Annoying Ossa Mar

[neandethal]

Just been at the Trialsday.com training course today with my Ossa MAR and whilst i can wholeheartedly recommend the course, the Ossa let me and itself down by dying.

It had been starting first kick, running sweetly and i was really enjoying it until it died. It was drizzling, which may be important. Back at the car i stripped the carb, flushed out all the jets and every now and again it would pop or fire up but wouldn't sustain life. Once i got home, a 2 hour drive it fired up instantly. The course was the first time it had been used in anger since a full rebuild by Steve Sell so guess seals should be fine.

I'm thinking water in the period metal kill button or the coil or wiring?

Anybody ever had similar? Also are there many options on after market ignitions, i know InMotion do one, who do people rate this? The motoplat system could be breaking down once really hot.

[pjw123]

Motoplat can be problematic, they were like that back in the day.  As a teenager in the 70's I vividly recall the eye watering cost of saving up for a new coil.  Your MAR is  fast approaching is 50th birthday, so your electrics haven't done too bad.  

Kill buttons usually work on the "switch to earth" principle, so easy to take out of the loop for testing. I'd check / clean up connectors & then try a coil substitution in the first instance. Check the routing of the wires from the generator, as I have heard that this can be modified for the better. 

Steve Sell is the "go to" man for OSSA, so you should be able to receive some good advice.   

[neandethal]

Thanks for those thoughts.

Have left a message with both Bradford ignition and Steve Sell (Who rebuilt the motor). The stator has at some time recently been serviced as the cable is very new and the wire colours wrong, eg brown and blue not black and blue. All ignition components checkout to the readings but i suspect the coil may be breaking down once hot. the motor fired up again this morning without hesitation so time has cured something either damp or overheating.

I see there are 3 options on alternatives coils, InMotion do a version, there is an aesthetically nice one on ebay and Rex speedshop advocate using a PVL coil, and anyone tried  any of these alternatives. May get Bradford to rewind the original for originality reasons if cost not stupid. has anyone had one done and know the approximate cost? cheers Ian

[woody]

I had a stator renovated many years ago by Bradford ignitions and it still works, can't remember cost as too long ago but not silly money. I recently had a coil break down and replaced it with one from In Motion which works fine

[trialsrfun]

Like Woody I had a troublesome Motoplat stator with symptoms similar to those you describe repaired by Bradford Ignitions and its continued to work well ever since. Steve Sell produces a full replacement ignition system for the OSSA should you need to go there. Electronic systems seem to be perfect just fit and forget until its troublesome then sometimes you think its anything but the ignition.

 

Edited January 31, 2022 by trialsrfun

[section swept]

Your suggestion that the ignition coil may be breaking down sounds about 99% correct, its that 1% that can catch you out. When the engine was rebuilt do you know if that included an electrics ( ignition check), however a check on the coil when cold might not show any fault. With the engine bursting into life when cold and running for some time and then stopping does point to the coil.