Topic: Thought I would say Hi

[Shea]

I'm new to the forum and world of sohc/4s I've got a 78 Cb750a thats in rough shape thought I would find a place to get trouble shooting ideas
She runs only with the choke on/up has a nasty back fire out of the number 1 or number 2 cylinder other then that she seems to be in good shape all original 39k miles on it but it sat out in the rain for a good year before I rescued her.  So if anybody has one of these CB-As and wouldn't mind suggesting things to check I would greatly appreciate it.

[GreenHornet74]

Since it was sitting for a while in the rain I would recommend to start with regular maintenance such as oil, carb adjustments, valve clearance, timing, etc. Then you can get start eliminating possibilities. I had that happen once to my 750, turned out the previous owner changed 2 of the carb floats from an entire different bike and the only way it ran was with the choke up.

[Shea]

Since it was sitting for a while in the rain I would recommend to start with regular maintenance such as oil, carb adjustments, valve clearance, timing, etc. Then you can get start eliminating possibilities. I had that happen once to my 750, turned out the previous owner changed 2 of the carb floats from an entire different bike and the only way it ran was with the choke up.

  So I was futsing with it this afternoon carbs are all good looking for some reason the number 2 carb is running  a bit rich  but the number 1 cylinder isn't firing until I run up the rpms fairly high,  Changed the oil not futsing with the valves.

Went to check the points hoping that might be part of the issue and everything was corroded and nasty looking so I think I'm gona have to figure out whats salvage-able and find parts........

[splitt]

The first thing to do will be to check the basic mechanicals. Valve lash, compression, timing & points. Then install new spark plugs & new gasoline. Because it has been sitting, the connection from the plug wire to the cap may be corroded on the cylinder that is not firing. Unthread the spark plug cap from the plug wire, trim about 1/4" of the plug wire off, then rethread the spark plug cap back onto the plug wire.

If it still is not running correctly then the carburetors would be next.

[Shea]

The first thing to do will be to check the basic mechanicals. Valve lash, compression, timing & points. Then install new spark plugs & new gasoline. Because it has been sitting, the connection from the plug wire to the cap may be corroded on the cylinder that is not firing. Unthread the spark plug cap from the plug wire, trim about 1/4" of the plug wire off, then rethread the spark plug cap back onto the plug wire.

If it still is not running correctly then the carburetors would be next.

I'll have to give the valve lash/cylinder/plug wire a try if that doesn't help I'll move onto the points Just got done cleaning the points with a bit of emery I'm a little nervous about doing the valve lash but I'll give it a shot tomorrow morning

[Stev-o]

First off, welcome!

You'll need to give it a full proper tune-up to see where you stand.
Then, it will rule out possible issues. Replace plugs, caps, points and condensers and do a search for the 3000 mile tuneup.
And get a service manual and read it twice! And then again!!

Good Luck.

[wrenchmuch]

Cylinders that don't run at idle usually have clogged slow jets or some other blockage in the carbs . If the bike sat for a while with fuel in the carbs its likely they need a good cleaning . You might also check battery , charging system , points/timing , plugs and plug caps . The manual link at the top of the forums page you started this thread in has manuals for download for the 750 . The "A" engine (tranny aside) has some differences from the manual models but tune up ,carb  , ignition info should be the same . I've never seen a manual for the auto on the site .

[Shea]

Cylinders that don't run at idle usually have clogged slow jets or some other blockage in the carbs . If the bike sat for a while with fuel in the carbs its likely they need a good cleaning . You might also check battery , charging system , points/timing , plugs and plug caps . The manual link at the top of the forums page you started this thread in has manuals for download for the 750 . The "A" engine (tranny aside) has some differences from the manual models but tune up ,carb  , ignition info should be the same . I've never seen a manual for the auto on the site .

I would love to actually pull my slow jets out and clean them but the 750a has a smaller carb and the slow jets are press fit into the carb.  Had em all appart the other week and cleaned everything best I could replaced a few float bowl gaskets.   Added some seafoam to my gas and let the bike run for a few minutes I'll let it sit for a few days see if that helps clear out the slow jet if thats the issue.   I'll have to hit the plug caps when this liquid sunshine goes away.    Screwing with the timing looks a bit iffy.