Scooter won't start, seems to have a fuel problem

Hey guys, I've been having a bunch of problems with my scooter and I'm all out of ideas. It ran well for a long time then I replaced the cylinder and now it wont even start. I checked the plug and it was wet and sparks a lot when kicked over, but doesn't want to fire up. I figured it was a fuel problem but I don't know what else I can do

Bike is a 2001 Yamaha bwsr
70cc MXS sport cyl
19mm stage2 phbg 94 main, 45 pilot, w7 needle in 2nd leanest clip (stock)
Doppler s2r reedblock, new carbon reeds
Doppler airbox and intake
Doppler s3r pipe
Stock ignition and coil
Removed oil injection

Yesterday I put new mixed gas in, replaced the fuel pump,battery, reeds, spark plug, completely rebuilt carb again and It only ran for a few seconds with the choke on and throttle slightly open, then nothing. Didn't seem to smoke at all when it started, and now I can't get anything from it. Are my carb settings really wack?

The top end is new,(160psi compression) as is almost everything else on the scooter. It is the exact same one I had on previously but I can't seem to get initial settings that it will idle on. I have lots of jets and needles and a milder pipe I could try but not sure where to go from here.

Edit:
Tried again this morning, bypassed the carb and poured gas right into the filter box, it will now start and idle high if you hold 1/4 throttle. If I close the throttle it dies at lower rpm but it seems to be acting better at wot and through the upper range. The choke didn't seem to affect anything. I'm leaning towards a under/oversized pilot jet? Or maybe my stock ignition can't handle low rpm anymore?

 

Air leak maybe?

 

I have a new intake, reedblock and all new boots and gaskets, I checked them all again while it was running and it doesn't seem to be leaking anywhere

I just changed it for a 50 pilot jet and it seemed like it was closer to starting but still needed additional fuel to start. After starting it hangs at 3500rpm (no throttle) and revs out normally to 14k before resting at 3500. Whenever it dips below it sounds very rich and dies. Im going to try a 40 pilot to see if I can get some progression back in the low end.

After looking at a ton of diagrams of phbgs I noticed I don't have an o-ring on my mixture screw, i guess that might be a possible leak?

Edit: srry for the floods of text, been frustrated with this thing for a while. If my idle circuit is too rich maybe it fouls the plugs? It seems like it still wants the choke though.

 

Leave the pilot jet stock size, start dropping the main jet size one at a time. Set the fuel/air mix screw at 2 turns out from fully home.
I've found that most 19mm carbs come with a 90 jet fitted as standard but it is too much for most 70 setups.

If your compression is good and the spark is strong then it seems like it is being over-whelmed with fuel.
Don't be surprised if you end up in the low 80's.

 

Yeah, check your mixture screw or your idle screw, and as Steve says. Main jet
Worth checking your float hight too

 

Thanks for the tips, I really appreciate the outside perspective. The float height is good, operates properly. I've tried a few different floats without any difference, and for every jet change I've started with the mixture screw 2 1/2 turns out.

I started with the small pilot (40) and it was obviously a step in the wrong direction so I went back to the stock 50 jet. Then I tried 10 main jets between 75 and 90 but still no start, seemed worse so I tried a 100 which was a little rich at the top end but still started much easier than the rest.

The last time this bike was driving I was running a 96 main and it was almost perfect, just a bit lean for long trips.

The best luck I've had today is with 50 pilot, mixture screw 5 full turns out, 92 main and needle on second clip. So basically it's back to factory settings other than the mix screw almost falling out. Under full choke it will start and again hangs at 4000, but it did drop to 2000 briefly before dieing again.

It only ran for a few mins but gave me a bit of hope

After a few hours of testing I destroyed the kickstarter so I'm pretty done for the day. I'll put some new gears in it tomorrow.

I'm starting to think the missing mix screw o-ring from the breakdown sheet is a critical component. Maybe I should just pick up a new carb.

Edit:
Ordered the o-ring and a few other things, I'll be able to try it and report back in a week or two. Pretty confident it will make a difference, The last two phgb rebuild kits I got didn't have it included. It may have been missing for two+ years.

In my experience the standard universal 19mm Dellorto comes stock with a 75 main and 40 pilot, I got the black body "race" version which came with a 92 main and 50 pilot, and much easier needle/jet access.

 

Minor update, I got the o-ring and it was definitely the main source of my tuning issues. I've got the bike to idle (still somewhat poorly) and now the mixture screw actually works! I played around with the carb until it got dark, warmed it up and revved out a few times. it's a lot louder than I remember, and very snappy on the throttle. Haven't even got it off the stand yet and I'm already getting dirty looks from the neighbours lol

Looks like snow in the forecast so I don't think I'll be able to ride in a while, but I'm going to try to get it dialed in over the next few days. Still a touch rich in the bottom, currently at 50 pilot and 102 main.

 

Oh damn I hope my snowchains are still knocking about somewhere. Without my scoot I'm up poo creak without a paddle.

 

Full throttle, with rear wheel spin. In the snow is the best. Makes you feel like a drifting pro.

 

If it has an air leak it should still star

 

If you say so...
Guessing you've not spent much time working on bikes....

 

I'll give another update, ended up with two feet of snow and sub zero temps so I still haven't been able to road test it.

I did have an air leak, aside from the mixture screw o-ring, but not on the intake side. After a bit of running I found the exhaust manifold gasket didn't seal properly. New gasket paired with the carb o-ring and now it all operates like it should.

On another note I got the Dio up and running, with a new fuel pump, tires and brake cables. Now I just have to figure out why the headlights and turn signals don't work, and get some new shocks. I have a technigas pipe for it already but I don't have any jets for this carb... Might be leaving this one stock for a while just to keep things simple.