my new/used Yamaha PW50 thread

[Blender]

the jets came with the xtra off correct sizing! lucky!! lol

reading back a bit i saw you were planning on doing the monoshock upgrade, is that still on the cards ?

 

[my67xr]

nah, wont be doing the monoshock for a while, i don't have the time.

still waiting for the Carbon Fibre reeds though, hopefully i'll get them in the next couple of days,
he is riding it Thursday afternoon at the MX track

 

[my67xr]

today i decided to check out what was making the clunking noises in the PW gearbox.
i pulled the engine out, and side cover off.
first thing i noticed was the circlip that holds the flywheel onto the clutch was sitting on the shaft loosly.
on closer inspection i noticed that the circlip groove in the driveshaft had been damaged and sheerd the outer edges off.
lucky i had a spare driveshaft to swap it with.







this is the shaft i used to replace it with, after i cleaned it up.






next thing i did was to spin the primary drive gear on the crankshaft, it has rubber dampers inside it.
they dampen the drive to the flywheel/clutch to make things run smooth.
but the inner section spun around over 200 degrees, normal movement is about 30 degrees.
i took it off the crank and pulled it apart, i found there were no rubbers whatsoever there.
lucky the spare engine has reasonable rubbers
i swapped them in and refitted it

old gear is on the bottom, note no rubber dampeners at all.





PAX Racing still haven't got back to me about their heavy duty clutch spring either.
so today i called into a spring manufacturer, not far from home
i told the owner what i wanted and he said he could make up some new ones for me, but would cost $50 for a few pairs.
i asked if he might have something i could modify and cut down to suit, something with a heavier tension.
we went out into the workshop and went through his assorted spring shelves.
he has a thousand different types as you could imagine.
we found a couple of suitable replacement springs that i could cut down and try.
he also showed me how to compare spring rates, i learnt something new there.
if you hook the new spring into the old spring and pull them apart, the weaker spring will open more than the heavier one, nice now i know !!!

i also asked him about making springs for my IT200, he said yeah no problem, he can make me some now progressive rate ones if i need them
i think i will be going back to him when i pull my IT forks apart

i also called into a bearing shop and picked up a new Viton crank seal for the PW50, it cost $3.50, Yamaha wants 16.95ea for them and they need to get them in ex sydney too.








and lastly i called into a Plastics shop,
i was looking for some Urethane, something to cut and use for the primary gear dampeners.
i'm not sure if it will be better than the rubbers, but they said it is oil and heat proof, so it's worth a try.
i found an old offcut in the cheap box, and it just so happens to be the correct size to suit the gear too !
it has a 40mm o/d, and a 23mm i/d what are the chances of that happening ???
the offcut cost me $3, i also asked if they had any fuel hose, he said they used to sell it but didn't have any stock left, but then he noticed some, it is 5mm id, and a pinky/red colour, it was a good price $1.50 per meter, so i grabbed a couple of meters just in case.







so the engine is all back together now, Cj and i started it this afternoon, and he did a few laps of the back yard
the engine is pretty quiet now, no metallic noises, it'll last a lot longer now.

 

[my67xr]

i've been trying to tune the peewee over the last couple of days, and haven't had much luck.
it is still so rich off idle, tried rejetting it, dropped the Pilot jet 2 sizes from standard, and the Main down 2 sizes too.
and found it to be not much better...


all i have changed since it was running sweet is the expansion chamber.
so i took it off and may have to revise my design.
i have cut the original OEM one expansion chamber apart and done a bit of panel beating to get it back to original shape as it was fairly knocked around and squashed in quite a few areas.
and a couple of little mods to it while i had it open.


you can see the dents in it here and there, some of them were 5mm - 6mm deep.







and even though i burnt out the carbon and oil not so long ago, you can see what i had missed
inside the tube was almost 2mm thick still and those 2 small holes towards the front of the tube were almost blocked closed !




after a bit of panel beating it is starting to regain its' original shape






i was pretty happy with it now, so gave it a degrease and sand blast, ready to weld it back together.
i shortened the tube down the middle approx 25mm.








and then welded it back together and resprayed it with high temp black.





the pipe is back on now and i started it up, wow there is a huge difference in the way it is running, and also to the sound.
it is now an angry, crisp, and tinny 2 stroke again
it has decent throttle response, and revs out sweet.
this is the best it has ever run i think, i will post up a quick video once i refit the seat/plastics

 

[Blender]

Good to hear Craig, how did the south coast MX ride go ?

and u gotta love that 2 stroke sound

 

[my67xr]

no ride that night, due to the running issues.


i had cj take it around the backyard this afternoon, to see how it went,
still bogs off idle, tried rejetting/adjusting it but can't sort it.
the carby is 33 years old now i guess, so it could use a few new parts, including the needle too
but i reckon at the least the Needle Jet needs to be replaced, i noticed it was an oval shape, and i reworked it to try and fix it, but i guess it is past it, and is still letting too much fuel in.

i might even look at a carby upgrade, go up to a 16mm, or possibly an 18mm ?
depends what i find in my price range.

i saw another Mikuni at the wreckers the other week, it is a clamp on same as the PW50 use.
but i need to measure the i/d of mine and compare it to the one he had, it was off a Suzuki FR70, so may be jetted bigger too ?

