1979 GS750 black plugs - jet needle height?

[Coady]

I did clean and oil the filter during this process, with air filter oil, as well as fixing a gap in the air filter foam gasket that it sits upon - was only about 40-50 mm long but maybe that could have made it richer?.

I'll check the filter to see if its over oiled.

Thanks for the suggestion.

I'm also going to pull carbs again and check for any anomalies. Especially floats and needle seats.

[almarconi]

One thing I did not see mentioned is the fuel level. Even if your float heights are all the same the fuel level may not be same. You can check the fuel level using a clear piece of tubing with the bike on the center stand. I prefer to check it with the carbs off the bike. Very small changes in the float tab make a big difference in the fuel level. If you fuel level is too high (rich) it will effect all throttle positions.

[Coady]

Fixed!!!!!

Thanks for the reminder about fuel height - checked and they do seem to be about 2 mm apart from one another. In fact whilst I was doing that I noticed the choke plunger looked a bit more raised than I remembered and looking closer it had no up and down play in the little plastic part that it gets raised by.

Well turned out the choke shaft was binding across the carbs just enough to hold them all slightly open - hence the bike was... choking.

This explains, obiously the richness, but I guess also the drop in vacuum at sync and the fact that it idled OK on the sidestand as the choke plunger is on the right of the carb.

In fact took a bit of fiddling to get all the plungers sitting shut evenly as one wanted to shut before the others (due to uneveness of the lifters(?)). That one plunger would then hold the others open. Looks like it was a combination of this and the end lifter being too tight against the 4th carb.

Obvious really....

Went sweet this morning - idle rough as need to redo the vacuum sync. But otherwise ran smoother than ever.

Thanks heaps for the suggestions and for the GSR.

[crapwacker]

Thanks for the reminder about fuel height - checked and they do seem to be about 2 mm apart from one another. In fact whilst I was doing that I noticed the choke plunger looked a bit more raised than I remembered and looking closer it had no up and down play in the little plastic part that it gets raised by.

Well turned out the choke shaft was binding across the carbs just enough to hold them all slightly open - hence the bike was... choking.

This explains, obiously the richness, but I guess also the drop in vacuum at sync and the fact that it idled OK on the sidestand as the choke plunger is on the right of the carb.

In fact took a bit of fiddling to get all the plungers sitting shut evenly as one wanted to shut before the others (due to uneveness of the lifters(?)). That one plunger would then hold the others open. Looks like it was a combination of this and the end lifter being too tight against the 4th carb.

Obvious really....

Went sweet this morning - idle rough as need to redo the vacuum sync. But otherwise ran smoother than ever.

Thanks heaps for the suggestions and for the GSR.

Thanks for the follow-up! That will point someone with your problem in the right way. Oh, give your oil a sniff, if you've been running rich, you may very well have dilluted your oil with gas!