PW50 running bad

[ricky_191]

Hi all , My peewee is having trouble starting and takes a few kicks when it used to take just one. And when it starts to run, it dies and then you start it up and repeat that a few times and then it runs ok. And when you lift the back wheel up, it revs out and goes good.

But when you ride it , it idles fine and runs ok till it gets up in the revs and when the clutch fully kicks in it struggles and cuts in and out and starts to die. Kinda spluttering and just not running right.

I replaced the coil not that long ago and the carbie has been cleaned out not that long ago also. I'm thinking it could be the reeds starting to fail but i'm not sure.

I'm thinking about burning all the crap out of the exhaust but I don't have a blow torch or compressor , which seems to be the most popular way to do it.

Any help would be good.

 

[zwebx]

clean the carby again, remembering to clean any vein and whatnot and take the reeds off and inspect after cleaning (brake cleaner should do the job easy)

 

[ricky_191]

Thanks for your reply. I have never dealt with reeds before so I have no idea what to do with them or even how to take them off :/

I just burnt all the crap out of the exhaust and it smoked for a good 20mins till I run out of butane on the cooker. I'm going to clean out the header pipe to and get rid of all the stuff in it.

I might take the rest of the cables off it , left over from the start run switch and clean the reeds. New ones are about $35 and I don't really want to spend that much.

Any more ideas ??

 

[Blender]

you've got te mixtures right? and the right oil? definately de-carbon the expansion chamber, and check the throttle cable for sticking.

 

[gottagetacheaperhobby]

what does the compression feel like on the kicker?

 

[ricky_191]

I think I have a good mixture worked out.. I cleaned out the expansion chamber so it should be better now.

Also should I use the spark arrestor ? that little pipe thing that goes in the muffler ? It come with the bike but it didn't have a screw in it so I never ended up putting it in.

Oh and the compression feels ok. I don't know how strong it should be but i'm guessing not much because it's only a 50cc. But it has compression.

 

[Blender]

the spark arrestor is there pretty much to just take sparks to the spark-prison. you dont really need it, them sparks are just restricting your exhaust, like the little hooligans they are

 

[ricky_191]

I started it with the exhaust off and it went first kick :/ I think it might be a clogged exhaust.

Also with the choke.. So should I start it with the choke and how long after it starts should I turn the choke off ? Some times i forget to turn it off and it seems to run better :/

 

[Blender]

you can start ity with the choke on, but if it starts without it, you dont need to use it. once the bike starts with it on just blip the throttle a bit then turn it off and you should be right. and if its running better with the choke on, i think you've gotta adjust your mixtures to allow more fuel and maybe less air.

 

[my67xr]

the expansion chamber would take a while to burn everything out.
i spent an hour or so burning out my PW50 expansion chamber.
keep turning it, and keep moving it along the chamber.

our PW needs the choke for about a minute, you can tell, as the engine starts to slow a little as the plug is slowly fouling.


the reed valves are bolted to the bottom of the intake manifold, pics in my PW thread.
a new set, including all the gaskets costs $19 plus freight-
http://www.pwonly.com.au/products/pw...l#.UmT8bnCnp9U

the compression of a brand new PW50 is 5.8 to 1, it is a pretty low comp engine
shaving the head back 1mm, will take the compression up to approx 10 to 1.

what air filter are you using ?

and if you don't have the spark arrestor in the muffler, you will need to richen the Pilot jet
the 2 strokes do need a bit of back pressure to help them run well.

the standard Pilot jet is a #40, with a cleaned out expansion chamber, no spark arrestor, and a decent air filter i would go to a #50
http://www.peeweecycle.com/miniracer...rformance.html

what Main jet is in yours again ?

 

[ricky_191]

I have no idea what any jets are :/

I'm running a modified pit bike pod filter. It could do with a new one. I cooked my exhaust for about 20-30 minuets.

