Yamaha PW80 bogging / dying

Mini Dirt Bikes & Pit Bikes Forum

Help Support Mini Dirt Bikes & Pit Bikes Forum:

atomik boy

Well-Known Member
Joined
Nov 24, 2009
Messages
1,127
Reaction score
34
Location
near willowbank/rosewood qld
hey fellas,
gotta problem and hoping you guys could help out.
ok so we have a 2000 pw80 that wont stop dying :(
i can clean everything i can and it will run sort of ok but when i turn/hit a rock/bounce the bike it dies (loss of fuel?)
ive tried everything i can think of.
fully dissasembled and cleaned carby about 20 times (no joke)
tryed cleaning fuel tank.
fiddled with fuel/air ratios for days on end
just about ready to bin it :frustrated:
is there a way to disconnect the auto mixer for the oil? (ive heard that running pre mix may help)
thanks heaps guys,
james
 

zwebx

Well-Known Member
Joined
Sep 3, 2012
Messages
3,296
Reaction score
16
Location
Melbourne
gonna turf it :p turf it my way :)

have you done the float level sounds like the issue to me if you hit a bump and it dies...
 

zwebx

Well-Known Member
Joined
Sep 3, 2012
Messages
3,296
Reaction score
16
Location
Melbourne
gonna turf it :p turf it my way :)

have you done the float level sounds like the issue to me if you hit a bump and it dies...
if its not that... try putting the bike on either side before starting and then try to start it.. or overfill the gearbox oil a bit if that certainly helps it then you need new crank seals
 

my67xr

Miniriders Legend and Master Spanner Spinning Mode
Joined
Jul 29, 2010
Messages
11,982
Reaction score
77
Location
South Australia
^^ highly likely Damo.
they will still run usually though, just a bit restricted.
see my PW50 thread re cooking the oil/carbon out the expansion chamber.


they are well known for blocking up the pilot jet in the carby, and or the air gallery that feeds it too.



check the electrical connections are tight, and clean.
from the stator to the loom,
loom to coil,
coil earth points on the frame should be to clean bare metal.
and the connections to the throttle switch, in behind the top of the front fender.

is the start / run / off switch still working ok?
eg, cant rev the motor on the start setting ?
needs to be switched to run to ride it ?




is the air filter clean ?

is the restrictor gasket taken out of the exhaust?
undo the 2 front bolts that hold the exhaust flange to the head and check it it is still there.
it sits inside the exhaust gasket, like a washer.

to stop the oil flowing into the carby, when using premix
you can pull the oil tube off the carby and put a self tapper in the end of the hose.
then fit a rubber bung over the brass tube where the hose went to on the carby.
 
Last edited:

my67xr

Miniriders Legend and Master Spanner Spinning Mode
Joined
Jul 29, 2010
Messages
11,982
Reaction score
77
Location
South Australia
i wonder if your needle ( needle and seat) is gummed up ? and making it a bit sticky
so when you hit a bump when riding, it jambs shut?



i have just spent the last hour dismantling and rebuilding a Rover lawnmower carby, from a mower i just picked up off the side of the road.
it has the Suzuki 2 stroke engine, the Mikuni carby was covered in dirt/oil, and hardly visible.

i took it off, and pulled it apart and found the needle was stuck tight in the seat.
the previous owner obviously let it sit with premix in the fuel bowl after each time he mowed the lawn
the inside of the carbys' fuel bowl was coated in Gum, the yellowish leftovers from dried up fuel.
it took a bit of scrubbing to get it all off, the needle needed a wire brush to remove the gum buildup.
then i had to find the right size drill bit and clean out the gum built up in the seat.
the white plastic float was half yellow with gum, the carbys' pilot jet was totally blocked too.

i have it all back together now,
after cleaning out the tank, and adding a clean air filter and some fresh fuel
it kicked first pull off the starter, and idles now like a new one would.


if the jets and float were discoloured, make sure you give it a thorough clean with carby cleaner, let the parts soak if you can.
and clean them up with one of the tiny toothbrush wire brushs, bunnings and cheap $2 shop sell them.
at least if you ever have problems with the carby again, you will know what and where to look.

i tuned my mates PW about 6 weeks ago, it had always been painfull to start since he bought it.
after pulling his carby down i found the channel/port where the fuel flows through the pilot jet and into the main bore of the carby was gummed up a bit.
i have a 20 piece drill bit set from .3 mm - 1.2 mm and a pin drill.
i started with the small drill bit and gently turned it through the holes,
the dried up gum drops off like old yellowed clear car paints do.
you can see the flakes fall out as the bit goes though
with enough of this build up, eventually the jets block up, or loose flakes of it can block ports and gallerys.

i tuned his bike after i got the carby running nicely, and ended up fitting a bigger Pilot jet too
it needed a #17.5 in the Mikuni, instead of the factory fitted #15
mates bike has a high flowed airbox on it, which allows approx 3 times the air though it.
 

Latest posts

Top