83 Heritage Special left side not firing

turk64

Ah spring a time when a young(ish) mans turn to motorcycles of course. For those of you that have been following the nightmare that is my 83 HS you know that if I could just get my hands on a couple sticks of dynamite...

So during the winter it sat. I cleaned the carbs and was relieved to see that there were no blockaged and I replaced the little black rubber plugs that belong there. The battery was toast so I bought one and I was able to get the bike to run. I even managed to take it arround the block! It backfires like mad on the roll off the throtle but I figured that was another project for another day and parked it.

The next day was nice so I pulled it out of the garage, choked it and started it. Took a couple trys but it got there. I just left it choked and let it got for a couple minits. I was feeling the exaust and noticed that the right side was warm but the left was cold. I pulled the left plug wire and there was no change, when I pulled the right wire the engine immediatly quit.

This year is a PITA because the ignition is electronic, does anyone have any idea how to trouble shoot this? The plugs are new BTW.

grizld1

Your plugs aren't new anymore. Running any significant amount of time on the enrichers ("chokes") will foul 'em. Pulling a plug wire while running isn't a real good idea with the TCI system; that spark needs to get to ground. I'd start troubleshooting by removing the cap from the left plug wire and ohming it. It should show about 5K Ohms (gotta have a working resistor system to keep interference from making the TCI box unhappy). If you get more or less than that, replace the cap. With a good cap in place, put a good plug in it and ground the plug firmly on the head (not with your fingers--that can hurt) and spin the motor. If you get a nice blue spark, install good plugs and go. If not, you probably have grief in the left plug wire out of the coil or the coil itself. Unfortunately, Mamayama potted the plug wire connections in those early double-output coils, so that one amounts to the same thing.

When you inspected your carbs, did you remove the pilot jets? You can have a clean-looking orifice but still have obstructions in the bleeder holes. Your backfiring could have been caused by pilot circuits leaned by garf, or just by the bike needing more warmup, or by plugs that were already starting to foul due to overuse of the enrichers. If I were you I'd get try to get 'er firing on both sides and see what happens with fresh plugs on a long enough ride to flow some fuel and warm things up.

Good luck!

turk64

Thanks for the info. I am not sure about some of your acronyms though. What is a TCI box? What do you mean by Mamayama potted the plug wire connections in those early double-output coils, so that one amounts to the same thing. I am guessing that the box the spark wires goto that sits under the tank? It that the same thing you are calling a coil?

I am not sure that the caps can be removed from the spark plug wires, it looks like they are part of the wire itself.

As far as the carb goes I did remove the pilot jets and cleared them all.

Lets just say worst case senario the TCI box is toast, where can I get a replacement and how much would it cost?

grizld1

TCI=transistor-controlled ignition. Your plug wires are permanently installed at the coil end, so if the wires's bad you may as well replace the coil. Yep, that thing under the tank at the other end of the plug wires is your ignition coil. The caps should twist off; if not, cut 'em off and get new NGK 5K Ohm caps; there'll be a point inside the caps that penetrates the center of the wire; they twist on. I don't think your TCI box is likely to be the problem. Usually both cylinders would be affected.

turk64

Well I was able to unscrew the caps and they tested out at 10K Ohms, yea. I ordered a pair from Mikes. I though what the heck I will call the yamaha dealer. Get this. $22 each!
Obviously the old caps are shot, I will check back with you all to let you know how i made out.

grizld1

$22 each for NGK resistor caps?! Jeez Louise! They go for $9 a pair at my local independent shop! Trim the ends of your wires to get fresh material to screw into when you install the new caps.

turk64

well that made a big difference! No more back fires, and for the first time since I bought it Iwas able to go Somewhere 40 miles away and not have local buddy with a truck to come get me. So could it be that I have finally gotten rid of the engine demons that have haunted me? Now on to the brakes....

Wulf

You may want to go ahead and replace the coil and the plug wires as well, considering the age of the bike and they probably are original anyway. Less than 35.00 for both from MikesXS.
Wulf

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