73 GT250 Rex Caunt HT Coils installation

[shackleford]

Hello all. I read a suggestion on here that Rex Caunt HT coils were a good option for older two strokes. I recently received mine and I've ran into an issue with the installation. This is my first bike so please be patient with me if I fail to provide any needed information.

I've got the old coils off, but I've ran into an issue I haven't been able to find on the web anywhere. The Rex Caunt HT coils have a (+) on the right side of the coil and a (-) on the left side of the coil.

I'm not sure how to transfer the wires from the old coils to the new. Does anyone know which should go to the positive connector and which should go to the negative? Per the wiring diagram it looks like the black and white wire go to an AC generator and the orange wires go to the engine kill switch. I'm not sure how that transfers to the new coils.

Please see the attached pictures.

Any suggestions on how which wires go where and how to best wire the new coils is much appreciated.

Thank you.

[jabcb]

I'm surprised there no wires on the coil primary side terminals. The coils I purchased from them did.

I take it you want to reuse the coil wire harness. Either way works. Let us know if you want to make a new harness.

The bike is negative ground.
The two orange wires are hot from the ignition switch & connect to the coil positive terminals (+).
The black & white wires connect the coils to the points.

Those terminals accept standard spade connectors. You can get crimp on spade terminals at auto parts stores.

Attach the coils to the coil bracket & test mount them on the bike before attaching the wires.
This is how I mounted them on my GT250:

GT250_LeftCoil.jpg

GT250_RightCoil.jpg

Check to make sure you didn't switch the coil wiring when you are done.
Manually operate the left point & make sure the spark is on the left plug. Also test the right side.

[shackleford]

Thanks for the info. I got it all wired up today and I kicked it over. It fired up after about 5 kicks and idled really nicely. I got exhaust from both pipes, which before I was only getting exhaust from the right side. The bike died after a minute. I kicked it over again about 5 times and each time it would quickly die despite my attempts to give it some throttle. I'm hoping that was a product of it being so cold out and when it warms up I'll be able to get her to idle.

[jabcb]

How old is the fuel? Is it from last summer & you didn't use Stabil (or similar product)?

Check the condition of the points.
You can get another ignition system improvement by using fine wire spark plugs.
I use NGK B8EV plugs in my GT250. (Use non-resistor plugs with the resistor plug caps.)

Might need to clean the carbs. Pilot jets are quite small and easily crud up.
Am not much help on this, but others on this forum know a lot more about carbs.

[pearljam724]

I also bought the Rex Caunt coils for my 750 thanks to Jabcb. Rex Caunt needs to add a wiring harness.

[tz375]

That's probably a good idea, but our bikes are all the same and are all very simple. Power from switch goes to teh +ve side and the leads to the points/triggers go on the -ve side of the coil.


It's just that simple.

[pearljam724]

That's probably a good idea, but our bikes are all the same and are all very simple. Power from switch goes to teh +ve side and the leads to the points/triggers go on the -ve side of the coil.


It's just that simple.

Yeah, but I sold my old ones before I confirmed that the Rex Caunt's came with one.

[tz375]

I see what you are saying. Stock GT750 coils come with a 6 pin connector and Rex Cant coils do not, so they need a matching 6 pin to coil harness.

I'm so used to custom building everything that I sometimes forget that others just need to replace one part and it's easier if it's a plug in. Good point.

What did you end up doing? That info may be useful to others traveling that same route.

[pearljam724]

I see what you are saying. Stock GT750 coils come with a 6 pin connector and Rex Cant coils do not, so they need a matching 6 pin to coil harness.

I'm so used to custom building everything that I sometimes forget that others just need to replace one part and it's easier if it's a plug in. Good point.

What did you end up doing? That info may be useful to others traveling that same route.

At this point nothing. I have been working about 16 hours a day for the last 2 weeks with no time in between. I intend to just buy the wiring, connector pins and 6 pin connector when that time comes. Copy the wire layout from my 550 coils. I'll probably just swap out my 550 coils to fire up the 750 once it's complete. It's something I can finish at any time having the other. But, it kinda stinks those little extras will probably cost an extra 30 to 40 bucks on top of what I paid for the coils. Unless, someone has a better suggestion ? I could rule out the 6 pin connector and just use new pins, wiring and shrink tubing.

[jabcb]

Early model years used non-latching connectors & later model years used latching connectors.
Connectors are also available in two sizes.
Make sure to get the correct one.

The different types of connectors are available from Vintage Connections & Oregon Motorcycle Parts.
Spade connector are also available at local auto parts stores -- don't know if they have the other connectors.

Links for both companies + pics of my GT750 coils are here: viewtopic.php?f=29&t=4824

[pearljam724]

Does anyone think it would be beneficial to use one gauge thicker on the coils wiring ? Or would it be wise to stay with the same gauge ? Would it cause a problem if I did, being that only the coil side of the 6 pin connector would be thicker ? I don't think it would create a problem. But, the draw would change between the two points at the connector. What do you all think about that ?

[jabcb]

The coil wires are short & carry around 3 amps max. The benefit of a thicker wire would be unnoticeable.
Getting good reliable connections is much more important than wire thickness. You can use a thicker wire so long as you can crimp the connection properly.

[tz375]

The only counter argument to that is that on old bikes, there tends to be a voltage drop across connections and old corroded switches. In some cases it may be beneficial to install a relay in circuit so that only a very light switching load is carried by the switches and the heavier load goes via the relay to coils.

I have relays on the Ignition and headlamp circuits for just that reason.

[pearljam724]

The only counter argument to that is that on old bikes, there tends to be a voltage drop across connections and old corroded switches. In some cases it may be beneficial to install a relay in circuit so that only a very light switching load is carried by the switches and the heavier load goes via the relay to coils.

I have relays on the Ignition and headlamp circuits for just that reason.

I imagine that the relays improve the dimming and brightening of the headlight. Which seems all old bikes have that same problem. Or is that due to bad connections only ? If you have improved that dimming and brightening behavior, I'd like to see pics of what you did.