No gas getting through carbs

[Anonymous]

So I put my 1980 GS850G together last night. Had it down to pistons sticking out of the crankcase the night before. Replaced all the gaskets in the cylinder, head, & cams. Cleaned & rebuilt carbs. I hadn't ever done this before, but needed to because of a massive leak in the head gasket.

Followed the book's instructions, got it timed and all the bolts torqued. Started at 7:30pm, finished at 2am. Crossed my fingers, held my breath, and fired 'er up. Cranked VERY nicely, much better than before, but nothing fired. Did this a few times with the petcock in different positions and the choke on full.

Pulled the plug wire, started, saw a spark. Pulled a plug, smelled, no gas.

So, I'm pretty sure no gas is getting through the carbs. Gas is definitely getting to the carbs, as it drips through with the petcock set to (gravity?). I tried adjusting the (idle adjustment?) knob on the carbs, but didn't notice any difference.

Anything ya'll could suggest?

 

[earlfor]

Re: No gas getting through carbs

With the fuel line removed from the petcock and the petcock set to prime/gravity feed, fuel should flow like a water faucet. It aint no drip.
Did you connect the vacuum line to the petcock correctly. Its not uncommon for newbies to mistakenly connect the petcock vacuum to their float bowl vent fitting.

Earl

So I put my 1980 GS850G together last night. Had it down to pistons sticking out of the crankcase the night before. Replaced all the gaskets in the cylinder, head, & cams. Cleaned & rebuilt carbs. I hadn't ever done this before, but needed to because of a massive leak in the head gasket.

Followed the book's instructions, got it timed and all the bolts torqued. Started at 7:30pm, finished at 2am. Crossed my fingers, held my breath, and fired 'er up. Cranked VERY nicely, much better than before, but nothing fired. Did this a few times with the petcock in different positions and the choke on full.

Pulled the plug wire, started, saw a spark. Pulled a plug, smelled, no gas.

So, I'm pretty sure no gas is getting through the carbs. Gas is definitely getting to the carbs, as it drips through with the petcock set to (gravity?). I tried adjusting the (idle adjustment?) knob on the carbs, but didn't notice any difference.

Anything ya'll could suggest?

 

[Anonymous]

I meant gas was dripping quite rapidly out the bottom of my carbs with the petcock set to prime.

The vacuum line is smaller than the other (?) line, right? The larger hose connects to the "T" fitting between carbs #2 & #3, right? The smaller hose connects to a brass fitting on one of the carbs, right?

Thanks!

 

[retrex]

Gas line hookups

Gas line hookups

Sounds like you got the right hookups. I have a set of carbs on the bench that I was just finishing up on last night with the same setup as you describe. You are doing CV carbs on the 850 right? When you cleaned them did you make sure all the gas circuit paths flowed free. That is did you blow carb cleaner throught the low, high and choke pathways to make sure there were no restrictions? Especially the one in the floatbowl that feeds the choke circuit. The one that the brass post slides into on the floatbowl. Are you trying to start without the filter airbox on, if so put it on with filter in it. This will provide the suction to draw in the gas. It won't work without it.

 

[Anonymous]

my airbox has always been mostly disconnected from the carbs. the rubber boots connecting the two are old, hard, and shrunk. They've always been aligned, but not remotely positievely connected. It ran fine before, though, with this same setup.

I didn't spray carb cleaner through all the pieces. I soaked them all in degreaser, but skipped the carb cleaner spray step. After I confirm the basics tonight, I'll try that.

Are there any settings (like idle adjustment) that would prevent it from starting, or would it just run/idle poorly until it's dialed in?

 

[retrex]

Gas flow problem

Gas flow problem

my airbox has always been mostly disconnected from the carbs. the rubber boots connecting the two are old, hard, and shrunk. They've always been aligned, but not remotely positievely connected. It ran fine before, though, with this same setup.

I didn't spray carb cleaner through all the pieces. I soaked them all in degreaser, but skipped the carb cleaner spray step. After I confirm the basics tonight, I'll try that.

Are there any settings (like idle adjustment) that would prevent it from starting, or would it just run/idle poorly until it's dialed in?

I had the same problem you are describing, gas in the float bowls but none getting to the cylinders. It was because I had the airfilter box out of the bike. I got the bike started by putting my hand over the airbox intake which created a blockage in the opening. What this did was to create a vacuum situation in the carbs which sucked up the gas from the various circuit orifices. The engine started and raced high because the blockage created too much of a vacuum. I could modulate the engine speed by spreading my fingers. Eventually it would run without the hand induced vacuum and run with my hand pulled away from the opening. If you have CV carbs you need to make sure there are no leaks in the airbox system. Before you tear the carbs apart tonight try getting rid of any leaks. Try the hand blocking the opening trick. I can't beleive all your carbs are blocked up. You have to look at a probable choke point and the airbox is looking good for this. What I mean by this is you have to look at what can possible cause all four cylinders to be dry. OK?

