I could really use some help with my CB550

Skuzzrat

Skuzzrat

Been Around the Block
I am having trouble getting my bike to idle. The bike starts with the choke open just a little bit but then the issues start, no matter how long I warm the bike up for I have to keep the choke open just a little bit otherwise it turns off. Also the idle seems to fluctuate a bit (especially if I give it gass, it then stays higher sometimes or drops at other times) but I assume its cause it is warming up. After it warms up for a few minutes it starts to have issues when I'm revving it, as I twist my wrist the bike starts loosing power at first, then kicks in but often shuts off right after wards. Its worst when I put it in gear and try to test ride it, it dies every time no matter how much gas I give it. I am not experienced at all with bikes and know no one that is so I am completely confused. At first I assumed it was a problem with the main jets cause the bike has a short exhaust, a Pingel petcock and aftermarket air filters so I changed the jets from stock(100) to 120's. Here is some pictures of the bike.
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Skuzzrat said:
...... no matter how long I warm the bike up for I have to keep the choke open just a little bit otherwise it turns off......
Click to expand...

This is your clue. The choke richens the mixture, so if you need to put the choke on, it's running lean.

First of all, have you cleaned the carbs? I mean taken them off, pulled the bowls and jets and blown out all the galleys with compressed air? Have you flushed your tank / fuel tap? Do you have fresh fuel?

If that is all done, then you will probably need larger pilot jets and need to adjust the idle circuit to richen it up.
 
I have only opened the carbs when I was changing the main jet and and they looked really clean then, but of course that doesn't mean much I know. The tank is clean, I re-lined it a few months ago, the petcock is new and I just put fuel in for the first time right before trying to fire it up so I don't think the problem is with the fuel.
 
Pod filters, open exhaust, stock jets? Bad recipie. Where did you fill up? Its pretty rare, but sometimes you can get dirty/shitty gas. Are your carb boots sealing properly? I see you have inline filters. Are they in correctly (I know its dumb, but sometimes dumb stuff happens.) and in the right direction? Even new parts can be dirty. If you pull the fuel lines off of the carbs, and open the petcock, is the fuel flowing out freely?
 
The open exhaust and pod filters came with the bike, the PO did that. I just ordered a two set of pilot jets, size 35 and 45 just in case. I filled up at Arco I believe but I used a can and transferred the gas from the can to the tank and I've been told that is a safer way to prevent dirt going in the tank. The fuel was coming out right when I tested it after installing the petcock but I will double check it tomorrow.
Is there a way I can test or check if the carb boots are sealing correctly?
I keep thinking that it is an air problem and I was really hoping that the bigger main jets would do the trick but since ordering I have realized that its the pilot jet that matters at idle. When the jets come in I will clean the carbs out too, is there anything else I should do??
 
what main jets did you fit?
stock pilots work ok with a 'quiet' exhaust, with open pipe, anybodies guess.
Your going to need around a 115~140 main jet with your set-up, drop needle at least one position

PJ
 
I installed a 120 main jet, I did not drop the needle however, what exactly does that do??
 
Its running rich mid range when you have correct jet for top end, dropping needle leans it out slightly.
you may have to adjust float height as well (23mm)
stock pilots are 40 or 38, you probably need 40 or 42, 45 will work but be a bit rich
I think your going to have to go bigger on mainjet with short open pipe

PJ
 
the pilot jet effects idle or when the throttle is closed then the jet needle takes over through the midrange throttle position, then at wide open throttle the main jets do there job,

It sounds like you need to up all your jetting , more air going in + more air going out = Need for more fuel try the next step larger pilot, move the needle position up, by lowering the clip down a groove (towards the fuel bowls) then try one or two steps bigger on the mains, if you poke around enough or find some people that vintage race the 550's they should know exactly where to set the jetting to.
 
Garage_guy_chris said:
if you poke around enough or find some people that vintage race the 550's they should know exactly where to set the jetting to.
Click to expand...

That would be me then, I've been messing with them since 1977
The main jet affects just about ALL throttle openings (try removing it and see how well engine runs off idle)
The jetting is different for a low restriction silenced system compared top a race system designed to work at specific rpm and a chopped up 'thing'
My '550' in 1982, 106,000miles (70,000 as a 591cc)
Found the cam spec this evening, didn't know I still had it. 8)
 
Way ahead of your suggestion VonYinzer, I posted the question on both sites just to boost the amount of advice people could give me. I will drop the needle when I install the new pilot jets that I just ordered. I'm also going to clean everything and re-check my fuel lines/petcock. In the meantime I'll keep searching the web to see if there is anything else that might be causing it.
 
I had a 1978 cb550 with the lean burn carbs, so slightly different but this could give you a base line to start from....
with pod filters and mac 4-1

105 mains
stock pilots
needles set 1 step richer than stock
IMS 2 turns out

this combination was super easy to crank and ran well through the rpm range

hope it helps
 
Skuzzrat said:
I am having trouble getting my bike to idle. The bike starts with the choke open just a little bit but then the issues start, no matter how long I warm the bike up for I have to keep the choke open just a little bit otherwise it turns off.
Click to expand...

Where do you have the throttle rest screw sitting? I have a 76 CB550 with pods and 4/1 open exhaust, stock jetting (with rebuilt carbs)... I choke it for only a few seconds to start it then casually reduce the choke off... but to keep it idling, I have to screw IN the dial on the top right of the carbs... usually 2-3 1/2 turns... as the bike warms up, blipping the throttle now and again, the idle will gradually rise and I can then turn down that dial back til its right around 1k.

Skuzzrat said:
Also the idle seems to fluctuate a bit (especially if I give it gass, it then stays higher sometimes or drops at other times) but I assume its cause it is warming up.
Click to expand...

Are you springs and throttle cam moving freely? smoothly opening up and springing closed? Throttle cable moving freely? I'd blip the throttle AT THE CARBS by manipulating the cam pulley to rev the engine... as to eliminate any question of the throttle cables being sticky. Again, make sure the resting point for the throttle plate is high enough to maintain an idle by making sure that adjustment dial keeps it from going too low.

Skuzzrat said:
. After it warms up for a few minutes it starts to have issues when I'm revving it, as I twist my wrist the bike starts loosing power at first, then kicks in but often shuts off right after wards. Its worst when I put it in gear and try to test ride it, it dies every time no matter how much gas I give it.
Click to expand...

Again, as others have stated, a quick easy $100 carb rebuild and cleaning could remedy all of this. It did for my bike when I bought it. Four $25 rebuild kits with new stock jetting and a proper adjustment of the floats, a thorough cleaning (lots of carb cleaner, toothbrush, ultrasonic... re-grease all the exterior moving parts/springswonderful)... The air mixture screws I have set at 1-1/2 turns OUT (gently turn them all the way in, then back them out 1-1/2 turns... gradually go 1/4 turn adjustments OUT to fine tune it).
BTW, my bike runs very well but not perfectly... It fires up, idles (after a few minutes warming up idling and especially after the first 1/4 mile on the bike, its idling at temp and I can twist down that dial for the rest of the ride) and runs great but I'm also underjetted also so when I wanna crank on it, I actually have choke it out to richen it up. I can run full throttle til well into redline in 1st and 2nd gear but under a 3rd gear or more loaded gear, it falls flat in several areas. It's no tunes track bike but it gets me around juuuuust fine :)
 
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