this is a new thing to me

[two-stroke-brit]

dicovered this after going for a sunny afternoon ride ,halway to the bar and bike starts to loose power and wont pull.
idles fine but under load bogs down.
pullover ,feels like gas starving, sparks on all cylinders,,plugs were a lttle oily but not bad, change out to new plugs same deal ,
turnaround start for home 2 miles down the road it revs to the moon.
turn it off pull over and the pin in the sldie has vibbed out and center slide is stuck wide open.
push it back in and carry on home.
get home and find the above condition.
and this also

right jug not fireing see plug.
but has spark replaced float and still the same.
i have looking into the spark hole and cant see and damage .ie holed piston.
did comp test (gage not working right) but all cylinders read the same.
why is it not getting gas??
any help would be great.
thanks mark

[Suzsmokeyallan]

Mark you say that cylinder is not getting any gas, so the first suspect is the fuel to that carb, did you remove the jets and check all the passages.

[tz375]

Mark,

Pull the drain plug from that float bowl and see if any gas is coming out with teh tap on RES.

If not, pull the carb and inspect the float valve for dirt or debris. If that's clear, check the feed tube to that cylinder and see if it flows gas. Might be easiest to check that first.

[two-stroke-brit]

thanks guys,
i have the carb off and the jets are clear on a cursory look( daylight showing when held up to the best light sorce.)
when i emptied the tank on prime i noticed it ha good flow from all three but when it was almost empty only one line was running (the one nearest the curb)see pic.

why would you do the flow test on res ??
the float valve seems a little notchy( dont know of a better description)
there is a little back story which may or maynot be conected .
a month ish ago i changed out the petcock. have used the bike on a 4 or 5 occasions no leaks and no probs.
also change the filters and lines without issue.
my bigest fear is what carnarge have i done riding it home two up on two cylinders for 30 miles.
will try the drain plug test at the weekend.
cheers mark

[tz375]

My bad. I meant PRIME. Sorry for any confusion.

When there's almost no fuel, it's normal to run in only 1 or maybe 2 pipes and not all three - line of least resistance.

Notchy isn't a term I expect to see on float valves. That's worth looking into to see if it's the needle and seat or the float pivot.

[two-stroke-brit]

well i got the wrong inlet rubbers so while i wait i put a new float and valve in the offending carb.
it started right up smoking more from that chamber but i expected that with it ni fireing amd all.
but when under load it bogs and when the revs climb to 5k it has an intermitant misfire .
returned to home and if i put my hand behind the chamber i get moister on it. i dont think its gas.
could it be a blown headgasket. or a coil breaking down.
or just blocked jets or passages.
the mistery moister is bugging me.

[tz375]

Slow down Mark, I think your keyboard is have conniptions there old buddy.

I think you said that it was smoking a lot from the chamber that wasn't firing earlier and that could be an exhaust pipe full of fule soaked carbon or semi blocked/wet packing around the baffle pipe.

Moisture usually means a pipe that isn't getting hot enough to spit it out as steam in the exhaust stream. If one pipe stays cold, it usually indicates it isn't firing properly. Check header and pipe body temps across all three headers and all 4 pipes to see what's going on. It is quite likely that the one cold cylinder is dead for some reason. It could be electrical or fuel related. Check for sparks on all three and check timing just to be sure. If sparks are MIA do all the usual tests/checks to find where the electrons are hiding out. Lazy little buggers are skipping work on one pot by the sound of things.

[two-stroke-brit]

the right cylinder was the unwilling one but since changing the float and valve it is fireing again and all the chambers feel the same temp but need to borrow a temp gun from work to get an accurate picture.
more info to come
cheers mark

[two-stroke-brit]

ok this has been frustrating ,, went on dillons site look up the 73 k gt750 , order 3 carb mounts (13110-32200)
they arrive wrong year (1972 ),
return the parts, talk to them .
reorder (13111-31201)
the resend ,parts arrive , wrong year 1974 on.

my pc has died so am doing this from my phone so no access to normal referance stuff

does anyone know the correct part # before i call them again.
thanks mark

[Suzsmokeyallan]

Mark, the 32200 last number should be the correct ones for the 73.

[two-stroke-brit]

hi alan , i had to return them again , so i will go down to my local dealer and try and get the through them . they are normally fairly helpfull as long as they are not busy.
the first ones had the 32200 number on the packet but were for the 72.
i will go today.
not long to the gap , i am jealous. hope you get good weather ,
cheers mark