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Spluttering And Backfiring


bob
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Hi,

I have just started having problems with my bike, it is an 03 rev3 200cc.

the bike used to go fine, but I went out on it this morning and every time I got above about 1/4 of a turn on the throttle it started spluttering and pinking and all sorts. The bike runs fine otherwise below this speed with plenty of power.

The spark plug has a white residue on the area where the spark jumps across.

I have tried a number of spark plugs but not a new one.

I have also tried resetting the float level slightly higher incase it was fuel starvation, but I have not started messing about with mixtures or ignition timing yet.

I suspect it may be that ignition module problem which everyone fears. :P

What would you reccomend doing to fix it and how can I do this. I have done a search and there are many suggestions, but no accurate instructions of what to do. I have never got much further than the clutch and carb when taking bits off my engine, so any help would be helpful eg torque settings, tips, tools.

Thanks,

Bob

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I have been for a very short analysis ride, and the problem appears to be not as bad now, but I took the plastic cover off the brake side of the engine and behind this is the metal flywheel thing over the stator, there are four screws on this, what do these hold on?

I had a look through the holes in this 'wheel' where you look to see TDC and you can also see a small part of the coils on the stator from here, two of which looked to be slightly corroded. Would this be causing my problem.

Would you reccomend any particular sparkplugs, could this be caused by bad fuel, I am not sure how long this fuel has been in the tin :P .

I am going to change the fuel though to check.

Bob

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Hi Mate,

I've got an '02 270 and I had similar problems, had to have the CDI unit, and then the stator replaced on mine. But I think I was pretty unlucky.

The recommended Spark plugs in the manual are Champion N7YCC (I got a 4 pack from Halfords with a dual-copper core).

Andy

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P.S. Regarding fuel, I always run mine on Optimax, helps to keep things clean and has a bit more power due to the extra RON.

Chuck yer old fuel out, drain/syphon your tank and bang some Optimax in.

P.S. If you're really stuck (like I was). Take it up to Lampkins in Silsden, very helpful bunch, they even waived the labour charge for the Stator job.

Edited by arturner51
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Doesn't sound like the usual stator problems: all those I've seen go have failed totally. Running OK one minute, dead the next. By the way I think the screws you refer to on the flywheel sound like those that hold the additional weights. Personal preference if you run with them or not

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I have cleaned my carb thoroughly, and lightly blown all the jets through with compressed air.

I have taken the air box off and I have given that a good clean out, and since I had to remove most of the exhaust to get the air box out I figured that I might aswell give my front pipe a good clean out aswell.

Is it worth taking a look at the ignition timing, I suspect it could be a little too advanced?

I am going to deain the fuel and remove the petcock to see what is sat in the bottom of my tank.

I am going to get some optimax on friday, my nearest garage is a long way away.

Cheers

bob

Edited by bob
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Bob,

Your symptoms sound like the ones I had on my '04 Beta last winter. Turned out to be a sheared flywheel key. You will will have to get hold of a flywheel puller to find out. This would be a very cheap fix compared to the CDI and Stator possibilities. Good Luck.

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Never thought of the woodruff key. I was going to suggest swapping the CDI with a known good one but the key makes perfect sense considering the symptoms. Agree that it's unlikely to be the stator since as has already been mentioned, the "classic" Beta stator failure symptoms are fine one second, completely dead the next.

I have a flywheel puller if you need to borrow one...

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Take off the flywheel cover, put a mark on the casing and the flywheel (at tdc), attach a strobo, start the engine. If the timing is ok at idle, moves backwards but starts behaving erradically when given more rpm, its probably a faulty cdi.

Just my .02

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I am going to get a flywheel puller from birdies hopefully.

If I take the flywheel off to check the woodruff key, which I might aswell before doing what manz said to try, do I need to mark the flywheel and casing before I remove it and put it back in exactly the same place?

Also is there anything else I should do whilst I have got it off, someone told me once to spray WD40 on the stator, all of this is completely new to me, and I don't really know how any of it works so what I am saying may sound pretty stupid.

If the woodruff key isn't bust then I will get back, what would cause the CDI unit to fail?

What do you mean, rig up a strobo, do you just mean to connect a light to the bottom of the coil between it and the spark plug?

Thanks alot! :P

Edited by bob
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The key ensures that the flywheel can only go on one way.

If you don't have a torque wrench, mark the nut (ink, paint) so you get it back to where it was.

The only way you can change your timing is by loosening/moving the stator.

You can spray WD40 all over that stuff if you want.

Some clean everything and spraypaint to keep corrosion away.

I suppose you'd want to mask the pickup/trigger thingie on the stator.

I always vent my flywheel compartment.

There seems to be no keeping moisture out altogether, so I go with the flow and let some air get in there.

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Thanks,

I allways remove the casing after riding in teh wet or washing anyway, so corrosion shouldn't be too bigger issue, I am going to borrow a flywheel puller off betatrials99 if he remembers to bring it to school tomorrow, so i should be able to see whether it is going to be easy or hard to fix tomorrow I suppose.

bob

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No, not a regular light, but a strobo intended for adjusting timing. You mark the casing and the flywheel just to see how the timing moves. You connect the strobe to a car-battery, and one clamp goes around the sparkplug wire. Your local car accessoryshop probably has them.

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Sorry to disagree with stevel and neonsurge, but my friends beta 270 had exactly the same symptoms as Bobs. New stator, no more problems. Bob, although the manual recommends champion N7YCC, Lampkins recommend NGK BP5ES, which i have had no problems with, and its the plug they run their bikes on also! :P

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