1979 gs1000

[Meweeble]

Hi All,

I have appreciated all of the info I have gleaned off the site. This is my first GS and I have followed a number of the guides and have a kinda descent running bike now. But, I have a problem and I am stuck!!! This is what I have done so far...

VM carb rebuild
Dynajet Stage 3 kit
New intake o rings
New Dyna coils
Dyna s ignition
New spark plugs
New plug wires
Pet cock kit
New Battery
(Brake kits and misc chassis stuff)

The bike started and fired up right away 10 seconds (no carb adjustments just bench settings) but was running a bit rough. after checking a number of settings... timing is perfect (followed info on site) spark seems to be equal across all plug wires, but when you pull off either number 2 or 3 plug wires engine hardly changes (does not drop RPMs) If you pull 1 and 4 motor RPM drops significantly and almost dies. Exhaust temp of 2 and 3 is also alot cooler than 1 an 4. Plugs are clean on 1 and 4, sooty on 2 and 3. Lots of compression and spark. No sputtering or backfiring, actually seems to run fairly smooth except 2 and 3 aren't working well. No odd sounds from motor (valves, knockes or such)

- OK coils maybe? but these are brand new sooo..... this is what we did.
Adjusted pickup clearance to .025 which helped maybe.
- Checked voltage at coils = 10.5 v so jumped from battery to see if 12v made any difference (nope).
- Switched dyna pickups at crank (no difference)
- Switched coils (no difference)
- Checked all connections and cleaned them.
- Pulled off carb pods looks like equal amounts of fuel ( a little fuel seems to be blowing back equally from all the carbs. a little wet on the air cleaner side) Is this normal?

I've tested and swapped everything I think I possibly can in the electrical system, but 2 and 3 aren't firing well. I don't know what else is consistent to both cylinders?All I have left that I can think of is mechanical?

Any ideas?

Thanks,

Kevin

 

[Guest]

Check valve clearance tight valves will cause week cylinder
Could just be dirty valves and seats if they check to be lose

 

[Nessism]

Did you test spark by holding a spark plug against the engine and cranking it over? You should get a nice spark with each plug. If you have spark, then the obvious question is the carbs.

 

[Meweeble]

Yup... checked spark looks pretty blue and strong jumps out the boot. Consistent on all four plugs. Im not sure about how to check the carbs. All 4 carbs are set the same right now and with the pods off, there is an equal amount of fuel around the air cleaner side on all 4 of them a little damp. (not sure if this is normal?) a little blow back through carbs after blipping the throttle when RPMs dropping. 1 and 4 plugs are clean (maybe a little lean even) 2 and 3 are sooty. Pull the wires on 2 or 3 and motor RPM doesn't really change, 1 or 4 wires get pulled motor almost dies (no power coming out of 2 and 3)

 

[Nessism]

You might want to check fuel height (you need to make a gauge) and vacuum sync the carbs. If they are really far off it will effect your idle pretty noticeably.

 

[Meweeble]

You might want to check fuel height (you need to make a gauge) and vacuum sync the carbs. If they are really far off it will effect your idle pretty noticeably.

I set the slides all the same on the bench so at least they are really close, the idle is really smooth at 1100 rpm, floats were set on bench with depth gauge. but, sooty plugs on 2 and 3 clean on 1 and 4. 2 and 3 are not putting out any power. Runs like a 500cc under load.

 

[Nessism]

It's either spark or carbs. You say both are good...but something isn't. Maybe you should take a pause and adjust those valves and then have another go verifying everything is as it should be. Maybe wire the Dyna S direct to the coils, bypassing the main harness? Perform the coil relay mod. Even is these are not the problems they are good to do regardless.

Hope you figure it out soon.

 

[BassCliff]

Greetings and Salutations!!

Greetings and Salutations!!

Hi Mr. Meweeble,

Check the electrical section of my website for troubleshooting suggestions. Have a look at the VM carb cleaning tutorial too. You've got a 30 year old motorcycle that needs 20 years worth of maintenance. You must address every item on the maintenance lists in your "mega-welcome". Skipping steps or taking shortcuts will leave you stranded on the side of the road at best, injured or severely killed at worst. Do it all correctly the first time so you and your bike will be insanely happy.

Let me dump a TON of information on you and share some GS lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. This is what NOT to do: Top 10 Newbie Mistakes. Now let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed. I will put you on my prayer list.

Thank you for your indulgence,

BassCliff

 

[resjudicata]

From your description it sounds like the carbs are not providing an even amount of the same mixture to each cylinder.

I didn't see you mention adjusting the air and mixture screws on the carbs or vacuum syncing the carbs. Bench syncing is not intended to provide a properly running bike. Only to get the bike started so you can do a proper vacuum sync.

For proper carburation (sp?) you need to adjust valves, vacuum sync carbs and then adjust the air and mixture screws on the VM carbs. No shortcuts.

I believe where Bass just pointed has the info on adjustment.

Chris

 

[Meweeble]

Thanks

Thanks

Thanks Guys...

I'm usually pretty good with this kind of thing, but this is my first GS.... or Suzuki..... or Japanese bike, so I'll definitely got through the list. I'm fairly confident I've ruled out electrical now and I'll follow the recommendations for the valves and carbs next. I'll post my progress.

