tappet adjusters

Has anyone out there had any experience with these after-market mushroom tappet adjusters?Any feedback would be
appreciated.

I put them on mine at the recommendation of Leo Geoff. Only 500 miles so far, so nothing to report. My originals at 13K miles had worn a dimple in the valves. You may have to pull the rocker shafts out to get the exhaust ones on unless the head is off.

Dave
69S

Ms Peel ran her's for 7000 miles, that is 2000 more after the tach needle dissapearing act and they are fine to use some more. Still not a bad idea to put hardened caps on the stems, which could mean grinding down stems in some cases. May have to lift head to get enough rocker lift to screw em in from bottom. A dash lighter than factory too to avoid valve float past the red zone.

I put these on my Combat about 55,000 miles ago. I've noticed that the valve clearances now stay within limits for many, many thousands of miles--perhaps two or three adjustments in all that time after the head gasket was finally cinched down


Tim Kraakevik
kraakevik@voyager.net
'72 Combat, '74 RH10 850

Oviously folks use them on intake and exhaust with success. I measured the arc length of face on the large radius mushroom tappets and compared it with the angle the short exhaust and longer intake rockers travel. According to my shade tree measurements the exhaust rocker had to rotate more than the arc of the mushroom tappet could accomodate. That would mean the contact point between the tappet and valve would run off the edge of the tappet face. Not so with the longer intake rocker which travels through a shorter arc to get the lift. I ended up using mushroom tappets on the itake, regular tappets on the exhaust. On the other hand, if Leo Geoff said they're a good idea that's worth a lot.

littlefield said:

According to my shade tree measurements the exhaust rocker had to rotate more than the arc of the mushroom tappet could accomodate. That would mean the contact point between the tappet and valve would run off the edge of the tappet face.

Click to expand...

I'll have to check that out when I bring it in for the winter. Almost went out today, 57°F (14C). I did drive the Miata into town topless.

Dave
69S

Dave,

I did drive the Miata into town topless.

Click to expand...

too much information old chap.

That would mean the contact point between the tappet and valve would run off the edge of the tappet face.

Click to expand...

I've never seen the witness mark on a mushroom adjuster run off the edge but it's something to look out for. They will still impress a groove in the valve stem tip though. The only solution, as Steve writes, is to turn the correct amount of metal off the stem tip and fit lash-caps.

All the best you guys and gal.

Cash

On Andover Norton valves you don't need caps because they have stellite tips. Mushroom is not a bad idea as long as the mushroom head radius is right. We use them on Triumphs on principle- valve gear with a very unfortunate geometry, valves nowhere near as good quality as the Genuine Norton ones.

Still on the subject, but used on Triumph triples, some owners modify the rocker by fitting Porsche (elephant foot) style adjusters. These are like the screw end of a Gee Clamp.
Apparently the metric thread is close enough to just run a 8mm 1.25 through the rocker on Triumph's so I am told. This design reduces valve guide wear, and valve to denting. Much better than type originally used in the T160 with a half ball embedded in the adjuster. I wonder if these would be benifical in Commado's ?

Cheers Richard

Another thread on the topic.