No spark from TS 250

[thomaskwscott]

I've been working on my friend's TS 250 that hasn't run in a few years and am getting an intermittent spark. Initially it had a knackered coil so we replaced that and it started and ticked over fine. The next day however it wouldn't stay running and eventually we identified oiling up plug. Since then we've found it hard to get a spark so checked points gap and replaced the condenser. Still we're getting an intermittent spark (visible 1 in around 8 times) and the bike will no longer run for more than a couple of pops. The only thing I can think of now is that the replacement coil was a dud however, before I go to all the effort of sending it back I wondered if anyone could think of another possible cause for this? It seems crazy that it was running well and has back tracked with no apparent input from us.

Any help much appreciated.

[Lone-Wolf]

Wotcha.

Start with the simplest thing first . . . . try another plug.
There have been some decidedly dodgy NGK plugs on the market lately.

[DAVID THOMPSON]

and are you working with a new points and condenser set ..

have had several bike set for a long time and the spring in the points goes weak
and does not run proper on the cam lobe
a fresh set is best as new old stock can be bad if the spring was coiled up in the working
position and there several years old
dave

[thomaskwscott]

Thanks for the replies, we've tried new plugs and new ht leads all to no avail. As for the points they are far from new but they seem to open and close fine from my visual inspection. Sounds like a good thing to try though so I'll pick up a brand new set and let you know how it goes...

[DAVID THOMPSON]

the real word is NEW

not NEW OLD STOCK

i have about 20 sets for /5 bmw that are junk they set for years with the spring wound into the ready to install
position and are worth less

dave

[therealche]

I lean towards the new coil being a dud. I once spent a few happy hours in the Shetlands getting a blokes Supa5 running. It looked immaculate, fully rebuilt with new / nos parts. When kicking it over with the plug out I noticed that the spark was yellow. Took the (very old) coil off my Supa5 and after kicking it over for around 10 minutes ( engine full of fuel!) it fired up and ran like a dream. I dont know who was happier, me, the bloke, the village he lived in ( a few of whom had come out to see the bike run after hearing me blasting about on it), or his long suffering wife who had been told that the bike was coming with them on their forth coming holiday on the mainland to get it sorted

[thomaskwscott]

Many thanks to David. I fitted a new set of points at the weekend and produced a strong blue spark! However, I'm still having trouble getting the bike to start. I've gapped and timed the points according to the manual (actually I did it 3 times to be sure) but I get rough running and a lot of backfiring. I've timed several bikes over the years so I'm confident I'm doing it right, could there be any other explanation?

[arry_b]

Sounds coil-y to me. Had the same symptoms on my first ETZ, but I avoided changing it because it was giving a nice fat spark.

Much fault finding and swearing later, I gave in and replaced the coil. Cue five years of faultless running thereafter.

[thomaskwscott]

You were right, we replaced the brand new coil with a 15yr old one and it worked perfectly. Time for a refund!

[DAVID THOMPSON]

a single 6v coil from a /5 bmw works great
remember to use a series resistor if it runs from 12 volts

in the original use on the 1970,s BMW they run 2 of them in series
and i have never had a dead one on a bike