Topic: Does this sound like the accel. Pump??

[ZanVooden]

So working on my 78 750K. Just recently got it running (see progress and pictures over in the project area). I rebuilt the engine top end, with new rings, new springs, new guides, all new gaskets and had a machine shop grind the valves and seats.
I also rebuilt the carbs, cleaning them and all. (yes I know they have to be very clean). tuned them and sync'ed them

What's happening is, the bike will start up fine. but as soon as I twist the throttle the engine "bogs" down almost to the point of dieing. But if I ease the throttle on it will rev up just fine and in the higher revs, there is plenty of response. Just from idle to any revs it has trouble.

Now does this sound like an issue with the accelerator pump on these carbs? or does the bike just need to be run and broken in a little more?

Any help is appreciated.

[Johnny5]

Stock intake? Clean air filter?

[Inigo Montoya]

Easy way to check the accel pump. With bike off but petcock on. Twist the throttle and watch the carb instakes(make sure airbox or pods are off). There is a little brass nozzle the sticks up and you should a stream of gas shoot into the carbs on EACH carb. If you do not see this, it is not working right. It could be dirty or just not adjusted right.

[ZanVooden]

Stock intake? Clean air filter?

Yes, stock intake, and brand new filter.

[Johnny5]

Doesnt sound like it needs to be broken in more. You did basically what i did with my 77 this year and I was able to take right off. Are your floats set to spec?

[ZanVooden]

Yeah, I adjusted the floats and measure a couple time and even had my dad check them. When we put gas to the carbs they just poured gas out the overflow tubes, so I tweaked them just a touch to get that to stop.

[Johnny5]

Im assuming the bike has been timed correctly?

[ZanVooden]

Correct, Timed the engine, synced the carbs, set the valves, set the timing chain tension, adjusted the air-fuel mixture, all per the shop manual.

[Johnny5]

Is your spark advancer sticking? It's behind the points plate. Take that off and make sure it's free of rust and grime. Put a little dab of oil on it.

Did you check the accel pump to confirm the it's working?

[ZanVooden]

Yeah, the advancer was sticking, but it as well has been off and cleaned.

I will check to make sure the pump is working some night this week, just haven't gotten around to working on the bike lately.

[Inigo Montoya]

What did you set your floats too? Older carbs were 22mm - 26mm the 77/78 bikes are 14.5mm.

[ZanVooden]

They are set to 14.5mm

[Johnny5]

How many turns out are your fuel screws?

[Inigo Montoya]

Have you checked your plugs after running for a bit?

[mystic_1]

Easy way to check the accel pump. With bike off but petcock on. Twist the throttle and watch the carb instakes(make sure airbox or pods are off). There is a little brass nozzle the sticks up and you should a stream of gas shoot into the carbs on EACH carb. If you do not see this, it is not working right. It could be dirty or just not adjusted right.

Do this simple diagnostic before tearing into too many things.

mystic_1

[Spanner 1]

3 out of 4 of my acc. pump nozzles were blocked on my 750A ( ex-bike!) and it would completely die/stumble with any throttle above idle.....so, I think your on the right track too, good luck......