Help! Carburetor/fuel mixture problem (I think) 1979 GS1000

[rmantell2012]

Hello all,

This is my first post here and I hope to gain some knowledge from you folks that probably know quite a bit more than I do.

I purchased a 1979 GS1000 about 10 months ago for $800 (not running). I have slowly been installing parts, fixing what needs to be fixed and adjusting what needs to be adjusted. I have had no previous knowledge of motorcycles and this is kind of my first project. I recently got the bike running for the first time, and took it on a proper ride a month or so ago. Ever since then, the bike has not been running properly. I suspect it is a carb issue.

The first thing I did to the bike was clean the carbs I cleaned them out real nicely, replaced all gaskets and o rings, and replaced the jets that came with the kit (main and pilot). Keep in mind that when I bought the bike, there were only headers and NO air box/pods. Since then I have put on a 4-1 system and pods. I suspect that the original jets in the carbs were factory spec, and I replaced them as so.

Here are the symptoms of what is going on:
- hissing like sound when throttle applied
- bike dies when throttle applied
- dies when choke is engaged
- idles fine with warm, but has trouble starting
- when I try to ride the bike, it "lugs" and has a ton of trouble getting going (never really does "get going")

Here is what I have done to attempt to solve this problem:
- installed new contact points and set timing
- play around with different fuel to air ratios
- clean out main and pilot jets (again)

I am going to check the valves in a couple days once the valve cover gasket arrives, but until then this is all of the information I have. I suspect I may need to resize my jets, but I am not sure which jets or which sizes. I am not even sure of the correct turns out for the fuel and air screws to set due to the pods and exhaust system.

I am really stuck with this problem and I don't feel like taking it into a shop to waste a ton of $$$. After all, this was a project bike, but now I just want to ride it.

I appreciate any input you folks have for me,

Thanks a bunch.

[uk gs nut]

First off pods can be a pain. Check the pods don't obstruct the small passages in carb throats. Bottom fuel mix screws should be at one turn from gently turned all way in, thereabouts. Side air screws around one and half to two out. Your pilot jets standard are 15, try 17.5. Mains std are 95, try 110. Also try lifting the needle. You could also give air corrector jets a go. Vacuum sync should be done and a colortune helps. Of course the valves need checked and ignition strobe checked.

[zed1015]

First off pods can be a pain. Check the pods don't obstruct the small passages in carb throats. Bottom fuel mix screws should be at one turn from gently turned all way in, thereabouts. Side air screws around one and half to two out. Your pilot jets standard are 15, try 17.5. Mains std are 95, try 110. Also try lifting the needle. You could also give air corrector jets a go. Vacuum sync should be done and a colortune helps. Of course the valves need checked and ignition strobe checked.

For the pods just fit air correctors, leave ALL other setting, pilot jet,needle position stock and fit 105 mains.. That's it..

[rmantell2012]

For the pods just fit air correctors, leave ALL other setting, pilot jet,needle position stock and fit 105 mains.. That's it..

Awesome, I really appreciate the information. I never thought of fitting air correctors. I'll go ahead and fit some 105 mains as well and see if this could help.

Thanks a bunch.

[rmantell2012]

First off pods can be a pain. Check the pods don't obstruct the small passages in carb throats. Bottom fuel mix screws should be at one turn from gently turned all way in, thereabouts. Side air screws around one and half to two out. Your pilot jets standard are 15, try 17.5. Mains std are 95, try 110. Also try lifting the needle. You could also give air corrector jets a go. Vacuum sync should be done and a colortune helps. Of course the valves need checked and ignition strobe checked.

Great. I have my fuel screw at 1 out and air screw at 1.5 out. I'll go ahead and try 2, but I think it is already running a bit lean. Not too sure though.

Thank you for the info!

[rmantell2012]

First off pods can be a pain. Check the pods don't obstruct the small passages in carb throats. Bottom fuel mix screws should be at one turn from gently turned all way in, thereabouts. Side air screws around one and half to two out. Your pilot jets standard are 15, try 17.5. Mains std are 95, try 110. Also try lifting the needle. You could also give air corrector jets a go. Vacuum sync should be done and a colortune helps. Of course the valves need checked and ignition strobe checked.

