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Beta Lost All Power And Backfiring


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Spoke too soon :banana2:

Took it out, to see if she was running O.K.

When I let off the clutch it wants to drive backwards!

Tried it in 1st 2nd and 3rd but just wants to go backwards!!!

Is there a secret reverse switch or something that I don't know about :dunce:

What's the chance that the piston has started pushing the crank round in reverse?

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It is quite possible the engine is running in reverse, and this in fact supports the idea there is a timing issue, whip the flywheel off and have a look, check the woodruff key (semicircle shape, about 1cm in diameter) to see if that has sheared, if not then check the timing against the example on the beta UK website.

You will need to mark the nut and flywheel before taking the off so you definitely tighten it correctly when you replace the flywheel unless you have a torque wrench, in which case tighten it back on to 140Nm, thats bloody tight.

You'll also need to figure out how to hold the flywheel, wither make some sort of tool, or take it to your local bike shop where they may have an impact wrench if you haven't got one. You'll also need a flywheel puller. If you're stuck then I think JLI should have everything you will need.

Bob

:dunce::banana2:

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Errm, I may be wrong (and please tell me to bugger off if I am) but it sounds to me that you're confusing 4-stroke and 2-stroke engine internals. Your Beta is a 2-stroke which means there are no valves, cams etc. in the head - intake (via a reed valve) and exhaust is taken care of by ports in the cylinder (like you said). Much simpler than a 4-stroke car/bike engine! HowStuffWorks.com has an excellent explaination.

That'll be why it's called a 2stroke then :wacko:

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You certainly didn't need to remove the engine to check the woodruff key, but whilst you've got it out I suppose you may be well advised to check the piston rings and bore for damage especially since you did run it without oil in the fuel.

If the petals are new then there would be no harm in replacing the old ones, making sure that they fit closely together as I believe is shown in the manual.

I'd have a good look at the woodruff key first.

Good luck,

Bob

Well, considering I didn't know what 2-stroke meant until the other day I decided to dismantle the bike. get a better understanding of it and improve my ability to look after it.

Anyway, the piston and bore look fine, a fair bit of carbon deposit on the top of the piston but nothing unusual.

Bob, I'm about to take your advice and check the woodruff key but I'm not certain that I'm looking at the flywheel. I'm used to seeing flywheels with teeth, clutches and starters connected to them :wacko:

I think I'm on the right track:

Click for larger image

thumb.jpg

Before I proceed, am I going to bugger anything up trying to remove the flywheel this way, and do the four screws need to come out?

Thanks for everyone

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The 4 screws are holding the flywheel weight onto the flywheel. Should nt need to remove the weight to start with or never at all, depends how you want the bike to ride. Weight off bike is very zippy and poor in the mud.

That is the flywheel nut you are about to unlock, the woodruff will be visible once the wheel is off but you will need a flywheel puller to get the flywheel off the crank.

Hope you know where all the bits go back together :wacko: If you do remove the weight you will need an impact driver to get those buggers off or you will round them, and if you want to take the stator out to clean everything up behind it (casing) make sure you mark where it fits before it comes out. This position sets the timing for the bike. Lampkins site may show the correct timing position for the stator worth checking whilst your at it

Timing/Stator position for 2000 rev 3

Doesnt say if this is for the 270 though on the site

Edited by Betarev3
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I may be wrong but on the newer betas the flywheel weight is on the outside of the flywheel, so it looks like it has already been removed so you'll have no problems there. I think that the diagram on the beta website whould be about right for timing, it shows a stotor with six coils, so if youre has six coils aswell which I think all pre03 bikes had then set it to that.

Would it be best to replace the little end bearing and or piston rings whilst the top end is easily accessible anybody?

Looks like you've about got it sorted though.

Bob

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  • 2 weeks later...

Not a happy bunny :banana2:

Finally received my parts yesterday and got the flywheel off.

It doesn't look good :D

thumb2.JPG

That thing with the coiled wires, is that the stator?

And if so has anybody used these guys before?

http://www.uk-motoplat.com/home.html

Also, where would I find the woodruff key, if I can't see one does that mean it's disintegrated?

Or do I need to delve further?

Much appreciated guys :blink:

And lasses :beer:

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Yes, the thing with all the wires is the stator. If it's knackered JLI will be happy to sell you a new one of course, but there are a couple of companies out there who will re-wind and re-seal it for you.

If you can't find the woodruff key on the crankshaft, the odds are that it's sheared off completely and the bottom half has fused itself into the shaft. Look at the surface of the shaft very carefully and you should see a rectangular mark on there somewhere. That's what's left of the key and you'll have to carefully prise it out somehow. If the key's sheared then I wouldn't bother messing with the stator until you've replaced the key, reassembled and tried to start and run the bike again. Virtually all of the symptoms you describe could be attributed to a broken woodruff key which costs a couple if quid as opposed to

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Looking at my previous image you can see that the coils of wire have snapped.

Probably my own doing when I was undoing the flywheel nut.

Is it safe to try and start it up like that?

Looking at the shaft I can see what looks like the remnants of a woodruff.

Click for larger image

thumb3.jpg

To be honest, if it costs me another

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well, i would say that your stator doesn't look too bad, unless there is rust on the core. However if the coils are broken it will probably need replacing. unforturnately I don't think that there is anybody in the UK with the correct cores for your type of stator, so you'll need a new one from JLI. Have a check of the timing though aswell, it looks a little off, you can get this info on the UK beta website

The woodruff key looks about right to me, it is surprisingly small.

Good luck - if the rings were wrong you should get them changed foc surely?

Bob

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