1060 Model 20 - running problems

Charles · Post by **Charles** » Mon Mar 17, 2008 12:15 pm

I have been running a model 20 with concentric carb, Boyer trigger in lieu of magneto with the boyer box firing twin coils. It has run beautifully for thousands of miles. I took it out for a ride on Saturday and did 12 troublefree miles before it would not pull, misfired and died.

It will start, revs up nicely and after a short period it won't hold the revs and dies with a spluttering noise. It does not sound like fuel running out but at first I thought it was and that the float needle was jamming shut so I could run it on a bowls worth of fuel and no more. The carb has been stripped, cleaned, replaced and it definitely lets fuel in as it is used and seals so it does not continuously run through so I am happy the carb is OK.

The timing has not slipped as when it runs for 30 seconds or so, it revs nicely before dropping back and spluttering to death.

All the connections seem to be OK to have done the 12 miles and it starts and goes for those few seconds.

Any ideas on where to start (no pun intended) looking on the electrical aspect of the ignition system? Could I have a faulty coil that fails after a short while? Has anyone heard of a Boyer box thats fails after a short while?

Looking for a torrent of advice and please don't ignore the obvious as this is me with the problem after all, and the Westward Ho beckons.

regards
Charles

paul knapp · Post by **paul knapp** » Mon Mar 17, 2008 12:59 pm

A competent auto electrician could soon eliminate the coil if that was OK.
But, having twice been let down with 'trigger' electronic ignitions failing (not Boyer) I would be finding somebody who could check your unit out.

Cheers,Paul

g80csp11 · Post by **g80csp11** » Mon Mar 17, 2008 6:45 pm

low battery voltage would my guess . The boyer system needs a good charge to work correctly . have you checked that the alternator is charging OK

any less than circ 9v will cause a problem

Charles · Post by **Charles** » Tue Mar 18, 2008 9:37 am

The battery status is fine. I keep it topped up with an Optimate anyway and it was showing a small charge on the run, with the lights on and the charge state is still very good. I have run this bike without a battery in the shed as with the capacitor in the Boyer, when fed as normal from the powerbox, it will run.

A pal with a Triumph and the same set up said he had identical symptoms and it proved to be a bit of dirt in the pilot jet in the concentric carb. Why this would have the observed effect as you enter Needle/needle jet territory I don't know but maybe it does so I will check that out tonight. Perhaps a carb expert could add something on this.

Don Madden · Post by **Don Madden** » Tue Mar 18, 2008 3:12 pm

Check the vent hole in your fuel tank cap. A blocked one will produce such problems.

Cheers, Don.

Janet · Post by **Janet** » Tue Mar 18, 2008 3:46 pm

Hello Charles, are you going to Poland?

As you are aware, I know nothing about these bikes but have you checked the fuel tap and filter?

Charles · Post by **Charles** » Tue Mar 18, 2008 4:07 pm

Hi Don,

that was my first thought when it happened so I ripped the tank bag off and released the cap - Still the same when there i sno cap on the tank.

Janet, there are neither wax nor pins in the tap or filter and fuel floods down the pipes to the carb and the nylon filter in the banjo is clean. I am going to Poland and trailing the bike, probably the single as all three of us in the car will have a Model 18 of some vintage on the trailer.

regards and hoping to hear from a concentric carb expert
Charles

Rick.Edwards · Post by **Rick.Edwards** » Tue Mar 18, 2008 7:25 pm

Change the spark plugs

Chazzyb · Post by **Chazzyb** » Tue Mar 18, 2008 7:44 pm

Eh, Carlo! My mate Mr. Ed riding an A65+Boyer had a similar problem going to the John Bull rally last year. Robin and me lost him after he fell by the wayside in a Belgian 'road through town up - find your own way' diversion. It was one or both of his coils. Bike would cough and stop. Ten minutes later it would start again... for a while.

deshollier · Post by **deshollier** » Tue Mar 18, 2008 7:59 pm

Yes Chazz that is exactly the problem I had on the Commando's Boyer system. Took me a while to sort because the seller swore (hand on heart) that he had changed the coils, and my checks did not reveal a problem at first. Evenually I got a varying reading on the coil primary. I fitted a pair of new coils and it has been fine ever since.