Help with a chinese 50cc scooter - Page 2

martinwest · 23rd February 2016, 16:39

Quote:

Originally Posted by Sprinter

did it run with the old carb?

Just asking because the needles might be at a different height. Try raising it by one notch and see if it makes a difference.

No I tried moving the needle in the old carb and it stayed the same or got worse

Mr Bone · 23rd February 2016, 18:16

Joking about bonfires aside

, check the main jet is the same size as the one in the old carb. If not swap them, often a 2 stroke will bog down if over fuelled. Have you tried riding it, does it pick up as the trottle is rolled off from fully open.

Used to tune Kawasaki 400 triples for proddy racing, I know how fickle they can be.

clf · 23rd February 2016, 18:42

Quote:

Originally Posted by martinwest

def not a collapse or air leak I have checked the intake and re-sealed gaskets etc the choke is a different matter its auto choke but again I have checked that.
I wish I could afford a old 1970's jap bike for him at least I could fix it with my eyes closed

Does it matter warm or cold? I had an issue with an auto choke on a Toyota, when it was warm. It seemed to stay on permanently. Loss of power when warm, struggling to accelerate. Unplugging it helped until I put another carb onto it. It was easier to replace the carb than the choke mechanism lol.

Avulon · 24th February 2016, 14:36

given that it worked properly the one time the tacho worked.... disconnect the (probably faulty) tacho completely. any feed from the coil for the tacho disconnect at the coil to ensure you rule out the wiring loom. The wiring on these things is really poor quality.

martinwest · 24th February 2016, 15:30

Mr Bone
don't know what size the jets are they are not marked and no I haven't ridden it due to no MOT and yes back off on the throttle and it is back to normal. I took the air filter off and as soon as you give it full throttle it spits fuel back out of the carb so it is starving itself

Avulon
I have tried it today but can only disconnect at the rev counter at the unit I have run a separate wire from the CDI to the coil no difference
but spark improved now both cap and plug had resistors so I changed the cap

clf
I have checked the choke with a temp probe and off the carb and it is working properly

Other stuff tried today
Checked float level no faults
checked exhaust box and cant see any excess carbon did attempt running it with it off but it was too loud for the village

So my conclusion today is it will run up until the point the carb starts spitting fuel back at me and held on full throttle it will stall and at that point I checked the carb there is still fuel in the carb it seems like back pressure almost instantly on full throttle

Again Thanks to every one for the suggestions

Martin

timtheenchanteruk · 24th February 2016, 18:34

try on here.
http://chinesescoots.forumwise.com/

TBH sounds like not enough fuel at full throttle, try partially covering the air intake and full throttle it, to restrict the airflow, and see if it still dies.

2 strokes are picky about the mix, how many miles has it done?

Check the carb is sealed properly.
The filter should be oiled, not just left dry, I use a bit of 2 stroke oil on em.
If its high miles, it could be worn piston rings, on a 2 stroke this can allow it to suck excess air up from the crankcase, weakening the mix and causing your symptoms.
Overfuelling, it wouldnt pick up that quickly when you let off the throttle, itd cough and splutter whislt it evened out the mix.

Mr Bone · 24th February 2016, 18:44

Quote:

Originally Posted by martinwest

Mr Bone
don't know what size the jets are they are not marked and no I haven't ridden it due to no MOT and yes back off on the throttle and it is back to normal. I took the air filter off and as soon as you give it full throttle it spits fuel back out of the carb so it is starving itself

Avulon
I have tried it today but can only disconnect at the rev counter at the unit I have run a separate wire from the CDI to the coil no difference
but spark improved now both cap and plug had resistors so I changed the cap

clf
I have checked the choke with a temp probe and off the carb and it is working properly

Other stuff tried today
Checked float level no faults
checked exhaust box and cant see any excess carbon did attempt running it with it off but it was too loud for the village

So my conclusion today is it will run up until the point the carb starts spitting fuel back at me and held on full throttle it will stall and at that point I checked the carb there is still fuel in the carb it seems like back pressure almost instantly on full throttle

Again Thanks to every one for the suggestions

Martin

Unusual for jets not to marked, but spitting back is an indication of over fuelling. Try the jets from the old carb. Dont clean them out with a wire/needle, use vinegar for a few hours.
I'd wager your main jet in the new carb is too big.

COLVERT · 24th February 2016, 18:44

Ignition timing.------------------

Spitting back because it's Firing too late. The burning fuel in the crankcase with give spitting back as it's not had time to combust properly before the next charge arrives.---

Mr Bone · 24th February 2016, 19:19

Quote:

Originally Posted by COLVERT

Ignition timing.------------------

Spitting back because it's Firing too late. The burning fuel in the crankcase with give spitting back as it's not had time to combust properly before the next charge arrives.---

A perfectly jetted S3 triple at Pembrey in cold weather will a week later in similar temperature
at Knockhill (about 600ft higher) run rich and show a fuel mist at the carb mouth. Timing unchanged.
Saying that, its worth checking the spark is spot on first.
If its combusting in the crankcase there will be no need for matches.

martinwest · 25th February 2016, 12:57

Hi Bone
swapped the jet and its still the same and Tried blocking ½ the carb intake off it run on full throttle but not revving up fully and very rich until I took my hand away the revved at full for about 2 seconds then died.

Sorry I have the petrol are you supplying the matches.

