E: Engine BTH magneto

[vibrac]

So I think my take off delays on the 2020 is the mag behaving badly.
I have pulled the BTH off the Comet Racer (thats not going anywhere this season) now when we were racing we removed the cut out lead because of the remote possibility of feedback (and to save the weight of wire and button) now I would like to refit a cut out as this is a road bike but its lost in the mists of time how I removed it can I get to a terminal inside the outer cover? there is a single domed alan screw there but I am loath to just jump in with both feet....

 

[BigEd]

So I think my take off delays on the 2020 is the mag behaving badly.
I have pulled the BTH off the Comet Racer (thats not going anywhere this season) now when we were racing we removed the cut out lead because of the remote possibility of feedback (and to save the weight of wire and button) now I would like to refit a cut out as this is a road bike but its lost in the mists of time how I removed it can I get to a terminal inside the outer cover? there is a single domed alan screw there but I am loathe to just jump in with both feet....

All the wires come out of the same hole in the body. The black wire should be in that bundle. I'm just about to go out now but I can have a look at the magneto and confirm when I get back.

 

[greg brillus]

There is no harm at all in removing the end cover, the wiring grommet fits into a small groove cut in the rear of the cap, good time to check that the ends of the poll pieces have no corrosion on them.

 

[vibrac]

Thanks Eddie & Greg now I know its one hole I can see a very neatly taped stub of cut out wire must have been Bens work its to neat for me
Now to find a cut out wire route that wont get near the ignition wires (I mount the coil high up on the sidecar boss ) its a Y wire cut out as it earths either to the handlebar button or the switch to isolate the walkernator
I recall the problem Greg referred to with rusting poles my guess is the racers R would have kept it clean I will look, but not before I have got the bike running you never know it may not be the mag it could be that new 32mm Mikuni.....

 

[greg brillus]

I think so long as the wires including the HT leads are in good condition there should be no issues if the earth wire is close to the HT leads. The supplied HT lead that is available these days tends to have a plastic insulation that will readily melt on hot cylinder head fins, unlike the old stuff that had a more rubber or silicon type of insulation that resists heat better. So try and keep these away from the head and exhaust nut fins and you should be fine. I use short lengths of fuel/oil hose about an inch long and cut along its length, then slip this over the oil return pipe that wraps around the head on the left side in a couple of places. Then you can use zip ties or rubber ties to hold the HT and kill wires securely so they don't touch anything hot. I always do them like this, looks neat and works very well.............This is a great way to insulate similar items on a race bike too, done it loads on the Vincent racer and the new ESO/Norton racer I have just finished and ready to race next weekend.................................Cheers...........Greg.

 

[Robert Watson]

I have my HT leads and the ground wire zip tied together all the way up the front of the engine on a BT-H and have no issues with it cutting out. Did it that way several years ago before someone said it was an issue..................... Ignorance is bliss.

 

[Simon Dinsdale]

Just get yourself some small diameter shielded coaxial type wire. Earth the shield part of the wire at the mag end only and use the center conductor for your kill button. You can then run it along the HT wire.
Here is an example of whats available:
https://tinyurl.com/y7ftvnbf

Simon

 

[vibrac]

Thanks Simon, but hopefully that does not apply as the advantages of mounting the coil (or coils) in the front sidecar hole ( I thread the securing screw through a rubber bung) are:
I can see the connections, they are not cramped under the cover, they are out of the way of water and the cut out lead never gets near the short HT wire as that goes off to the right and the cutout wire goes off to the left. Disadvantage is people can see it under the tank so it doesnt look standard (I should worry) and the wires are more prominent.
I never mind a few tidy wires showing I am always reminded of the MD secretary of a firm where I worked, she gave my stick until every vestige of wire was not visible, her desk was always pristine and it would take an age to check or change the connections, but her computer directory structure (folders to new guys) was an absolute mess she could never find a file when she wanted it,