Backfire Moto

Yesterday I took the bike to my first Backfire Moto event, a local vintage motorcycle meet-up that happens on the 3rd Wednesday of the month. Last night was Backfire Moto #37. The bike ran great, no problems and good power. Here are a few pics. Only the red Honda SL350 is mine. The other pics are a few of the other bikes that were there (there was probably around 100 bikes there).

What Next?

OK, in my last post I mentioned that I was going to try and top up my battery. After an overnight charge on a 1 amp float charger, it only got up to about 11.36V and was falling (with nothing attached to it). The battery definitely seems toast. I took it to the auto parts store and asked them to load test it. They said that they don't load test motorcycle batteries. But they did have some other sort of tester, which they attached to my battery. It said that I have 0 cold cranking amps. The battery is only 6 months old, but I guess I have to replace it anyway.

Another potential problem, my new voltage regulator/rectifier is allowing my DC voltage to climb to over 16V at higher RPMs. I am hopeful that this has something to do with the bad battery. But I'll have to wait and see.

Got the new battery, filled it with acid, and gave it an initial charge. I put it on the bike, and thought that everything would be good to go. But, it wasn't.

The good news is that the issue that I was observing with the regulator/rectifier unit was indeed caused by the bad battery. With a new battery in the circuit it now doesn't go above about 14V. The bad news is that it ran like crap again. It didn't want to idle and it had no acceleration power.

I pulled the spark plugs. The right plug looked fine. The left looked dark and wet. I pulled the cover off of the points housing. The right cylinder points were sparking, the left were not. I pulled the left plug wire off with the engine running. No change. Clearly the left cylinder is not firing at all. I started to suspect the coil. As far as I know, you can't buy a new replacement coil identical to the original. You either get to modify or buy an old coil. And they aren't cheap. But, before assuming the coil was bad, I wanted to check for wiring problems. I undid my charging system wiring mod (the one that bypasses the headlight switch). No change. I pulled the tank and checked the wires to the coil. I noticed that the connector for one of the wires wasn't fitting snugly. And as I unattached and reattached it a couple of times, one of the connectors crumbled. I created a new pigtail to bypass the bad connector. Boom, I get spark on the left.

Well, it was after dark and getting late so I haven't done a thorough test. But my one trip around the block went great, the best power from the bike yet. Of course I need a longer test, but I am encouraged to say the least. I will consider redoing the charging system wiring mod. And the clutch needs adjustment. But I am shooting for a trip to Backfire Moto tomorrow night.

Charging Sytem Upgrades

Given that my charging system appears to have problems now, as I fix it I might as well upgrade it a bit. Apparently these bikes have always had a charging system that was barely adequate. And that was in 1971, before bikers ran their headlights all day. And on a bike that didn't come with turn signals (which I have added). So, I decided to do these two mods:

headlight switch bypass mod: http://www.hondatwins.net/forum/viewtopic.php?f=53&t=6185
regulator/rectifier mod: http://www.hondatwins.net/forum/viewtopic.php?f=46&t=14530

The first of the 2, on my bike, will only help when the headlight is off. That should be pretty much never. But I can see turning it off to try and limp home if I have another charge issue.

The second mod allows me to replace the existing regulator and rectifier on my bike with a single combined rectifier/regulator unit. Here are the old bits:

The stock voltage regulator

The stock rectifier. I dissembled it to get the wires out, I intend to reuse the pigtail.

I replaced both of the units above with this new combined unit (front and rear view):

I modified the pigtail like so:

Here is the modified pigtail attached to the new unit:

And here it is attached to the bike (where the old rectifier was mounted):

Unfortunately I cannot yet report on how it works. It appears as though I may have killed my new battery by discharging it too many times. I am going to try and top it off and see if it works. But if not, I will have to get a new battery and then test this mod.

Still Tuning

OK, so I haven't posted in a while. What have I been doing? Lots of tuning, some repeating old work but trying to do it better. For example, twice I adjusted the point gaps and set the timing. But I ended up doing it a 3rd time when I decided to put in new points and a new condenser. Similarly, twice I have disassembled and cleaned the carbs. But I just did that for a 3rd time with new internal parts (i.e. jets, needle, gaskets, etc.).

The bike now seems to run a lot better, but only under certain conditions. First, it is harder to get it started. Once it starts it runs well and has more power ... for a while. Twice I have ridden it to work. It ran well, both time, for the initial part of the ride. But it was running rougher by the time I got there. Both times I was barely able to keep it running for the trip home. I concluded that it ran fine cold, and even warm, but hot was a problem.

That is until I discovered another problem. The charging system wasn't working correctly. I had attributed the change in how the bike ran to its change in temperature. But I now think that it was simply how long I rode. You see, I was putting the bike on a trickle charger at home. But when riding it, it eventually drained the battery to the point where it runs poorly. I am now putting this theory to the test.