Idle/Running problems with a 1983 GS750E

[GSstiny]

I think that might be my problem! I'm using 1/4" fuel line, and a 1/4" inline fuel filter in between.... I'll try 5/16 straight fuel line from a funnel tomorrow and see if that's my problem! I was reading up on inline fuel filters here, and I did see several people mention 5/16 is needed.. Would my 1/4" fuel line with a 1/4" fuel filter explain my super lean carbs? (Won't run unless choke is out, or pilot screws are 4+ turns out)?

That very well could be it. I had roughly the same problem with a 1/4" inline filter. I didnt mean to misinform on the pilot settings. I forgot you had BS carbs.

[chef1366]

Hey, my carbs aren't BS:-)

[John Adams]

I hope that 1/4" fuel line and 1/4" inline fuel filter is my problem.. [-o<

That would be great! \\/

I'm temped to go out in the dark right now and try straight 5/16" fuel line :-D, but I'll wait until tomorrow when it's light outside and the misquotes are not feeding! :shock:

Yup, I have BS carbs, and hopefully BS fuel lines and a BS fuel filter

Thanks again!

[frosty5011]

For just getting it to idle, the 1/4" fuel line won't make a difference, but the fuel filter might. Do try it without the filter.

Here's a quick stupid question, but you do have your idle adjust knob turned in far enough, right?

[John Adams]

For just getting it to idle, the 1/4" fuel line won't make a difference, but the fuel filter might. Do try it without the filter.

Here's a quick stupid question, but you do have your idle adjust knob turned in far enough, right?

Yup, I basically tried everything. I also tried to come off the choke into throttle but any throttle would just kill it. When I have the pilot screws 4+ turns outward, I can increase the idle RPM just a little bit with the idle adjust knob.. If I turn it in too far, it just stalls out..

When I was actually pouring fuel into the funnel, I watched it run down the first 1/4" fuel line, then fill up the filter, but it would not fill up the fuel line below the fuel filter so I'm puzzled why that would happen? I guess the inline fuel filter that I'm using must require pressure and gravity is probably not enough to pull full through it fast enough. I would expect that the open funnel would completely fill up both 1/4" fuel lines.

[frosty5011]

Yup, I basically tried everything. I also tried to come off the choke into throttle but any throttle would just kill it. When I have the pilot screws 4+ turns outward, I can increase the idle RPM just a little bit with the idle adjust knob.. If I turn it in too far, it just stalls out..

When I was actually pouring fuel into the funnel, I watched it run down the first 1/4" fuel line, then fill up the filter, but it would not fill up the fuel line below the fuel filter so I'm puzzled why that would happen? I guess the inline fuel filter that I'm using must require pressure and gravity is probably not enough to pull full through it fast enough. I would expect that the open funnel would completely fill up both 1/4" fuel lines.

"Assuming" the fuel is definately flowing into the carbs now (you are trying without the filter now, right?), just for kicks, turn the pilots in to about 2 turns out from bottoming (somewhere around normal range). Then move your idle adjust knob up 1/2 turn or so, see if it'll run then. It's slightly possible that the order you tried it in was flooding the engine (with the pilots out 4 turns already).

[John Adams]

I haven't tried removing the inline filter yet. Tomorrow, I'm going to try removing the filter and the 1/4" fuel line, and go with a straight 5/16" fuel line from the funnel right to the carbs and try ~2 turns out on the pilot screws.

I'm sure the inline fuel filter I was using is the problem. I think it's way too restrictive for gravity feeding. I think the inline filter I was using was designed for a pressurized fuel system. I don't remember where I got the fuel filter.

Here is a picture of the setup I was using. I thought I was being smart with this one, but i think it made a fool out of me

[chef1366]

Man, you even got the filter on backwards:-)

[david suzuki]

Coming from my personal experience in the trade as a mechanic, and without looking at the bike my self, i would check the following things to give yourself a general picture of what is going on within the engine.

1. You have established you have fuel
2. You have established you have a sufficient air supply
3. You have established you have spark

Now you know you have the three things you need to make an engine run, we have to start searching within these items for the root of the fault.

1. Check your filters, tank outlet, petcock (You said you are doing the hose and funnel thing so it cant be anything before the carbs....)

You also said the bike was showing the same symptoms before you pulled down the carbs, so it cant be anything you have done while working on them. Are you sure you cleaned out all of the air jets, air bleed holes, emulsion tubes etc???? get a small peice of wire and poke every single little bastard hole in the carbs, use some carb cleaner and get those babies shining.

2. You said you removed the air box so you cant have an air supply issue.

3. You have established you have spark, is the spark a nice blue spark from each plug???? are the plugs clean?? Are the leads attached to their corresponding plugs???? ( I KNOW THAT SOUNDS STUPID BUT FUNNIER THINGS HAVE HAPPPENED.)

4. Check your timing with a timing light.

5. Adjust valve lash FOLLOWING THE PROCEDURE IN THE MANUAL EXACTLY.

6. Take a compression test of each pot on the engine.

If everything i have suggested comes out looking ok then dont start worrying, because there is probably nothing majorly wrong with your bike.

what have you touched on the bike recently??? done a service or anything like that where you could have mixed up some leeds or something????

[John Adams]

Man, you even got the filter on backwards:-)

The fuel filter is on correctly.. Unless you think I'm pouring fuel into the hose and attaching the funnel to the carbs :shock:

[frosty5011]

That specific filter that you're using (Purolator F21124..or maybe you have the NAPA equivalent??) is a piece of crap, has a tendency to "lock up" after the filter paper has been wet and then allowed to dry, unless you have a pressurized system. I've tried the exact same one myself.

[John Adams]

I'm not sure what brand they are. I bought them from Ebay awhile ago. I think this is where I got them from:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=8076043870

I can't wait to try a straight 5/16" fuel line without one of those damn filters.... [-o<


I'm almost positive now that damn filter has been my problem from the beginning.

[John Adams]

Well, removing the fuel filter definitely made a difference, but i still have a problem. I think my float level is wrong.

My service manual says the float height is 22.4mm +/- 1mm. I think I measured from the top of the lip (not the gasket surface). I did end up bending all 4 tangs downward to raise up the floats.

On my '83 GS750E carbs, I think I should have measured from the gasket surface (without the gasket), but now I'm wondering what part of the float I should measure to. There is a step so could someone tell me exactly how to measure the float distance so I can correct them?

thanks in advance!

[John Adams]

I did a search here, and found this image that someone else posted.. Is this the correct method for '83 GS750E carbs?

[chef1366]

That would be the one. Everyone wrestles with their carbs at first, but soon you will be an expert.