Topic: I fought my bike and my bike won

[Magilla]

3 days and many hours later it runs exactly the same....crappy.  It sputters from the 1 and or 2 cylinder at low rpm.  It takes no choke to start and it runs rich.  The cylinders on the right side of the bike seem to run perfectly.

I changed the plugs and it made no difference.  I turned the idle mix screws all the way in, opened them 1/2 rotation at a time and rode it between each change. No difference. I changed the coils and wires.  No difference.  I checked the points and regapped them.  No difference

I removed the float bowls and cleaned the carbs.  No difference.  I changed the gas tank and put new gas in.  No difference.  Not one thing I
have done has made it better or worse. It runs exactly the same. 

I have never touched the jets in the carb so I can't tell what size they are.  I do know that the bike runs rich and I can't see to lean it out.

76 cb750
Stock exhaust
Stock motor
15k miles on it
Stock coils
No mods that I am aware of.

[Old Scrambler]

If you NEVER TOUCHED THE JETS you have not cleaned the carbs........most or all of the pilot jets are probably blocked and the mains could be dirty, blocked and /or the emulsifier tube is mostly blocked. Your floats could be high.

Did you bench-synch the carbs?

I use a tip cleaner from a gas-welder kit to clean the carbs.  Some use guitar-wire. Do NOT use a drill bit. With the air-screw removed, be sure you can blow air from the small inlet at the venturi through the air-screw area. Then set the screw at 1-turn from a soft bottom. You may need to adjust each carb in 1/8-turn increments. 

[jneuf]

If you NEVER TOUCHED THE JETS you have not cleaned the carbs........

What he said. If you only removed the float bowls, not the whole rack of carbs from the engine itself, nothing will have got cleaned. I'd get 'em off there, strip them down and give them a real thorough cleaning.

[Rigid]

Someone could have drilled 2 jets in a misguided attempt to balance the engine.  You won't know until they are removed,cleaned, inspected, and verified correct. 

[TwoTired]

If you are going to fight your bike, use two hands rather than just one.  Very difficult to knock out your opponent if you only punch at the feet.

[harisuluv]

Everyone is pointing you in the right direction.  Those carbs definitely sound like they need to be gone through.   There's plenty of info around here to walk you through it and people to help.  If you get stuck somewhere feel free to pm me or even call me.  I am always willing to take calls from SOHC members for help. 

[Magilla]

Once the carbs get pulled, do they have to be resync'd?  I have no way to do this so that is why I have been trying to avoid it.

[sir funk]

Once the carbs get pulled, do they have to be resync'd?  I have no way to do this so that is why I have been trying to avoid it.

Yes. There is a $50 set of vacuum gauges on amazon to take care of the sync yourself. You can also make your own sync tool out of aquarium hose. . . Psychonaut recently posted A how to for a sync tool he made for $10.
http://forums.sohc4.net/index.php?topic=107357.0

[BobbyR]

Once the carbs get pulled, do they have to be resync'd?  I have no way to do this so that is why I have been trying to avoid it.

Taking off carbs and giving them a good cleaning cannot be avoided. Get a set of gauges and synch them up. You will use that tool every two years.

[matt mattison]

They only need to be synced if you remove the slides or otherwise change the slide adjustments. If your really gonna dive in the carbs all that stuff needs to be disassembled,inspected and cleaned anyway. Your already in it this far, why not spring for the tool. Besides, when you had the bike running before, we're you even certain the carbs were in sync? The worst thing that could happen is the bike could actUally run better.

[ekpent]

If you have tiny long fingers and a very short screwdriver and you don't swear or lose your temper easily-unlike me- it is possible to at least pop out the main and slow jets without removing the carbs and give them a look and a cleaning. Not nearly as good as removal and getting all the passages though. When you dropped the float bowls for the first time what did you see in there,was there much varnish or sludge or any sign of rust particles ?? As mentioned those jets,especialy the slows are fussy.If it is a 76 look for the number 40 on the slows and #105 on the mains.

