Barn find 1981 GS 1000 GL not starting

[pbarber]

Hello, thanks for letting me join. I've been looking at posts, GREAT INFO. On to my question. I'm trying to restore a 1981 Suzuki GS1000 GL and I can't get it started. Here's what I've done so far. Gas tank was drained of old gas, cleaned and fresh new gas added, about 3/4 gallon. 

1. Tested for spark and yes I see spark on #1 and #4 cylinders.

2. I pulled the carbs, removed float bowl covers, removed main jets, cleaned and put back in.

3. I pulled the pilot jet rubber plugs, did not remove the pilot jet, but added some Marvel's Mystery Oil, let sit, they sprayed compressed air down the hole and could verify that air was coming out of the carb hole. Same for main jet. Both seem to be functioning. 

4. I rebuild the petcock, verified it has gas flowing from prime position, and from "Reserve". I did this by connecting a spray bottle tube over the vacuum opening, while in petcock set in reserve position. Gas flows.

5. I tested to see if the engine is "sucking air" (for petcock), by disconnecting vacuum hose from petcock, engaging the starter, and holding my finger over the opening. It "sucks air".

6. I primed the carbs, then unscrewed the carb bowl drain plug to see if there was any gas in the bowl. Yes there is. 

7. I did not remove the top carb cover, but tested the slides. They seem to be moving freely and do make the "whoosh" sound. 

8. I put in a new battery and it's fully charged. 

9. Floats move freely and are in spec height-wise, no carb leakage anywhere. 

Question: Is the problem with my pilot jet? Do I need to remove it for each of the 4 carbs and thoroughly clean? Also, is it necessary to remove the top carb cover and clean the slides and remove the needle jet, and clean as well?

I'll assume yes to all of the above. If I've done all this, is there anything else that would keep the engine from starting? Have I missed anything?

[Captain Chaos]

30 minutes ago, pbarber said:

1. Tested for spark and yes I see spark on #1 and #4 cylinders.

how about 2 and 3?

[pbarber]

4 minutes ago, Captain Chaos said:

how about 2 and 3?

Is it necessary? Does the ignition coil on the left spark #1 and #2, and the right #3 and #4? Or do I have it wrong? Also, wouldn't the "sparked" cylinders still at least try to fire? Not trying to be a "smart-alek", just really asking because I don't know. 

[Jaydee]

1 minute ago, pbarber said:

Is it necessary? Does the ignition coil on the left spark #1 and #2, and the right #3 and #4? Or

Nope, one coil for cylinders 1 and 4, other coil for 2 and 3.

[pbarber]

Just now, Jaydee said:

Nope, one coil for cylinders 1 and 4, other coil for 2 and 3.

Ah Ha!! Thank you, I will test that. If the 2 and 3 coils was bad, this could be the reason for "no starty"? I also should mention that I did not examine the pilot air jet.

[pbarber]

OK, I just confirmed that I do have spark in #2 and #3. So I'm pretty confident it's not the coils. It has to be the pilot jets right?

[gs7_11]

Possibly blocked choke supply drilling in the float bowls.

[jameskat]

The usual is -

- check for spark

- check compression

- check fuel 

Try easy start to see if it fires and confirms the ignition system is good.

[pbarber]

3 hours ago, gs7_11 said:

Possibly blocked choke supply drilling in the float bowls.

Sorry, I'm not sure what you mean by this. 

[pbarber]

1 hour ago, jameskat said:

The usual is -

- check for spark

- check compression

- check fuel 

Try easy start to see if it fires and confirms the ignition system is good.

Thank you for responding.

- I do have spark in all 4 plugs.

- I don't have a way to check for compression other than the "thumb over the plug hole" method, but I'll check

- Fuel gets to the bowels but not to the cylinders. I should be smelling gas in the spark plug holes after an attempt to start, right? There isn't any. 

The only thing I can think of is that the main and pilot jets are still not 100%. 

I just learned (from another source), that the pilot jet rubber plugs must be there. The pilot jet actually grabs fuel (at start up) from the main jet, via another "hidden" channel. So, I'm thinking (I know dangerous), that the pilots need to be removed and some carb cleaner sprayed down the holes. 

 

[gs7_11]

18 minutes ago, pbarber said:

Sorry, I'm not sure what you mean by this. 

There's a passage/jet in each floatbowl that passes fuel to the enrichment circuit. If you examine the float bowls closely, you'll see it. Check it's clear by squirming WD40 or something through it.

If it's blocked, you'll have trouble starting the engine.

I'd also remove the pilot jets and check they're properly clean.

Also there's an airway from the inlet side of the carb that supplies the pilot circuit which needs to be checked.

[andyroach]

One way to check if you are getting a firing spark is to remove all plugs.

add a small amount of petrol directly into the cylinder and replace the plug as soon as you've put the fuel in to each cyinder.

make sure the float bowls are full .

crank the bike over, whilst opening and closing the throttle.

