Can cast rocker arms be "REBENT"

[GSScoobie]

If the cobbled up repair is going to cost more than $50.00 in time/effort/expense, why not just buy the new part and be done with it?

[hjfisk]

Chuck, give a little time this weekend , I think I have a whole head and valve train assy for that Yamaha. We tore one down about 15 years ago and I believe I have the remainder out in the trailer . I just have to spend some time going through totes. I'll look either tonight or Saturday.

[rustybronco]

Do you also agree that shimming the rocker to center the tip over the valve will also effect the way the wiper sits on the cam?

Yes I do.

What I think is, find out the reason why and if it's the arm correct it.

[chuck hahn]

Scoobie...and what if I buy these off Ebay and that "just the way they made them" and I get shanked out of the cost and the shipping? Soon as i can get back to Randys shop I will put the cam blocks back on tnhe head and set in a valve and do some eagle eyeing of the situation. I will measure the valve seat placement for comparison from side to side etc etc etc.

[sedelen]

If the cobbled up repair is going to cost more than $50.00 in time/effort/expense, why not just buy the new part and be done with it?

New rockers are no longer available (NLA).

[GSScoobie]

Chuck,

This experiment indicates the rocker arm and/or base is bad. I'd be concern with machining the rocker since it may mess up the way the cam wiper pad contacts the cam. Since these parts are readily available and cheap, getting some new/used parts seems like the appropriate thing to do.

I'll defer to you guys when you say they are not cast iron, but how can they be forged with numbers like this on the side?

http://www.ebay.com/itm/Yamaha-NOS-A...e4e91a&vxp=mtr

Didn't he see this post?

[rustybronco]

Soon as i can get back to Randys shop I will put the cam blocks back on tnhe head and set in a valve and do some eagle eyeing of the situation.

I'd say he has seen it.

[chuck hahn]

Dale..yes Randy has seen it for a bruef minute but he was up to his azz in alligators at the time I pulled the head. I am gonne go over there tomorrow afternoon and set everything in place and take lots of pics. The cam blocks show nothing worn or ground down on either side of the rocker either..stay tuned.

[chuck hahn]

Took some pics...and I didnt recall that the right intake was off just a bit from center also..but it was the left cylinder that was trashed. They surely didnt have things laid out very closely on theses bikes. Not damage of any kind to the cam blocks as you can see. I just find it hard to believe aqnyone reviewing the data siad.."what the heck...close enough i guess" and signed off on this.

[chuck hahn]

This is from an email exchange i had with the English Gent that is a respected authority on these. He has tried all the old AND new camblocks and it seems the misalignment issue prevails regardless of what blocks you aquired. I posed the idea of cutting slots on each side of the stiff back and rewelding..heres the exchange::



to argo1974

I am almost tempted to cut a small slot on each side of the stiffening ridge and give them a smack till the adjustersare over the stem correctly. The reweld the slots with my MIG welder and finsh grind the repair smooth. I was told the rockers are made of cast steel, so i can presumably weld it with a MIG.

[chuck hahn]

Argos response to my inquiry:::




to me

Yes, you can weld them. I have had the same idea and tried TIG welding on some scrap TX rocker arms. It works.
I don't know the quality of MikesXS elephant foot adjusters but they look somewhat suspect due to plastic retainer rings.
I know a lot of XS650 owners using VW elephant foot adjusters with great success:
www.ebay.com/itm/120359789745
www.ebay.com/itm/120356238716

[chuck hahn]

I like this possible explanation from Argo as well. Might just have to keep a feeler guage to them and be sure they stay well within tolerances...VERY often!!!


Argo Raudvee
10:26 PM (30 minutes ago)
to me

Charles,
frankly, I not sure if bending the rocker arms is a good idea. The more I consider, the more I think the misalignment is intensional.
This will turn the valve little by little within each lift and change the contact area of adjuster screw on valve stem. That means less wear on valve stem and valve seat.
Though, it doesn't look ńice.

[john82q]

But if thats a intentional innovation, why isnt the offset the same both sides??

[Nessism]

If that's intentional I'd call it a failed experiment by Yamaha. You never know but that one valve is clearly more off center than the other. At minimum, I'd get that hammered one back to where the other is. Those mushroom head adjusters may be worth a try.

[rustybronco]

I dont have the head right here to take any pics, but basically heres what we got. 1973 Yamaha TX750. ALL the holes for the adjuster screws line up perfectly with the center of the corresponding valve stems ..except the left cylinder intake rocker and valve stem.

The only thing I've ever seen a valve rotator being used on is an exhaust valve.