it’s off one tooth
on the cam sprocket
It will run up but fall flat around 7000-8000
 

·
Registered
Joined
·
50 Posts
Discussion Starter #19
quote:Originally posted by midge

I’m pretty sure stock jet was 105 main and a 70,

Are you certain the cam is aligned with the crank properly, if it’s off one tooth
on the cam sprocket
It will run up but fall flat around 7000-8000
Ok so an update...
1. I am running a 135 main jet... sorry for the wrong info earlier
2. Fully charged battery made the engine run much smoother
3. i have rather large bubbles in my fuel lines and I feel like my petcock is not keeping up well.
4. did not do a chop test last night as i left my plug wrench at my garage

midge... That is a good idea to check. I am fairly certain that I aligned it correctly, though with my novice status its certainly possible that its slightly off.

On another note I am going to take my petcock apart and clean my filters. I have some rather large bubbles in my lines and even when I bleed the line so that the air gets out, it comes back.
 
1 - 20 of 44 Posts
Top