Once you get it started we can go over how to adjust the idle and sync the carbs.

 

[Anonymous]

I appreciate your idea and know that properly sealed connections anywhere are ideal, but for the last four months the rubber boots have been sitting in their openings in the airbox w/o being connected AT ALL to the carbs- and the bike has run relatively well with only minor hesitation. I will certainly try this trick at home tonight, though.

I'm also interested in your point that you're suspect that all four carbs aren't working. Are you implying that the engine would sputter if one or more carbs were not working? It isn't even pretending to start. So, I'm now more curious that there's a larger issue beyond dirty carbs.

 

[retrex]

I appreciate your idea and know that properly sealed connections anywhere are ideal, but for the last four months the rubber boots have been sitting in their openings in the airbox w/o being connected AT ALL to the carbs- and the bike has run relatively well with only minor hesitation. I will certainly try this trick at home tonight, though.

I'm also interested in your point that you're suspect that all four carbs aren't working. Are you implying that the engine would sputter if one or more carbs were not working? It isn't even pretending to start. So, I'm now more curious that there's a larger issue beyond dirty carbs.

Vaccum is a very large issue. Fixing leaks is small. In those past four months you had gas in circuit passageways. I am willing to bet at the present time you have none or very little. I assumed that you looked at all your cylinders to verify there was no gas getting to any of them, and if that is the case there has to be a choke point of failure. Which is why I wrote

I can't beleive all your carbs are blocked up.

Meaning the problem is probably not your carbs. This is the same logic that earlfor was applying when he said

Did you connect the vacuum line to the petcock correctly. Its not uncommon for newbies to mistakenly connect the petcock vacuum to their float bowl vent fitting.

He was exploring a choke point of operation. No vacuum to petcock, no gas flow to carbs, dry cylinders.

As for operating of less than four cylinders, yes. That is the reason I am working on my carbs. Only two or three of the cylinders are working at the present time. The bike runs, badly but it runs. The carbs were in bad shape with clogged main and pilot circuit passageways. I will start it up this weekend, with the airbox and filters in :wink:

 

[Anonymous]

Thanks for the clarification. Is there a simple way to look at the cylinders? If I removed the cover, should I see gas in there?

If I understood better how these damn things worked, it'd be a lot easier...

I followed the directions for carb cleaning & assembly (found here) exactly, but I now really think (hope!) it's a vacuum problem.

 

[retrex]

Thanks for the clarification. Is there a simple way to look at the cylinders? If I removed the cover, should I see gas in there?

If I understood better how these damn things worked, it'd be a lot easier...

I followed the directions for carb cleaning & assembly (found here) exactly, but I now really think (hope!) it's a vacuum problem.

Pulling the sparkplugs and looking at the electrode tips after trying and failing to start a bike tells you if there is gas getting to the cylinders. If the tips are dry then gas is not getting to the cylinder.

You need 4 things to start a bike.

1. Air
2. Gas
3. Compression
4. Spark

Err, sometimes 5

5. Luck

Good luck tonight!

 

[Anonymous]

ok, I got the four boots on with the help of two buddies and a heat gun. unfortunately, it didn't change a thing. fuel still doesn't seem to be getting to all the cylinders, though it does seem to be getting to one, but I'm not sure- it seems to have gas on the plug.

it cranks and cranks, occasionally quiet pop, but otherwise nothing.

when set to prime, fuel pours through the carbs.

any other ideas?

 

[Anonymous]

just sprayed starter fluid into the carbs through the airbox... still not the faintest hint of a start.

crap.

I followed the instructions for timing exactly- but, say I did have the chain off by one pin, would that cause this problem, or would it just run bad?

I'm trying to isolate what could cause the utter failure of combustion. most things I think about could cause poor performance, but not the absolute lack of firing. why isn't the gas getting into all the cylinders? I'm going to go pull all the plugs to verify their condition... be right back.

 

[FTGRET]

Run a compression check. You may have the cams out of time and not pulling a vacuam.

 

[Anonymous]

is that what I use that (tool that has a light connected to the spark plug or something) for?

 

[retrex]

One thing at a time

One thing at a time

ok, I got the four boots on with the help of two buddies and a heat gun. unfortunately, it didn't change a thing. fuel still doesn't seem to be getting to all the cylinders, though it does seem to be getting to one, but I'm not sure- it seems to have gas on the plug.

it cranks and cranks, occasionally quiet pop, but otherwise nothing.

when set to prime, fuel pours through the carbs.

any other ideas?

