misfiring problems

jaydr · Borekit Bruiser Joined: 10 Oct 2005 Karma :

hey all!

ive got a chinese copy of a gs 125 although its a copy of a suzuki apparently it has a copy of the cg125 engine!?! Anyhoo recently it started to just be a bit hesitent at times mostly at full throttle and over the last week it has got progressively worse and now it struggles to do 30 mph and backfires like mad no matter how gently you throttle it. I have been told to check the points on it but i have no idea where they are Rolling Eyes

and also i think it could be a timing problem but again i have no idea how to adjust that?

please help as its driving me mad!!!!

cheers
jay
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the grim reaper · World Chat Champion Joined: 29 Jun 2005 Karma :

The first two places to look on a stroker are the spark plugs and the exhaust. I'd change your spark plug first and also check to see if there's a spark, then check the exhaust to see if it's coked up or not.

Cheers

Grim
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bidman · Crazy Courier Joined: 01 Oct 2005 Karma :

Hi any chance you could post a picture of the bike so i can tell you how to fix it because although they are all simple, single cylinder 4 stroke engines some differ where timing is concerned, also what age is the bike and what is the make, Dan
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jaydr · Borekit Bruiser Joined: 10 Oct 2005 Karma :

heres a pic of it. its called a kangda zs 125-11 its a y registered bike 2001 i think?
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bidman · Crazy Courier Joined: 01 Oct 2005 Karma :

yeah your engine is a cg 125 replica, so all the parts are in the same places etc...
First check the spark plug and make sure it isn't fouled or oily and has the correct gap, also change the oil and ride it to see if this has any effect on the problem.
If not you need to check the points gap. The points are situated under the flywheel and as such are a bugger to get right. My advice is to take it in to a bike mechanic and get them replaced and checked. While your there get them to check the advance/retard mechanism. This is fixed inside the flywheel and are known for going wrong. Theres just springs and bob weights which fly out under centrifugal force and advance the timing. The springs get slack and advance the timing causing farting and popping and flat spots etc... Also check that the exhaust pipe has a sealing ring in the exhaust port. This can cause a backfire if it is missing. Now pull apart all the iginition bullet connectors and clean them. Do the same for the battery leads. When you have done that carefully nip up all the female bullets so you have a snug fit. Then make sure the spark plug is in firmly because if it is loose it will cause loss of compression. Let me know how it goes or if you get stuck Thumbs Up

, Dan
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jaydr · Borekit Bruiser Joined: 10 Oct 2005 Karma :

cheers dan! Thumbs Up

have you got any idea what the plug gap should be i just changed it last weekend but i just stuck it straight in without looking at the other first! also i got a new ht cap and chucked a bit of redex in the tank as i had let it run nearly dry i thought maybe the bike had sucked some crap into the carb? im gonna have a look at work tonight give it a good clean.
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the grim reaper · World Chat Champion Joined: 29 Jun 2005 Karma :

OK, scratch my comment, I didn't twig that it was a four stroke Embarassed

Cheers

Grim
____________________
Adverts don't always work: Remember that advert, where the army are running across the desert and they have a wounded man on a stretcher. They get to a ravine, the bridge is down and a caption pops up that says, 'What are you thinking?'. I don't know about you but I was thinking, 'Christ, I'm glad I'm not in the f***ing army'.

bidman · Crazy Courier Joined: 01 Oct 2005 Karma :

well i'm presuming it'l use the same plug as the cg which is a DR8ES-L and a gap around 0.7 and 0.8 should be fine a new plug comes with the correct gap for the cg so maybe just get hold of a new 1 Thumbs Up

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jaydr · Borekit Bruiser Joined: 10 Oct 2005 Karma :

the plug is a dr8ea so i dont know what the gap is i hope its the same. can anyone give me a guide how to do the points and check the gap myself and also what the gap should be

cheers

jay
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bidman · Crazy Courier Joined: 01 Oct 2005 Karma :

Hi, the gap will be the same anywhere between 0.7 and 0.8 will be fine Thumbs Up

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Don't ride it, RAG IT!!

jaydr · Borekit Bruiser Joined: 10 Oct 2005 Karma :

thanks bidman Thumbs Up

is that gap you quoted for the spark plug or the points?
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bidman · Crazy Courier Joined: 01 Oct 2005 Karma :

