[Damname]

imported post

I ran 3 tanks of gas out with half a can of seafoam in each tank of gas with little change if any. i ordered 4 air cutoff valves and 4 manifold to carb o rings (which were toooo small).

We spent the day putting the valves in and the original air cutoffs looked like new. there was 1 o ring for the carb to manifold that looked bad so we doctored it a bit and put it back in. we fixed the sticking choke on one of the carbs and adjusted the butterflies a bit. the bike runs better now but not great.

it now acts like it wants to idle at about 1000 rpm after its good and warmed up. it does this knocking sound when its idleing low, (sounds like trying to take off in a standard shift car in 3rd gear from a stand still). it will idle for about a minute and then die. you can smell its getting may too much gas. my friend called this spark knock or pre ignition.

after the partial rebuild it no longer revs up 2500 rpm when ya pull the clutch in to switch gears, it revs up about 500 rpm now which shifting. this might improve after riding it some.

my friend seems to think its not getting enough air at idle.

i myself am at a loss here. checked the needle valves and there sharp and not bent. sprayed starting fluid and wd40 around it while it was running looking for it sucking it in...nothing.

i had another card guy look at it a few days back and he suggested it was air cuttoffs and the choke sticking.

im running out of cash to do much more to it and im at a loss.

anyone?

 

[Damname]

imported post

k1w1t1m wrote:

I suggest pulling the carb rack out again and double checking everything. If you have a compressed air source blow through the idle jets and make sure they all sound the same. Check the float height and make sure they're all the same. You do know to check them with the rack almost standing vertical and the needles closed but with no weight on the little spring in the middle of the needle? Make sure the idle mixture screws are all turned out the same. Last but not least bench synch the carbs. I use a drill bit for this.
From this point on it is just check and double check, measure and measure again. It shouldn't cost you anything but your time.

Great! sounds like i am close to getting it running right.

K1w1t1m
what height should the floats be typically?
the idle mixture screws are the ones that kinda resemble a flag right?
when you say to bench sync the carbs using a drill bit...i dont understand that. do you mean making sure the butterflies are closing and opening at the same time? we made sure the butterflies are closing at the same time.
(we are not afraid to try just need more explanation)

we didnt do anything in the vertical except with the butterflies.

if you could give me a little more detail i would greatly appreciate it. we are trying to fix it out of a garage with an ordinary set of tools typically just enough to work on a car.

i do know someone with sync gauges but when they worked on the bike they synced them by ear and refused to use the gauges. wonder what it would cost to have them syncd at a shop?

 

[Damname]

imported post

ty for the info im going to study it and try again.

 

[Damname]

imported post

hey guys thanks for the great advice! i decided to ride it a little after the partial rebuild and parked it in the garage and guess what? its idling now somewhat stable at 1k rpm!!!! woot!! the longer i let it idle the better it was idling so i kept having to turn down the idle screw to get it to idle at 1k. sounds like it cleaned something out that the last carb guru forgot to clean. the tack needle is jumping by about 200 rpm with the heartbeat of the motor though and theres still spark knock.

aside from that its running better. it still seems to be running a but poorly until you lay on the gas while riding it though.

so syncing and adjusting fuel mixture screws is what i need to do now right?

 

[Damname]

imported post

ok. i got em synced as good as i could. carb 1 was way out and showing 3 times as high as the rest. i dialed them in close as i could. took me all day.

first thing i noticed is it still spark knocks and almost refuses to idle. i adjusted the idle but its either 3k rpm or 1k rpm and dies soon after...no in between. i took it down the road and it runs a lil bit better but still feels like its running bad at normal throttle. when i get on it boy does it scream and sounds great! its just that. it is still revving up when ya pull in the clutch to shift gears about 1k rpm.

this is what i have done so far.

cleaned the carbs
2 bottles of seafoam
replaced air cuttoffs
replaced manifold to carb o rings in the horns
and synced it

after i replaced air cuttoffs i was able to get it to idle at 1k rpm no problem but with spark knock and feeling like its running on 3 cyl at normal throttle

after i replaced manifold to carb o rings and synced it, it doesnt want to idle at all and im back to where i was when i first got the bike.

during the syncing, (took from 2 to 8 pm and wasnt easy cause it wouldnt idle for me) i did notice a blue flash under the gas tank twice.



whats next to try?

 

[Damname]

imported post

ill drain the bowls in a lil bit and see what comes out. it was running bad and not idling before i seafoamed it though. with the seafoam i saw a small improvement. we actually were able to get it to idle after replacing the air cuttoffs but after the sync it is acting like it did when we got it running after sitting for years.

ill look into the blue flash....problem is i saw it happen twice in the span of 4 hours and i dunno how to test to look for it. i might have to go ahead and take it to the shop and hope they do me right.

 

[Damname]

imported post

sandcastcb750 wrote:

You can balance a CB350 twin by ear, but not a wing.

Damname, you can balance the carbs with a single 30 psi gage and 3 rubber stops covering the air holes. Actually, you need the 5mm extentions from the air hole in the manifold too.

Start with finding the vacuum on the back right carb, then move around the other three matching the vacuum. Pinch (by doubling over) the rubber hose to stop the violent pulsating of the gage.

Go around a few time matching the back right carb and you will be surprised how well it works.

i have a mercury manometer x4. saber cycles has it on ebay for 36 buy it now! i will try the pinching and see if i can get a more accurate syncing. i ran into a problem with water finding its way above the mercury in the lines. the biggest problem syncing is it will not idle long enough to sync it so i have to have someone cracking the throttle a lil bit which im willing to bet throws off the sync.

first i want to check my electrical out. does anyone know what voltages and resistance i should be checking for and where to check?

 

[Damname]

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uh oh lol....i take it pple have bad experiences with saber cycles or the mercury gauges?