[Roach Carver]

You can get get it decent with a bench sync. Search here for how to do it. I would just suck it up and take them off. Couple cans of carb cleaner, compressed air and put them back on. I think you will be glad you did it. Your carbs wont be a mystery to you any more either. Good luck.

[bollingball]

Not one thing Ihave done has made it better or worse. It runs exactly the same.

Did all that work and did not do the most important thing. You did not pull the jets. So the jets are dirty along with there pasage ways.

Ken 

[Really?]

I used the link below to get an idea of what my carbs were about and how to clean them.  It is not the greatest layout but it does the job.  Click on the top most image to get started and then there is a link "Next" to go to the next page. 

http://www.salocal.com/sohc/tech/carb/carb.htm 

You need to at least be sure that the carbs have been cleaned.  These carbs are super easy to do and there are not many parts to it, you may just need to get over the intimidation, if any.

[750K]

As everyone has said, pull the carbs and properly clean and sync them. Buy a set of vacume gauges, you'll thank yourself next time you need them. You might as well check and adjust your valves while your at it, I did the same thing recently. Checked and re set the valves, points, plugs and did a carb sync and got my mixture adj proper. Runs like a new bike.

[iron_worker]

If you really really really don't want to pull the carbs and re-sync them (but know that it is HIGHLY recommended) then as said before you can get a stubby screwdriver and pull all the float bowls, and then pull the pilot jets and give them a good cleaning with a guitar string and some solvent. I'm almost positive you have at least 2 clogged. I just rebuild my carbs and my bike wouldn't hard start for sh!t when it was cold. I found 2 plugged idle jets, one of the choke mechanisms was out of sync with the rest, and general grunge and grime which I cleaned thoroughly. The bike  now starts up great and idles smooth and I haven't even synced it yet. (If you are careful you can bench sync them fairly close.)

IW

[Magilla]

I pulled the float bowls.  Removed the floats and pulled the two jets in each carb. The jets in carb one were partially blocked. They are now all clean.  I also removed the idle jet and cleaned out the passage with wire and a blast of air.

The bike runs better now but not perfect.  It still runs rich.  My eye sight is not good enough to read the jet numbers when I pulled them. It sucks to get old.  So like I said its better but needs to be leaned out.  I tried the idle jet screws but I guess I don't know what I'm doing because it runs rich no matter what.  Also it never requires a choke to start.

[Johnie]

Are you sure your gas tank is free from crapola? You would hate to have to clean those jets after each ride.

[Magilla]

Are you sure your gas tank is free from crapola? You would hate to have to clean those jets after each ride.

I changed the tank just to be safe.  No rust or residue in the new tank.  Still need help leaning it out.  How do I go about that?

So far this forum has been a GREAT help.  Bike is running better for sure.

[Roach Carver]

Is the timing and ignition in good shape?

[ekpent]

I keep a magnifying glass in the shop to read those numbers on jets and other uses and the occasional ant burning    Be nice to know what size you have in there now. If you take those carbs off someday a float height measurement would be good also.

[Magilla]

This week I will pull one of the carbs apart again and check the jet numbers (with a magnifying glass). One question on the float height, I checked each one while the bowl was off and they all work.  With that said is it possible for a float to cause it to run rich if it is now set at the correct height?  I would not have thought so.

Question on the idle jets:  will it run leaner if the jets are turned in or turned out?

[phil71]

"If the jets are turned in or out?" I think you need to go back to the beginning and get some background on how your carbs work.

[Magilla]

Yeah I think I worded that incorrectly.  I am referring to the idle mixture screws.

[Roach Carver]

idle mixture screws will affect the idle mixture. I turn mine all the way in and then back out, I believe 1.5 turns each. there are two holes at the intake side of the carbs. one goes to the idle jet and one goes to the idle mixture screws ( it think) both passage ways need to be clean for proper operation. if the idle jet passage is not clear it can cause rich readings due to poor atomization of the fuel according to what I read in my hondaman book.