B25 Valves

[2LZ]

Hev yah! Yosemite is about an hour or so away.

I'm going to be measuring both sets of rockers today for differences in lengths and angles. Then I'll be assembling all the new stuff in the old boxes to see if the valve lifter interferes with anything. I'd sure like to keep it for my old right knee.

[2LZ]

Interesting discoveries today. Not only are the new rockers longer (along the spindle) than the old ones, but the newer rocker box is machined differently, and not just the wall that needs to be removed. The end boss's that the rockers sit between are machined further apart on the new rocker box to fit the longer rockers. It's not just making up spring washer room. In short, rocker-no-fit-mahn. Interestingly enough, the new rocker box is not yet the new part number, and is still stamped 40-961.

While the difference between the new and old intake rockers seems negligible, the exhaust rockers are very different, even though both still have the flat spot for the valve lifter (see pics). I think that's the angle/reach the Mother Ship wanted to fix by upgrading. Maybe some old ones snapped because of the long reach and steeper angle???....compared to the shorter reach, and less angled new rocker? They definitely didn't run the old setup very long.

The new style rocker has a less angled and more direct hit on the valve stem. Both the new intake and exhaust rockers have the same angle of attack on the valve stems, where the old ones are different.

Well, Looks like my right knee is out of luck. Either I go back to the original complete rocker box setup with the valve lifter, or upgrade to the new complete rocker box, since the individual parts really aren't easily swapped (as the BSA TSB states. Imagine that? )

[Spaceman]

I can see the rocker arms appear to be different in shape but are the distances between the pads and the rocker spindle axes different? In other words, are the rockers designed for a different distance between the top of the valve stems and the rocker spindles, for example, because the spindles are reversed? I suspect the answer is that both sets of rockers are the same?

What you ideally need is a 1968 rocker box (70-7818) because that incorporated all the mods but also retained the valve lifter.

It still looks as though the fundamental question that needs answering is why, with the old rocker box set up, does the inlet rocker interfere with the valve spring with the spindle eccentric in the 6 o'clock to 12 o'clock position? If you were to assemble the later rocker box on to the head, would you still have the same problem? As said, I didn't get any interference on my OIF engine with a reversed spindle.

Although the simplest solution would be to reverse the spindles on your original rocker box, this may result in unforeseen problems. One possibility is a rocker oil supply issue which may be related to why the original spring thrust washer was deleted. If it was me, I would definitely want to get to the bottom of the interference problem. My gut feeling is that this is due to a problem with the location of the inlet valve spring rather than a problem with the rocker box?

[2LZ]

More discoveries today. This may effect my rocker interference problem, but whoever assembled the rocker box last time did it incorrectly.

1- The spring washers were on opposite ends of the rockers. The intake rocker spring washer was on the adjustment end of the spindle. Not the drive side, throwing it out of alignment with the valve stem.
2- I was wondering why the underside of the flat surface on the exhaust rocker was worn oddly where the valve lifter cam hits it. Then I found that the washer/o-ring was on the inside of the rocker box, instead of being on the outside, pushing the lifter actuator into the rocker.
3- There were no alignment dowels between the rocker box and cylinder head! Lord only knows if the rocker box was on correctly. This could also effect rocker alignment.

I got everything cleaned, lubed, and reassembled according to Mr. Ratio. Can't wait to see what else I find.
I'm truly starting to believe that Brit bikes aren't bad or unreliable. It's all the ham-fisted mutants who wrenched on them for the last 57 years.... The bike and design itself is unbelievably simple.

[Spaceman]

It sounds as though a complete mechanical moron assembled the rocker box last time - without the 2 x alignment dowels, the rockers could well be misaligned and this will explain why the inlet rocker was interfering with the valve spring. Hopefully, you'll now be able to adjust the tappets as per the workshop manual?

[2LZ]

It sounds as though a complete mechanical moron assembled the rocker box last time - without the 2 x alignment dowels, the rockers could well be misaligned and this will explain why the inlet rocker was interfering with the valve spring. Hopefully, you'll now be able to adjust the tappets as per the workshop manual?

Not just the lack of alignment dowels but also the spring washer being on the wrong end of the intake spindle. That would definitely shift the rocker position.
I'm currently in touch with CBS about locating some dowels. If Pt# 60-3074 are made of Unobtainium, I'll take the one I have that was stuck in the Ebay rocker box, measure it out and buy some generic dowels. I hope whoever worked on it last didn't dive deeper into the motor.....

[Spaceman]

The dowels are nothing special - I normally just machine a new one when required out of mild steel.

[2LZ]

The dowels are nothing special - I normally just machine a new one when required out of mild steel.

Measured the one and only dowel I had. Basic 8x12 dowel. Got a pair coming.

[2LZ]

According to Mr. Ratio, the B25 has had multiple rocker box changes....and I found out by experience now, he's not kidding. It's taken me four different rocker box gasket orders to finally (almost) get the correct one. I still had to adjust two of the stud holes. The one gasket I received that had all the holes line up, had the exhaust span of the gasket run almost a mm out and wasn't sitting on the head casting correctly. Didn't want to risk the possible leak.

Not only that, but once I supposedly correctly assembled the rocker box with the spring washers being where they are supposed to live (according to the manual), once fitted, the foot of the intake rocker was not centered on the valve stem. Back apart it came. So, the end result is, I swapped the spring washer to the other end of the spindle, and the intake spindle still clocked where it was earlier.

I rotated the motor multiple times and rechecked. No interference and the adjustments held true. I'm going to run with it. Time to prime the oil system.