Schwinn sport 50, odd problems By dtjason (Read 7,477 times)

[dtjason]

This is my first post, I have decided that I might want to upgrade this schwinn after my wife bought a Yamaha c3 and left me in the dust. I want to make my schwinn slightly faster (especially after learning no one will take it on trade for another C3...)

2007 Schwinn sport 50.
Engine is a BZ139QMB
everything is stock. it has 960 miles.
Never disconnected the battery........

I began by changing the oil, made absolutely sure the level is good. took the spark plug out and it was perfect, showed a perfect combustion. reinstalled.
Checked air filter, good.
looked at cdi, disconnected to find a part number so i could match or investigate a high performance cdi that would work with this bike.
Didnt find a number so i plugged it back in.

Now the motor runs a idle, but when accelerated, bogs down and will try to die. i can play with the throttle, keep it alive, returning to idle, then hit the gas, get a short burst, then bogs again.......
changed spark plug, no improvments........

What in the world could i have done? Ive about scratched a hole in my head....... and before i order parts (scrappydogscooters stage one gy6 performance is what i am eyeballing and a iridium plug)
I am wondering what is messed up, and if it has anything to do with that cdi...... anybody have suggestions?

[dtjason]

Yeah, i agree with going bigger, but since this one is paid off........ hahah

The cdi connection only connects one way on this, solid clip connection.. ive double checked that too. The dealer wants 60 bucks for the cdi........... so that made me search online for a test procedure (which i have found none....... know of one? or a good explanation of how to?)
I found scrappy to have that whole setup for 40....... coil and cdi.......

But id hate to spend the money if it isnt the issue....... maybe tomorrow ill tear the carb down, clean it and hope that is the issue..... maybe some dirt got in there (dealer says they have that problem all the time....)

Fuel lines are all good, vacuum pump, etc, all seem good as well. and it will hold idle.....

would you reccomend hp cdi if it is cheaper than a dealer stock cdi?? and would installing it back up with battery hooked up cause it to toast off?

(and that link is my bike, right now all the fairings are off..... damn thing ran before this just fine......) Also, wife and I weigh the same....... that yamaha is just a beast i know......

[Alleyoop]

Could be when you took the plug out and put it back in you hit the end of it against the side of the hold and closed the gap. Another thing is make sure the Plug is on there SNUGE otherwise it will leak and you will loose compresion, Also make sure the BOOT on the Plug is on there right all the way on. Make sure you did not create air leaks when you checked the filter, tighten the rubber boot that attaches the intake to your carb as well as the filter to the carb.
Alleyoop
Alleyoop

[dtjason]

alleyoop, all good!
even tried with the air box off so see (since it seems starved........somehow) and it didnt help either.

after cleaning that carb, if it doesnt help, could it be the cdi?
I also plan to get my multimeter from work and test the coil........

Any clue how to test the cdi? i have very vague insrtructions from a gy6 service manual.......
unless im reading it worng..... but ive read it several times over.

[jhbietz]

Just to give you some Ida this is what it took to make my large frame 50cc faster then a C3 with my fat but on it.

Big bore kit what they call 100cc. IMHO best bang for the buck.
Large Valve ported head.
150cc intake and carb.
Custom made exhaust.
Complete transmission upgrade. Sliders, torque and clutch springs, and variateor
Iridium plug
Racing CDI. No noticeable difference.
Last but not least. Many hours of tuning and testing.

[Alleyoop]

Jhbietz,
What were you looking for in performance wise, more top end, climbing ability, low to mid-range exceleration etc. And after all those mods what are the performanace results from stock.
Alleyoop

[jhbietz]

My initial goal was to keep up with my wife. At the time I was around 300# and my boy would ride with me adding another 50+#. Then we started riding with another couple who have a C3 and a Zuma.
If I had it to do all over again I may have just bought a 150cc but I did have a lot of fun tinkering with it and its still a blast to ride.

From 0 to about 35 its faster then my stock 150. Cruises comfortably at 45 and tops out just a touch over 50.

[gmalcolm77]

Sept 26, 2010 5:59:18 GMT -6 dtjason said:

alleyoop, all good!
even tried with the air box off so see (since it seems starved........somehow) and it didnt help either.

after cleaning that carb, if it doesnt help, could it be the cdi?
I also plan to get my multimeter from work and test the coil........

Any clue how to test the cdi? i have very vague insrtructions from a gy6 service manual.......
unless im reading it worng..... but ive read it several times over.

This site has a pin out for the Gy6 cdi. If you can't get it, I could send an attachment for it. It sounds like carburator or as someone else said, a vacuum leak. As was said, the intake manifold nuts are a prime place to look as they have loosened up on me several times. Also, cracks in the rubber manifold. I wound up mounting a small block of wood under the carb to keep it from bouncing up and down. Also, could be the electric choke. Check for 12v first, then pull it out and let it cool all the way down(put a cold pack on it), put 12v on it and check for movement of the silver pin. Should be aprox 1/2 inch. Good luck.

[Alleyoop]

I think this is a dead thread it was from 2010 we are in 2015 the scoot is most likely buried by now.