What are Tappets?

I'm trying to understand how bike engines work and wanna know what is the
role of tappets exactly.

thanks!
suraj

 

Exactly the same as all other four-stroke petrol engines

On an overhead-valve engine they fill the gap between the lobe on the
camshaft and the end of the pushrod. Pushrod runs to the rocker-arm,
rocker-arm works the valve and typically has a screw-and-locknut arrangement
to set the valve clearances. On an overhead-cam engine where the camshaft
operates the valves directly the tappet goes between cam-lobe and valve stem
and there are shims located in the tappet to set the valve clearance.

HTH

SteveM

 

they're the cam followers, the pieces which rub on the cam.

sammmmm

 

No, they're not.

 

Another informative post from the simpleton lol

 

Well, for the benefit of the hard of thinking - that's you, that is -
cam followers are the bits that rub on the cam. That end of the rocker
arm.

The tappets are at the *other* end of the rocker arm, and they bear on
the end of the valve stem.

Now, what were you going to say they were?

(Clue: adjusters)

 

Hmmm.... yes, I suppose so. But an extraordinary number of DOHC engines
have used screw and locknut adjusters rather than shims: more than
enough to consider the use of them rare.

 

For ****'s sake.

Who said "a little learning is a dangerous thing"?

 

Tappets refer to the valve actuating mechanism. Specifically, they are
what directly follows the cam. Sometimes tappets are in the form of
lifters, or bucket and shim assemblies. They have even been referred to
as rockers with threaded adjusters. But generally, they are what is
directly touching the cams.

 

These are generally called "cam followers"

They are the bits *at the other end* of the rocker arm which touch the
valve.

 

Thanks a Ton! I understand now.

Can somebody point me to a 3d animation etc. where I can see?

thanks
Suraj

 

Hoh yus.

I remember shimming a Yamaha FZ750 once: 20 bloody valves, and cams
out.....

 

Shimming the Ducati Desmoquattro -- two shims for each valve, cams out!

 

"The Older Gentleman" <>
wrote in message

I remember checking the valves on a 80,000+ mi GL1000.
Popped the valve covers off loosened the lock nuts in
anticipation of adjusting the valves...no need to adjust. I
hate when that happens...all that work for nothing.

--
Nefarious Necrologist 42nd Degree
Some people ride, some just like to show off their butt
jewelry once in a while.
Dum vivimus, vivamus
<3 )3~~ <3 )3~~ <3 )3~ <3 )3~
<3 )~ <3 )~

 

I *don't* hate to inform you, but you are not completely correct. the
point is, the person with the question has been satisfied, but a tappet
is not always the parts that *ahem* "touch the valve"
check some manuals, you'll see.

 

Yeah, I was just complaining the other day on what a pain in the ass it
is to adjust the valves on my BMW Airhead. :> After doing the valves on
my GPz550 (16 shims, cams out), I bought the BMW.

 

I've a sneaking suspicion I can remember the bike you're on about - it
wasn't a project bike for a magazine, was it?

If so it had me looking for a cheap FZ for a wee while, at least until I
found a cheap VFR.

 

it's always nice to have someone watch the group so that errors don't creep
in.
you're correct.

often the tappet doesn't touch the valve. it generally, however, touches
the cam.
sammmm

 

Lovely wee bikes - IIRC they went mono shock then rising rate mono shock
a year or 2 later. Not sure when they stopped selling them here but it
was well into the '90s.

The pre-diversion (Seca 2?) Yamaha XJ600 was a very similar bike albeit
not quite so pretty while the Honda & Suzuki equivalents (CBX550 &
GSX550E) didn't seem nearly as nice.

 

Absolutely, the uni-trak was rising rate. However, IIRC, the very first
mono shock Z550GP (in the UK anyway) came with a triangulated swingarm
rather than a uni-trak as can be seen here:

http://www.jmurray3.us/newsite/newimages/gpz550.jpg

I've also got vague memories of a friend having to retire his example of
this in a hurry after the paint flaked of the shock mount to reveal lots
of rust & not much metal...