Scooterotica

hi all,

ive been dabbling with the air grinder on an old SR barrel and after studying the various material out there have become a little confused regarding a sensible timing for the inlet port.. webster uses timings around 160-175 in his well respected tuning manual.. but some others (including broady) seem to think 150-160 is extreme..

what is the opinion out there.. i am looking for a sensible road tune using a ts185 piston, clubman, 25mm bored jetex, that will lug an S2 along the highway..

currently i have 170 exhaust, 123 transfer 160 inlet.. too extreme? gonna try it anyway, but interested to hear anyones opinions..

perhaps in your case your best bet is to cut your piston skirt ....rather than lower the inlet on barrel....................at least ,this way you can do it say 1 or 2mm at a time until you find it suits you best ,and then if you go too far.... back track by getting just a new piston.....


but especially on your scoot and weight/ areodynamics etc i would be first looking to maximise port widths.....before increased timings

Have a look at these threads if you havent already.

http://scooterotica.org/forum/viewtopic.php?f=5&t=26

http://scooterotica.org/forum/viewtopic.php?f=9&t=13

Like Sean has said why not look at area its not just about port degree timing
Its quite a miss conception to just think about Timing degrees, look at port area
Transfer angles into bore.

Plus on the Inlet side the tuned length & Diameter of the manifold also effects power/RPM
similar to the exhaust.

Smiffy

thanks for the input chaps..

i have taken a bit of care to widen the exhaust port as far as reccomended for the piston involved (ts185) and shaped it with radiused corners... ive also taken a bit of time cleaning up the dodgy SR transfers so they now are square and open at the same time rather than looking like holes a woodpecker would make..

will report back when i get it running..