new issue

[oldyam80sg]

So today I went to start the bike up and it seemed fine after a short ride down the street. I spritzed the pipes and noticed #4 exhaust pipe was slightly warm to the touch. The other pipes were hot. I replaced the o ring in the float seat and also adjusted the float previously. I understand the floats for my 80 SG are .23 mm instead of .25mm-is this correct? Maybe I measured in the wrong spot. Does the measurement go from the top of the black highest part to the gasket? I took the cap off the spark plug wire and trimmed it slightly and screwed it back on and it got a little warmer but was going to be running late for work so had to stop and shut off the bike. All the other pipes are too hot to touch except #4.

[red bandit]

It's 25 not .25 and I think that is the correct float height. Measure from the top of the float to the gasket surface, no gasket in place. If you suspect electrical you can swap spark plugs 1 & 4. And check the pipes. If no change, swap plug wires 1 & 4. And check the pipes. If you have the original coils you might want to consider replacing them.

[bikerphil]

The correct float height for the 80 carbs with the plastic floats is 23MM (29/32") measured from the bowl gasket surface, gasket removed. The manual states to use the clear tubing method for the 81-82 models, but I have found that measuring to this area of the float is extremely accurate and totally acceptable.

[oldyam80sg]

So today I went and started the bike-in my opinion weak spark on #4 plug wire. The spark plug was wet but didn't want to fire The pipe (#4) got hot but then after starting it multiple times, cutting the wire it didn't help and was able to touch it. I cleaned the connections and no change. I have 2 more stock coils in my storage unit but my Jeep was in the shop, so could not go there to get them. One of the coils has the new wires in old coils modification so will use that. I took off the carbs and took off #4 float bowl to measure the float level. I adjusted it using a slide ruler and put the carbs back on the bike. I started it up and did a sync. I had to adjust #4 mixture screw and bike now idles nicely. I had to lower the idle as the revs started to climb. Finally bike seems to be running nicely and idles around 1000 rpms. Will see how it runs tomorrow. My question now is could the wire in the coil be bad? Since #1 and 4 share the same coil and #1 is very hot is that a possibility?

[DiverRay]

Yes, one wire can go bad and cause all the energy to go to the other plug. Coils fire both plugs at once, and electricity likes the easiest path to ground.

[oldyam80sg]

Thanks for that- I have the new wires in old coils mod I think the wires are made by Accel. I will put them in tomorrow.

[Radioguylogs]

Actually, #1 and #4 spark plugs are wired in series. Both plugs should always have the same spark if they are good plugs.

I don't know which direction the current actually flows, but you can imagine the current goes from the coil through #1 wire, through #1 plug, into the engine ground, then back up #4 plug, up #4 wire, and back to the coil.

When I am testing the ignition spark with the plugs out, I use car jumper cables to connect the plug threads of #1/#4 and #2/#3.

[oldyam80sg]

I put the other coil on today and all 4 pipes are hot now.

[oldyam80sg]

Here is the coil

[oldyam80sg]

For those who have done this coil mod-you need to have the terminal stud that is on certain NGK sparkplugs which is what I run. I know the stock coils don't need this part attached.

[bikerphil]

Want some hot spark? Spend some $$ on the Dyna coils, if you plan on keeping the bike. Forty year old coils not the best thing.

[oldyam80sg]

Dyna coils-which ones?

[bikerphil]

The coils are the Dynatek DC1-1, they are about $179 a pair.
They are green in color, beware for cheap imaginations from China that are out there.
They don't come with wires, the solid core wire set is DW-200
They are not completely plug and play, you need 4 small L brackets and some simple hardware to bolt them in.
Money well spent IMHO.

https://www.ebay.com/itm/31400063437...3ABFBMyNLR9

[oldyam80sg]

Not cheap at all. Do I need to run the ballast resistor? Is that even a factor?

[DiverRay]

I don't have the Dyna part number handy, but they do make a set of coils that you do NOT run the resistor with.