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Rebuilt and stripped the carb on my 85 GS after having issues with it running (hadn't run in nearly 20 years, played around with a lot before deciding it was something with carb), it will now run with a shot of starter fluid and keeping it above 2500 RPM. But it will not start on its own and it will not idle, if I have someone else turn it over while I watch, I can see that no fuel is fed to the motor until it fires with a shot of starter fluid and its kept high in the RPMs. I've searched and searched and cannot figure this issue out, I appreciate any help
Last edited by Spinnytriangle; Jun 25, 2023 at 05:33 PM.
I honestly have not tested that, but the bowls are always half full. I can have someone keep it up in the 4k range and watch and bowls are always half full. I very well could be wrong but I just assumed that meant "enough" fuel pressure from the pump.
KC REPU has a good recommendation to look up the factory service manuals. I strongly recommend the Carburetor Training Manual.
Otherwise here are some random thoughts. They may or may not be applicable (or even potentially true).
Are you using the choke to start? This increases the vacuum in the primary side of the carb to help suck fuel into the carb. My carbs have not had a choke for years (racing application) and without pumping the accelerator (and thus injecting fuel into the engine through the "accelerator pump" system) the car will not start.
Is the accelerator pump working? You should be able to tell by "pumping" the throttle by hand while looking down the throat of the carb. If you don't see shots of fuel coming through the ac pump jets, they are not working. If this is not working my car will only start with an "ether infusion".
Is the idle fuel system working? Are the pathways blocked from sitting for 20 years? Is the idle jet adjusted so that the engine can suck fuel into the carb below the closed primary throttle plates? These are a lot harder to check, so this is where the carb training manual could be helpful to better understand what is going on. I believe that if the idle system is working properly, you should be able to idle at normal RPM once the engine is warmed up (with choke or not). Mine does anyway once water and oil temps reach about 140 degF (no choke).
I believe that if the fuel level in the bowl is really always half-way up the glass, that the needle valves and fuel pressure are not the immediate problem. They could end up being problematic later, but.....
I'm not sure when I'll have time to actually get into it again, but I just pumped the throttle and not a bit of fuel came through so it looks like the accelerator pump is my issue, or at least one of them.
Sounds like your idle circuit is just plugged up or misadjusted. You shouldn't be able to see fuel leaving the carb until above about 2k rpm anyway, so what you noticed is actually a good thing (otherwise you would probably have a stuck float). The fuel at idle and during idle transition is fed into the carb down near/below the throttle blades, so you can't visually check that.
I'd first double check that your idle mix setting is correct (baseline 3.5 full turns from lightly seated) and then go from there. If that doesn't do the trick then most likely your carb just wasn't fully cleaned out when you had it apart and some part of the idle circuit is still a tad gummed up. If you do take it apart again also double-triple check that all the jets and bleeds are in the right places.
The idle mixture screw is currently 3.5 out from light seat, but I have played with it at all ranges. It is possible that something is gummed, but I did take every piece apart very meticulously and chem dip and scrubbed it. I appreciate the help
Here is a clip from the factory carb manual. It shows generally how the idle circuit works. I don't know the locations of all the jets and air bleeds, but I am sure someone can help with that. Otherwise, I think you can spray carb cleaner in jets until you see it coming out of the idle air/fuel port below the throttle valve.