Hi, thats the spark plug gap the points gap is 0.35mm Thumbs Up

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jaydr · Borekit Bruiser Joined: 10 Oct 2005 Karma :

thanks m8y do i have to remove the flywheel to adjust them?
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bidman · Crazy Courier Joined: 01 Oct 2005 Karma :

Yes i think the points are inside the flywheel, well they were on a similiar replica cg125 engine i had, removing the flywheel is an easy job as long as you have the right tool for it if not just take ti to a garage for them to take off for you Thumbs Up

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jaydr · Borekit Bruiser Joined: 10 Oct 2005 Karma :

thanks m8y! Very Happy

will have a look when i get to work!
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jaydr · Borekit Bruiser Joined: 10 Oct 2005 Karma :

just a quick update on the problem. I tried to take the cover off the flywheel but to no avail, it seemed solid even after id removed all the bolts, Anyway there is a large screw that you can remove and you can see the flywheel and also iam greeted with loads of oil being flung at me! Rolling Eyes

i dont know whether this is how it should be but i thought the flywheel should be dry? also the wierd thing is if i take that screw out for a minute and run the bike it runs perfectly for about 20 miles then does it again!?! i cant get any parts for this bike ive been told that the parts from a cg engine will not fit this bike at all so i was thinking maybe i could get a cg engine for it if its a straight swapout?
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bidman · Crazy Courier Joined: 01 Oct 2005 Karma :

Hi, from what i can see, the engine is almost an exact copy of the new electric start Honda cg engine the front mounts are the same no doubt the rear ones i am not so sure about as I cant see them. If i were you i would stick with this engine it really doesn't sound like anything major. The flywheel should be in oil thats nothing to worry about. The problem you are getting, does it sound like this.. you are riding along firing on each stroke fine pulling nicely then start to simply not fire on alternate piston strokes then the occasional stroke it will fire till nothing? Dan
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jaydr · Borekit Bruiser Joined: 10 Oct 2005 Karma :

phew thought i had a strip down on my hands then lol yes dan it is something like that but when it goes funny the rev counter goes off the clock and you only have very low revs that are useable. if you try give it any revs it bogs and misfires. also it stinks of fuel when it goes wrong
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bidman · Crazy Courier Joined: 01 Oct 2005 Karma :

Hi, strip the carb make sure its all ok as i think it is most likely to be a fuel problem, make sure that the choke isn't loose starving the bike of air which would cause the bike to bog down as you describe, Dan
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jaydr · Borekit Bruiser Joined: 10 Oct 2005 Karma :

hi again just got cover off flywheel and couldnt see anything so i thought id take a look in the air box where i was greeted by a puddle of oil! is this ok or is it a sign of trouble? gonna take carb off and clean it up a bit!
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jaydr · Borekit Bruiser Joined: 10 Oct 2005 Karma :

took carb off and cleaned it all out, fuel was clean and not much muck in the carb, ive put it all back together now and the problem is no better so now im really baffled Confused

can anyone tell me how to get the flywheel off please as ive got no idea how! it has 3 allen key bolts and a large centre nut but there is nowhere for me to jam the engine to undo it as the flywheel is solid.
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Robby · Dirty Old Man Joined: 16 May 2002 Karma :

From what I could decipher from this, you undid one of the timing inspection covers over the flywheel and the bike ran ok for a while.

And then you found a puddle of oil in the airbox.

Sounds to me like a blocked crankcase breather and/or overfilled oil. The breather pipe runs from the back of the crankcases to the airbox, take it off and make sure its clear. Make sure the oil level is where it should be.

jaydr · Borekit Bruiser Joined: 10 Oct 2005 Karma :

is this what you mean? it doesnt fit properly on the engine dunno why?
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jaydr · Borekit Bruiser Joined: 10 Oct 2005 Karma :

ok took the pipe off there and it seems to be clear (blows plenty of air out when running) blew through the pipe and that seems clear too.
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i smile because i have no idea whats going on!

gimpy limp · Nearly there... Joined: 19 Mar 2005 Karma :

you still having no luck mate? make a list of what you've checked to date and chuck it up here it might be easier to follow and work out that way. It's frustrating problems like this but these sort of things you learn loads from I find, better than any mechanics course imo - you'll know where to go first if it happens again on any future bikes.
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