Electrical Problem On Montessa Cota 200

[glenn]

Hi

I wonder if theres any one out there that can help me. I am doing up an old Montesa cota 200 and have found that it has no spark. I have tried a new plug, coil and plug cap. is there any way of testing the generator? also could the condensor cause this? Thanks for any help.

[bullfrog]

It could be as simple as dirty points. . . . and yes a bad condenser would result in no spark.

The usual procedure for restoring a bike from the dead which has no spark is to replace 1) spark plug, 2) check the condition of the spark plug cap (replace if ugly) 3) points and condenser (setting timing is part of this process), 4) high tension coil. After all that, if you still don't have spark go back to points and condenser and check the solder joint on the condenser (that's a common place for garage mechanics -like myself- to mess up).

Have fun!

Ed

Keep the rubber side down!

[jaylael]

Just thought I'd put in my two cents worth as you know I can't resist. What I do is connect an ohm meter between the wire from the points to the coil. (with the upper coil disconnected) This is the coil negative or switched lead. It should switch from close to zero ohms with the points closed to whatever the lower coil value is. On some bikes this is a very small difference so you have to watch closely for the change. For example, on a Maico point system the value on my meter changes from .2 ohms closed points, to .7 ohms open points. Keep in mind that the turning of the flywheel induces AC voltage into the wire even when moved slightly. These surges of ac voltage influence your ohm readings so the flywheel must be still when getting actual readings. The old Montesa lower coil probably reads higher than a Maico. I'd estimate anywhere from 12 to 25 ohms, but it isn't really critical unless the readings are near zero or high. (like 250 ohms and up or something) If the reading is too high thre may be weak or no spark. More likely, as Bullfrog has stated the points could be corroded. If the points need help, what I do is take them off the bike, and take the two parts of the points apart from each other. Be careful not to loose any of the tiny near microscopic fibre washers or the tiny fibre bushing the fits in the eyelet on most older point sets. They must be assembled in such a way as to prevent full time grounding of the wires, and the wire routing is critical to prevent rubbing on the flywheel, etc. Anyhow once the point halves are separate, I buff their contact surfaces on a wire wheel 'til they are bright and shiny. After they are reassembled then pass a business card through them to take off the last bit of oily residue. NEVER EVER use a points file or an emery board or sandpaper on points! If anyone has done this, they are ruined and need to be replaced. The sanding process hopelessly scratches the point surfaces which must be bright and smooth as glass! Then apply a tiny dab of thick grease to the cam rubbing block, reinstall the flywheel and set timing with an ohm meter as previously described. If there are no timing marks, a verinier caliper can be used to measure the time before top dead center that the points just open. My old COTA 304 which was really a 250, had a factory spec of 1.9 mm btdc. I found it ran very well up around 2.5 mm but no higher as the kickstarter gears, and shaft in these bikes are extremely fragile. The slightest kickstarting mishap could break something mostly un obtainable. Hope this helps. Jay

[glenn]

Thanks lads. I,ve ordered a new set of points and a condensor. hopfully this will cure it.

Next thing is setting the timing. Could anyone give me a step by step set up guide. the last bike i had that wasn't electronic ignition was a bultaco sherpa and that was nearly 20 years ago. and i never touched the timing on that anyway.

Cheers Glenn