Baking Brownies

I got the rest of the head disassembled and all of the parts bagged and tagged. I bought a used cam chain roller and a new valve off of ebay to replace the broken/bent ones. I spent last weekend cleaning off all of the mating surfaces that will be getting new gaskets. There was some old gasket glue on them and I wanted them to be clean, smooth and shiny. I also cleaned off all of the buildup in the combustion chambers and in the valve ports. When I cleaned out the exhaust ports, 35 years worth of carbon dust came billowing out. Good thing I did that outside. I also noticed that the exhaust valve seats were pretty cruddy. I think they were not seating right which might have led to some of my low compression and poor engine performance. Although it is hard to see in the picture below, there was a whole lot of crud baked on there.

I also painted some of the other parts I had previously cleaned and given the brushed metal finish to. The brushed metal parts are painted with a clear enamel and the satin black parts are painted with a black enamel. The enamel should be heat cured for full hardness, but I didn't want to stick my parts in my oven. So, I hung them in front of a small space heater I had for about 20 minutes each. The second picture is the tachometer being "baked". They got too hot to touch and hopefully that is enough. I still have some more parts to do as well as the carburetors.

No Dissassemble Johnny5!

Made some more progress on the engine last weekend. I removed the exhaust cam, torsion bar springs and valves. The torsion bar springs which are the hallmark of this engine were a lot easier to get off than I had expected; a lot easier than I hear standard coil springs are to remove. Lets hope they are just as easy to reinstall. I've already made the special tool required to install them out of a cheap socket. The left exhaust valve is the one I bent. You can see it kind of pointing off to the side in the second picture. Since the valve guides that the valves slide in are reamed to exactly fit the stem of each valve, the bent valve was obviously not going to just slide out. I thought about cutting it just above the valve guide with my trusty dremel tool, but decided to try to bend it back as straight as I could first. I got my big set of channel locks and started bending. It took about 20 minutes of bending and rotating and bending again, but it eventually just slide out. I know the valve is scrap and I am going to replace the guide as well just to be safe. Next I will take the intake cam, springs and valves out. The head and valves will get cleaned and the valve seats redone.

I also took the cylinders and the pistons and piston rings off. As I said, the bike had low compression and was blowing smoke before I bent the valve so the cylinders and rings will get redone as well. I'm going to go ahead and polish the pistons and head as well while I have the engine apart. Now I just need to find a good machine shop.

Pop The Top

Engine disassembly has begun. To remove the top end which houses the overhead cams and the valves, you have to remove the cam chain that feeds through it. I had to buy a chain breaking tool since the master link on the cam chain is riveted. Once I received that, and figured out how to use it, I was able to get the cam chain off. The directions in the motorcycle manual say to make sure to tie off the cam chain so that it does not fall down into the engine when you break it. I did this with electrical wire, which I quickly discovered was not strong enough. Luckily, I had not pushed the chain link pin out all the way and the chain got caught on something before it fell all the way down. I got some wire hangers and bent those up to hold the chain. I took the head off and took a peek inside. The pistons and cylinders didn't look too bad. The valves looked pretty cruddy though. I could see the valve that I bent would not close all the way. Definitely going to going to need to be replaced. I also notice that the pin for one of the cam chain rollers was loose. I was actually able to pull it out and I couldn't figure out how it was supposed to stay in. After looking it up online, I realized that one end was supposed to be deformed like a rivet. Apparently that deformed part had broken off of mine. How did this thing not explode when I took it up to redline?

Breaking the cam chain

The broken cam chain roller pin

Gone to Pieces

And so, the teardown begins.....

A Broken Heart

OK, where do I begin? I borrowed a compression gauge from Autozone because I wanted to see if low compression was causing my idling problems. Nixon is also burning oil so I figured the rings were worn. I got reading of 130-135 psi in each cylinder. I was told it should be around 180 and anything below 150 warranted new rings. So, I figured I could ride it the rest of the summer and replace the rings and hone the cylinders this winter, since that means pulling the engine off of the bike. But first, I had to fix this pesky oil leak from the ignition housing.

I may get a bit technical here so if you don't care, just skip this part. I actually didn't know about all of these parts until I opened it up. I ordered a new gasket for ignition housing. When it arrived, I took the housing off, and discovered that the housing also acted as the bushing that the exhaust cam spins in. So I took the housing off and cleaned the mating surfaces and gave them a light sanding and cleaned them with some denatured alcohol. I spread a thin film of gasket glue on both surfaces and then put the gasket on the engine. I then put the ignition housing back on and sliding cam back in the bushing. But, it wouldn't go all the way back on. There was about an 1/8th of an inch gap between the housing and the head. Hmmmm. It was kind of tight when I pulled it off. I tapped on it a couple times to coxe it in. Nothing. I started turning the screws and the seemed to be closing the gap. They were kind of hard to turn, but as long as I kept going around the bolt pattern, the housing continued to go on. I finally got the housing all the way on and put the rest of the ignition parts back on.

Since I had take one of the valve clearance locking nuts off to get the housing off, I had to reset the valve clearance. This is where everything started to go wrong. I took the altnernator cover off so I could rotate the engine. Oil started gushing out. Normally, this doesn't happen. In fact, you have to have this cover off when you set the timing so only a little oil sprays out. But this time, it kept coming and coming. I had to scramble to catch it all and all I had was paper towels and plastic grocery bags. I seemed to have that under control and then noticed that one of the grocery bags had let the oil through and it was now all over the garage floor. Unfortunatley, my garage is carpeted with industrial carpet (don't ask) so the oil made quite a mess. After I had that as clean as I could get it, I went back to setting the valve clearance. I got the valve cover off and checked the valve clearance. There was A LOT of clearance. Hmmmmmm. I tried rotating the engine and it was very hard. And, I didn't see the valve move. Uh-oh. That's when I noticed it. I could see the end of the valve. I shouldn't be able to see that. The cam follower was supposed to be on in. Where was it? It was NEXT to it! Huh? I took the ignition parts off again and started to take the ignition housing off. I heard a loud pop and the cam follower popped up and sat partly on the valve. I took the housing off and the cam follower fell off next to the valve. I managed to get everything reassembled the way it was supposed to be and the housing went on all the way easily. But now the cam follower was only slightly sitting on the end of the valve and that's when I realized exactly what I had done.

I BENT THE VALVE! When I took the housing off, that allowed the cam to shift a little, and the cam follower fell off of the valve. I didn't see this because the valve cover was still on. When I put the housing back on, the cam follower got stuck between the valve and the cam bushing. When I forced the housing on, the bushing pushed the follower which pushed the valve to the side which bent it. Engines don't run with bent valves. I'm screwed.

So now, I have to take the engine off of the bike and take it apart and replace the valve, the valve guide and probably a bunch of other parts. Since I'll have it apart, I might as well redo the rings and cylinders. So, it looks like I won't be riding for awhile. I have no idea how long it will take to do all of this work. Oh well. I bought this bike so I could learn how to work on engines, so I guess now is my chance. I was just hoping to get a good riding season out of her first.