Tobywatson
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jaffa90
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Teflon-Mike
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 Posted: 11:57 - 21 Apr 2018  Post subject: Re: Suzuki gn125 choke and smoke issues |
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| Tobywatson wrote: | Changed the carb and spark plug. |
Why?
If it ent broke, dont fix it.. so what was broke to suggest you change the carburettor.. more, DID you change the carburettor.. as in replace one carburettor for a completely different carburettor.. if so, still first 'whby' and second, what? Was it another GN carburettor? Was it new or used? Was it for the same year and model GN? Did you use all new gaskets?
There is a lot more to be asked, than what you did here...
Carburettors need good seal to work; they operate on the pitot-principle, air sucked through a tube, causes a vacuum in a tube at 90-deg to the flow of air.... like a flute or blowing over the top of a milk-bottle..... simple principle... complicated execution..... carburettor basically just mixes fuel into the air going into the engine to make a mixture that will burn... too much fuel, 'rich-mix' then the plug cokes up.... looks rather like a plug thats oiled from burning oil... check the photo's in the haynes very carefully! too little fuel... 'weak' mix... engine possibly wont run, or if it does, pinks and hestitates, doesn't like accelerating, and in more dire cases, burns out valves or melts pistons.... mixture all controlled by the size of the pipes, or 'jets' compared to the main tube, and the speed of air-flow through it..... like I said, complicated execution....
CHOKE... enriches the basic mixture... old fasioned way of doing this, was litterally to 'choke' the flow of air into the carburettor... putting a hand or a flap over the mouth of the carb... that caused a pressure drop from the suck made in the engine, so more fuel got sucked up the jet, for the less air being drawn through the carb..... extra fuel, a rich mixture, isn't good for power or economy, but it is good when the engine is cold, and the fuel not so want to 'evaporate' and burn. Hence you choke an engine on start up, and turn off the choke when warm....
Fact you needed choke, suggests that there's a good chance that the carburation is screwed, and it needs a rich mix just to run at all.... this, would suggest, you have re-used old gaskets or omoitted gaskets, or torn the rubber carb-mount, so that the engine is sucking, but when it gets to the carb, its easier to suck through the cracks, than through the carb, and the mixture is hence 'weak'... and turning on the choke, compensates, and the engine runs.... and soots up the plug..... make sense?
Go back to basics, and revisit what YOU have done, and why... in this sort of instance its nearly always operator error, and carburettors are about the most intricate delicate little device on an engine, that really dont like being effed with by folk that dont really know what they are about.... they are also usually one of the most reliable devices that just dont need to be effed with by any-one all that often... yet ARE!!!! 'cos lore says so, and its less scary than looking at oily bits to fix stuff...
LIKE, doing a propper basic service, and adjusting the tappets, that lurk in an oily bit in the top of the engine, and are far more likely to go out of tolerance and need fiddling with... regularly... but often aren't!
In short... we cant diagnose your problems by voodoo..... you have the bike infront of you, you have the spanners... and you have already done stuff... start there, in what you have done, and probably not done so brilliantly.... then look at what you HAVEN'T done, as in the list of stuff in the routine-maintenance-list..... do that... base line the issue, so you are working from a known start point of what 'should' be good..... THEN go from there.
IF it is a carburated GN..... by my reckoning Suzuki';s official importers haven't sold one of them here in the UK for at least a decade..... there have been a fair few unofficially imported from mediteranian markets, I believe they are/were still made in Portugal long past them being dropped from UK brochures..... this may offer more ops for consternation, BUT odds is its an old bike, worse an old learner bike, its likely not been best looked after, and its likely had umpety fiddle-fingers owners not knowing what they were about trying to 'fix' stuff.... so the 'base line' could be way off what we'd hope or expect... and YES it COULD be that the motor's dragging oil, down worn valve guides past hard old stem-seals, and or past worn out piston rings in a worn out cylinder bore... BUT... we are guessing... we dont have bike infront of us, we cant see obviouse signs, we dont know the historyt, and we dont even know why you started messing with the carb to start with.... so start at the beginning....
If its any solace, fact that it runs, suggests bore and rings, guides and seals are probably not 'that bad'.... but on older learner bike, usually thrashed by wanna-go--- I would say faster. but no, just wanna go, I think is probably a high enough ambition! Learners or NOT (I ride 125s on full licence, quite a few do; esp for cheap commuting) Those little motors, do wear out, and nature of the beast isn't inclined to imortality.... even the legendary CG is LOW maintenance not NO maintenance.... but still.... on an older learner, odds is that the motor is tired, and at some point probably will need an overhaul by way of new guides and stem seals (or a new head) and a rebore and rings (if not new cylinder/piston).. question is how far away is that point... or is it actually behind you! B-U-T.... not really the big issue at the moment.... need to back-track your mechanics a bit and try see why what you done hasn't worked as well as hoped.... THEN maybe, tackle other things......
But... there's your start point... look at what you done, and why, and try and get the thing back to book, as far as soing all the stuff book says should be done as 'routine'..... THEN you canb start worrying what it dont do as book says it should, identify real problems, and try sort them. Its all pretty simple, 'logic-puzzle' stuff, not rocket-science, BUT it is laboriouse, and there's no short cuts or quick fixes, using voodoo, I'm afraid.
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
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Tobywatson
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Joined: 20 Apr 2018
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