GTS OWNERS CLUB

Bunter · Posted: Tue Dec 16, 2008 2:18 am Post subject: Tappets

As some of you know, Russpeed has dabbled in 4T tuning, a tip I got from him was to set the tappets 2 higher than stated in the book, ie, if the book recommends 8 and 10 thou, go 10/12.
I'm due a self service soon, and as my top end is creeping down, (new belt just fitted so it should not be belt wear) I suspect the tappets being the culprits.
Before I do the service I would like to know if anyone has tried the larger settings, and if so was any improvement noticable, and how involved/easy are the tappets too set.
my tappet setting experiance is from way back, on 1960's cars, i would imagine it's quite similiar but would I need a rocker box gasket Question

_________________
GTS 250+PX 200+Dragster & Runner 180+ Hexagon 125+Hexaphoon project.
Darkside and Norwich Broadsmen SC member.

monty9120 · Posted: Tue Dec 16, 2008 4:49 pm Post subject:

Dont you mean valves. im sure he said that piaggio say set them to 0.15 but if you do the exhaust ones 0.12 and the others 0.18 it makes them alot better

The 0.15 setting used is a good setting but basically russ's way is fine tuning it
_________________

GILERA NEXUS 500
DANGER HIGH VOLTAGE!!!!!
NORWICH BROADSMEN SC

CheekyThomas · Guvernor Joined: 18 May 2007 Posts: 1374

You wont gain performance from adjusting the valves... as the clearance is only there to prevent valve damage from the fact the valve itself gets slightly longer with heat from the engine.

darklord · Posted: Tue Dec 16, 2008 6:12 pm Post subject:

I suppose if you took up some of the free play by closing the gaps up a bit it would alter the dwell time a fraction? whereas opening the gaps would do the opposite? Shocked

_________________
Vespa 300 super BSA Bantam, pushbike

CheekyThomas · Guvernor Joined: 18 May 2007 Posts: 1374

You could slightly alter cam duration... but you wouldnt notice the difference unless the gap was stupidly huge and you reduced it... on a highly tuned engine with very specific ignition timing etc then it might be noticeable, but on a GTS the valve gap would be so big it would rattle so loud you couldnt hear yourself speak before you would notice a power loss from a over large gap.

CheekyThomas · Guvernor Joined: 18 May 2007 Posts: 1374

....but back to the topic at hand.. valve clearances are dead easy to do, and you wont need a gasket unless you refit it wrong and nip it up.

Reaching the bolts is a little tricky, but do-able with normal tools (10mm ratchet spanner with flexi head is ideal)... it takes about 20mins to do.