So I just installed both the air corrector jets, and the new mains (105's were unavailable so I had to go with 107.5). Unfortunately, nothing has changed. The bike is still having the same issues. I played with the air and fuel screw settings, and again, nothing changed.

I am fairly certain the bike is running very rich. I pulled the plugs and all 4 of them were covered in soot, as well as the inside of my exhaust. I did forget to mention that I don't have a muffler on the 4-1 (not sure if this plays an important role). Even after attempting to make the mixture leaner, the bike still has the same symptoms.

I am not too sure what is going on and this has become quite the headache to me. I am seriously considering taking the bike to a shop and have some guys that know what they're doing help me out, but with that comes a lot of $$.

I recorded a video of the bike running very roughly: https://youtu.be/cq0rIcenwac

Thanks to you guys for helping me out again, I sincerely appreciate it.

[alke46]

You should do NOTHING until you have checked the valve clearance. You say you cleaned the carbs but did you do it properly?
Did you dip them for 24 hours in Berrymans carb dip?

You need to look up forum member Nessism and read his newbies mistakes before you go much further.

A lot needs to be done to a non running bike before trying to make it run.

[zed1015]

What pods are those?
If they are cheap chinese, Emgo, Hi, Level, etc etc they are garbage and will cause restriction and over rich running.
Either remove them altogether while you get the bike running or get some quality free flowing pod such as K&N, S&B, APE or RamAir fitted now.
Also from your video the engine isn't even managing to run and idle on all cylinders.
The likely suspects are fuel supply/float heights, blocked pilot jet or jets, very tight valve clearances or ignition issues/fouled plugs.
You also mention replacing the jets from a "KIT".
If this "KIT" wasn't genuine Mikuni or Keyster you should remove them and re-fit the originals ( leave the 107.5 main as it isn't affecting the starting)..
Unless damaged there is no reason to replace ANY brass internals except the mains for correcting the upper rpms fueling.
Your current main jetting is fine but you should re-fit the original STOCK SIZE pilots, make sure the jet needle is in the middle (3rd) groove and leave the mixture screw settings alone at 1 on the fuel and 1-1/2 on the air..
Changing any of those will NOT affect starting..
Please note that with air correctors fitted NON of the carbs settings, pilot jets or needle position need changing from stock EXCEPT for the larger mains despite what others may say..
You should also check that any of the fuel mix screw tips are not broken off and blocking the fuel outlets in the floor of the venturi.

[rmantell2012]

You should do NOTHING until you have checked the valve clearance. You say you cleaned the carbs but did you do it properly?
Did you dip them for 24 hours in Berrymans carb dip?

You need to look up forum member Nessism and read his newbies mistakes before you go much further.

A lot needs to be done to a non running bike before trying to make it run.

Thanks for the insight. I decided yesterday I’m not going to mess around with anything until I confirm the valves are to spec. I’ll be checking them the next free day I have.

As far as the carb cleaning, I used a K&L kit. I mainly just needed new o-rings and gaskets since the jets looked great. I cleaned and soaked all parts. I don’t believe I did anything incorrectly.

Thanks for the recommendation to that form. I looked that over a couple months ago and it has a lot of great info. A good read for sure.

Thanks again for taking the time to respond.

[rmantell2012]

