VM26SS issues?

[HarlemShake]

I have a 78 GS750C,

I got the bike about 2 months ago. Cleaned the carbs, rebuilt them and it ran like a top!

Took the bike out for my first “long ride” (60+ miles), at about the 40 mile mark the bike started surging and cutting out, popping and back firing.

I limped the bike home via back roads, cause I couldn’t go over 30mph and quarter throttle with a load, it would fall on its face. I can rev the bike with no problems, it’s just under load where I have the issue.

so, I pulled the carbs and cleaned them again. I bought a color tune and tuned the carbs, bench synced them and it ran better, but it’s not zippy. Once the bike warms up it’s popping and surging still.

I replaced the o-rings for the “intake” and there were no cracks in the rubber. I’ve went through and checked timing, valve spacing and all was good.

I’m now confused, only thing I can think is maybe it’s the jetting? I used jets from a rebuild kit. I’m not savvy on carbs and I can’t find anything on the VM26SS. I just want to know what the stock sizes are for all the internals of the carb.

Any other ideas what could be going on? I’m at my wits end.

[Nessism]

Did you adjust the valves? Clean & adjust the points?

[chuck hahn]

I would supect condensors went bad

[chuck hahn]

SERVICE MANUAL HERE........... https://gsarchive.bwringer.com/

PARTS FICHES HERE................ https://www.partsoutlaw.com/

[HarlemShake]

Did you adjust the valves? Clean & adjust the points?

Yes, the valves didn’t need adjusting. I did clean and adjust the points.

[KiwiAlfa156]

Yes, the valves didn’t need adjusting. I did clean and adjust the points.

By "adjust the points" you mean set the gap? Or do you also mean set the ignition timing using a timing light?

[HarlemShake]

I would supect condensors went bad

You may be right, I’ll get some on order and see if that’s the culprit. Considering I changed the coil packs and nothing came of it, that could be it.

I was getting pretty frustrated with everyone telling me it’s the “Carbs”. I’ve gone through those things 5 times in the past 3 weeks.

[chuck hahn]

He means setting the gaps AND using usingtiming light to adjustntiming to the F mark. You set the timing on the left ones first with the big plate and the right one last with the subplate

[unfocused]

I am going to throw this out there - but where are you floats adjusted at? Even 1mm to high can cause issues - my VM26's I run at 25mm but still tweaking.

[HarlemShake]

I am going to throw this out there - but where are you floats adjusted at? Even 1mm to high can cause issues - my VM26's I run at 25mm but still tweaking.

I set them at 25mm as-well. They still need a little adjusting, but I’m not sure that the floats would cause power surges. It literally jolts as if I’ve got power then bogs, then jolts again and back fires. It’s a cycle.

[Nessism]

Carbs won't typically cause the bike to cut out when hot. That sounds like an ignition problem or maybe fuel flow, petcock or tank vent problem.

[Big T]

But a set of quality points and condensers from a reputable seller.
Don't buy cheap parts from eBay or Temu.

Check your points again, they're probably burnt.

Best solution is a Dyna S ignition

[oldGSfan]

Did you stop to fuel up along the way?

[HarlemShake]

Did you stop to fuel up along the way?

No, I was on a full tank when I left the house. Fueled the day before.

[HarlemShake]

But a set of quality points and condensers from a reputable seller.
Don't buy cheap parts from eBay or Temu.

Check your points again, they're probably burnt.

Best solution is a Dyna S ignition

I ordered condenser and points from a reputable dealer, should be here today. I’m thinking ignition too. It idles fine, it’s under load where it misses.

I’m definitely going to convert to the Dyna S later this summer, just want to make sure the bike is running right before I start making changes.