81 GS 550 Project bike - almost runs

[Murphy67]

Ok I have been getting some great help for the past few weeks with this project bike. Sorry I haven't posted any photos. I get immersed in work and forget to take pictures. Anyway I am making progress. I got all the carbs gang mounted and and installed on the bike. The carbs were bench tested to check float level The idel screws were set to 2 1/4. #2 carb drain stripped out but a helicoil kind of fixed it but thats for another post. informative. The intake runners to heads are new with new orings and retainers. I made a temp fuel supply from a one gal gas can so not have to deal with the tank at this point.

The bike ran off within the first few cranks. Oh i got this bike not running and carbs in boxes....

Now to the issue. #4 cyl is not running at idle properly. It's hard to say by sound but I suspected it none-the-less. I pulled the plug and it appeared dry. The real identifying factor was the exhaust pipe off the head on cyl 123 were too hot to touch but 4 was almost able hold. I was able to get this carb off without pulling them all. I went though the idle circuit and it all seems perfect. ( used Mikuni carb manual found here ). I put back on bike same thing.

I then checked compression and this cyl seems low but ran some marvel oil in it and improved. 80-85 psi. I pulled the plug for sychronizing and the idle went to about 2000 and is sounded like it was running on cyl 4 and the pipe was hot. I tried the same thing on cyl 1 and the bike died.

I can't figure out if this is really a carb problem or something else. the spark is enought to arc weld with lol.

Mike

 

[Baatfam]

Did you clean the carbs? If so, how?

 

[Steve]

Did you adjust the valves? If so, how?

.

 

[Who Dat?]

Yeah, valve adjustment and carb cleaning are the two biggest items on the forum besides cleaning the electrical connections. Neither one is all that hard, but requires VERY CLOSE attention to detail.

On the valve adjustment, you have to have the cam lobes in the correct position. All the manuals have the same goofy picture that shows the position, but only the Suzuki manual actually puts it into words that mean something.

On the carb cleaning, you can't just spray some cleaner into the carb and call it good. You have to strip them down completely, soak them in carb cleaner dip overnight, then flush them with some spray, and install all new o-rings befofre they will work right.

 

[Big T]

When you pulled the carb. was there gas in the float bowl?
If so, your carb is still plugged up.

 

[Murphy67]

All:

I did not touch anything with the valve train. I don't know any of the service history. The bike was purchased by someone not running and they said it just sat a long time and they started working on it. hence fuel related parts removed and in boxes.

The carbs had been cleaned well both inside and out Both dipped and ultrasonic. These carbs look great for the age. not corroded. Carb #4 the one that won't respond to idle was pulled apart a second time by myself and the idle passage was closely inspected. Per the carb manual i can get carb cleaner through the smallest of orifices as shown.

Yes the fuel level is correct although maybe a touch low by a mm. This is the carb that someone broke the float post off and actually did a good job with epoxy. The bike definitely runs on all 4 on power circuit. No stumble no backfire.