Yamaha 1981 LB50 PH Chappy resurrection

Discussion in 'Japanese Mini's' started by twosmoke, Apr 28, 2015.

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  1. May 9, 2015 #21

    twosmoke

    twosmoke

    twosmoke

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    Ok, Thanks 67, That's funny, the 1st time I had it runnin, the taillite came on, it looked like it was the stop lite, prob cuz the stop switch that the brake lever actuates was shorting, I broke it moving the bike, I got another 1 from that Yamaha parts dealer you posted.
     
  2. May 9, 2015 #22

    twosmoke

    twosmoke

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    Hi my67xr,
    Well, I got another question, as usual, haha, I had the scoot runnin for awile yesterday, it seems to run better w/that bigger carb, doesn't stall w/the choke open nemore, but seems that it should rev higher? would the main jet clip position affect this? Now for the main question, the engine still smokes a lot even after runnin for so long, hasn't changed. Is there a chance that the oil pump is dumpin in too much oil @ that throttle setting? I noticed an adjustment on the pump cable, wondering if ya had any experience w/those Yamaha pumps metering adjustments? BTW, I'm using golden spectro synthetic racing oil, it says "less smoke" hahaha, yeah,rite! Thanks in advance-------twosmoke
     
  3. May 10, 2015 #23

    my67xr

    my67xr

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    You could try disconnecting the oil pump and trying it out to see if it smoke's less.
    Add some hose to the end of the hose and run it back up to the oil tank.
    Are you giving it a bit of a ride or just starting it up ?
    Sometime's they need a good ride to clear them out.

    Have you checked the exhaust pipe for oil/carbon ?
    Drop the pipe off at the barrel, unscrew the castle nut.
    If that is restricted then it won't rev too well.
     
  4. May 10, 2015 #24

    twosmoke

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    Hi 67, I did have it out in the street today, seemed to run ok but w/some tampering tho, so I took it back to the shop and got it revving nice @ WOT, let it idle down, then it stalled and wouldn't start again, this time it had wayyy less compression. said oh f@#k, I think I broke sumthing! so I took off the head, barrel, reeds and carb and found that one of the rings was glued to the piston w/carbon! as well as the xhaust port was 50% blocked too! douched both of em, put it all back 2gether, wayyy more compression, started rite up but wouldn't stay runnin w/the choke open, seemed like it was flooding out, so I took the carb apart and changed the clip for the jet to the 2nd from the top thinkin I could lean it out a lil, but got too late and I garaged it. now it's a challenge! so I'm gonna win cuz this lil ride is too much FUUUUNNNNN! so if ya got ne ideas, solutions or permanent fixes, I'm all ears! thanks 67,-------twosmoke
     
  5. May 10, 2015 #25

    my67xr

    my67xr

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    You'll need to retune the mixture screw to suit the way it's running now with more compression.
    Warm it up, and turn the idle speed screw in approx 1/2 a turn
    You want to raise the idle speed about 500 rpm higher than normal.
    Next, adjust the mixture screw in till it start's to stall then wind it back out slowly 1/4 turn at a time, let it settle for 10 seconds between each turn, till it reaches the highest / smoothest rpms
    Then turn the mixture screw back in 1/8 of a turn.
    Now drop the idle speed back to normal rpm's and try it out again.

    Take note of how many turns out the mixture screw is out when you are done tuning and let me know too.
    What main jet number is in it?

    Oh and do you have any pics for us yet?
     
    Last edited: May 10, 2015
  6. May 10, 2015 #26

    my67xr

    my67xr

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    Another cheap mod is you can shave the head to boost the compression.
    Take 1mm off it will give it a heap more., from about 6 to1 up to about 10 to 1.
    It'll need to be retuned but thats easy.
    You can diy the shave with a hard sanding block and some 80 grit dry sandpaper
    Keep the block square to the head
    When you've taken approx .75mm off, swap your paper to 180 grit to get rid of the 80 scratchs, then finish it with 320 wet and dry.
     
    Last edited: May 10, 2015
  7. May 10, 2015 #27

    twosmoke

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    Thanks 67, I don't know what make the carb is, no name, but a logo, it says TK enclosed by a circle? never saw 1 b4, so IDK what jets r in it. I figured it would work cuz it came off an old mx80. no need to mill the head cuz if I git this lil b@#$h runnin, imma gonna get a hi-comp head for the polini b/b kit from treatland 4 38$, but is that clip position ok? Also, Im runnin it w/out an air filter cuz I wanna get it runnin perfect and that a/f is a pain in the b@#ls to reinstall! could this be part of the problem? the oil inlet on the reed manifold seems to be pumpin a small amt of air out when I kick it hard, is this how this works, forcing air in2 the oil tank to pump oil out? IDK, but, like I said, it's a challenge now! Thanks again 67-------twosmoke
     
  8. May 10, 2015 #28

    my67xr

    my67xr

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    No air filter would make it run lean.
    The 2x small pipe's on the intake are both vacuum, the smaller one run's back to the fuel tap, larger barb is for the oil feed ( hose comes from the oil pump)

    [​IMG]


    If you are getting air coming back out of it then your reed valve's aren't closing.