Remeber the list. You have to have each of the items checked off before a bike will start.

Yes timing matters. Does no good to spark if the cylinder isn't charged with air and fuel under pressure at the wrong time. This could very well be the problem, we will worry about the timing issue a little later. We will try and get bike specific information from one of the 850 owners. We are working on the basics for now.

Couple of notes
Never crank more than 10 seconds at a time, 30 or more seconds rest in between tries to avoid over heating wiring.
Make sure you have the right amount of oil in crankcase

To do list:
1. Verify that you have spark on all four plugs. Pull all the plugs, clean and gap. One at a time, with the others not attached to caps, ground (rest) the tip of the attached plug electrode on cylinder head and observe that you have a nice fat spark as you crank engine. Keep away from plug hole when doing this test! Do this for each plug . You may have done this already, I don't know.
2. You really do need to have gas get each of the cylinders. The fact that you have sprayed starting fluid into the airbox with no results bothers me. We'll ge back to this also. After you attached all the airbox boots to the carbs, did you put the filter back in the airfilter box before cranking? If yes, try removing filter and blocking hole where filter butts up against the airbox with your hand while cranking. This should create a good vacuum and suction gas into the carb passageways and into the cylinders.
3. Compression test is next if after doing the above two items and you're still no go. You need to borrow or buy a compression tester from somebody. We won't get into this until I hear back from you on the two previous items.

Even if you have screwed up the timming the above items are not all dependant on that problem. Don't start to disassemble before you diagnos and test the basics first.

 

[Anonymous]

Retrex, thanks for your to-do list. I really am hoping to be able to isolate what the problem is before I just go hog-wild and tear the whole thing down again.

I did pull all four plugs. I had installed them new maybe 400miles ago. They still looked good- had a little black carbon and the gap was still the same. They all got a solid spark.

I'm not exactly sure what test you wanted me to do with the airbox. After connecting the airbox boots to the carbs, I left the side-panel off (but had the air-filter in) and sprayed starter fluid into the top of the airbox- pretty much right into the carb boots. Do you want me to pull the air filter and cover the hole inside the airbox with my hand, or the hole on the bottom of the airbox (on the outside, with the side cover back on)?

Thanks again!

 

[retrex]

Retrex, thanks for your to-do list.
Do you want me to pull the air filter and cover the hole inside the airbox with my hand, or the hole on the bottom of the airbox (on the outside, with the side cover back on)?

Thanks again!

Pull the airfilter and cover the hole inside the airbox with your hand. If you have linked up the cams correctly to the crankshaft then as the pistions are on the downward stroke with the exhuast valves shut, intakes open, the resulting vacuum will suction the gas from the floatbowls through the various passageways into the cylinders. What we are trying to do is make sure all the passage ways are primed with gas. Sometimes normal operating vacuum pressure is not enough to get the gas through dry passageways. If this works your engine should start and rev fairly high until you pull your hand back a bit from the opening. If this doesn't work, meaning your sparkplugs are still dry then we have to check the compression. You may have hooked up the crank and the cams so that on the above mentioned downward stroke the exhaust valve is not shut down as it should be, or possibly the intake valves aren't open as they should be. Your comment on it cranking much better than before the redo may indicate this. Anyway what this results in is little or no vacuum on airbox side, or not enough draw or pull on the dry passageway to suction up the gas. It could also be pushing air back out on the upward stroke through either/and/or exhaust and input valves. Hence no compression. Try the hand thing. It don't cost nuttin.

I won't be online today after 4:00PM EST until Monday morning. Hope things work out before then. Don't get discouraged. These bike want to work, we just have to let them.

 

[KEITH KRAUSE]

The vacuum line is smaller than the other (?) line, right? The larger hose connects to the "T" fitting between carbs #2 & #3, right? The smaller hose connects to a brass fitting on one of the carbs, right?

The smaller hose, the vacuum, goes to the brass nipple at carb #2 (as you sit on the bike.) Make sure the vacuum goes there or you'll have no fuel flow except on prime. The other two nipples are for the float bowl vent lines. Make sure they stay clear and route them so they don't kink.
Even if you do have the vacuum hooked up wrong, the bike should have gas in the cylinders from priming it.
Did you at least do a good bench synch? If the throttle plates are too closed from a poor synch, it'll never start. Also, did you re-set your mixture screws to their previous setting?
One more thing, if fuel is overflowing out the carb overflow lines, you have float valve needles that aren't sealing. The high fuel level in the bowls would hinder starting too.

 

[retrex]

Status update

Status update

So where are we with this j2x?