It may take a while (10-15 seconds) for the liquid fuel to be pumped out of the cylinder, but the residual fuel should start the bike.

I usually use this method to check if the problem is fuel i.e the bike starts, then dies once the fuel in the cylinder is used up.

or it doesn't fire at all and the problem is more than likely electrical.

Hope this helps

[andyroach]

forgot to say that whilst it is a pain, pulling the carbs, stripping them, cleaning and blasting through with  canned carb cleaner and a compressor then re-assembling and fitting them. It really is the ony way to sort a fueling problem if the bike has been sat a long time and has cacked up the carbs

[pbarber]

11 hours ago, andyroach said:

forgot to say that whilst it is a pain, pulling the carbs, stripping them, cleaning and blasting through with  canned carb cleaner and a compressor then re-assembling and fitting them. It really is the ony way to sort a fueling problem if the bike has been sat a long time and has cacked up the carbs

The main and pilot jets are all clear as a bell. Gas is getting to the bowls. The vacuum tube is "sucking" on the petcock diaphragm. All 4 plugs have spark. 

If the cylinders ARE getting gas during startup, and it still does not start, I should be able to pull a spark plug and smell gas from the hole, correct? Then this would seem to point to a problem with either the coils or the spark plugs. I did verify, they are all 4 getting spark. So I don't think it's that.

If the cylinders are not getting gas, pulling the spark plug, I should not smell gas, correct? The main jets and the pilot jets are all clear though. 

NEW SYMPTOM - when trying to start, I held the throttle down all the way and the cranking speed increased. When I let off the throttle, it slowed a bit but still cranked. What would this mean?

I have my battery on a trickle charger and I'll try again in the morning. This is just too baffling.

On 11/6/2024 at 2:43 PM, gs7_11 said:

There's a passage/jet in each floatbowl that passes fuel to the enrichment circuit. If you examine the float bowls closely, you'll see it. Check it's clear by squirming WD40 or something through it.

If it's blocked, you'll have trouble starting the engine.

I'd also remove the pilot jets and check they're properly clean.

Also there's an airway from the inlet side of the carb that supplies the pilot circuit which needs to be checked.

Gotcha!! Thank you!! Will do. 

[gs7_11]

Cranking speed changing with throttle position is normal.

You've got enough information in the replies you've already been given.

1. Try starting the engine on Easy Start, WD40, carb or brake cleaner, or even fuel in the cylinders. If it runs, even a little like this it eliminates the ignition system.

2. You've said compression is good, so we'll assume it's OK, and that cam timing hasn't been disturbed.

3. If it's still fuel, and assuming you're using fresh petrol, the problem must be carbs. Having clean jets isn't enough, you need to check each and every drilling and passageway in the carb bodies, and floatbowls. The pilot system needs air to function, as well as a clean jet.

[pbarber]

8 hours ago, gs7_11 said:

Cranking speed changing with throttle position is normal.

You've got enough information in the replies you've already been given.

1. Try starting the engine on Easy Start, WD40, carb or brake cleaner, or even fuel in the cylinders. If it runs, even a little like this it eliminates the ignition system.

2. You've said compression is good, so we'll assume it's OK, and that cam timing hasn't been disturbed.

3. If it's still fuel, and assuming you're using fresh petrol, the problem must be carbs. Having clean jets isn't enough, you need to check each and every drilling and passageway in the carb bodies, and floatbowls. The pilot system needs air to function, as well as a clean jet.

Thank you for the update. I have not tried #1, but will. On #2, I was told from the owner's daughter that her father rode the bike into the barn and left it as is, back in 2004. So, it was running. On #3, yes, fresh petrol. I have not removed the floats, but have measure the height and they are within spec. Also, the float jet "pin" does rebound, opens and closes. And the carb bowls do hold gas and will not leak after the petcock has been left in "prime" for several seconds. 

One step at a time, I'll test the #1 and report back to the board. 

Thank you all again for all the help. 

[pbarber]

1 hour ago, pbarber said:

Thank you for the update. I have not tried #1, but will. On #2, I was told from the owner's daughter that her father rode the bike into the barn and left it as is, back in 2004. So, it was running. On #3, yes, fresh petrol. I have not removed the floats, but have measure the height and they are within spec. Also, the float jet "pin" does rebound, opens and closes. And the carb bowls do hold gas and will not leak after the petcock has been left in "prime" for several seconds. 

One step at a time, I'll test the #1 and report back to the board. 

Thank you all again for all the help. 

Ok, so I used some carb cleaner down the intake of the carbs and YES, it started and ran for a couple secs. Revved at high range and it ran like a "top".  It also pushed out some "insulation" (mouse nest) from the exhaust. I took a shop vac to the exhaust to get whatever was left. So, 2 problems solved. 

So now the problem, most likely, is the carbs not getting gas to the cylinders, correct? Would you suggest a complete carb rebuilt kit? I have one lined up. All I have to do is hit "Buy now". 