    They might be bent, warped or broken

    [​IMG]
     
  9. May 10, 2015 #29

    twosmoke

    twosmoke

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    Thanks 67, I'll take em out and check em out and clean em if they need it, I also have the reeds from that mx80 2, if I need em, but I'm still unsure of that clip position, ne ideas? I also put the plug from the mx in it, cleaned and gapped it, it has a lil longer electrode, so I guess it's a lil hotter? gonna go tamper w/it now, thanks for the info,67-------twosmoke
     
  10. May 11, 2015 #30

    twosmoke

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    Well, I checked the reeds, they were perfect, but cleaned em up neway. I think the bigger tube that goes on the barb goes to the fuel tap and the smaller 1 comes from the pump. so I took the pump cover off and saw that there was slack in the cable @ idle, so I took out the slack w/the throttle closed. Is this correct? I also disconnected the line @ the manifold, held the throttle bout half open and kicked it several times and didn't see ne oil coming out? what's up w/that? so I put the line back on and started it and it didn't smoke @ all!, so I shut it down. 2 seconds later, gas came pourin outta the carb throat! WTF! took the plug out and kicked again a few times, and gas came flyin outta the cylinder! @ this point, IDK what's up! took the carb off, thinkin it had a stuck float, it didn't. took it all apart and blew it out, put it back on and couldn't even get it runnin! IDK what my next step is gonna be. could you or some1 pleeeeaaaase help? sorry for all the questions, and I still havn't figured out how to post pix, but it looks like now I'm gonna hafta learn! Thanks again,-------twosmoke
     
  11. May 11, 2015 #31

    my67xr

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    Sound's like something was in the needle and seat.
    Might need to take the bowl off and blow it out with compressed air.

    Is the float level right ?
    Any chance you bent the little centre tab on the float arm ?

    You might need to bleed the oil pump of air.
    To adjust the pump maybe look at this PW80 service manual (engine is basically the same as a Chappy), page 13 - http://www.yamaha-motor.com/assets/service/manuals/2005/LIT-11626-18-30_1089.pdf



    The needle clip being on the second slot from the top is just fine tuning of the main jet ( 1 step leaner than stock).
    You can only start moving it around after the carby is all set up and jetted correctly.
    Leave it on the middle clip for now,
    then once the carby is all good, you can do a spark plug chop and make adjustment's on the clip then
     
  12. May 11, 2015 #32

    twosmoke

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    Yeah 67, I did chk out the carb bowl and float valve, all good, and no, I don't think I bent the float arm, but IDK what make the carb is, so IDK what the float height should be, the logo on the body is a TK w/a circle round it. ne ideas? gout the pump, don't think it needs to be bled cuz it never ran outta oil! but Ill chk it neway, hope I didn't blow it, don't feel like spendin big $ on a new 1! 1st I squawk bout it smoking too much, now Im cryin bout no smoke @ all! go figure! Thanks again, 67-------twosmoke
     
  13. May 11, 2015 #33

    my67xr

    my67xr

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    This is one thing where pic's would help
     
  14. May 11, 2015 #34

    twosmoke

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    Yeah, I know, Im workin on it! r ya sure ya don't know what make that carb is? If I cant get it figured out, think I mite get a mikuni vm 18mm carb from treat 4 80$, whatcha think?-------twosmoke
     
  15. May 11, 2015 #35

    twosmoke

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    Hey 67, found the float height, its 20.8-22.8mm, mine is almost dead nuts @ 21mm, so I guess I didn't inadvertently bend the tang, so now what can it be? doesn't that float valve needle usually have a rubber tip? this 1 doesn't, wonder why?-------twosmoke
     
  16. May 11, 2015 #36

    my67xr

    my67xr

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    Most needle's from the needle and seat's have a either a rubber or viton tip, but there are some that are brass and some steel.
    Does it have a tapered pointy end on it ?

    [​IMG]
     
  17. May 11, 2015 #37

    twosmoke

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    Hi 67, yeah, it has a tapered point on the end, it looks almost xactly like that top xample, I wonder if its is stickin in the bore? whatcha think of that carb I was tellin ya bout from treatland, the mikuni vm 18mm ? thanks-------twosmoke
     
  18. May 11, 2015 #38

    my67xr

    my67xr

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    I don't know, i still haven't seen this bike or either carby
    YeAh go for the VM18, the VM16 isn't in stock anyway
    You might need to check the height's olr ask if you need the manifold to go with it.
     
  19. May 13, 2015 #39

    twosmoke

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    Well my67xr, I did it, I ordered a polini big bore kit, a hi-comp head, a gianelli pipe and a mikuni vm 18 carb from treatland today, I also ordered an oil pump from ebay too. I just got sick of ****in round w/all the different problems, ya know? Gonna start over w/a lil different pkg. I also swapped out the wheels w/mx 80 wheels, how do ya think this combo will perform? -------twosmoke
     
  20. May 13, 2015 #40

    my67xr

    my67xr

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    Sound's good what you've bought for it.
    It'll keep up with the modified late model, light weight scooter's easily with those mod's.
    Cant wait to see a video and see how it sound's too.

    What is making it hard to post pic's ?
    Are you using a PC, mobile phone or tablet to see this forum ?

    I just take pic's on my Samsung Galaxy S4 then upload it onto my PC, then you can add them by clicking on the insert image tab (3rd from right above the text box)
    Select from computer, then double click on the pic in your album, and select ok
    Then when you post the pic will come up here

    or it's also explained here too, the link for the thread is at the bottom of my post, #12 above
     

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