Head machining

[VonSchmitt]

Can anyone tell me if a mis-matched head/rocker box can be re-surfaced & honed or bored for the cam journal to be reused as a whole? I understand it could be costly. But I wouldnt think that mis-matched ones are just trash? Are they? Every other motor can be machined. Can the xs650?

 

[angus67]

Idk, but I do see alot of heads separated from covers on ebay. somebody must know something!!

 

[5twins]

No, they're just people selling parts to make money, they don't have a clue or don't care that they may not fit. Personally, I feel it was a bad move to outlaw flogging for minor offenses like this, lol. If I was King .....

Anyway, yes, the parts are matched but mismatched ones may work. It just depends how far off the bolt holes and cam bearing mount area is.

 

[VonSchmitt]

Seriously? I just cant believe that Yamaha would have that big of variences in thier machining. I can understand that the cam bores might differ enough that you would need to rebore & hone for the bearing tolerences to be on. But, if the holes are drilled so far off from head to head? wtf? Then how come you can buy big bore kits w/ jugs? If the heads are drilled slightly different from one to the next, then shouldnt the barrels be matched to the head too?

 

[gggGary]

No expert on this, I have noticed how all the cam holders are numbered on DOHC 4s so you can put the proper holders back to where they were when the line bore took place. I am with you 5 twins. Used to drive me nuts when I'd see KZ1300 heads split up like that. Somehow the seller figures a head with no cam holders is worth more? Sorry Von you are stuck with the same old grumpy curmudgeons over here too. As you say it might work helter skelter but if it's good why do they bother marking them in the first place. Detroit does the same thing to bore the crank bearing holders on engine blocks.
I think when they rebore they go slightly oversize and use oversize bearings? With the cam riding in plain aluminum head and rocker box there isn't much recourse, once the aluminum is chewed you are done. Good reason to be sure you have an effective oil screen and filter in your XS.

 

[VonSchmitt]

I kinda see what youre saying. Ive done car motors, I understand why they are numbered or marked. But, still, why cant this be done on these engines? If the head & box was stripped, surface milled flat, the, theoretically you should be able to line bore the cam holders back to spec. I know a car motor can be done similar. You can machine meat off of the main caps then bore back to size. I never bought oversized main bearings for a car. In all honestly, I am not trying to argue with anyone. I just REALLY wanna fuggin know!

 

[650Skull]

you have the missed matched parts put them together and have a look at where they are misaligned and just maybe they arn't so bad. The cam seals do have a leaking problem if not fitted right and even then they can leak so any mismatch is asking for trouble. If you could mill and re-drill the cost would out way the value of the parts.......maybe in another 20 years ...................

 

[yamaman]

xs1961 has put together mismatched pairs with no drama. Just a case of trial & error. I'd imagine there is not too many variations, though it's going to be a stroke of luck to get you through if you don't have a few pieces lying around. Goodluck.

 

[VonSchmitt]

Well here is an answer from Heiden Tuining, MikesXS referred me to them because they couldnt really answer the question. I find this amazing that this is the case. I absolutly cant believe it! Glad I picked up another motor for my project. So essentially, if you have a mismatched set, melt em down for fishing lures....
Hello Jim

That is correct the head + and rocker box are 1 set.

In some cases it can work but then you have to measure it correct.

Line boring + flatten the surfaces is more expensive then a good used head.

Regards jerry

 

[VonSchmitt]

Maybe a thread should be started to list head & rocker box numbers on here to try to get some of these back together as a set? Just a thought. I would think an XS forum would be the perfect place to do it.

 

[XSLeo]

You have to worry about more than line boring for the cam bearings. Planing the mating surfaces will alter the valve adjustment cover mountings also. The bolts won't line up, the cover won't fit into the hole.
Way too much hassle to rework.