1977 GS400 Running Lean

[gorillafan208]

Put in the VM jets and they did indeed work. I can start it without the choke now but I have to hold the throttle a bit open or it will die. Messed with the idle air adjustment screws but couldn't seem to get it. I'm hoping when I replace the intake gaskets it might help. Should I do a valve adjustment as well just to try and cover all my bases?

[rphillips]

Surely you tried dialing the idle adjust knob in just a little.

[gorillafan208]

Oh yeah i tried to adjust the idle knob too, I think it won't run right until i put these new intake gaskets on and do the valve adjustment

[gorillafan208]

I checked valve clearances and finally got to replace the intake gaskets, the battery is dead after trying to start so many times, but after charging the battery I am hoping I will be good to go! Probably will have to mess with it more, but I am hoping the new gaskets fix (at least help) the lean condition. The old intake gaskets on there were totally junk.

[rphillips]

hoping all is good.

[Hokano12]

Sounds like you are getting on the right track. I have a 79 gs425, essentially the same bike as yours. I have pods and a 2-1 pipe on mine and increasing 1 size on the pilot jet helped quite a bit. This is assuming your carbs have been fully cleaned and rebuilt. What size mains do have in currently? You will most likely need to increase since you have pods. Another thing to check is your float height. Make sure they are in spec on both carbs.

[gorillafan208]

I have the stock mains which are 112.5. My carbs have been fully cleaned and I did check float height on both carbs. I am expecting to have to increase the mains and maybe the pilots. Have you been able to get yours to run right with the 2-1 pipe and pods?

[Hokano12]

Yes my bike runs very well with pods and a 2-1. Starts very easily, no flat spots, pulls smooth and hard to redline. Learned a lot about CV carbs with this bike. Of course every bike is going to be different but currently I have in 117.5 mains and 22 pilot jets (stock for my bike is 110 MJ and 20 PJ) with the fuel screws 2.5 turns out. Idles at 1100rpm smoothly all day. I do have a tapered needle in which helps quite a bit as well but you should be fine with stock needle.

I would start with 2 sizes up from stock on your main jets, so that would be 117.5 for you as well. Ride it for a good 30 mins and check your plugs. If still not a good tan/grey color, move up a size on the mains until you get a good plug reading.

Make sure you have good quality pod filters like K&N. You will be chasing your tail with cheap amazon/eBay pod filters. Keep me posted I love a good gs400!

[gorillafan208]

Thank you I will do that! I just ordered some bigger pilot and main jets and I think I am going to buy some K&N filters, the pods on it right now are of ambigous origin and I really just wanna eliminate any factor making it run crappy. I think I may have missed spraying out the choke tube holes or some other little hole (though I thought I had gotten every single one) because when starting with the choke the bike would rev to around 3k, and without the choke would start but die 30 seconds later. I think I ought to make sure timing and electrical connections are all good, haven't done that yet, because I am generally confused by electrical stuff lol.

[Hokano12]

That sounds about right when starting with the choke. The choke on these carbs actually gives the bike more fuel instead of blocking air. I’m usually at about 2k-2.5k rpm when I cold start with choke. I leave the choke on for a good minute or so and then am usually good to flip it off.