hi guys im looking for a little help sorting the 21 im doing up at the moment. it wasnt running when i got it so i had the carbs off, the left hand one was all gummed up, so i cleaned it up the best i could then put them back on, with a little mucking about it ran, but at tickover nothing but cold air comes out of the left pipe, with a little rev it chucks out loads of white smoke, more revs and it clears. but the revs take there time to come down again even if i snap the throttle shut. iv had it out on the road and it flys with3/4 to full throttle, but lower down it couldnt beat sleep. any help would be very very much appreciated. im hopeless unless iv got a manual in front of me. thanks in advance miff87
Are the jet settings stock? Are you using the airbox? Make sure the filter is clean.
Check the settings against the table in the Technical Resources section. (Make sure use identify the correct carburettor for your bike - MC21 will either be TA22A or TA22B.)
It's very important to synchronise the carbs and to get the air screw settings correct for a smooth idle. You should also have a good, well charged battery, and start the motor with the lights turned off to reduce the drain on it.
Make sure the oil pump is set correctly as per the instructions on the Tech pages. _________________ Andy.
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You need to pull them apart, check the settings against Andy's spec chart, and then make sure that all the jets and orifices are spotlessly clean.
Pay attention to the needles and throttle slides (especially MC18 & 21). Look for signs of wear. These bikes are old now. many with a high mileage and I've seen quite a few that run bad because of dodgy needles and throttle slides.
Andy doesn't mention float heights, which although very important seems to get forgotten on many occasions. Start with 12mm float height, and if it's still a little foggy off the bottom then go to 12.5mm then 13mm.
I use an excellent carb cleaner from Permatex, doubled up with an ultrasonic cleaner (thanks Mike) to make sure that everythings nice and shiny.
However, my 'old' tools consist of a bunch of cotton buds, pipe cleaners and the frayed end on a throttle cable for poking down into the little holes.
Brasso on the cotton buds and pipe cleaners can bring things back into life, but don't be too savage as you only want to get rid of the poo, not the brass itself!
Leaky float needle valves can be restored if the damage is minor by fine valve grinding paste, mixed with oil on the end of a cotton bud, spun at low speed with a drill. Just cut enough to clean up the face and no more. Doesn't always work, but cleans up small corrosion. Then polish with Brasso.
Make sure that the rubber tip of the needle valve is clean and soft. I use contact cleaner and a soft rag to wipe away any deposits here. Gently now or you could knock the tip off which is a pain in the bum.
Synching the carbs is quite straight forward. and can be done with the carbs off the bike. Wind up the idle screw so that you can just sneak the unfluted end of a small (say 2mm) diameter drill bit under the slide. jiggle the adjuster screw around until both slides are equal. Then check at full opening that both slides hit the top at pretty much the same time. Concentrate on the small opening rather than the WOT setting.
All that's left is to make sure your air filter is clean and oiled and you should be good to go.
Sometime there's a problem with the small filter hidden under the airbox that the white thrree way plastic joint plugs into. It's a paper filter and if your bike washing technique is a bit too thorough then this can soak the filter and suffocate the air solenoid circuit. Easy way of checking is to unplug the joint and run the bike to see if any problems are resolved.
Bit of a long post this, but I think that's covered most of it.
hi andy,matt iv no idea if the bike is running stock settings but i will check.
the float needle valve was jamed in, and i had to pull it out with long nose pliers. i honestly dont think i got half the gunk out of all the orifices, as i only used cotton buds & compressed air to blow out any blockages. i also got the needle valve sliding in & out freely. iv bought a set of carbs off ebay last week but im still waiting on them to arrive. also the small fillter at the front matt was talking about wasnt attached. i was thinking about useing open fillters like k&ns are they more hassle? i stay in scotland dry days are few & far between thanks guys
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