nsr 125 starting/running issues

[paul651975]

hi all, i have a problem with my 51 nsr. i have deresticted it following alains's guide. now have a few issues with it. i have changed my jets a advised but when i went to set my needle on the second notch from the top found it was actually all ready different from standard and in the fourth notch down and this is the only place i can get the bike to run, but if I'm riding with the rev's about 5000rpm the bike sounds like its spluttering altho seem's to be running OK, and Clear's when i open the throttle up, also when just started the bike up when i get to about 5000rpm it splutters until i get to 7000rpm and then fine, once this has happened the bike run's fine until next time its started. also bike won't run on the choke as sounds like its flooding and i have had the choke out and wound the adjustment right down, now this is better but still won't run with choke out. have spoke to a guy at dellorto and he recommends for the jets i have fitted (main 138 , slow (idle) 42 , power 65) that i should have a needle sized x84 fitted, will this cure my problems? if so what setting should i put it on?

[chillpill]

check the colour of the plug mate

also give your carb a clean , a bit of dirt could of found its way into one of the jets while you were changing the jets

does it lag power ? ie it splutters then comes on the power , because that would mean its running lean, moving the needle from the fourth notch from the top to the second leans the mixture d

any mods to the bike ?

was the bike running ok before you changed the carb settings ?

[paul651975]

checked the plug and it look's ok. also cleaned the carb and no sign of dirt. no always had the problem of the stuttering, yes it seem's to be when your acclerating, stutters and then pick's up. but wouldn't moving it to the second notch make it leaner, and also already tried this and bike dies when you acclerate

[paul651975]

once you have got past the stutter the first time as you go up the gearbox all seems ok then, ie could stop the pull away and all fine. no other mod's as far as i'm aware apart from the derestriction mod's that is

[fuzz]

The needle position alters the fuel mixture in the mid range. The lower down the needle the clip is placed, the richer the mixture gets at 25-75% throttle. You need to find out whether it's running lean or rich. From what you decribe originally it sounds rich, as running it lean with the choke on would help, not worsen the problem. Does it get worse as the engine warms? If so, it's definately showing signs of running rich.

What were your original jet sizes? You don't need to rejet when derestricting every time, it depends on if it was jetted for the restriction, or whether they simply left that alone and used the inlet plate/exhaust restrictions only. It's been that long ago that I can't remember what jet sizes I used on mine. Exactly what did you do to derestrict it?

Are you warming it up well before ragging it? 2-strokes do stutter when cold at around 5-7k. Once they're warmed up a little though they'll go through the rev range quite happy. Trying to force it to the redline when cold is a good way to seize a piston.
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Bikes: '99 NSR125R, '00 SV650S, K1 GSX-R600, '97 CB500, K3 SV1000S, '16 VFR800

[paul651975]

wasn't sure what size the jets were, so just fitted the jets recommended in alains guide. yes always warm the bike up before i go anywhere. once i get over thereally bad stutter the bike just sounds like its spluttering when travelling at about 5000rpm if you open the throttle slightly it picks up fine and sounds alot better. so if i put the needle clip on the second setting that should do it then and sort out the choke problem?

and to derestrict the bike i removed the inlet and exhaust restrictors, upjetted. new cdi and r'c controller ci626 & tv-78

[paul651975]

also if i start the bike from cold and then put choke on the engine dies

[alains]

i think you've got an air leak or a wrong floats level . other question when you take off your carb , do you take off the reed block ? if yes , do you put back the white plastic block in the reeds ?
with this jetting , the needle must be on the 2nd notch from top . if you set lower , it goes richer but the mixture spray goes coarser and the rate goes down . i suggest you take off your carb and reeds block , check if your plastic block is still inside , then refit with sealing pasta on each contact surface . in the carb check the fuel level in the floats chamber , then i think you'll be ok
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the worst day fishing is better than the best day working

[paul651975]

yes the white plastic block is in the reed assembly, will check the float level.

many thanks for all the advice

[paul651975]

had the carb and reed block off, white plastic bit there, refitted and sealed up. checked float level and that ok. changed to second notch on needle, now can't get bike to tick over at all, and when riding it splutters at about 5000-7000rpm when accelerating (no speed increase) then pick's up, but if riding holding at 5000-7000rpm the spluttering not to bad and does go if you slightly open the throttle (well for a bit until you stop accelerating and then starts again).

[alains]

what kind of plug have you got ?
did you check the servo pulley sequence
- key on , initilazing LO
- start and idle under 2000 HI
- over 2000 until 7000 LO
- over 7000 HI
what can change timming ?
- blocked cables , dismount pulley side & WD40 making them working by hand and if you feel some hard points your valves are stocked by coke.
- valves full of coke
- faulty RC/valves control unit or red/white wire coming from the CDI and going to the RC/control unit on the 3 wires connector (check terminals for loose contact)
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the worst day fishing is better than the best day working

[paul651975]

already checked the valve timing and that all appears ok. my plug is a ngk br9ecs. now to me it seem's to be running worse since i've moved the clip to the second notch.

[alains]

now fit a NGK BR9EIX or BR9EG , champion QN84 , denso IW27
BR9ECS is bull shit
____________________
the worst day fishing is better than the best day working

[paul651975]

ok will try that but will that sort out all the problem's?

[alains]

i hope so
____________________
the worst day fishing is better than the best day working

[paul651975]

partial success, fitted a new plug ngk br9eg and now bike running loads better, the only problem left now is that when starting with the choke the bike starts but won't run with the choke out to warm the bike up, now the adjustment is on the minimum and it sounds like its flooding.

[alains]

you may have a choke which does not close properly when out . the bottom of the choke piston close a hole , but with stiff cable , tired spring , cable sharp bend , dirty piston it wont close causing this and making the engine dying when warm . do this test :
- set your pilot screw (the smallest) at 2 3/4 turns out
- start bike on choke without acceleration
- let it running until the engine begin to stuff
- apply a bit of acceleration and take choke off
- stay like this for 1 mn then release handle
- set idle screw (the biggest with spring) at 1500 rpm
- if the engine dies , push firmly on the head of the choke level and start again (without choke)
- if the problem has desappeared , you may dismount all the choke and replace eventually cable , piston , spring
all spares avaiable at https://www.dellorto.co.uk
____________________
the worst day fishing is better than the best day working