Topic: 1974 Cb550 Running rough (backfiring with flames)

[hondacaferacers]

I wanted to see if you guys canhelp me out. When I got my bike it already had the exhaust and the guy was running the stock intake set up. So now that the bike is up and running I got rid of the stock intake system and just have the plastic piece that connects the 4 into one exit. And at the exit. I placed a foam filter. And the bike would run but not at its best. When I would Open the throttle all the way the bike would hesitate then the power kicked in. So i added some carb cleaner in the fuel tank and now the bike is hard to start and will back fire and shoot flames on the left side of the exhaust but not on the right. I thought this was interesting so I checked the jets on the carbs and they were 100mm for the main jet and 38mm for the poilot. This confused me even more because I thought that if the bike backfires and shoots flames that means the mixture is rich. But with the exhaust and intake setup I have the bike should be running lean. If anything. Do you think this has anything to do with the float levels? And why would only one side back fire? Also could the points be of time and cause this issue?

[mrfish2]

Why would you get rid of the stock intake system? As you can see, you've already ran into many problems by doing this.

Pics would also help explain your situation

[flybox1]

Why would you get rid of the stock intake system? As you can see, you've already ran into many problems by doing this.

ditto 

[harisuluv]

I wanted to see if you guys canhelp me out. When I got my bike it already had the exhaust and the guy was running the stock intake set up. So now that the bike is up and running I got rid of the stock intake system and just have the plastic piece that connects the 4 into one exit. And at the exit. I placed a foam filter. And the bike would run but not at its best. When I would Open the throttle all the way the bike would hesitate then the power kicked in. So i added some carb cleaner in the fuel tank and now the bike is hard to start and will back fire and shoot flames on the left side of the exhaust but not on the right. I thought this was interesting so I checked the jets on the carbs and they were 100mm for the main jet and 38mm for the poilot. This confused me even more because I thought that if the bike backfires and shoots flames that means the mixture is rich. But with the exhaust and intake setup I have the bike should be running lean. If anything. Do you think this has anything to do with the float levels? And why would only one side back fire? Also could the points be of time and cause this issue?

I don't even know where to start.

-"So now that the bike is up and running I got rid of the stock intake system" 
-From what I'm gathering, you're referring to "4 to 1" in reference to the airbox (or part of it) and just stuck a piece of foam over the exit?  I don't even understand what this is supposed to accomplish, it doesn't even have the aesthetic element of pods.
-100mm and 38mm jets. 
-You... added carb cleaner to the fuel tank??  Like actual carb cleaner?

After all this, prime suspect is float levels?  No offense but you either need to do a lot of reading, and research on here, or take your bike to a mechanic.  If you want to pursue things yourself, myself and others would be happy to help you.  But if you don't provide information, pictures, and are willing to take instructions without putting your own little "twist" on them, you will be ok.  If not you are probably more likely to cause damage than fix your bike.

[hondacaferacers]

(I will take some pictures later today of the whole set up and post them here) I am not sure if the bike ran good in the first place. I got the bike from an auction and it had major damage to the motor (the crank shaft was bent). So I ended up rebuilding the motor.
I got rid of the stock air box because it was big and took up lots of room. I did keep a part of the air box and I attached a piece of foam on the end of it to prevent dirt and things from getting in. Eventually I will get individual pod filters.
With this set up the bike would run. But the idle would be higher than normal. Also when I gave the bike full throttle the bike would want to die at first. Then it would take off.
That’s when I picked up some carb cleaner mixture that mixes into the gas tank. So I pored that in and that’s when the bike would start shooting flames from the left side of the exhaust.
I also read that if the exhaust has less back pressure I would have to get bigger jets to compensate for that. So that’s when I checked the jets that where on there already and they look like they are the stock size.
I’m sorry I don’t have any experience working on carburetors. so it is still confusing to me how to tune them and get them to run right. 

[turboed13b]

Sounds like you need to get the carbs cleaned or have a professional do it.

[DaveBarbier]

You'll probably be asked soon to put back the intake box and such and then see how it runs. Might be a good idea to do that now. After you get it running you can move to pods. It can be quite a big and frustrating undertaking to move to pods.

Do you have a manual?

I think you'll be running lean by removing the intake system like that. So either replace the intake system or tune carbs.

Jets aren't measured in mm. It's the hole that the measurement is measuring so a 100mm (or 10cm) main jet would probably be found in the carbs on the ISS.

[RAFster122s]

He must have used the Carpy's world of cafe racers with a id like hondacaferacers.

You have been given good advice,  follow it and you might be able to get it running. 

How did you determine the crankshaft was bent? It didn't have any case damage when it was bent? You will need to dump the gas and carb cleaner concoction and replace with only gas, preferably without ethanol so it doesn't go off from breaking down over time. Don't go crazy and buy racing gas (high octane gas) unless you plan on using it always.

[mrfish2]

I got rid of the stock air box because it was big and took up lots of room. I did keep a part of the air box and I attached a piece of foam on the end of it to prevent dirt and things from getting in. Eventually I will get individual pod filters.

Either get pods now or put the stock airbox back on. There's no sense in tuning it for whatever you've rigged up and then re-tuning it for pods, you'd essentially be beating a dead horse. Tuning for pods is hard enough, many members will tell you that. These bikes run best with the stock airbox.

[nicks2319]

Sounds like you need to do a ton of general maintenance / tune up before you start messing with things. Points, condensers, point gap, spark plugs, plug wire caps, timing.

[lrutt]

Crap ass carb cleaner in a can is not a cure for much of anything, other than to make them rich and you a little poorer.

Plus do you have a clue as to what jetting you might have? stock or not?

I would strongly suggest you download some of the myriad of documents on the net that discuss carb and ignition theory. Once you've digested that, and read through the myriad of posts on this site regarding carbys and intake mods, then you can assess what you have and where you're at and make an informed decision. No need to ask folks here to regurgitate information that has been posted......a myriad of times (word of the day).

Sorry, don't mean to come off harsh, It's just same #$%* different day. Nothing wrong with taking time to do a little research on your own before you start asking questions.

rant off/

[DaveBarbier]

Plus do you have a clue as to what jetting you might have?

Clearly stated in his first post what jets he has.

[lrutt]

Plus do you have a clue as to what jetting you might have?

Clearly stated in his first post what jets he has.

do NOT take it for granted those jets are what they say they are. Have you never run into jets that have been buggered by some ham fisted PO? I know I have several times.

[DaveBarbier]

Plus do you have a clue as to what jetting you might have?

Clearly stated in his first post what jets he has.

do NOT take it for granted those jets are what they say they are. Have you never run into jets that have been buggered by some ham fisted PO? I know I have several times.

You're absolutely right, I have been screwed by the PO of my 550. He drilled out the pilot jets to larger than the main jet size. But generally you can trust the number. But if you can't, then what luck do you have aside from measuring with jet drill bits? I think for now one can trust the number unless other things point to richness when there shouldn't be.

[BomberMann650]

Mine was a little spitfire when a condenser was dying.

[Duanob]

Crap ass carb cleaner in a can is not a cure for much of anything, other than to make them rich and you a little poorer.

I will disagree with that too a point. I wouldn't use carb cleaner to "fix" anything but I run some in about every 3 or 4 tankfuls just to keep things clean and the carbon build up to minimum. Seafoam or Berryman's works.

[Lostboy Steve]

I'd pay extra for some flames coming out of my tailpipes. Just saying.... 

[DaveBarbier]

I'd pay extra for some flames coming out of my tailpipes. Just saying.... 

Maybe this should be moved into the tips and tricks section...