Engine does not start after carb clean

[chance_rider]

I'm hoping you guys can help me get my '81 GS650G out of storage onto the road. Your advice last time on carb cleaning was great! I have taken the bike out of storage after 16 years, taken apart the carbs, cleaned and reinstalled them, and am now trying to start the bike to synchronize and tune air mixture screws but can't get the engine to run continuously.

With choke on, it takes several cranks before firing, revs up to 5000 rpm then dies. The engine doesn't start on the second attempt and after a couple of minutes wait, on third attempt it fires, goes to 1200 rpm and dies. This goes on until I give up or the battery dies. I can't get the engine to run continuously and I'm almost ready to ship the bike to the shop to get it fixed. It's almost like it runs out of fuel or there's no flow into the cylinders. I think there is enough fuel from the tank being delivered. There's a constant head of fuel in the supply line but it doesn't run full from tank to carbs. I've tried adjusting the idle knob for more idle with no results. Do you think I need to open the air mixture valves more? Right now they're set at 1.5 turns.

The battery is new, though I have to recharge it after draining the power out of it. The spark plugs are new though points are now black. I see a spark though it seems faint or weak (I wouldn't consider this as a bright zappy spark). The cylinders are not flooded since the plugs are not wet and there is no gas smell when I pull out the plugs. Should I take the carbs apart again?

I'm looking forward to hearing your advice on what I should do next. Thanks in advance.

 

[Nessism]

Run it until it dies and open the drain plugs on the carb float bowls to see if there is any gas in there. Sounds like the bike is fuel starved. Air mix screws are not going to cause the problem you discribe.

Good luck.

 

[Guest]

See if you can get the bike to run by bypassing the petcock and tank with a funnel with gas. If it runs you need a new petcock.

 

[ggreenfield]

I have exactly this same problem. Freshly rebuilt carbs on a 81 GS750. The bike will start but only if I give it some starting fluid and then only for a few seconds until the starting fluid is gone. The bowls do have gas and floats were set exactly per spec @ 22.4 mm. I can blow gas out of the vents through the vent lines. I have the gas tank completely disconnected and poured gas into the carbs via funnel. What else might be causing this apparent fuel starvation problem?

 

[frosty5011]

I'm hoping you guys can help me get my '81 GS650G out of storage onto the road. Your advice last time on carb cleaning was great! I have taken the bike out of storage after 16 years, taken apart the carbs, cleaned and reinstalled them, and am now trying to start the bike to synchronize and tune air mixture screws but can't get the engine to run continuously.

With choke on, it takes several cranks before firing, revs up to 5000 rpm then dies. The engine doesn't start on the second attempt and after a couple of minutes wait, on third attempt it fires, goes to 1200 rpm and dies. This goes on until I give up or the battery dies. I can't get the engine to run continuously and I'm almost ready to ship the bike to the shop to get it fixed. It's almost like it runs out of fuel or there's no flow into the cylinders. I think there is enough fuel from the tank being delivered. There's a constant head of fuel in the supply line but it doesn't run full from tank to carbs. I've tried adjusting the idle knob for more idle with no results. Do you think I need to open the air mixture valves more? Right now they're set at 1.5 turns.

The battery is new, though I have to recharge it after draining the power out of it. The spark plugs are new though points are now black. I see a spark though it seems faint or weak (I wouldn't consider this as a bright zappy spark). The cylinders are not flooded since the plugs are not wet and there is no gas smell when I pull out the plugs. Should I take the carbs apart again?

I'm looking forward to hearing your advice on what I should do next. Thanks in advance.

It could be it's running too rich right now, after the carb cleaning. Plugs can be carbon-fouled (be black, looks like the porcelain is covered with powdery soot) and not be wet.

Are you sure you set the float levels correctly?

You do have a proper (and clean) air filter installed, right?

I'm assuming that you have the hoses routed correctly and that your petcock is functioning properly.

 

[spyug]

I believe I am experiencing the same thing on my 83 750. Bike had been sitting 7 years and I foolishly put on my remot gas tank and a fresh battery. Cranked a few times and she came to life on choke. Ran til warm and turned off choke she idled back to 1100 or so and would rev effortlessly and drop back to idle on throttle chop. I didn't get to ride,

Following day no start no way. Concensus is I stirred up crap in the carbs. Too right I did. Brown sludge everywhere. Cleaned thoroughly , reassembled and reinstalled today.

Starts up on choke runs to 5K for a few minutes and dies. Starts on full choke any number of times but won't run without choke or start even when warm.

Pulled carbs again tonight but clean as a whistle. Checked every orifice again and reassembled.

I can't figure this one out either guys. I've cleaned many sets of carbs and never run up against this before. Usually witha good cleaning they run well enough even before setting mixture, idle and balance.

Perplexed in Ontario
Cheers,
Spyug.

 

[robertbarr]

Get a shallow container ready and open a bowl drain screw. How much comes out, and how does it look?

Very little fuel? Petcock.

All nasty & phlegm-like? Get busy.

Plenty, & clean? Go to next carb. Repeat, repeat, then suspect ignition.

 

[chance_rider]

Thanks,guys. I think I finally figured out my problem. I did what Chef1366 and Nessism suggested. I checked the float bowl drains after the bike died -there was gas leaking out so bowls were okay. I bypassed the gas tank and used a funnel, blew into the carb crossover vent pipe and also adjusted the air mixture screws from 1.5 to 2.5 turns and guess what the bike started. I think the mixture was lean and adjusting the screws did the trick.

I also figured out something is wrong with the petcock. I blew and sucked on the vent line back to the gas tank and it was unbelieveably hard to get any gas out to the fuel line. I am going to soak clean the petcock first and if this doesn't work, buy a new petcock. So I am good to go now to sychronize and color tune. I hope to get the bike out soon hopefully before the end of summer!!