'79 XS project by a mechanical newbie. (But hey, it was free)

[stoneairsoft]

Maybe I'll just put them back on for now and see if the bike can even try to run after all the engine work I did, then I can worry about swapping the coils out.
My bike has the shiny resistor attached to the frame under the fuel tank, so it must, indeed, be way off.

[skids]

Maybe I'll just put them back on for now and see if the bike can even try to run after all the engine work I did, then I can worry about swapping the coils out.
My bike has the shiny resistor attached to the frame under the fuel tank, so it must, indeed, be way off.

It has a ballast resistor? An XJ? Check the coils primary. I would think 3 ohm unless someone swapped them out for 1.5 ohm coils and figured they needed the ballast resistor, but I am not sure about the XJ...

[stoneairsoft]

Take a look at my sig and the thread title. It's a '79 special. In THIS case, it'd be nice if it were and XJ

It has a ballast resistor? An XJ? Check the coils primary. I would think 3 ohm unless someone swapped them out for 1.5 ohm coils and figured they needed the ballast resistor, but I am not sure about the XJ...

[skids]

Hi Stone,
I grabbed some OEM coils out of my parts box today and tested all 4 of them. They have primary readings between 2.5 - 2.9 ohms. the secondary's with plug caps removed measure between 14.9k and 15.3k on the 4 of them.
Hope that helps.

Those coils probably come from the 81 bikes, right? The 81s did not have a ballast resistor. If stone uses that type he will need to bypass the ballast resistor assuming he has an earlier bike.

Uh, read DiverRay’s post (165) as he may have better info on the coils.

[motoman]

The late 80's to I think early 2000's Honda VFR 600-1100 models that used dual coils like the XS will bolt right up to the mounts. The plug wires are removable, and they are 3 Ohm so no ballast resistor required.
On your primary reading, if the coils are a later model, they will be about 3 Ohm, so you would be good. If you have a late production '79, it could have come from the factory with the 3 Ohm, and no ballast resistor.

If he can access some VFR coils locally, I would sugesst he take his meter with him to check them before purchase. Reason being, some of the Honda VFR coils are 1.5ohm and some are 3ohm. They are NOT marked as such, so having a meter handy to check across the two poles of coils is a good idea prior to purchase. I am using the Honda VFR1100 coils and one checked out to 2.9ohms and other 3.1ohms.....close enough to work just fine. That was some 9yrs. back and they are still working fine.

[Ranger_xs1100]

Those coils probably come from the 81 bikes, right? The 81s did not have a ballast resistor. If stone uses that type he will need to bypass the ballast resistor assuming he has an earlier bike.

Uh, read DiverRay’s post (165) as he may have better info on the coils.

Skids, The 4 coils that I have are from 80 SG's. obviously from 2 different bikes, but they all read aprox the same for some reason, and they did have the ballast resistors as well. I know the manual states 1.5 ohms, but it seems very odd to me that 4 different coils off of running bikes would read almost double that. Could they increase in resistance with age?

[skids]

Skids, The 4 coils that I have are from 80 SG's. obviously from 2 different bikes, but they all read aprox the same for some reason, and they did have the ballast resistors as well. I know the manual states 1.5 ohms, but it seems very odd to me that 4 different coils off of running bikes would read almost double that. Could they increase in resistance with age?

Well, DiverRay indicated “On your primary reading, if the coils are a later model, they will be about 3 Ohm, so you would be good. If you have a late production '79, it could have come from the factory with the 3 Ohm, and no ballast resistor.” As far as whether or not they could increase resistance with age, I am not sure... They need to be in the spec range. If I remember correctly, my coils from an 81H were marked as 3 ohm right on the coil. (I hope that helps) I can say that when coils are bad, the output can increase dramatically (plug wire to plug wire) with heat. I do/did not know that 3 ohm coils were oem on anything but 1981 bikes (USA)._________________

[skids]

PS. If the VF coils are purchase from ebay or where ever, make sure the rubber inserts and caps are supplied as well. Also, Motorman said that plug wires must be less than 8mm or you will break the screw-on caps.

[skids]

The Honda coils I installed were ‘83, ‘84, ‘85 VF750F or VF1000 coils FYI. They were easy to install.

[motoman]

The Honda coils I installed were ‘83, ‘84, ‘85 VF750F or VF1000 coils FYI. They were easy to install.

Easy, meaning literally plug'n'play' as the VF coils use same mounting holes as original coils.

[skids]

Easy, meaning literally plug'n'play' as the VF coils use same mounting holes as original coils.

Yeah, you still have to rig wiring connectors, bypass the ballast resistor if you have one, and rig new plug wires. A lot easier than the Dynas IMO.

[DiverRay]

Ranger,
You need to bypass the ballast resistor. You have the late model coils, 3 Ohm, not 1.5 Ohm. You can unplug the resistor and plug the two wires together. DO tape up the connection, as I was left stranded because I did NOT do that!

[Ranger_xs1100]

Ranger,
You need to bypass the ballast resistor. You have the late model coils, 3 Ohm, not 1.5 Ohm. You can unplug the resistor and plug the two wires together. DO tape up the connection, as I was left stranded because I did NOT do that!

Thanks Ray,
If the ballast resistor was used along with the OEM 3 ohm coils, what effect would that have? Could that cause the bike to run sluggish? Or would it not start or run at all?

[DiverRay]

It would start, but run poorly as you would not have the spark you need. A quick "check" is to bypass the resistor AFTER you have it running, and see what the difference is. You will probably like the way it runs once you do that. You do NOT need to remove the resistor, just in case you want to go back to "stock". But as it's one screw, I usually remove the resistor, as it also makes it easier to remove and replace the valve cover.

[stoneairsoft]

Something like these if they are 1.5ohm primary? My coils even say use with resistor on them, so I’m quite certain they’re supposed to be 1.5.

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F232860849698