Jinlun jl125-2 rev problems

its cannot seem to hold a smooth rpm count.

spark plug looks normal,
air intake is clean,
fuels getting in to the carb fine.
plug looks to be getting enough power.

worked well for a couple of months (if not a bit slow) now revs drop, seems to work better if doing very high revs. 8-9k.

just thought,,, are these bikes 2 stroke? i havent been putting oil in the petrol tank??? any ideas?

EDIT> bike is old, i mean really old, light cables are not attached any more, kind of rusty, speedo stopped at 60k km, rev counter and geers counter (n , 1-3 working, 4 not , 5 temperamental)
plates possible from another bike, also back fires from time to time

This bike? http://mvgg.com/vehicle/model/225/8766fe4.html
It's just one of those bike with OHV "cg125 clone" engine. / Valve clearence normal ? / Change the front sprocket to 16 or 17T if won't overload as those peasent bike/ The 17T (Genuine Qjiang parts) http://item.taobao.com/item.htm?id=138875154

Right I got it fixed.

I got the carb replaced and... dont know what its called on a bike, on a car its a distributor/cap + rotary arm and all that. (the bit that goes into the top of the spark plug (not the lead)).

Also following some of the advice above, once i got it working (with the help of the guy that lives above me), we then tightened the chain (it was quite loose before) and changed something in the rear drum brake area.

ITS WORKING!!!! although not to great, it has a tendency to still cut out when left to idle. mostly when going down hills i just pull in the clutch and let gravity get me there, now it stalls. to counter this i put the idle revs at about 2k. but it does not seem to make much difference. So iv changed it back and will just learn to live with it cutting out.


But im happy it works again. THANK YOU FOR YOUR ADVICE. the mvgg link didnt work when i tried to open it, but since you have added the description of it being a peasent bike... well yes that sounds like my bike :-)
they are used around here as taxis. I only bought it because it was cheap and if the peasants drove them they must be ok.

Quote:

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Originally Posted by lightend

they are used around here as taxis. I only bought it because it was cheap and if the peasants drove them they must be ok.

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where is "around here"? this is a global forum, and many of us would love to know where you are posting from. Perhaps update your profile so your location appears in your avatar whenever you post!

glad you are moving again!
cheers

good point,
Im in Ningde, Fujian, China, small city of mabye 300k people. 1 westerner and 800 students :-)

NOT every "peasent bike" are equal, the "taxi" NEVER use this brand . Guangdong & Chongqing made are "superior" compare to that brand. (You can comapre the reviews from UK sites about this brand :mwink:)
Typical "mechanic" in Fujian, exchange every "parts" ONLY & hopefully the problem GONE. I once saw a story in chinese bike forum , noone dares to rebore a 125 to 150 in Fujian hometown, the "biker" done it in a Guangdong friend visting trip (~7xxkm away)
Carb replaced -Did they heard something called "carb cleaner" ?
Changed Spark coil but there's spark in bike...
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Weak spark / idle DEAD is often releated to Magneto's ingition windings (AC) ages / The cheap soultion is a DC ignitor (the black small box) to bypass.
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http://www.dansmc.com/cdiignition.htm

Thank you Humanbeing, my situation is that i bought the bike to last me 6 months. My school has provided me with a Ebike but i felt like something that didnt rely on needing to be charged up every day. If the bike makes it to Jan, i will be very impressed and would have got my moneys worth. if not,,, meh- what can you do.

regarding your post>
thats why i get on so well here. :-D
i replace parts willy nilly until the problem is solved :-)
start with educated guesses then get more feeble as time goes bye (that is when i reach for the hammer) I found a good kick sometimes helps things,,, maybe not the bike but it sure as hell makes ya feel better.
the taxi bikes round here all look the same, different names but all they do is rip off each others engines and make a slight difference then away they go. its great, you dont need to get specific parts, just point to a bike that looks about the same and describe what you need... and it all works :-D
To be honest, if it came to reboring a bike, i would throw it away and start again. (saying that i dont know where to throw a bike away,,,, am wondering if i just leave it out side with the key in the ignition if someone will steal it) (never mind, i have 3 months to decide how to get ride of it before i leave)...... (maybe i could tape it to a dustbin cart)

cheap second hand bikes are made to be abused, if you lay them down or they break in a hard to fix way, it doesn't matter.

The "taxi" looks the same because they're either Genuine Suzuki GN125 OR OHV "CG clone" engine stuck on a similar frame & decal. Fujianese just loves that style. Some "wealthy" costal area uses the smuggled REAL thing since 80's & good reputation since then. / The Guandong "taxi" is another style because Honda CG125 's good reputation.