Spark plug wires

[logan]

So I got this bike almost a year ago, I still really like it, and I browse this site very often. It was all started with the introduction of my 50$ special. Well progress has been really slow with working away from home all summer, and now I've started to get to it again. I tried to search and read all the topics on plugs and wires, with no luck to this question. I have some 8.5mm MSD wires left over from when I re-did the wires on my pick-up truck, would these work well on my 78-79 XS400? The old wires seem to be hard and brittle, and the spark from the plug looks dull to me. I thought the spark should be quite sharp and snappy. Any thoughts?

 

[Daddio]

8.5 is more than enough, you would have little resistance. As long as the ends give a snug fit you are good to go.

 

[logan]

Good to know, thanks! Would you have any ideas on the weak looking spark? Im back and forth from the shop to the computer, and to me it still doesent seem like a good strong spark, maybe thats normal? Most engines that I've worked with have a really good snap to the plug when they fire. this just kinda sparks? Oh ya, new plugs, coils, wires (now), full charged battery (also new).

 

[bcware]

You can measure the resistance of the coils and wires as described in the manual for a more objective analysis of your bike. The appearance or sound the spark makes is fairly subjective.

 

[logan]

Well I got it to fire, and run for 2 twist of the throttle, I figure its just a timing and carb issue now, the spark seemed weak to me, but I geuss its enough to make it run for now. Someone has been into the points and timing before me for sure! Im gonna keep playing around with it tonight, Im to close to quit now! (carb issue, yay,...... on going item with these bikes,eh? From what I read!

 

[OliverB]

Are your replacement wires resistor wires? If so, IMHO, not the best for our older bikes. For some reason, in our area I couldn't find ANY shop that had the old style wire center ignition wires so I bought a set from MikesXS. Those and new non-resistor plugs and plug caps - old ones burn out - and the bike doesn't miss a beat.

 

[bcware]

Yes, if your bike sat for any appreciable amount of time I am sure the carbs need to be cleaned. If you crack them open take notes on jet sizes and your float height for reference. If you have any other trouble that information will be useful for trouble-shooting.