Hitchcocks Forum

anyone had experience with 535 bullet running hitchcocks[omega] 8.5 comp piston.at present on app 27btdc with strobe, pinks if i go to 32btdc, this is running on 98 octane bp fuel, should timing be advanced or retarded with this piston/fuel combo. over to the experts.

Hi SCOTTY---------- need to know what cams you're using as well---and the carb. details would be useful........... It's all about fuelling and how much of the stuff you're trying to cram in there..Plug type ??. Just as an aside, what con-rod do you have ??? (ie.. will it take the loading ?)

Also need to know what ign you're running.Stock will go to full advance before 2000rpm whereas a Pazon or Boyer will be up around like 3,500 to i think 4,500rpm.
So essentially the new electronics are going to be better suited to higher compression.
jack.

I have a 535 with sports cams and a skimmed head and use the alloy barrel spacer (1mm , 2mm ,3mm ) to go up or down for comp/ratio changes but at the moment it's about 9:1 , I have the Boyer electronic ignition with our hosts timing set info sheet , set at static with all the slop of the gears taken up and the boyer on full retard in static . Our hosts info sheet shows how to get it more or less bang on with their TDC plug measure tool giving reference in mm before TDC .
I trust our hosts instructions very much as my fitting is just one bike and our hosts have done hundreds if not thousands , the leading edge of the magnets can be done by eye , a center punch can mark your zero and you can punch every 2 to 4 degrees .
I run on 98 octaine as well and seldom get kick back on starting and so far no pinking .

Hi running boyer mk3 ign std cams and btm end head has been ported 28mm micarb 140 main 27.5 pilot needle 1 notch up frm centre pos short muffler pancake airfilter bike ran very well on 7.2comp pistonfor years [ex burtons] but no longer available. usually set ign timingby makks on rotor/stator and at just over half throttle and line marks up on strobe. pulls ok on hills but juat dont seem to want to rev, got me stuffed.

Yes, strobe timing of 27-28 btdc at full advance sounds spot-on to me. It's what I successfully used years ago with a similar set-up to yours at 535cc, and also what I use now on my 612cc engine. You could allways try it slightly further advanced and check for pinking at medium/high revs under full-throttle acceleration up a steep hill - you won't fail to hear if it does!

REgards,
Martin C