Topic: possible carb tuning issue off?

[Jason_jp]

Hey guys. I have been working on 1974 cb550 build the last few months. When i purchased the bike the PO had already rebuild the carsbs. Well long story short I am just about done with the build and have got it running. After a few minutes of idle pipe 2,3 are super hot while 1,4 are warm to the tough. Is this normal? The guy I purchased it from said adjusting the carps to make 2,3 richer would cool them down. Does this make since?

[TwoTired]

After a few minutes of idle pipe 2,3 are super hot while 1,4 are warm to the tough. Is this normal?

No

The guy I purchased it from said adjusting the carps to make 2,3 richer would cool them down. Does this make since?

No

1 - Tune carbs AFTER the entire 3K tuneup checklist is completed.

2 - Carb internal settings and parts are selected to match the intake and exhaust parameters.  IF those aren't stock, you have a rejetting adjustment job for the carbs.  Your bike is therefore far from finished.  And, the hard part is to get the carbs to run right for your applied changes.

3 - I saw no mention of vacuum sync.  Which can make a big difference.

4 - PO rebuilding carbs means nothing (and possibly worse than nothing with his comment to alter #2-3 carbs), unless he was a professional carb rebuilder and used the correct Keihin parts appropriate for your existing intake and exhaust set up.

5 - Find out what your carbs have inside them for parts and adjustments.  They would originally have a set up stamp on them of 022a.  But, meddlers can change internals without bothering with the stamping.

[Csrgti]

For starters http://forums.sohc4.net/index.php?topic=58514.0
You should post in the correct forum

[Jason_jp]

Sorry for the invconvience Csrgti. This is a project so I assumed the project shop section was correct.   

[Jason_jp]

Thank you for the help, this tells me I could have gone completely in the wrong direction! I never herd any mention of the vacuum sync from the PO so I do not belive he did that. From what he mentioned it was a carb clean and rebuild kit and he mentioned putting in the jet screws all the way down and they are all backed out the same amount so it doesnt sound like anything correct at all from what you mentioned. Now I guess i need to see what he used in the carbs!

Thank you for your reply!

After a few minutes of idle pipe 2,3 are super hot while 1,4 are warm to the tough. Is this normal?

No

The guy I purchased it from said adjusting the carps to make 2,3 richer would cool them down. Does this make since?

No

1 - Tune carbs AFTER the entire 3K tuneup checklist is completed.

2 - Carb internal settings and parts are selected to match the intake and exhaust parameters.  IF those aren't stock, you have a rejetting adjustment job for the carbs.  Your bike is therefore far from finished.  And, the hard part is to get the carbs to run right for your applied changes.

3 - I saw no mention of vacuum sync.  Which can make a big difference.

4 - PO rebuilding carbs means nothing (and possibly worse than nothing with his comment to alter #2-3 carbs), unless he was a professional carb rebuilder and used the correct Keihin parts appropriate for your existing intake and exhaust set up.

5 - Find out what your carbs have inside them for parts and adjustments.  They would originally have a set up stamp on them of 022a.  But, meddlers can change internals without bothering with the stamping.

[MCRider]

For starters http://forums.sohc4.net/index.php?topic=58514.0
You should post in the correct forum

Had you started with a project thread showing the start and progression of the project, this would just be a part of the flow.

AS it is, it is a specific problem, better in the SOHC thread.

Defer to TT for carb problems, he seems to be the best at it, better than me for sure.  In general I would say you want the 4 cylinders running as 4 separate engines as close in tune to each other as possible. Don't tune 2 out to cover up a problem.

It is suspicious the pairs that are running and not running correspond to the ignition. Unplug the 2-3 points at the coils, and see if it still runs on 1-4. If not, its an ignition problem.

[Jason_jp]

For starters http://forums.sohc4.net/index.php?topic=58514.0
You should post in the correct forum

Had you started with a project thread showing the start and progression of the project, this would just be a part of the flow.

AS it is, it is a specific problem, better in the SOHC thread.

Defer to TT for carb problems, he seems to be the best at it, better than me for sure.  In general I would say you want the 4 cylinders running as 4 separate engines as close in tune to each other as possible. Don't tune 2 out to cover up a problem.

It is suspicious the pairs that are running and not running correspond to the ignition. Unplug the 2-3 points at the coils, and see if it still runs on 1-4. If not, its an ignition problem.

Thank you for responding and sorry about the location of this topic I am still new to all of this. Carbs are not something I am familiar with so this is easily over my head unfortunately. I am curious about the ignition as you mentioned. I will pull off 2,3 this evening and see if it will run. When i was working on the bike I initially tested for spark with the plug touching the black and all four seemed ok but it may have been weaker that I thought. Wires are also kind of "loose" at the boots so that could be an issue also. I will do that shortly and respond with the results.

Thanks again!