Timetheenchanteruk
Thanks for the reply
It has done 10000km air filter washed and re-oiled compression at 175psi so the rings are ok.
I have spent hours trawling the Chinese forums with no luck which is why I have asked for help here, I think most of our members have more knowledge forgotten than the young lads I have read posts from in the Chinese scooter forums
Have tried running with exhaust removed ticks over but dies as you open the throttle

colvert Hi
The timing is done by a fixed pickup on the flywheel and the CDI unit no adjustment available

23rd February 2016, 18:16	#12
Mr Bone Gets stuck in 75 Cdt. VW Touareg V6 Tdi. Galaxy 1.9Tdi (x2). R1200GS Join Date: Sep 2012 Location: Planet Zog Posts: 742 Thanks: 169 Thanked 206 Times in 145 Posts	Joking about bonfires aside, check the main jet is the same size as the one in the old carb. If not swap them, often a 2 stroke will bog down if over fuelled. Have you tried riding it, does it pick up as the trottle is rolled off from fully open. Used to tune Kawasaki 400 triples for proddy racing, I know how fickle they can be. __________________ If the world was run by decent honest leaders, we'd have a decent & honest place to live in.

24th February 2016, 14:36	#14
Avulon This is my second home 1.8t Tourer Join Date: Oct 2011 Location: Tanelorn Posts: 4,830 Thanks: 956 Thanked 1,148 Times in 916 Posts	given that it worked properly the one time the tacho worked.... disconnect the (probably faulty) tacho completely. any feed from the coil for the tacho disconnect at the coil to ensure you rule out the wiring loom. The wiring on these things is really poor quality. __________________ Need a T4 ?: T4 Owners Map thanks to Stevestrat ( use at your own risk) Where?: https://en.wikipedia.org/wiki/Tanelorn Mods/Retrofits: PCV vortex 'filter'; bluetooth; inline thermostat; reversing sensors; plenum spyhole ; headlamp washers ; Diy mp3 player replacing CD multichanger; FBH with remote; Headlamp washers; black/chrome front grille, rear blind; Xenon projectors To do: puddle lights; 2 Din cd/nav to fit; boot release button Last edited by Avulon; 24th February 2016 at 14:40..

24th February 2016, 15:30	#15
martinwest Regular poster MG ZT + Join Date: Jul 2009 Location: Bedfordshire Posts: 88 Thanks: 10 Thanked 12 Times in 6 Posts	Mr Bone don't know what size the jets are they are not marked and no I haven't ridden it due to no MOT and yes back off on the throttle and it is back to normal. I took the air filter off and as soon as you give it full throttle it spits fuel back out of the carb so it is starving itself Avulon I have tried it today but can only disconnect at the rev counter at the unit I have run a separate wire from the CDI to the coil no difference but spark improved now both cap and plug had resistors so I changed the cap clf I have checked the choke with a temp probe and off the carb and it is working properly Other stuff tried today Checked float level no faults checked exhaust box and cant see any excess carbon did attempt running it with it off but it was too loud for the village So my conclusion today is it will run up until the point the carb starts spitting fuel back at me and held on full throttle it will stall and at that point I checked the carb there is still fuel in the carb it seems like back pressure almost instantly on full throttle Again Thanks to every one for the suggestions Martin __________________ [SIGPIC][/SIGPIC]

24th February 2016, 18:44	#18
COLVERT This is my second home R75 Saloon. Join Date: Feb 2009 Location: France/or Devon. Posts: 14,003 Thanks: 3,851 Thanked 2,167 Times in 1,816 Posts	Ignition timing.------------------ Spitting back because it's Firing too late. The burning fuel in the crankcase with give spitting back as it's not had time to combust properly before the next charge arrives.--- Last edited by COLVERT; 24th February 2016 at 18:47..

25th February 2016, 12:57	#20
martinwest Regular poster MG ZT + Join Date: Jul 2009 Location: Bedfordshire Posts: 88 Thanks: 10 Thanked 12 Times in 6 Posts	Hi Bone swapped the jet and its still the same and Tried blocking ½ the carb intake off it run on full throttle but not revving up fully and very rich until I took my hand away the revved at full for about 2 seconds then died. Sorry I have the petrol are you supplying the matches. Timetheenchanteruk Thanks for the reply It has done 10000km air filter washed and re-oiled compression at 175psi so the rings are ok. I have spent hours trawling the Chinese forums with no luck which is why I have asked for help here, I think most of our members have more knowledge forgotten than the young lads I have read posts from in the Chinese scooter forums Have tried running with exhaust removed ticks over but dies as you open the throttle colvert Hi The timing is done by a fixed pickup on the flywheel and the CDI unit no adjustment available __________________ [SIGPIC][/SIGPIC] Last edited by martinwest; 25th February 2016 at 14:37.. Reason: extra info

24th February 2016, 18:34	#16
timtheenchanteruk Regular poster MG ZT Join Date: Feb 2016 Location: Leeds Posts: 71 Thanks: 5 Thanked 13 Times in 11 Posts	try on here. http://chinesescoots.forumwise.com/ TBH sounds like not enough fuel at full throttle, try partially covering the air intake and full throttle it, to restrict the airflow, and see if it still dies. 2 strokes are picky about the mix, how many miles has it done? Check the carb is sealed properly. The filter should be oiled, not just left dry, I use a bit of 2 stroke oil on em. If its high miles, it could be worn piston rings, on a 2 stroke this can allow it to suck excess air up from the crankcase, weakening the mix and causing your symptoms. Overfuelling, it wouldnt pick up that quickly when you let off the throttle, itd cough and splutter whislt it evened out the mix.