Kevin

 

[SqDancerLynn1]

Did you ever do a compression test ? If compression is good I would suspect carbs
BUT since it is for carb 2&3 that are fired by the same coil it could be electrical.. First fix your problem with having 12V at the coil

 

[Guest]

Check the bowls for fuel.
If ya got fire and compression the only other thing you need is fuel.

 

[hampshirehog]

3 other suggestions. Choke plungers worn / not seating on 2 and 3. Blocked pilot circuits on 2 and 3. Synch too far out and slides on 2 and 3 are shut on tickover.

 

[Guest]

How far out are your fuel adjustment screws?

 

[Meweeble]

3 other suggestions. Choke plungers worn / not seating on 2 and 3. Blocked pilot circuits on 2 and 3. Synch too far out and slides on 2 and 3 are shut on tickover.

I'm close to pulling the carbs off and checking them. I was really meticulous with the rebuilds and thought I did a good job. New kit and all o rings, but I didn't change the choke plungers. Initial Carb settings were set as the stage 3 kit recommended. I haven't synched them yet, but they were set identical on the bench. they will need setting but it shouldn't account for this much difference. What is consistent with both the 2 and 3 carb is that I can try to adjust the pilot air screw or the fuel screw and nothing changes whatsoever. Where as 1 and 4 are working properly. I thought it was unusual that 2 and 3 would both be identical and pooched. One question though... I have the pods off now and I seem to be getting some fuel vapor (an equal amount on each carb) on the air cleaner side of the carb... looks like a little blow back through all 4 carbs at idle. Is this normal?... I blip the throttle and get a fine mist blowing back out when RPMs drop. I've ruled out electrical as I've got 12v at the coils, switched coils too, and also switched pickups at the dyna s just to check them.

 

[Meweeble]

How far out are your fuel adjustment screws?

Whatever the stage 3 kit suggested as the initial 2 or 2.5 i believe... I'm at work so can't check. I tried to adjust them on 2 and 3, even all the way out and in, but didn't make a difference.

 

[Guest]

Try one turn out on the fuel screws. Adjust the air for highest rpm. You will most likely find one that shows a good change in RPM. When it is at it's highest try the next that shows the most change. Don't expect more than a needle width of change on the others, but it makes a huge difference. Then go back and tweak the fuel screws toward lean, no more than 3/4 turn in from seated for any. That gives you a 1/4 turn to play with between 3/4 and one turn. Repeat the air adjust. You might have to go back and fourth several times. When you get good power on the low end you will be dialing in to where it likes to run. I thought mine wouldn't adjust on three of my carbs until I noticed I was turning the screws as much as the one that showed a good change to get those small changes. Pipes, pods and stage 3 jetting is not easy to tune. You will find that permanent sync tubes with 1-4 and 2-3 connected together with vacuum hose will help the low end power and low mid range.

 

[resjudicata]

Whatever the stage 3 kit suggested as the initial 2 or 2.5 i believe... I'm at work so can't check. I tried to adjust them on 2 and 3, even all the way out and in, but didn't make a difference.

If adjusting the fuel screw does nothing on those carbs then something is wrong with those carbs. It could be lack of vacuum (since you haven't synch'd yet those carbs could be completely closed and the other two open slightly), or clogged pilot fuel jets, or the tip of the fuel screw is broken off blocking the idle passage, or your fuel level in the bowls on those two carbs is too low and not feeding the pilot fuel jet properly.

Check all those. And do the valves.

Chris

 

[Meweeble]

Try one turn out on the fuel screws. Adjust the air for highest rpm. You will most likely find one that shows a good change in RPM. When it is at it's highest try the next that shows the most change. Don't expect more than a needle width of change on the others, but it makes a huge difference. Then go back and tweak the fuel screws toward lean, no more than 3/4 turn in from seated for any. That gives you a 1/4 turn to play with between 3/4 and one turn. Repeat the air adjust. You might have to go back and fourth several times. When you get good power on the low end you will be dialing in to where it likes to run. I thought mine wouldn't adjust on three of my carbs until I noticed I was turning the screws as much as the one that showed a good change to get those small changes. Pipes, pods and stage 3 jetting is not easy to tune. You will find that permanent sync tubes with 1-4 and 2-3 connected together with vacuum hose will help the low end power and low mid range.

Thanks I'll try this. I think I'm getting closer. I seem to have a couple of issues that in combination are creating a bigger problem. I'm not getting full 12 volts to the coils or the pickups (9 - 10v), so I'll do the relay mod this weekend then do what you suggested. I have almost 180psi compression across all cylinders, looks like enough spark on all cylinders and fuel in the bowls... so we'll see this weekend.

Thanks,

Kevin

 

[Guest]

Relay mod is nice, but it is just a work around for good clean connections. check all of your connectors. The ones under the seat coming from the stator like to discolor and burn. Discoloration is caused by heat. If you see any black, it's been hot enough to burn the connector sleeves. If you go through all the connectors replacing the bad ones, cleaning the others and coating the connection with dielectric grease before putting them back together you will have sufficient voltage for the coils.