the other option is to find another Chappy carby, and rejet that to suit, they have the mixture screw and idle sped screw on the same side

 

[my67xr]

i picked up another used carby yesterday,
it has the same clamp on mounting, same size air filter neck, and is basically the same as the original PW50 Mikuni VM12,
the new carby is a Mikuni VM14 though, off a Suzuki FR70 step through scooter.
the Pilot Circuit is jetted down a lot, and the Main jet is about 7 higher than the standard PW carb.



it was in poor condition when i found it,(wish i got pics now) was pretty dirty on the outside, had a seized slide,
blocked ports, blocked jets, blocked needle and seat, and to top it off, inside was full of white fluffy corrosion.
so i gave it a soak in some 2 stroke fuel with a bit of thinners in it.
i undid the top and sprayed some Inox down onto the slide, and up from the bore of the carby,
it took a bit of work to get the slide out, and i found it is pretty clean, no scars from sliding up and down etc.
next i stripped it down to a bare body, and used a wire brush to clean out what i could, just the little toothbrush type.
then i fired up my compressor and got my sand blaster onto the corrosion, it made short work of it.
i blew the compressed air through all the ports to make sure they were clear, and then cleaned up the jets, needle, needle and seat, and screws etc.
i haven't hooked up the choke yet, so have just blocked it for the time being.
i needed to fit a 45° bend to the top of the carby to take up the slack in the cable, due to this carby having a straight up cable adjuster in the top of it.

i hooked up the fuel line and gave it a few kicks, and got nothing, so sprayed some degreaser down the carby throat.
it fired first kick, so i bumped up the idle speed, and richened the mixture screw.
2 more kicks and it fired and ran.
i felt a little hesitation off idle, so i pulled the carby off, and fitted a #20 Pilot jet, original was a #15.
the standard PW50 Pilot jet is a #40.
it is a bit better with the #20, so i'll try another couple of bigger jets and see how it goes.
at least these jets are easy to get, Show and Go keep them in stock,
they are the Mikuni VM22 style, the same jets are also used in my IT200, DS80 and the Chappy, so i have a couple of spares.

here is a pic of the carby,

 

[motorman]

Sounds like the hard work is slowly paying off!!

I can't believe how nice that pipe came up.

Jetting does my head in. You need to have so much patience. lol

 

[my67xr]

thanks nick,
yeah it look's a lot different now being straight, clean and painted up.
i'm looking for another cheap expansion chamber to cut up and modify to suit.

the worst part is i can't do a Plug chop at home, to check how it's running and then tweek the Main Jetting, the back yard isn't long enough.
if Cj flattens it off the line, it only just gets into powerband, then he needs to hit the brakes to stop before he hits the back fence.


cheers, craig

 

[motorman]

Difference is night and day.

Yeah I have the same problem jetting my bike at home. The LXR's are bloody loud. lol.

That's next on my hit list after I get the forks and shock back. Man I gotta start a build thread. This is going to be the site's race bike.

 

[my67xr]

i ended up making a little knock in tip for the muffler a couple of weeks ago, so i can run it at home a bit more and not make too much noise.
it makes the outlet under half the size, and doesn't seem to restrict it that much either.

i have the PW running pretty good now,
ended up drilling out the Pilot Jet into a #40
and i have dropped the Main jet down from the original #76 to a #67.5.
i might try a #65 at some stage too, just so i have something to compare it to

Cj did a few runs down the back today,
the bike is now getting a bit loose across the lawn under full power, i must be doing something right lol

 

[my67xr]

here are a couple of pics of my silencer tip









i made up one new H/d Clutch spring today (left bottom), 1 to go.
it'll sound like a PW50 with a High Stall Convertor, lol





and i don't think i've posted a pic of the bike with the Miniriders stickers on it yet too?

 

[my67xr]

here are a couple of pics showing how it currently looks,

 

[my67xr]

South Coast MX Club has another ride day this Sunday too,
but we are heading out to a 3rd Birthday party for my Niece, damn !

 

[timeeh]

Awesome work again, C.J must be stoked

 

[motorman]

Talk about clean!!!!!!!!!!!!!!

Loving the Miniriders Stickers as well.

 

[my67xr]

thanks Timeeh and Nick,

yeah he really is stoked with his PeeWee.
we have talked about respraying a couple of parts on it too, to make it look better again.
i have to start a Paypal dispute with that German seller of the Carbon Fiber Reeds, still haven't received them !


i spotted some new release parts coming out this month for the PW50 too.
they have made up a 12hp kit, to make them more competetive !
65.5cc, 47.5mm bore, new high comp head and piston, a new design 4 petal reed valve, new design Expansion Chamber, new Inner Rotor Ignition kit, new adjustable Rear Shocks
i might use some of their ideas to make up something for our PW50, just my own version of them ?

oh, and i found a couple of PW's with a monoshock set up too, here is a PAX Racing modified bike,
pity they never got back to me about the heavier clutch springs !
but then i can make my own cheaper anyway!

 

[my67xr]

^^ how nice is that race pipe ?

i dunno if i'm keen on this look ?

 

[my67xr]

Woohoo!!,
i made it into the Level 100 club too !

 

[GooseMan]

If you put that in a showroom Craig it would not look out of place at all.