exciter 570 jetting for warm weather

88 yamaha 570

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hey y'all i need a bit of help here, i put an exciter 570 engine on a gocart and having difficulties getting it to start, ive done a ton of research on it but haven't found anything close to what im running. im currently just trying to get it to start with no filters or airbox so i can do some test running and it wont fire unless i hold my hands over the carbs and crank it, then it bogs like crazy. eventually it will start to run better once its warmed up but for what i need to test its too difficult to start. what my question is, is what i should run for jetting with open carbs, or i can clamp a couple filters i have from my sportsman that happen to fit it. im gonna order some uni filters but im not certain yet as to if im going to keep and tune these carbs or just pick up a set of flat slides off a vmax 500 or 600 but at the moment i cant source anything local. ive tried leaning out the air/fuel screw a bit and it seems to run a little better but just curious what you guys thought i should do for jetting if i do happen to keep these carbs. also the fuel pump hasnt been installed and i am just gravity feeding the carbs so it is less cluttered, this wont matter will it?



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By no means am I an expert, just trying to help, but the motor itself (as installed) seems to be canted WAY too far forward. Could this affect the float bowls levels and contribute to hard starting/running? Which carbs are you using? The carbs enrichment circuits all good?
 
Carb enrichment circuit is good, i have the factory exciter carbs on it. I was also worried that the angle of the engine would effect how it runs(ran into exhaust clearance issues after the frame was welded up and realized i needed to lift the rear with larger springs). I’m going to try to situate the carbs first and rule that out before altering the fabrication. Or try to find some angled carb boots if possible
 
So i held my hand partially over the carbs to get the sled to warm up and once she was warm i took her for a spin and this thing flies!! Idle is hanging but after a while it drops down and then i can’t get it to rev back up unless i put my hand over the carbs and get the RPMs up. I turned the air/fuel mixture screw down to 1/2 turn from seated and also tried 1/4 turn from seated so i’m assuming i need to lean her up in the jets but might just wait and order the other style carbs before i go messing with jetting. In the process now if hooking up the cooking fan but noticed the engine will get up to 250-250 degrees while the radiator is at 190-200, not sure if i have a weak water pump or if my radiator is mounted too high for the engine to pump coolant but i would imagine it should be sufficient. I’m gonna get the radiator fan going first and try again and if not i’m gonna but the thermostat and see if that helps
 
So i held my hand partially over the carbs to get the sled to warm up and once she was warm i took her for a spin and this thing flies!! Idle is hanging but after a while it drops down and then i can’t get it to rev back up unless i put my hand over the carbs and get the RPMs up. I turned the air/fuel mixture screw down to 1/2 turn from seated and also tried 1/4 turn from seated so i’m assuming i need to lean her up in the jets but might just wait and order the other style carbs before i go messing with jetting. In the process now if hooking up the cooking fan but noticed the engine will get up to 250-250 degrees while the radiator is at 190-200, not sure if i have a weak water pump or if my radiator is mounted too high for the engine to pump coolant but i would imagine it should be sufficient. I’m gonna get the radiator fan going first and try again and if not i’m gonna but the thermostat and see if that helps
If you have tohold your hand over the carbs to get it to rev up, then it is lean.
Yamaha was known for having restrictive airbox's, so my advice would be to install the airbox if possible, then install filter where air enters airbox.
The main jets could be lowered a couple sizes with the airbox in place.
I would also replace the needle jet, as the they will be worn out for sure.
Also agree with the other poster that carbs need to be level.
 
i polished the needles up and ran the machine a few more times and it seems to run allot better now, dont need to hold my hand over the carbs to get it to rev anymore but the idle still either hangs high or drops too low. my new carbs should be here this week and then im gonna get those hooked up and adjusted and see how she runs. maybe being for a 600 will give it enough fuel so it wont be lean without an airbox. ill do some plug reading and see what it shows
 


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