dead 50cc gy6 w/ BBK..help?

[nate]

hey everybody, i've been lurking on scootdawg boards for a while now trying to get to know my shenke/jonway/nst yy50qt-6 a little better. thanks for all the info so far, i've learned way more than i ever thought i could about gy6 motors!

my problem is a dead scooter (of course!) i was riding one day and about 5 minutes after leaving my house it just died at a stoplight. i pushed it back and got to work...as best as i could! while checking over everything i noticed i had a stuck intake valve and decided to put on a BBK while i was in there (since it came as a package deal with the new head). but now when i try to start it, nothing!

compression reads about 110 PSI and battery reads about 11.7V...i'm getting fuel to the chamber and have a spark when checking the plug. i tried to kick it over but the kickstart sticks (another issue!) so i'm relying on the electric start to try and get it to start up. when i use the electric start, i just hear a clicking/buzzing sound coming from the 2 red plugs mounted on the frame above the flywheel. any ideas, fellas?

i love my scooter but i'm starting to go a little crazy over here! any help would be appreciated

[nate]

just took the starter off and opened it up...there's a burnt plastic/rubber smell and a bunch of black grime on the inside (could just be grease?)
is there a way to check the starter? i have a multimeter if that helps any.

[meitianman]

the click buzz could be the starter solenoid, usually if they do that its due to a low battery. to check the starter get your multimeter and set it for 2k ohm's and measure the resistance from the wire comming of the back of the starter to the starter housing, it should be 0 or very close to it. if it is not, turn the starter and see if the resistance changes "checking for dead spots/burnt windings"

the black grime is probably a mixture of grease and brush material, if you get it on your fingers you will have a pickle of a time getting it off.

another quicker way to check the starter is to simply run a wire from the positive side of the battery to the red wire on the starter to see if it turns over, if it does go further up the circuit and look at the solenoid as the contact plates in them do get burnt after a while and not make contact. to check that you would hit the starter button so you hear the click and measure the resistance off the 2 large pins on the solenoid, again it should be 0 or close to it.
on a side note ive seen solenoids with 0 resistance but would not carry the current of the starter so keep that in mind.

[D-cat]

I think I'd be jump starting from a car battery. 11.7 means the battery is low (should top at 12.6) and you will kill your starter much quicker with not enough power than with too much... if there's not enough to make it turn over, all it does is build heat. The smell is not a good sign, you may have burned it out already.

[nate]

thanks for the replies...
i tried jumping the starter and got nothing, so i'll be replacing it shortly (ebay!)
on the plus side, i took my kickstarter apart, cleaned, re-greased and re-assembled it. i've got it back on and the bike REALLY wants to go but i'm still just getting a "PUTT-Putt-putt" when i try to kick it over. i've got my valves set @ .004" in/ex. gonna try .002" and see if that makes a difference(?)

[nate]

update: i installed a new starter, blue performance cdi, orange ignition coil and re-adjusted the valves to .0025"
still nothing! i've got good compression (about 110 psi), i've got a spark and when i try to start it and then check the plug, it smells like gas. i've tried kicking it over, but that doesn't start it either.
also, not sure if this is related or not, but when trying to start, if i open the throttle, the engine hesitates.
what am i missing? please, any help is greatly appreciated!

[nate]

double checked compression with another gauge (mine was malfunctioning)- got 130 psi this time.

[meitianman]

just for giggles give it a squirt of gas in the spark plug hole or through the carb itself. if you have spark, compression, fuel it should start.
when you say it hesitates does that mean when you open the throttle the engine has a hard time turning over?

[nate]

Aug 31, 2011 23:15:32 GMT -5 meitianman said:

just for giggles give it a squirt of gas in the spark plug hole or through the carb itself. if you have spark, compression, fuel it should start.
when you say it hesitates does that mean when you open the throttle the engine has a hard time turning over?

will do, thanks for the response.

as for the hesitation, yes, when i open the throttle the engine has a hard time turning over. i feel as though it may have to do with the bbk since i never noticed that before installing the kit.

[Pony66]

Basicly, if you have spark, fuel and compression, it has to be timing. Perhaps you put it together 180o out of time.

Also to double check, test for spark with the plug out and grounded to the ENGINE. Also check grounded to the frame. If it does not spark on engine, its the engine ground.

Spraying starter fluid into the intake nipple is a great check for fuel flow. If it runs a second then the fuel is not getting to the cylinder.

So, test for spark at engine and fuel. If you get spark and no result from the spray, it has to be timing. Because you already have tested compression.

