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Cota 247: Spark, Compression, Fuel, but won't start!

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I don't believe it - I have just shorn my flywheel key :(

Can someone tell me where to source a replacement engine # 21M23540 and;

how do I get the shorn off remnant out of the shaft - is dead smooth and tight as.... I tried a very powerful magnet ...other ideas?

Should I replace the spring washer - it appears tired to me and are left hand spring washers widely available?

Tap one end of the key remnant inwards with a flat-ended punch of a diameter slightly smaller than the width of the key and the other end of the key remnant should pop upwards.

Keys can be made from a piece of mild steel of circular cross-section (round bar) with diameter turned to match the curvature of the curved side of the key. Cut key from piece of round using hacksaw or parting-off tool then hacksaw and file to finish. Alternatively you can buy keys from In Motion.

The key is there only to get the flywheel to sit in the correct location while you tighten the nut and takes no part in the driving forces so should only ever be made of metal that is softer than the crankshaft, in case the taper allows slippage. A hard key may damage the crankshaft and/or flywheel keyways.

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Finding another engine for the Cota may be a bit difficult. They do come up occasionally on Ebay but mostly they are overseas sellers and most of the time not complete. To get that broken key out get yourself a very fine hard punch and tap the key on the edge and it should pop out. As far as that spring washer is concerned I would not bother changing it. I have reused those washers on my bikes many, many times with no problems. Once you put the whole lot together make sure you tension that nut to the recommended pressure. From memory it is around 70 foot pounds. I can check if you like and get back to you

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Thanks for the good advice footupfun - I have several brass bars - would these be a suitable material? I am guessing it's unlikely I will have the right diameter bar - anyone have any idea what that diameter would be.

I did try the tap on one end to budge the remains but no luck yet .... I guess I need bigger hammer - just kidding :shutup:

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I don't believe it - I have just shorn my flywheel key :(

Can someone tell me where to source a replacement engine # 21M23540 and;

how do I get the shorn off remnant out of the shaft - is dead smooth and tight as.... I tried a very powerful magnet ...other ideas?

Should I replace the spring washer - it appears tired to me and are left hand spring washers widely available?

The flywheel key is a half moon key. Use a small punch on one end and drive it out. No need to replace teh lock washer. Torque is 70 lbs. ft. for the nut.

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Ok so it took quite few hard blows to dislodge the key. Does anyone know the dimensions of the replacement - as far as I can estimate from the fragments it is 3 thick x 5 high x 12 wide but the 12 is very approximate as the shorn piece is not suitable for measuring so I am extrapolating that from the 3 x 3 x 10 mm segmnent out of the shaft. If I purchase a 3 x 5 x 13 does that matter as it only protrudes into open space on the flywheel.

UPDATE - I played around a bit more with sizes and I think 13 may well be the right size - so I have ordered that and now have to wait for the postman

Edited by keychange

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I managed to find an imperial sized key close to what I need and ground it back using a fine oil stone to the 5mm deep x 3 mm wide that I am pretty positive the original was - I also added a chamfered edge as per original. It is a snug fit but not a tight fit - does that mean I have gone too far (it is actually a little oversized by around 0.10 mm. I can't get it to stay in place as I put the flywheel on - I have ground the leading edge a little so that the flywheel slides onto the key easier. Should I use some glue to hold the key in place? Or do I simply need the correct key?

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That little key can be a *******. I usually dab a bit of glue on it and leave it overnight to set. That will stop it from sliding out when you are putting the flywheel on and having to dismantle the backing plate to retrieve it.

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That little key can be a *******. I usually dab a bit of glue on it and leave it overnight to set. That will stop it from sliding out when you are putting the flywheel on and having to dismantle the backing plate to retrieve it.

SuperGlue - hooray. The key started at 3.2x6x13 and ended closed to 2 x 4 x 10 but it finally fits and works - for now

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Hello all, I wanted to do an update on my Montesa that would not start, despite having spark, compression, and fuel. It is now running thanks to the help of two nearby trials enthusiasts who helped me track down the problem this past Saturday. What we found was a significant rust/corrosion deposit in one spot on the cam inside the flywheel. We believe this was making the engine spark twice per stroke, or making the spark erratic/unstable. We polished the cam, put in a new NGK plug and with a push-start down a hill it began running! Oddly, I could not get it to start or even fire by kick-starting numerous times, but it started right away with a push-start. Now after it has run a bit, it usually starts up with just one or two kicks.

This was a very strange problem and I wanted to share it here as it might be one for the "notebook." Everyone always says you need spark, fuel, and compression and an engine will run, but here was a case where I had all three in plentiful supply, yet an odd issue kept it from starting. Oh well, at least it was a good learning experience for me! Regards, --Kevin

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On 12/1/2010 at 3:39 PM, charliechitlins said:

...<snipped>

Check your clutch adjustment.

The slightest bit of slip can go unnoticed while kicking, but it'll keep the motor from turning enough to start.

So...how much did you pay?

Reviving an ancient thread.

@charliechitlins that was exactly what my issue was. Crummy, sloppy kicks, felt almost disconnected... wouldn't start. I was able to bump start it, but no joy with the kicker. I disconnected the clutch cable at the bars, stroked through the kicker twice slowly (with the de-comp engaged), and the 3rd kick it fired like it was brand new!

 

Thanks for that!!! Saved me an enormous amount of wasted time, and probably a bit of money chasing non-existent problems.

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Always good to resolve a problem on these old bikes. They all seem to have little hidden issues for various reasons ...

 

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