PW 50 carbie adjustment

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ricky_191

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Hi all. I have a 80's peewee I think but it's been running a bit sick under load. So I went to adjust the carbie and found what I think is the stock settings of about 2 turns out on the mixture and then turn that in or out till it idles really high and then fix it with the idle screw.

Any way after 30min I have cut my ankle and got fuel all in my cut and still have go no where :/

So can some one tell me what is going on and how I fix this. I'm going to pull the carbie off and clean it out and then try what ever some one post here.

If it helps there is a fair bit of fuel coming out of the over flow :/ I'm also running pre mix in the tank at about 35/1 and a modded pit bike air filter , no start run switch only a kill switch.

Any help would be good :) thanks
 
undo the top screw and pull the top off with the 2x slides attatched out.


remove the fuel bowl, and the then the float and needle and seat
blow out where the needle and seat come from, with compressed air.
and check that the float is not damaged or full of fuel, (shake it and listen)


now you need to clean the pilot jet out,
unscrew it and have a look for the size on it and note it down
poke some wire though it and check for any gum deposits (clear flakes)
now look through the hole where the pilot jet screws into, you should see light where it goes into the carbys' bore.
poke some wire through there too, sometimes gum can line the hole and close it up a little.


next remove the main jet, write down what the number is on it, and then clean it out.


then the brass threaded part where the main jet screws into needs to be removed.
push the jet tube up through the middle of the carby and remove it.

this is what the jet tube looks like, a filthy example at that.
clean it up well, inside and out, making sure all the holes are open and clean






now look into where it come from in the carby main body,
check that it is clean inside there too.


next pull the mixture screw out and clean the pointed end.


now with both jets and the mixture screw out,
blow some compressed air into the 2 holes on the filter side of the carby,
make sure you can feel air coming out underneath where the jets screw into.


remove the slide from the top of the carby and slide the needle out, check which slot the clip is located in.
remove the clip and fit it to the 2nd slot down

ok, once you are happy it's all clean, put it all back together again
turn the mixture screw in until it stops, then turn it back out 1.75 full turns

now start the bike up and check that the bike revs nicely/crisp when you blip the throttle.
if it doesn't then the problem is still in the Pilot circuit.
if it revs nice, then you can raise the idle speed to get it running at about 1800 rpm

now adjust the mixture screw (a little at a time) until you get the highest/smoothest revs
take note of how many turns out it is

now you can drop the idle speed back down to have nice idle (around 1000 rpm)

take the bike for a run and see how it goes, and post up what your settings were,
eg 2x jet sizes, needle clip slot, and mixture screw turns out
 
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I pulled it apart. There was only one jet in there o_0 There is a short one that has no holes and then next to it there is a hole about 1.cm deep. lol would there be a jet missing out of there ?

It used to run fine with no changes :/ I'm lost
 
the pilot jet is in the smaller hole, it is tiny
use a small flat screwdriver to get it out.
 
Yeah there is a small kinda flat one and then next to that there is a hole. Should there be two jets in the bottom or ?

I filled it up with some new fuel and now it won't even start :/ And when it did start the throttle was flat out and it kinda sounded like it was only like half throttle. I'm really stuck with this now
 
this is a PW50 Pilot jet, bottom left,
pictured with 3 Main jets

 
ok , I think i'm missing a pilot jet :/ But why would it run with out it and then have problems ?
 
try and get a decent pic of the pilot jet hole in the carby for me
the the slot/head of the pilot jet sits about 8mm down in the hole
 
running it with the Pilot jet sitting in the fuel bowl wont help it much, lol


here's a link to a new china reed block, reeds (may need gaskets too)
http://www.ebay.com.au/itm/Yamaha-P...orcycle_Parts_Accessories&hash=item4abf42de4c

brand new carby Miniky (Mikuni copy) $25 inc delivery
http://www.ebay.com.au/itm/PW50-PW-..._Parts_Accessories&hash=item25812f052d&_uhb=1

and a complete PW50 gasket set for $18 inc delivery
http://www.ebay.com.au/itm/81-87-YA..._Parts_Accessories&hash=item1e7a0fd548&_uhb=1
 
I got it started today and it was running like there was no throttle and it wouldn't rev that much even though I was holding it flat. Also there is fuel pissing out the overflow some times. I think the float slider thing is getting stuck :/

It could be the carbie settings also .. i'm so stuck with this.
 
was there anything in the needle and seat area ?
if there was dirt etc on the tip of the needle then it will cause it to flood and come out the overflow


does it have a metal float or plastic ?
and does it have a metal tab that contacts the tip of the needle ?
can you post up a few pics of it ?
 
this pic is of a DS80 carby from underneath,
the seat, for the needle and seat is at the bottom, the brass part.
are your fuel lines good, not falling apart ?
sometimes bit of rubber come off and get stuck inside the carby

 
I have a plastic float and a rubber tip needle. the top of the needle looks worn or broken off :/

I think the carbie settings are just really off. It's like it's running extremely rich. I did 1 1/4 - 1 3/4 on the mix screw but how far in or out should I turn the idle screw ? just so I get a good base to start it.

I have started it twice but it seems really rich. When I pulled the spark plug , it was really wet and so was inside of the head. Also some times it blows fuel back out the carbie, just small amounts.
 
with the rubber tip being worn, it wont seal off properly in the seat.
so the carby will continually flood.
pieces of that rubber will come off and get stuck in you jets causing you more issues too.


do you have any other old Mikuni's sitting around as parts carbys ?
you might be able to use the needle from one of them if it is the same length/diameter ?

if not, or they aren't the same size, then you will need to buy a new needle but they are expensive buying them seperately.
http://www.ebay.com.au/itm/Yamaha-D..._Parts_Accessories&hash=item3f298ee540&_uhb=1

you are probably better off just buying the complete china carby i linked to before
 
Yeah I do have a few spares, I will have a look. Thanks for your help. Do you want to buy a peewee ??
 
I found a spare carbie and the needle looks a bit thicker and has a different clip on it :( I might just get that carbie :( why is such a little part so much :/
 
here is a genuine Yamaha PW50 needle from US, $15 plus post

do you have a Yamaha dealer close to you ?



the other thing that can make them run rich is the choke,
you need to back off the adjustment for the choke cable a bit near the carby, so the choke slide closes properly
 
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