JOLTING/SHUDDERING/JUMPING

[lee8040]

bike = kymco zing 125


when i hold the accelerator in the same poisition while riding, proberbly around 30mph it will judder and jump forward and backwards. it doesnt do it when the accelerator is let go or when i accelerate. can anyone think of a cause?

[----]

sounds like the chain is loose.or at least in that general area.

not 100% though but its a good place to start.


dave
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DRZ-400sm

[Thom_NSR]

[lee8040]

yes when im mid range it happens to so if i downshift ill be over revving in a lower gear.

[Keir]

petrol full?

Chain and sprockets ok and adjusted properly?
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Current : '08 Yamaha FZ1s
Previous: '99 Honda CBR 600FX, 03 ZX636 B1H, 99 Fazer 600 (red), 02 GSX-R 600 K2, 00 SV650s (red), 2008 ZX10R, 97 Bandit 1200N, 04 ZX6RR K1H, 04 GSX-R 1000, 98 Fazer 600 (gold), 05 Madness 110 Pit bike, 04 CR125R, 00 SV650s (black), 06 KTM 625 SMC, 99 SRAD 600 track bike, 03 SV650, 98 Bandit 1200N, Bandit 600SY, 03 GSX-R 600 K3, 01 GSX-R 600, 01 Fazer 600 (black), VFR 400 NC30 x3, 78 Honda Dream, 00 Speedfight 50

[TUG]

set your fuel/air mixture propperly and it will dissapear
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Haz ER-5, innit!

[lee8040]

ive never touched it its ran fine for months now its strated to go funny

[TUG]

hmm dunno then, whats changed?
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Haz ER-5, innit!

[Spoon261]

The weather has turned colder.

When the outside air changes temperature, it changes your air to fuel mixture if you have a carb (not fuel injected).

If the air to fuel mixture is set up correctly it can manage with normal changes in air temperature.
But if its not set up correctly, could give the fault described.

A website all about how to set it up is below
https://hondanighthawks.net/carb14.htm
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Honda CBF125, CBR125 & Yamaha YBR125 Website https://125ccbikeclub.awardspace.co.uk/
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[lee8040]

after giving it some thought it seems very similar to the problem i had on my sccoter and that was caused by a damaged ht lead which eventually snapped completley.

im going to replace the ht lead and spark plug this weekend and pray it works

[Spoon261]

There are loads of possibilities for the fault you described.

The manufacturer / country (quality control) its made in also brings up loads of extra potential problems.

My Honda CG125 website could be some use, I am not sure if your engine is a clone of the Honda CG125, but even if its not, all the non valve clearance / spark plug information should be of use.

https://hondacg125.awardspace.com/

The following list is the basics you should check.

Air Filter clogged?

Spark Plug condition and colour (tells you how your engine is running).
https://www.verrill.com/moto/sellingguide/sparkplugs/plugcolorchart.htm

Valve Clearance

Its also possible you have got a fuel starvation / blockage some ware.
It would be a good idea to try a better quality petrol which has extra inbuilt cleaners in, see my Petrol section in my General webpage on my website.
Also see How to stop your engine clogging up on that page.

For the hell of it, check your spark plug connections, battery etc.
____________________
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Honda CBF125, CBR125 & Yamaha YBR125 Website https://125ccbikeclub.awardspace.co.uk/
I have left bikechat forums, I do not read pm (Private Message)