Cylinder numbers above the exhaust port?

[chriselmore_1]

What do those numbers on top of the front exhaust port mean? Mine say 0 0 but have seen a bunch of other numbers on other cylinders

 

[SuperJETT]

Supposedly it was how well the cylinder sleeves were aligned to the ports in the jug, but I think that was proved wrong.

 

[#ZERO]

That's the sleeve port alignment with the cylinder casting and 00 is perfectly matched.

 

[SUPERJET-113]

I thought this was "debunked" too, but i cant remember why? lol

Why would they care about marking which cylinders sleeves are lined up the best?

 

[Matt_E]

That's the sleeve port alignment with the cylinder casting and 00 is perfectly matched.

That's the urban legend, anyhow. Can anyone tell me why Yamaha would go through the trouble and do this?

On the other hand, might Yamaha have reason to stamp the cylinders for specific piston/wall clearance so the right pistons/rings get installed?

I think the answer is pretty obvious from an economic standpoint alone.

 

[fulltilt429]

I hope its not port match, mine says 18 & 12

 

[SUPERJET-113]

I hope its not port match, mine says 18 & 12

:haha:
Oh dude you got a late Friday afternoon cylinder! Your screwed!

 

[Watty]

It would have to have something to do with tolerance wouldn't it? The only think that seems to change between mass produced parts is the pistons and rings. You never get a set the same and all decent engine builders will need the pistons before they bore to suit.

I'm sure Yamaha have some sort of setup that drops the sleeve in perfectly every time, so unless the castings on the sleeves and cylinders changes a lots, I really don't see why it would be port alignment that those numbers represent.

I do know someone that has contacts within Yamaha Japan, so I will ask the question...

 

[Mile9c1]

Supposedly it was how well the cylinder sleeves were aligned to the ports in the jug, but I think that was proved wrong.

Was there a thread about it? I've had two Wetjet cylinders marked "00" and both had PERFECT port matching. No "yamaha" 61X cylinder I've ever seen has been as close. Coincidence? No way!

 

[WaveDemon]

Was there a thread about it? I've had two Wetjet cylinders marked "00" and both had PERFECT port matching. No "yamaha" 61X cylinder I've ever seen has been as close. Coincidence? No way!

the zeros probably had less to do with the perfect matching than the fact that they were wetjet motors. I've seen and heard that wetjet matching is way better than standard yamaha.

 

[shawn_NJ]

I have a 0 - 0 61x cylinder here at my house. The mystery of the numbers continues....

 

[Mile9c1]

I have a 0 - 0 61x cylinder here at my house. The mystery of the numbers continues....

Well, how do the ports look?

 

[Mile9c1]

the zeros probably had less to do with the perfect matching than the fact that they were wetjet motors. I've seen and heard that wetjet matching is way better than standard yamaha.

Didn't Yamaha make them all? My guess is Wetjet said, "Hey Yamaha, we only want your '00' cylinders".

 

[Mile9c1]

It would have to have something to do with tolerance wouldn't it? The only think that seems to change between mass produced parts is the pistons and rings. You never get a set the same and all decent engine builders will need the pistons before they bore to suit.

There's no piston mark though.... if the markings represent something about the bore sizes, then it seems fitting that the pistons would also have to be marked in a special way, or they'd get mixed up. Yamaha marked the 66E and 66V pistons, I believe (GP800 and GP1200R engines). Those cylinders don't have sleeves, the cylinder bores are nicasil coated aluminum. I forget if the 66E cylinders were marked.

I'm sure Yamaha have some sort of setup that drops the sleeve in perfectly every time, so unless the castings on the sleeves and cylinders changes a lots, I really don't see why it would be port alignment that those numbers represent.

The Yamaha stock port mismatch is horrible! Whatever they did, it was anything but consistent.

 

[cattledog]

my spare cylinders have the mystery 00 numbers, spooky what does this mean

 

[Matt_E]

There's no piston mark though.... if the markings represent something about the bore sizes, then it seems fitting that the pistons would also have to be marked in a special way, or they'd get mixed up. Yamaha marked the 66E and 66V pistons, I believe (GP800 and GP1200R engines). Those cylinders don't have sleeves, the cylinder bores are nicasil coated aluminum. I forget if the 66E cylinders were marked.






The Yamaha stock port mismatch is horrible! Whatever they did, it was anything but consistent.

So why mark them for sleeve match? What's the point?

 

[OCD Solutions]

The 66E cylinders are marked just like the pistons.

I don't see the point of marking the mismatch unless it means there will be something done about it. Unless the sole reason is for grading and deciding who gets the cylinders, which is believable.

 

[Dustin Mustangs]

Mine is stamped 00 and seems to line up pretty good. A little sleeve overhang on the top and bottom of the ex port. Is that where you look?

 

[QuickMick]

It would have to have something to do with tolerance wouldn't it? The only think that seems to change between mass produced parts is the pistons and rings. You never get a set the same and all decent engine builders will need the pistons before they bore to suit.

I'm sure Yamaha have some sort of setup that drops the sleeve in perfectly every time, so unless the castings on the sleeves and cylinders changes a lots, I really don't see why it would be port alignment that those numbers represent.

I do know someone that has contacts within Yamaha Japan, so I will ask the question...

I think you on to something there young man.

 

[Matt_E]

Mine is stamped 00 and seems to line up pretty good. A little sleeve overhang on the top and bottom of the ex port. Is that where you look?

You would look at the transfers, not the exhaust.