#4 slider not moving correctly

[van avery]

I've got an 83 venture for couple of years now. I cannot seem to get it running correctly, poor mileage ( 28 MPG) and back firing ( poping back through the carbs) slightly after making a corner then accelerating. After a pop or two it picks up and takes off. This is with both the original TCI and the new one I purchased last year. The bike normally runs better before it warms up. I readjusted the valves last year too.

I thought it was running rich so, had the carbs off last week to reset the floats and install smaller shims in the sliders. Still run bad maybe a little worse. Put the original shims back in. Now I have a float stuck and gas coming out the overflow line. So I get to pull the carbs again, oh joy.

Mainly, I also noticed that the #4 carb slider is not moving. Last week I pulled and cleaned the idle mixture needle valve and the two ports ( top and bottom sides of the diaphragm) into the throat. I set the idle mixture screws to 2 turns out. This week I reinstalled the original shims in the sliders I have reset the idle mixture screws in to 1 ½ turns out.

Once I get up to about 4000 RPM it seems to smooth out.

When I syn’cd the carbs I get about 9” vacuum on all cylinders at 1000 rpm.

Is there some other internal thing I may be missing that would stop the slider from working correctly in just one cylinder? I pulled that slider again and the diaphragm ( no holes in it also about one year old ) is seated correctly and I have already disconnected the YICS some time back and plugged the lines. I also have not found and intake leaks.

[Power Trippin]

I am wondering if the valves are adjusted properly. I have experienced back firing thru the intake, of cars, and both times it was just after someone had been inside the engine and had the valves adjusted incorrectly. I am not saying this is the problem, but it is possible. Did the bike run good after the valve adjustment was done?

[Snaggletooth]

Only two things off the top on that slider. It's sticking due to being gummed up or..... the diaphram is breaking down. Either way it's not hard to acess and remove to inspect.

 

I'd take a close look in a dark room with a flashlight behind it to see if there are holes or small rips developing.

 

Mike

[van avery]

I am wondering if the valves are adjusted properly. I have experienced back firing thru the intake, of cars, and both times it was just after someone had been inside the engine and had the valves adjusted incorrectly. I am not saying this is the problem, but it is possible. Did the bike run good after the valve adjustment was done?

 

Yes it was better and the compression was greatly improved. There were quite a few that were to tight.

 

When I push the slider back with a finger it seems to slide OK, about the same as the others.

 

I'm going to pull the carbs again and find my float problem and go through #4 carb again to see If I missed something. I inspect the diaphragm again but it looked very good yet.

[raybear71]

Inspect the slider itself very closely. I had the same problem and found a hairline crack in the slider was the culprit.

[van avery]

Took things apart cleaned the two carbs that had problems. One had stuck float (I guess) and the other with the slider not working cleaned again and and inspected closely. Put back together and things are working again. Sync'ed carbs and will try to test tomorrow afternoon if I get the time.

Thanks guy's for the responses.

[CaptainJoe]

Tip:

When working on carbs, I always turn the carb(s) upside down and blow a little air thru the fuel line with my mouth. The float(s) will put enough pressure on the needle valve(s) so that you cant blow air through them... then, rotate carb(s) till in the upright position and the air should freely go through

 

That way you don't have to wait till everythings re-assembled to find out about a stuck float.