Fee05 Posted August 3, 2011 Share Posted August 3, 2011 I recently picked up a 1982 chappy that runs, barely. I am currently reading as much as the interwebs can tell me about carbs and rebuilding and where I can find parts. i stumbled on a fair amount of people who have straight replaced the stock card with a polini 19mm (i think) carb. question is, what do people think, is stock better or worse than a replacement as far as fit, jetting etc? Also on the side of the stock I have a vacuum hose missing, anyone know where it might connect to? I have checked parts fiches to no avail. It has the gas tie in, the air and the top all proper, but there is an extra hook-up next to gas in that is listed as vacuum and I have no idea where the hose attaches to. thanks for the help! Fee Link to comment Share on other sites More sharing options...
YPVS TONE Posted August 3, 2011 Share Posted August 3, 2011 Personally I would try and clean out the stock carb. The only problem with fitting aftermarket carbs is that you have to start from scratch getting the jetting right. If I remember right the 80cc chappy had a vacuum operated fuel tap so you might find a pipe running from the tap that connects to the carb so when the engine is stopped with the tap in the on position it shuts off the fuel supply. Link to comment Share on other sites More sharing options...
Fee05 Posted August 3, 2011 Author Share Posted August 3, 2011 yeah the fuel on/off/res switch hose leads in right next to this fitting. I was thinking it might be a tube back to the airbox to help regulate pressure in the carb? but really computers and hardware I am better at than carbs and how they work. trying to do my first carb clean/rebuild on this one and learning as I go. Link to comment Share on other sites More sharing options...
oudou Posted August 6, 2011 Share Posted August 6, 2011 that's not a ON/OFF/RES switch : ON and RES are letting fuel go down with a vaccum hose wich is going from carb pipe to fuel switch (the hose need to be quite strong). The PRI mode is for bypass this system and let go down fuel anytime. if you want photos, drawings, maintenance sheets, i've lot of theses (in french, but you can see with photos, i can help to translate a little ...) If you plan to mount another carb (useless without a cylinder kit like polini's one, or a old DT50 kit with some adaptations) phbg from Delortho are good, but they need a larger intake pipe (from polini for exemple) Link to comment Share on other sites More sharing options...
Fee05 Posted August 8, 2011 Author Share Posted August 8, 2011 if you have a pic with the extra vacuum hose (not gas feed) and where it should go that would be killer. It will actually turn out that the carb I had was junk, all the screws were stripped so no way to change anything. Found a used one on Ebay and going to Frankenstein the best parts of each together and make one that works. Just interested to see if I can block the extra lead marked as vacuum on the carb or if there is an actual connection in the air box. Thanks for the info about the PRI part of the switch, I was unsure what that was all about. and ok, dumb newbie question. the switch is it on the setting when the | is over it or when it is opposite? I was running with lever is over the setting, but wanted to be sure. Link to comment Share on other sites More sharing options...
oudou Posted August 9, 2011 Share Posted August 9, 2011 if you have a pic with the extra vacuum hose (not gas feed) and where it should go that would be killer. Hum, i'm not sure to understand well if this is that you want to see... there is only one vacuum hose, there : It will actually turn out that the carb I had was junk, all the screws were stripped so no way to change anything. Found a used one on Ebay and going to Frankenstein the best parts of each together and make one that works. Just interested to see if I can block the extra lead marked as vacuum on the carb or if there is an actual connection in the air box. On the carb, there isn't vacuum hose !? there is a overflow pipe (not on all models) and a venting pipe. But maybe i understanding wrong Thanks for the info about the PRI part of the switch, I was unsure what that was all about. and ok, dumb newbie question. the switch is it on the setting when the | is over it or when it is opposite? I was running with lever is over the setting, but wanted to be sure. That's over, right ! Link to comment Share on other sites More sharing options...
Fee05 Posted August 10, 2011 Author Share Posted August 10, 2011 ok so only because I for the life of me cannot figure out how to post a pic without an http link http://www.bikebandit.com/houseofmotorcycles/1982-yamaha-lb50pj/o/m7364#sch218172 should be the OEM parts fiche for the 82 LB50, on the carb, part number 37 is listed as vacuum hose and come off just in front of a gas line feed. No idea where it goes though. Link to comment Share on other sites More sharing options...
oudou Posted August 11, 2011 Share Posted August 11, 2011 ho yes, i see now... but in fact i never see this carb on any chappy here ! we can find in France mainly LB50IIA type 13f, or rarely 439, (two speed auto), 1f1 (two speed auto with moutain gear switch), 1f3 and rare 511 (80cc), rare 543... But all have the mikuni VM14 carb. I know some LB80 have a VM16 carb... SO i don't know the LB50 PJ... one with pedals (bike mode) and from japan ?? It's looking exactly like our 1f1 model, but with a little different carb, as i see the drawing on bikebandit.com VM14 have this look : There is also a hose at the same place (marked 11), but it's just a venting pipe (often without hose) for letting the float chamber without air pressure. Hose is here just in case of a fall, to let go fuel under the engine and not on hot surface like cylinder I think it's surely the same for your carb. Maybe you'll want get off float chamber, blow in this hose, and see if air going out from a little hole on top of float chamber, so you'll be sure this is a venting pipe Link to comment Share on other sites More sharing options...
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