What pods are those?
If they are cheap chinese, Emgo, Hi, Level, etc etc they are garbage and will cause restriction and over rich running.
Either remove them altogether while you get the bike running or get some quality free flowing pod such as K&N, S&B, APE or RamAir fitted now.
Also from your video the engine isn't even managing to run and idle on all cylinders.
The likely suspects are fuel supply/float heights, blocked pilot jet or jets, very tight valve clearances or ignition issues/fouled plugs.
You also mention replacing the jets from a "KIT".
If this "KIT" wasn't genuine Mikuni or Keyster you should remove them and re-fit the originals ( leave the 107.5 main as it isn't affecting the starting)..
Unless damaged there is no reason to replace ANY brass internals except the mains for correcting the upper rpms fueling.
Your current main jetting is fine but you should re-fit the original STOCK SIZE pilots, make sure the jet needle is in the middle (3rd) groove and leave the mixture screw settings alone at 1 on the fuel and 1-1/2 on the air..
Changing any of those will NOT affect starting..
Please note that with air correctors fitted NON of the carbs settings, pilot jets or needle position need changing from stock EXCEPT for the larger mains despite what others may say..
You should also check that any of the fuel mix screw tips are not broken off and blocking the fuel outlets in the floor of the venturi.

I bought the pods right after I got the bike. They were $25 on eBay so I suspect they’re definetly not high quality. I’ll grab some K&N pods soon, thank you for bringing that to my attention.

Hopefully when I check the valves, they’ll be out of spec. That way I know somethings up. As far as the carbs go, all the jets EXCEPT for the mains are stock. Mains are 107.5 like I said before.

I appreciate all your knowledge and for helping me through this learning process! It’s great to have some specific insight.

[rmantell2012]

So I’m feeling kind of defeated. I checked all the valves and 6 of the shims were out of spec. I installed the proper sizes and also adjusted the float height which which was also out of spec. I put some new spark plugs in as well. I put the carbs back on the bike and finished the valve job, but still, the same issues. This time it took even longer for the bike to start up and when it did start, it died right away.

I feel like I have tested all of my options and am beginning to feel quite hopeless.

If anyone has any idea of where this problem could be coming from, it would be awesome to get your thoughts.

Thank you all.

[Suzukian]

Are those CV (Constant Velocity) carbs, in other words, do they have a diaphragm? If so, you will have to make an air box to build up vacuum to get the diaphragms to function, otherwise,it will never work. I just went through this with someone on a Kawasaki forum, same thing CV carbs will not run with air pods. The alternative would be to spend around $900 bucks, and purchase flat slide carburetors. That will fix you problem, and then some. Let me know what you got by taking off the top of one carb and seeing if there is a big diaphragm on top of it connected to the needle valve. I have a few ideas you can try.

Without the Factory Service Manual, which you can find on the web in .pdf form for free, it will be almost impossible to help you.

[KiwiAlfa156]

Are those CV (Constant Velocity) carbs, in other words, do they have a diaphragm? If so, you will have to make an air box to build up vacuum to get the diaphragms to function, otherwise,it will never work. I just went through this with someone on a Kawasaki forum, same thing CV carbs will not run with air pods. The alternative would be to spend around $900 bucks, and purchase flat slide carburetors. That will fix you problem, and then some. Let me know what you got by taking off the top of one carb and seeing if there is a big diaphragm on top of it connected to the needle valve. I have a few ideas you can try.

Without the Factory Service Manual, which you can find on the web in .pdf form for free, it will be almost impossible to help you.

From the video they are the stock VM Mikunis.

[Suzukian]

The stock were CV Carbs. Below is a link from Mikuni on how to tune VM Mikuni carbs.

Mikuni VM are manually controlled slides.

Don't you guys ever use Google? Google is your freinemy.

https://www.mikuni.com/pdf/vmmanual.pdf

[rmantell2012]

Are those CV (Constant Velocity) carbs, in other words, do they have a diaphragm? If so, you will have to make an air box to build up vacuum to get the diaphragms to function, otherwise,it will never work. I just went through this with someone on a Kawasaki forum, same thing CV carbs will not run with air pods. The alternative would be to spend around $900 bucks, and purchase flat slide carburetors. That will fix you problem, and then some. Let me know what you got by taking off the top of one carb and seeing if there is a big diaphragm on top of it connected to the needle valve. I have a few ideas you can try.

Without the Factory Service Manual, which you can find on the web in .pdf form for free, it will be almost impossible to help you.

The carbs on the bike are cable actuated, so I don’t believe they are the CV carbs. The service manual tells me they are VM26SS.