 

[coolmodee01]

yep exhaust clogged for sure

they are terible for it head to bunnings for some cheap ass degreaser and soak that ****
then burn the sucker again

i didn't think the pw 50 had an expansion chamber in the zorst hence why they clog up so bad

 

[my67xr]

the stock expansion chamber is pretty small and hides behind the side number plate
inside them, they have like a stainless steel mesh.
if the bike has ever run rich, then this mesh clogs up and restricts the flow.


in the picture below, the bottom/silver triangular part is an original PW50 expansion chamber, cut off from the header pipe.
the pipe/expansion chamber in the top of the picture, is a full custom one that i made for my sons PW50.

 

[my67xr]

and also when burning the carbon/oil out of the expansion chamber, you don't necessarily need a gas burner.
you could use a small wood fire, a wood/gas/coal/ barbeque, a Chiminea ( if the Wife/GF doesn't catch you)
just keep turning it, whenever you see the smoke coming out the pipe, starting to slow down
the expansion chamber will glow red hot while the stuff inside is burning, and burns off any on the paint on the outside.

blowing some air through it, from a gun and compressor helps immensely.
check my dodgy video's out in my PW50 thread.

 

[ricky_191]

Hi all, yeah I put it on a gas cooker because it's less trouble them starting a fire. No gf But I was burning it and puffed some air in it with a bike pump and flames were coming out like a jet engine

I painted it and put it all back together and it sounds hollow so that's good. But I tipped the bike over to fit the exhaust and there was oil in the head and it wrecked the plug. So I got kicked it till it all come out and then fitted a new plug. It started after about 4 kicks and run bad and then slowly got better with more starts till all the oil was gone. I'm guess it was from the crank case but could any one give me info with that ?

I took it for a run and it's a but better but still has that problem with breaking down at full revs. I'm going to drop the fuel and make a new batch up and see what that does. I think i made it a bit rich last time.

So I will let you all know how it goes. Any info with that oil would be good. Thanks

 

[my67xr]

the rings might be shot ?

have you had the head off yet ?
clean up the top of the piston, and see if it has a size on it, possibly oversize ?
a new piston/rings gudgeon pin, clips delivered in a week from japan, for under $20-
http://www.ebay.com.au/itm/YAMAHA-P...otorcycle_Parts_13&hash=item3a8663b342&_uhb=1

he has a few different sizes available too.

 

[my67xr]

another thing, have you tuned the carby yet ?

 

[ricky_191]

Ok , So to take the head off, I just undo the bolts at the front and pull it off ? And that is cheap so I might do it.

Also no , I haven't played with the carbi for a while. I don't really know what i'm doing with them. Is it like a pit bike one ? I don't really know what i'm doing on this little bike.

I lent it over and then there was oil in the head :/ it all cleaned out and burnt off but i'm guessing it's not good.

 

[my67xr]

yeah, it's very easy tyo do, takes 1 minute.

remove the 4x nuts holding the head on, remove the spark plug lead then slide the head, and head gasket off
get some thinners or petrol on a clean rag and clean the top of the piston
there will be a number stamped into it, eg std, .25, .50, .75 etc, this is the size of the bore.
so if it has a piston with .50, the cylinder has been bored out twice, making it .5mm bigger


if you take the exhaust off the bottom of the cylinder, the whole cylinder will slide off.
then you can check the condition of the bore and piston.

if it is scarred/scratched up a bit, it may require a rebore (costs around $50)
or you may be able to get away with a light sanding with W@D paper

the piston can be taken off the end of the conrod by unclipping the 2x retainer clips and sliding the gudgeon pin out.



i will see if i can get some pics for you
this is from my PW when i fitted the new piston



and this is after it has been bored/honed

 

[my67xr]

this is the old piston from my PW
with the top cleaned up, you can see there is the size stamped at the bottom
this had previously been bored out to it's first oversize



piston was pretty old, it had worn, and the sides of the piston were scarred
when fitted in the cylinder, it could move sideways a bit
the rings were worn out too, they only sat maybe 2mm out from the piston when held into the groove one one side.
they have lost their tension so weren't sealing properly against the sides of the bore.