Edited November 8 by pbarber
update

[gs7_11]

No.

You may or may not need to replace a gasket or an o-ring, but wait and see. Rebuild kits can have issues with the quality of the parts, so don't go giving yourself another headache unnecessarily.

Strip and re clean the carbs fully. Check EVERY orifice and drilling is clear by putting compressed air or WD40 through them. For instance, Make sure the pilot air jet is clear from the carb inlet through to the pilot jet, then the passageway into the carb venturi area is clear.

Remove the pilot screws (after noting their setting in turns out from fully home) and check the drillings from the pilot jet via the pilot screw are also clear. (Don't overtighten the pilot screws, only gently seat them when screwing them in).

Check the choke supply as previously mentioned.

You must meticulously check each carb is properly clean. There are other issues like split diaphragms etc, but this won't generally stop the bike from running, it'll just run badly.

[pbarber]

2 hours ago, gs7_11 said:

No.

You may or may not need to replace a gasket or an o-ring, but wait and see. Rebuild kits can have issues with the quality of the parts, so don't go giving yourself another headache unnecessarily.

Strip and re clean the carbs fully. Check EVERY orifice and drilling is clear by putting compressed air or WD40 through them. For instance, Make sure the pilot air jet is clear from the carb inlet through to the pilot jet, then the passageway into the carb venturi area is clear.

Remove the pilot screws (after noting their setting in turns out from fully home) and check the drillings from the pilot jet via the pilot screw are also clear. (Don't overtighten the pilot screws, only gently seat them when screwing them in).

Check the choke supply as previously mentioned.

You must meticulously check each carb is properly clean. There are other issues like split diaphragms etc, but this won't generally stop the bike from running, it'll just run badly.

OK, will do. Thanks. 

[pbarber]

Update: First thank you everyone for your input. I pulled the carbs again and cleaned every jet, hole, passage, etc. - pilot jet, main jet, needle jet, pilot air jet. I cleaned the passage way from choke hole, shot with carb cleaner and compressed air. Everything (every hole) I can think of is clear. Still no start. It runs really good with just carb cleaner sprayed directly into the cylinders. 

I also replaced the fuel line and vacuum line with "see through" tubing. When I turned on the "prime" at the petcock, I could see gas flow for a few inches but then it would stop, as if it was hitting and obstacle (air pressure?). And all I could see in the line was gas on one side (petcock side) and air on the other side. Shouldn't it keep flowing until each float bowl is full and the floats "float" to the top, shutting off the gas flow. Isn't there a vent in each float bowl to let out air? Could this be my problem?

[Gixer1460]

assume all the float valves are working and are set to open? Yes bowls are vented - usually biggish hose between bodies above bowls. have the bowls a drain screw - loosen till fuel flows out.

[pbarber]

4 hours ago, Gixer1460 said:

assume all the float valves are working and are set to open? Yes bowls are vented - usually biggish hose between bodies above bowls. have the bowls a drain screw - loosen till fuel flows out.

When turning the petcock to "prime", how long should I wait before turning the setting back to "reserve", and then trying to start? 

Then, assuming all jets and air passages are clear, and the bowls, are filled, it should start, correct?

[Blubber]

Maybe a dumb question, but does it run on an auxilary fuel tank?

 

This to rule out the fuel tap / petcock

[pbarber]

40 minutes ago, Blubber said:

Maybe a dumb question, but does it run on an auxilary fuel tank?

 

This to rule out the fuel tap / petcock

Update: It started!!!!! Yippee. Without taking the carbs off (again), I looked for openings, holes, etc. on the carbs. I found one on the left side which had some dirt clogged in it. Same on the right side (see photo below). So I cleaned it all out, shot some carb cleaner followed with some air. I then tried the "prime" setting on the petcock and could see fuel now flowing to the carb bowls (YES!!). When it stopped, I set the petcock to "RES" and tried another start. And it started, with choke full on. It was a little rough at first, but it gradually increased in RPMs. 

So I let it run for a while with the choke on, until the RPM's started rising. Then gradually eased off on the choke, until about 1100 RPMs and it seemed to idle fine. This is the normal setting correct? I still had some choke left, so I'm thinking my choke cable needs adjusting. I'll check. If the bike fell below 900 RPMs, it would stall. I've had other carbed bikes which did the same thing. 

I've read some other posts and have viewed some videos which seem to point to the pilot jets not fully functional, if it does not idle correctly. I've cleaned them already, so I'm thinking the next steps should be to spray carb cleaner in the carbs and air jets and start again, choke all the way out. Gradually ease off on the choke while continuing to add carb cleaner. 

If you were me, what would others do?

PS, I should also add that this time when starting the air box was off. Should I try putting the air box back on and start again? Will it make much difference?

Edited Wednesday at 06:48 PM by pbarber
add photo

[Gixer1460]

wind the idle screw in a bit - bikes aren't cars and don't idle lower than 1000 odd minimum! Usually 11 - 1200 is about right