750sx BACK IN THE GAME! Carb problems...

[Fenix169motox]

Hey guys! after years of being away i'm back in the stand up game!
FInally found another stand up to poke around on. Its a 93 750sx. Sat in a barn for 10 years, Removed carb. cleaned every fuel passage. new diaphrams/gaskets.
She will not start after sitting for a while, 3-4 hours at least.
IF you cover the inlet with your hand totally it will fire up, and if you dont let it idle for tooooo long she will run. and when it runs its perfect.
SO FAR.
I have made a block off plate for the stock water drain things, and a block off plate for oil. (running at 40:1 pre mix now)

IF i turn out my Low speed fuel screw 3 turns it will run better, but then it loads up at 1/8 throttle

what am i missing?

Comp: 145.145.
Stock everything.
BR8ES
Fresh Fuel
Pop off pressure is 25.
Even took a torch tip cleaner to the 3 other holes at the throttle plate since they were clogged up.

Hope to see some of you guys out in the cleveland/norther ohio area!

 

[Magyar68]

Did you replace the Needle and spring along with the Diaphragm? What type of Carb?

 

[Fenix169motox]

Yes, it's the stock keihin 38. Machine is 100% stock

 

[Magyar68]

She will not start after sitting for a while, 3-4 hours at least.

Is this after you have been running it and it has to totally cool down before It will run again?

 

[Fenix169motox]

Sometimes, or if it sits for a few hours it wont start back up.

 

[Fenix169motox]

i feel like it wasnt drawing enough vacuum to pull fuel from the pilot circuit. so thats why i got the block off plate for the water drain. which didnt help.

 

[Vumad]

Did you test the carbs, or just assume new parts tmeans they are working right.

 

[Magyar68]

Pop-off seems low, when you try to start it and it won't look at the plugs. If they are wet, its flooding when its sitting...

 

[Fenix169motox]

How would you test a carb besides doing pop off? I found that if I stuck a different 38 carb on there it works perfectly. So now we know it's in the carb that came on the ski.
For reference, the carb does pump fuel. Pop off was set. The new diaphragm on the jet side should be pumping fuel into the pilot circuit at idle. And it's not

 

[Fenix169motox]

And when I crank with no start plugs are dry.

 

[Vumad]

How would you test a carb besides doing pop off? I found that if I stuck a different 38 carb on there it works perfectly. So now we know it's in the carb that came on the ski.
For reference, the carb does pump fuel. Pop off was set. The new diaphragm on the jet side should be pumping fuel into the pilot circuit at idle. And it's not

That and make sure the fuel pumps arent leaking.

 

[Magyar68]

And when I crank with no start plugs are dry.

Is your Pulse line in good shape? And does your tank hold pressure? Are there any cracks in your Fuel Pickups? may have to take a look closer into the Fuel Pump, or the Fuel Delivery Circuits.

 

[Fenix169motox]

Pulse line is good, pressure tested it. Fuel tank holts psi, and the vent works. fuel pickups check out.

I was able to borrow another stock 750 carb to test on mine, and it works flawlessly. so i know its the carb.
so. what could be wrong in the carb that wouldnt let it idle

 

[Magyar68]

The plunger arm adjusted Correctly? Vacuum across the Venturi is supposed to draw the Diaphragm in and depress the Needle arm(plunger arm) If set to low the Diaphragm will not depress the arm. Covering the Opening to the carb causes your Vacuum to go way up and draw the Diaphragm in further than it would go normally. Other wise its in the fuel circuits, and I guess you would have to soak it in Carb cleaner for an extended amount of time.

 

[Rjdion5]

99,9

Hey guys! after years of being away i'm back in the stand up game!
FInally found another stand up to poke around on. Its a 93 750sx. Sat in a barn for 10 years, Removed carb. cleaned every fuel passage. new diaphrams/gaskets.
She will not start after sitting for a while, 3-4 hours at least.
IF you cover the inlet with your hand totally it will fire up, and if you dont let it idle for tooooo long she will run. and when it runs its perfect.
SO FAR.
I have made a block off plate for the stock water drain things, and a block off plate for oil. (running at 40:1 pre mix now)

IF i turn out my Low speed fuel screw 3 turns it will run better, but then it loads up at 1/8 throttle

what am i missing?

Comp: 145.145.
Stock everything.
BR8ES
Fresh Fuel
Pop off pressure is 25.
Even took a torch tip cleaner to the 3 other holes at the throttle plate since they were clogged up.

Hope to see some of you guys out in the cleveland/norther ohio area!

9999999999,9999999999,,of also not a, an animal like that and it would