Reading valve color

[nander]

Isn't that the right cylinder head we're looking at there? As in the Other left.

And the part of the crank with the blue part we're seeing seems to be around a lightening hole. Is it blue near the big end pin, or just out there? Since it's the web on the inside, the implication is that the inner bearing on that side may have a problem.

If the blue appears to have originated at the center pin or the big end pin, I'd strip the crank and inspect the bearings. If it's just around that hole I'd was things out with WD40 and see how the bearings sound.

You were right. I'm a knucklehead. That is the right side of the cylinder head we're looking at.

As for the blued crank, under good light I can now see that there is a band of bluing that wraps the hole in the crank below the blued surface we were looking at in the previous photos. The odd thing is that it is only visible from the rough cast side of the crank (first pic). I can't see anything on the other machined side of the crank weight (second pic).

As for the bearings, the inner bearing on the blued side of the crank doesn't seem to have any side to side slop. Both inner bearings slide off of their roller. In other words I can slide them along the shaft until they hit one of the center sprockets on the crank.

I'll post some pics of the pistons. The skirts had a lot of fine scoring, one particularly on the front and back, but they were otherwise undamaged. The color ranged from black to yellow. No heavy carbon deposits.

Anyway, that's a lot of information. Basically, I'm interested to know if that heating pattern indicates something in particular?
nander

[teazer]

The "Other left" will get you every time. ;-)

My take on it is that the heat effect you are seeing on the crank was done before the crank was machined. There is no evidence I can see of overheating or excess temperature since it was run. I'd replace the outer crank bearing if it's worn and refit the crank.

I'd like to see pictures of the pistons. side top and inside the crown if possible. That will tell us a lot more about what happened and may point to "why".

You mentioned scratches and they are usually caused by dirt rather than a seizure. Black and yellow sounds like a hornet or an ugly bruise, but not so common on a piston. Pics might help there. What are the barrels like - fine scoring signs of seizure or looking good?

Q - Could it have been that main bearing failing that caused the rough running and feeling like it was seizing? Is it damaged in any way or are the balls or cage blue and was it a roller or ball bearing? One of the outer mains was changed from roller to ball and that may have been a cost cutting or it may have been that they needed more flex and a balls are cheaper than Superblend rollers.

[jensen]

Hi,

The bluing (very hard to see)is indeed due to the production process.

The reason why Honda changed to ball bearings was probably due to the fact that the surface of the crank (where the pins run onto) gave problems after a while (the hardened surface tends to break of the inner soft material, this process is called pitting).

If the surface is pitted, you will need a new crank, but Honda thought of a cheaper way to fix that, with the bearing (cheaper for the customer).

Jensen

[nander]

Well it's good to hear you both think a honda machinist cooked that metal.

I've never heard of superblend bearings. I like the sound of them though. A quick Google search for [superblend bearings] seemed to turn up only references to Nortons. Is a roller bearing preferable to a ball bearing for those outer races if I am going to replace them?

I have to go by my little shop to snap some photos of the pistons. Which I'll do tonight.

As for the engine seizure. What I experienced was a low speed screech-to-a-halt. I actually wasn't riding it as hard as I normally do because I was making sure that nothing was wrong after the bike had tipped over a few nights earlier. I had ridden only about 3 miles and was in first or second, slowing to pull into a driveway. The motor seemed to be running normally. Without any warning it just froze with a horrible shrieking sound. I immediately stopped, put it in neutral and hit the starter button. It seemed as though the starter didn't have enough torque to turn the motor over. There was a lot of resistance on the kickstarter. As I pushed on the kicker, I could hear a the sound of something resisting rotation low down on the left side, in the area of the oil spinner. I assumed it was a seized left piston.

I dismantled the motor. The pistons were not stuck in the bore. There was some scoring in the sleeves and black ring marks in one barrel. I noticed the right outer crank bearing had some play, but the left outer bearing seemed ok. Of course, we know I seem to have trouble with left and right so I will double check all this and get back with some piston and sleeve photos.

[teazer]

I was referring to the Commando which upgraded form balls to rollers on the COMBAT motor and of course as the crank whipped, the rollers picked up on the "corners". The solution was superblend which are a sort of barrel shape, so they have the load capacity of a roller with the self aligning properties of a ball.

Honda realized that a balls is quite sufficient to handle the loads.

Back to that seizure though. It sounds as if the barrels and pistons may not have been the problem - when we see the pictures that may be more clear.

So if it seemed to come from the left side of the motor, have you pulled that side cover off yet? Did the primary chain tensioner disintegrate and jam the chain or did the centrifugal filter seize on ts shaft?

The plot thickens.

[nander]

Back to that seizure though. It sounds as if the barrels and pistons may not have been the problem - when we see the pictures that may be more clear.

So if it seemed to come from the left side of the motor, have you pulled that side cover off yet? Did the primary chain tensioner disintegrate and jam the chain or did the centrifugal filter seize on ts shaft?

The plot thickens.

Yes Teazer, it certainly does.

If I recall correctly, I had some concern that something must have bound up in the left side, but when I pulled the oil filter and clutch all the chains were where they should be and the tensioner was in it's place.

Seeing that everything seemed ok, the white valve and the scoring on the piston skirts caught my attention and I assumed they were the cause of the failure.

Here are some pics of the pistons. To try and limit confusion here's four pics of the first piston: top, front, rear, inside. I don't know which side it came out of, but it is the less scored of the two and my assumption is that it came out of the less marked up cylinder (the right). I'll create another post with the second piston.

Thanks,
nander

[nander]

Here's pics of the other piston. This one is more scored and the top is a little crustier.