Yam_Tech314's official build thread

[Brassneck]

Those marks look like tool created...not overheating. Losing oil to the top end causes all kinds of damage (I just found this out on my vintage race bike unfortunately) but not that kind of damage. Overheating isn't good for any engine, but again...don't think it would cause that kind of damage.

Something that came from the thread I linked to above seems plausible...here's what Twomany noted: "That sure looks like a history of intake valve float. Possibly from over-reving, followed by piston smack into valve, then bent valve stem, then piston beating the bent valve head against the outer edge of the combustion chamber"

If that's in fact what happened...my guess is it happened before you took over ownership..or you would have been dealing with much more than a blown head gasket.

 

[5twins]

This is the first time I've seen this so I don't think it's very common. Head gasket leaks, on the other hand, are very common on these bikes. Mostly that is due to the head nuts coming loose because of the rubber/metal sealing washers Yamaha used on them.

 

[Jim]

Just got an Ebay alert telling me this guy is accepting offers. It's already under a C note shipped. Might be worth looking at.
Cylinder head. $70.

 

[G_YamTech_314]

Jim, I took a look at that listing.

This cylinder head came off a bike with 27,000 original miles. I'll link the listing in the thread.

Here's pics of the chambers. One ran much nicer than the other by the looks of it. Am I being too picky? After the mess I discovered with MY cyl. Head, I DO NOT want any other problems from another one.

 

[G_YamTech_314]

Here's the ad. I am really just looking for a second opinion here. I'd hate to end up in the same boat.
https://www.ebay.com/itm/CYLINDER-H...-/141455291689?_trksid=p2349624.m46890.l49292

 

[Jim]

How they burned over all those miles comes down to the guide seals, the rings, carb jetting and how strong (or weak) the iggy system was on that side. None of that tells you anything about the head. The pics only go so far... so buying online is always a gonna be a crapshoot. I'd be more concerned with the sellers rating and number of sales...

 

[G_YamTech_314]

Well in that category both guys have a 99.9% rating but ones been a member since '17 and the other since '00.

I know I'm PICKY. But the older member obviously has more sales, but his ratings match the new guys which to me, show consistency. His description of the item was also better. He said they tested it with carb cleaner and it didn't leak... Albeit a crappy test, it's better than no test at all.

I think I made my choice.

Hopefully in this case I get what I pay for...

 

[Jim]

When a seller says in his ad to contact him for a resolution before giving a bad rating.... well I give 'em extra credit for that. It shows they're willing to go a little extra to keep their good name. At least that's how I see it. Seems a little steep to me, but other than that, I'd roll the dice.

 

[G_YamTech_314]

Yeah, I was thinking the same thing
It shows they're present in their sale and not just trying to dump their junk onto someone else.

I just feel that if it's original miles, after THIS LONG then the chances of it being damaged could be less.

Here's to hoping.

 

[G_YamTech_314]

Got the new cylinder head and cover in today.

Took the valves out and did a proper carbon removal with the bench grinder with an attached wire wheel. I was able to get them to come pretty clean, although the one exhaust valve lacks the color the rest have. It seems a lot darker than the other three valves. Is this an indication of too much heat?

All in all, the combustion chambers look to be in much nicer shape. No flaws that Ive found yet.

 

[5twins]

That may be an indication that the valve and valve seat got coated with carbon. Was that combustion chamber more carboned up than the other one?

 

[Jim]

although the one exhaust valve lacks the color the rest have. It seems a lot darker than the other three valves. Is this an indication of too much heat?

I'd suspect that valve was held open for years as the engine sat idle... causing the discoloration. You can chuck that valve up in a drill and hold some 400 paper against the face by hand to see how it looks.
you can see on this valve after the 400, there's some pitting and a ridge wore into the face. Mine will need re-cutting.

 

[G_YamTech_314]

That may be an indication that the valve and valve seat got coated with carbon. Was that combustion chamber more carboned up than the other one?

Yup. By quite a bit. The whole valve in general came less clean than all the others. I spent equal time and effort on all four.

As long as this won't affect performance I don't mind. Going to lapbthem all after cleaning the head again anyways.

 

[G_YamTech_314]

I'd suspect that valve was held open for years as the engine sat idle... causing the discoloration. You can chuck that valve up in a drill and hold some 400 paper against the face by hand to see how it looks.
you can see on this valve after the 400, there's some pitting and a ridge wore into the face. Mine will need re-cutting.

I imagine I should avoid the sealing surface when I do this? Is there a benefit to doing this to all four valves?[/QUOTE]

 

[Jim]

The face is the sealing surface. Yeah, that's what you want to clean up to look at. Valves are hardened. You could burn through ten bucks worth of 400 paper and still not hurt it. Just run it long enough to get it shiny and see what you have.

 

[Jim]

Keep in mind that you now have 8 valves to choose from... pick the best 4.

 

[G_YamTech_314]

So I can use either intake and either exhaust valve based off of which ones I like the most?

I assume I should look at the seat area and find the four widest (and least pitted) valves...

 

[Jim]

So I can use either intake and either exhaust valve based off of which ones I like the most?

I assume I should look at the seat area and find the four widest (and least pitted) valves...

Look in the book and go by that criteria. Use the best ones.

 

[G_YamTech_314]

Ohhhhh shiny!

This should make it pretty easy to lap the valves.
When I did it before EVERY part of the valves were full, but dull vs. shiny will be easy to decipher and measure to determine which valves are best.

Another thing I noticed... You'd more than likely notice a bent valve when it's chucked into a drill right..? None of them wobbled. I'm gonna say that's a good thing haha

 

[Jim]

Another thing I noticed... You'd more than likely notice a bent valve when it's chucked into a drill right..?

Yes, that's the main reason I chuck 'em up when I remove 'em... just to make sure they're straight. Puttin' a shine on the face is just a bonus.