87 SE50 won't start

[arick793]

I'm working on an 87 SE50 for a friend. The motor only has 500 miles on it (off of another 87 SE50), bought to replace the blown stock engine. I can't get this d*** thing to run! I have the bikes original carb on it (had 3,500 miles) I've soaked it in carb cleaner and blown it out with compressed air. I drained all of the old gas out of the tank and put in fresh 93 octane. It has plenty of oil. It currently has no air filter. I know that can make it lean, but it should still start, especially after adjusting the air screw. The engine will crank and crank, without so much as a putt. If I spray a little "quick start" in the carb, it'll run off of that, and then die after a second. Brand new spark plug and it's getting a nice blue spark. I believe the carb is getting gas, because when I loosen the screw at the very bottom of the carb, gas comes out of the tube. Could the float level be too low? Is it even adjustable?

[toboggan]

Get an airfilter on it... i bet you'll have better luck. It MAY start without it, but obviously in this case it's not. That'd be your best bet i think.

[konaking]

Did you try manually choking it with your fingers over the carb? I would check the float needle and float to make sure everything is good. Check the reeds too

[arick793]

Did you try manually choking it with your fingers over the carb? I would check the float needle and float to make sure everything is good. Check the reeds too

It's funny you should say that. I was thinking about the idea of the air filter creating a restriction and enrichening the fuel mixture, so for poops and giggles I covered most of the carb throat with my palm and guess what happened? It fired right up, and ran just like a brand new motor should. It idled nice and revved up nice, until I took my hand off of the carb opening. Then it died, and wouldn't start again unless I "choked" it. So I'm going to put a new intake and air filter on it, and go from there, These little motors are sensitive!

[konaking]

Yup tuning the air fuel screw in rich is not enough to compensate for the huge amount of air going into your carb. You gotta change out your jets to bigger ones to richen the mixture. I can tell you from experience that running no airbox on a stock bike never a good idea when your just trying to get it to run. My first moped in high school was a razz that I got from a buddy with no airbox and it wouldn't. Push past twenty and was really slow. I threw a airbox on there and it ran like a hog

[Bear45-70]

Yup tuning the air fuel screw in rich is not enough to compensate for the huge amount of air going into your carb. You gotta change out your jets to bigger ones to richen the mixture. I can tell you from experience that running no airbox on a stock bike never a good idea when your just trying to get it to run. My first moped in high school was a razz that I got from a buddy with no airbox and it wouldn't. Push past twenty and was really slow. I threw a airbox on there and it ran like a hog

Kona has it wrong. The only two jets that have any effect on starting are the idle mixture adjustment and the bystarter jet. Neither of which are changeable except for the mixture adjustment. The main jet has ZERO to do with start up. If the carb has a pilot jet it would effect starting, but none of the PA series of carbs have that, only the PB carbs have that.

[konaking]

Yeah I know the spree has a fixed pilot jet but I'm just saying in general the only way to make a scooter run right without the airbox is to move to a bigger pilot and ajust the airscrew richer.

[Bear45-70]

Yeah I know the spree has a fixed pilot jet but I'm just saying in general the only way to make a scooter run right without the airbox is to move to a bigger pilot and ajust the airscrew richer.

And if there is no pilot like in the PA series of carbs used on so many of the older scooter, then that info is incorrect and misleading. The SE50 has a PA carb with no pilot jet.

[konaking]

Ok then bear how would you fix the situation on his spree. How would you get it to run with no airbox

[Bear45-70]

The easiest fix is to put a stock air box on it. But it isn't a Spree, it is an Elite SE50. The other fix is to restrict an aftermarket airfilter by taping better than 2/3s of it off so it can't flow. Using a PB carb is not gonna work because it will not bolt up to his intake.

[Wheelman-111]

Greetings:

I dunno, Dawgs. Flash I ran just fine with the stock carb and a K&N filter. I suspect something else is wrong at that mileage. I recommend starting with the basics. Easiest things first:

1. New spark plug.
2. While the old plug is off, check compression.
3. If that's under 100, have a look at the crank seals.
4. If the seals are good, dismantle the reed block for a look at those petals. Have the replacement gaskets at hand, you probably won't be able to re-use the old ones.
5. If the reeds are good, the top end needs to come off for a look at the cylinder/piston.

Hope this helps.