m82s Posted September 10, 2012 Author Report Share Posted September 10, 2012 Thanks again grib. i had read that a while back but forgot the rule also: usually in conversions an increase in the Carburetor size also requires an increase in the main jet size of about 10 % for each 1 mm increase in the choke size, without changing the other setting parts i have the 125 main jet as per bike spec. will it 'need' to be increased in the long run? Taking into account your above post, i shouldnt think it would make too much of an issue at idle? thanks again grib Quote Link to comment Share on other sites More sharing options...
grib Posted September 10, 2012 Report Share Posted September 10, 2012 The main jet doesn't affect the idle at all but yes you should check it when you have got the bike running especially if you intend doing any trials with road work in them. The 28mm carb is about 26% bigger than the 26mm one but at idle when it is virtually closed the difference will be very small which is why I suggested you may need a 40 pilot but a 36 might be fine. Quote Link to comment Share on other sites More sharing options...
m82s Posted September 15, 2012 Author Report Share Posted September 15, 2012 Hi again all, im back with no great news again... Totally stripped and cleaned my new carb for the sake of it again just to see if there is anything that i had missed the first and second time! or if anything had dislodged etc but nothing. New 36 and 40 pilot jets making no real difference 125 main jet all jets are new and clear what i have noticed is i dont seem to have this 1mm of play in the throttle ive read about? how do i do this please if its needed? The bike has new fuel etc and all seems to be operating as it should. It will fire up and with throttle stay alive but no throttle and it dies. I have tried air screw from 1/4 turn to 3 turns and not much joy. It will run with throttle open a little with about 1.5 turns as grib said but with choke only. Bike will not start when warm without choke either. I think it might be leaning towards something else now aswell. The spark plug on spec says champion c6ycc and cross reference this to ngk gives BCP7ES although this plug is massively longer and will not slide in below the radiator cowl. The plug i have is another stubby ngk but is wrong if my cross reference above is right. Obviously the depth matters too but this plug has always worked since i got the bike and isnt fowled or discoloured at all. all other connections etc all look good. totally at a loss now again Quote Link to comment Share on other sites More sharing options...
m82s Posted September 24, 2012 Author Report Share Posted September 24, 2012 Hi again all. I have not had time to do anything with the bike due to work and weather but hope to do so tonight. Please can anyone shed any light for me on the last post or so that i put up as im totally lost now and need to get out on this bike before the weather continues to make it game over for the year! i eargerly await your most appreciated advice! kind regards, martin Quote Link to comment Share on other sites More sharing options...
grib Posted September 24, 2012 Report Share Posted September 24, 2012 Its difficult without seeing the bike. If it dies unless you open the throttle then wind the throttle stop screw in until it doesn't. If it won't run at all without the choke then there could be a blockage in the pilot system somewhere. Has your pilot screw got a spring, a washer, and an o ring on it? Is it a PHBH or a PHBL and does it have a pilot air screw or a pilot fuel screw? Quote Link to comment Share on other sites More sharing options...
m82s Posted September 24, 2012 Author Report Share Posted September 24, 2012 (edited) hi grib, thanks again for your input. yes agreed, hard to say over a keyboard! its a phbh28 but i also have a phbh 26 with a knacked jet in so i need to get that out before i can revert to a 26 carb. Ill wind the throttle screw in and give that a go. Yes it has spring and, o-ring and washer and is all brand new so to speak. never been ridden barring around a yard once or twice before i got it. im pretty sure there is no blockage as i had the carb apart three times and had airline on it etc. all jets are new and everything appears to operate as it should so to speak. im putting it down to the carb settings at the minute as at one point it did seem to idle fine for 15 mins and i have not really touched anything. The exhaust is pretty oily and it sounds fairly raspy. I currently have the back box hanging and has been draining of oil etc for the last week. Im pretty sure the rest of the exhaust needs flushing too and i need a new rubber o-ring between centre pipe (all in one front and middle) as this is pretty much non existant and leaks like hell before the backbox. om sure this wouldnt stop the bike idleing? im ordering a new rubber asap though. The air screw is on engine side rather than airbox side and large screw is fuel? it controls float height. Edited September 24, 2012 by m82s Quote Link to comment Share on other sites More sharing options...
grib Posted September 24, 2012 Report Share Posted September 24, 2012 If the pilot screw is on the engine side of the carb rather than the airbox side then it is a fuel screw not an air screw - screw it in to weaken the idle mixture and out to make it richer. the big screw in the centre is the throttle stop - all it does is hold the throttle slide open a little as if you were holding the throttle open. You need to take the carb to bits to change the float height. Reading and understanding the tuning guide will be the easiest way to sort out your carb. Quote Link to comment Share on other sites More sharing options...
m82s Posted September 24, 2012 Author Report Share Posted September 24, 2012 (edited) Cheers grib!! i bet you have just solved my problem... i have been assuming the small screw was an air screw! ill report back but hopefully this will solve my mysery. ill research (ask bill pye) what the original carb should be. I believe its a phbh26 xx model but unsure as to what air and fuel screws that would of had. fingers crossed with the 28 carb tomorrow! edit: original was phbh26 NS Edited September 24, 2012 by m82s Quote Link to comment Share on other sites More sharing options...
m82s Posted September 26, 2012 Author Report Share Posted September 26, 2012 Spoken to bill pye and he tells me that a 28 carb will not run on a 212 engine....pants! that stuffed me so in the van it goes and a 100 mile round trip I think coming up. Trying to get a 26 carb on fleebay but non available at a cheap price. Have to sell my two carbs I reckon. Is there any difference in a phbh 26 bs, cs and ns? I have a cs kicking around and the spec of bike says ns. An ns looks roughly the same with mixture screw on engine side etc. Not riding a bit then now Quote Link to comment Share on other sites More sharing options...
bambam_n_chunx Posted February 22, 2017 Report Share Posted February 22, 2017 Also having trouble with my roo carb, the bike came in bits with carb missing. Ive had no luck finding out what carb and jets i need but you seem to know a little. any chance you could shed some light on it Quote Link to comment Share on other sites More sharing options...
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