[nate]

thanks for the reply pony!
i finally got it to start up...kind of. after fiddling with some loose electrical connections, jumping the bike with my car battery and some starter fluid directly into the plug hole, i was able to get it to idle. i let it do its thing for about 20 minutes while it blew out a lot of nasty smelling white/gray smoke (probably excess motor oil from installing the bbk)
unfortunately, i've had to kickstart it if the scooter's not being fed power from my car battery. i know the starter it in good condition as it's just about brand new. my neighbor thought it might be something in terms of the ignition switch? idk...
ANYWAY, when i went to take my scoot for a ride, i was completely dismayed to find that my top speed went from about 35mph (pre-BBK and new CDI and coil) to a wimpy 10mph! from looking around i'm starting to think it is either the valves or it needs a larger main jet? my jet is whatever size comes stock in a 50cc gy6 carb (i think #75)...with the 50mm BBK (83cc?) i'm thinking i should up-jet to about #90- does that sound crazy? airbox and exhaust are still stock.
one interesting symptom is that giving the scoot any throttle while attempting to start completely bogs the engine down. once it starts up, throttle seems to work as normal (except for the fact that i get almost NO power)

anyway, i guess this post is more for myself so i can remember what worked, what didn't, etc. i'm going to adjust the valves and clean the carb tomorrow, maybe mess around with the A/F screw and idle screw combo while i'm at it. if anyone wants to leave advice, i'd love to hear it!

[Pony66]

Oh boy, order that new jet right away. They come lean already so now its starving for fuel.
Dont turn the throttle when starting, you have a fuel enricher that is already giving it extra fuel.

[nate]

so i went to do a valve adjustment today and guess what i found (or didn't find for that matter)- i'm missing the adjustment screws on the valve rockers!
THAT definitely may be my speed problem LOL...i also found out my A/F screw is missing...total drag, i'm ready to go for a ride!!!
i'm waiting on those parts to come in from a local dealer on tuesday, and ordering a #88 main jet and a new battery today from scrappy...sigh lol i guess it's better to laugh than cry!

[milllhouse]

I've got this idiotic rocker arm adjuster screw problem once. And it was just the same as yours,i couldnt get any more than 20kmh and when i opened the rocker cover i found no screws there. Although i ran more than 1000km with the screws in my engine,without any problems at all.

[nate]

this may seem like a dumb question, but where would the screws have ended up? i'm guessing (and going to check) the slot that the cam chain runs through. if it's not there could it have ended up in the crankcase? i haven't been able to find out if there is space enough for the screw/nuts to get from the back end of the cam chain into the crankcase or not...

[nate]

also to millhouse, yeah i'm definitely going to loctite the screws next time!

[nate]

update: i replaced the valve screws, a/f screw. starts up much better now on the kick but i'm still having problems with idle speed and power at all idle speeds.
my idle speed fluctuates greatly, no matter what position the a/f screw or idle screw are at. i'm a little stumped here.
also, i'm getting the back wheel to spin about mid-way between closed and open throttle, but nothing above or below that (when @ WOT there is no power to the back wheel, it stops spinning completely)
some specs i've observed:
-87 jet on a 50mm BBK
-compression is good (~130 psi)
-a/f screw 2 1/2 turns out
-sparkling clean carb (just cleaned it/replaced gas yesterday)
-white smoke from the exhaust @ higher rpms
-almost no power (if i were to ride it down the street i would be going ~5 mph)

any suggestions?

[50dude]

You may need a bigger jet, I run a 98 in my 47mm kit.

How old is the fuel in the bike?

[mainepeace]

Idle jet is too small. A hunting idle means a lean condition. If you can't adjust it enough with the A/F screw you need to upsize the idle jet.

Sounds like you might have low compression. Do a test.

Greg

[nate]

thanks for the responses. i found that the valve adjusting screws were missing when i went to do a valve adjustment (TIP: USE THREADLOCK!!!!) so i removed the engine from the frame and fished out the screws with a magnet tool. i'm thinking that this is what has been causing my problems, but we'll see...before i put everything back together i want to clean out the crankcase b/c the oil has little metal shavings in it now.
fingers crossed!

[mainepeace]

Wow, surprised the engine was even running with the screws missing! Normally you don't need to use threadlock on those screws since they have the locking nut. Glad you were able to locate the screws, as they can do lots of damage. Hopefully they haven't done anything significant yet. Fingers crossed.

Greg

[slawenm]

I got a much higher PSI off my 47mm BBK I think around 150 PSI blowing smoke could just be the watervapour thats in the exhaust etc while the bike is sat non running for days on end.

as for the tappers off your rocker arm falling into your crankcase here is a picture of the results of that happening to me Enjoy!





Quick fix for needing a higher idle jet I just turn in the screw at the right side of your carb on top of your circle bit that the throttle cable goes into, it makes the scooter react as if your giving it slight throttle but when your in need of using the scooter its a fix that can do for a short time ( not to long as it may burn out your clutch from back wheel spinning) I fixed that by throwing on some heavier springs for the time being. nothing better than bodging a job

[nate]

wow, that looks like a nightmare! everything looks good on mine, though i have metal shavings in the crankcase now, so i'm trying to remove everything else to split the case and thoroughly clean it. i read somewhere of someone just flushing out the system with a garden hose and h2o but i'm wary; it seems counter-intuitive to put water through the crankcase.

[medman1952]

Dec 28, 2011 22:42:15 GMT -5 nate said:

wow, that looks like a nightmare! everything looks good on mine, though i have metal shavings in the crankcase now, so i'm trying to remove everything else to split the case and thoroughly clean it. i read somewhere of someone just flushing out the system with a garden hose and h2o but i'm wary; it seems counter-intuitive to put water through the crankcase.

You seem to have some good sense there. Take it all apart and clean it out. Floating bits of metal will just cause problems.