SA50 hard start / low idle

[noiseguy]

OK, here's one I haven't run into before. '94 SA50. Stock carb and airbox, #78 main jet. Running 32:1 premix with pump in place (gear teeth ground off), GN2 oil. New petcock (GY6 replacement).

Bike has a hard time starting from cold (takes multiple attempts), even warm I find that I need to crack the throttle a bit to get it to rev up on the stand. Idle screw is completely ineffective... I can crank it all the way in and not get the expected response from the engine. In other words, it should be racing on the stand with idle screw in... it's not doing that.

Overall just seems to be idling too low. I haven't thrown a tach on it to check where it's at exactly.

Otherwise runs fine; topping out between 40-45 with 9:1 gears, so seems healthy once it's off idle.

Ideas? Typically with these bikes I find that they idle fast due to vacuum leaks... this one's doing the opposite.

[paulpauly7]

you have a air leak some where dude .Now the hard pard is finding it

[noiseguy]

I disagree. Air leak should run fast not slow.

[LMH]

Sounds like you need a new plug or low compression. Air leaks can make it hard to start, but typically if theyre not enormous leaks it will run fast once started. I would imagine doing premix and sticking to the stock jet it may not be too happy.

[Duke]

That oil ratio could be high for an otherwise stock motor, the plug could be loading up at low rpm. Try a hotter plug? If your idle screw has no effect there could be some mechanical damage on the slide or idle screw. Good luck

[patthesoundguy]

Bystarter issues maybe? I've had a bystarter leak air around the wires before caused funny issues kinda like that. It was a double whammy actually, it would move in and out right but didn't do its job it even passed the vacuum test, but nothing but replacing it fixed the issue. I also had munched reeds cause hard starting.

Sent from my Nexus 7 using Tapatalk 2

[LMH]

Bystarter is always a hard one to guess, reeds too. Its one of those things that it will be the last thing youll check. Get a list going of what it could be and read it a loud in front of the bike, then when you go to check those things do the last thing first. See if you can trick it.

[noiseguy]

The bystarter is funky on this carb... the brass fitting had fallen out at some point, and I replaced it with an insert from a Spree carb I had laying around. I'll double-check that... it seems to be (it's not 4 stroking, so not holding open... suppose it could be stuck closed.)

Also will check the idle stop screw. It may not be working... I've certainly seen stranger things... and this carb was a mess to sort out.

I think 32:1 is the right premix level. Plug is new. I think compression is fine b/c it doesn't have issues at speed, but I'll double-check that as well.

[maddog]

Only for you DON- main jet will be a #87 open up the blank on the airbox, do not premix just saefty wire the pump full open, thats it for the next 29,000 mi.

[Pete M]

Check for a fuel restriction before the carb.