PmWiki | CA95 / Restoration

The best resource for restoring one of these bikes is http://www.fourwheelforum.com . A few specific areas of trouble I ran into are included below.

I made a series of mistakes when re-assembling an otherwise very simple engine. My difficulties were as follows:

1) By a somewhat unfortunate design feature on these old engines, the kick starter mechanism can be installed in two positions. This is because the starter has a y on the end of it that latches into one of two notches on the top of the engine case. If you install this in the incorrect position it allows the starter to rotate too far when disengaging. Unfortunately you won't be able to feel this with the engine on the bench. It will turn the engine fine, but the engine isn't being started on the bench (hopefully) so it will never kick back. When this does finally do so (after you went through the work to put it on the bike) when the engine kicks and the starter rotates up (too far) the now spinning gear adjacent will bend and dislodge the spring on the ratchet mechanism. Result, you kick once, engine fires, kick starter never works again. Not until you open the case back up (and in my case make the same mistake a second time resulting in a total of 3 full engine tear downs).

 So, CHECK THIS when you install it. Don't be like me.

2) If you are used to working on cars you no doubt assume that the timing is controlled by a chain. It is not. The 'valve timing' is controlled by the cam chain, however the points are directly attached to the crankshaft and can only be put into one position due to the key on the tapered end of the shaft. As such, Weird timing issues can not be the result of internal mis-alignment unless you have a valve hitting the piston, but obviously that is valve timing not electrical. It unfortunately required me to change the valve timing from right to wrong before I realized this. In my defense I had a lot of input from other passing mechanics that helped me pollute this thought process : P

Also, since both pistons travel simultaneously in the cylinder, both are at top dead center at the same time. One piston is in full compression, the other is in-between exhaust and intake. As long as the valves are fully closed on one piston at top dead center, there will not be a valve clearance difficulty. This means you can actually have the engine run fine with the valve timing in 2 positions. As long as you are either dead on, or a full 180degrees off, you are fine. All this changes is which cylinder is firing and which is exhausting. The reason this doesn't matter, is that there is only 1 set of points. That is, both sparkplugs fire every time both cylinders hit tdc. The result is an engine that is stupidly easy to put back together unless, like me, you look for ways it can go wrong. I suppose it is sort of like target fixation. I created the problem by trying to find it.

That leads me to my last difficulty. The first time I rebuilt the engine the timing seemed to be about 20 degrees out. After resetting everything (and subsequently realizing I had done nothing but waste an afternoon) the timing was closer, but something was still definitely not right. The bike currently runs on one cylinder. The fortunate/unfortunate detail is that the cylinder it fires on follows the sparkplug wires. That is, I can switch them left to right and it is the opposite that now runs.

As it turns out, the previous owner of the bike had rigged something in the electrical to bypass the battery. As I was re-assembling I inadvertently undid this. The result was 1 plug firing, the other not. I don't have the details to explain why just yet, but once we checked the wiring and got power from the battery to the ignition switch, the bike took off like it was in a granprix. The bike is again running and, short of needing a little timing adjustment, it is running better than it did. The electric start even works.

SO... Don't assume you have a bad coil just because one side won't deliver a spark! These bikes will not run without a charged and working battery. If yours runs without one (as mine did) suspect foul play.

{Edit} That's not entirely true. I will explain in more detail soon.