timing

http://www.dragonfly75.com/motorbike/timingcurves.html here is a good read about advancing/retarding timing. contains exerpts from eric gorrs book, whom i think we can all agree is a master of all things 2 stroke.

Regarding the timing is better I guess. This means the increase in power will be even better?

i usually retard timing some from huskies specs, and it always helps them pull smoother into the top end, altho it gives up a bit of bottom/mid response sometimes.. less or no kickback and easier starting however makes the slight loss of snap acceptable to me. the engine being more willing to wind out is just a bonus.all engines are different, you have to play with it, just like jetting. i have ran every size of 80s husky 250 and up except for 430 until now, so im playing around with one currently. the book calls for the 2.3mm btdc with the external mini 6 plat, but im at about 1.4mm right now with no loss of power that i can tell yet and there is no kickback. pulls smoother as well..im playing with the vm and its close but i hope to have a lectron ordered for it soon.
a modern electronic ignition would fix this as it would retard the timing to zero for starting and idle, advance it harder for high load/wot midrange, then steadily retard it towards the topend as rpms increase....giving us the best of everything.

My 83 500CR is set at 2.8, pretty hard hit in mid range. I think I will try the 2.2 mm setting and see if it makes the power delivery smoother.

i would be very surprised if it didnt, likely start easier too. you still have the internal motoplat on the beast?

my 82 500 is at 2.2 its already pretty hairy hit . actually wouldnt want more . i still dont get full throttle many times during a lap . but when i do it will pass anything ive lined up

Advancing timing DOES NOT increase RPM, all other things being equal it will make an engine hit harder in the middle and taper off on top. Retarding timing will make an engine softer in the middle but pull longer on top. For someone who pontificates about engine tuning all the time, bigbill rarely actually gets any of it right.

Justintendo, Yes, still the internal rotor Motoplat

SilverstreakNZ, Still learning to ride the animal, It's my latest bike. Only got to race it once (vintage MX) last season. Picked myself up out of the dirt several times.

Thanks for the advice guys. I'll try the 2.2 mm timing and see what I think.

nice thing about that internal motoplat is the ease of adjustment, all screws are exposed. play around with it. i would try to get it retarded some and see if theres a loss of power anywhere vs. smoothness and starting..does it ever kick at you starting?

I have 2 settings marked on the flywheel of my 349 Cota . One about 2.5mm BTDC is for softer delivery while the 2.0mm BTDC is for more professional delivery(more aggressive)

It is funny how the obvious sometimes eludes me . You are right, TDC does not matter when using a timing gauge (as pointed out by Fran and Silverstreak). I've spent my life in automotive service and am so accustomed to the idea of using degrees BTDC (before top dead center). That same automotive experience would have led me to believe that more RPMs require more timing, a wrong assumption in two stroke land.

SilvertreakNZ: I set the 500's timing to 2.2mm this evening after work (backed off from 2.8mm). Didn't have time to ride it yet. I suspect that the real test will be on a track at the next vintage MX I attend.
I'll give some feedback on the results as soon as I can.

Justintendo: haven't experienced much kickback when starting this bike, just once I can remember. Never have experimented with timing on two strokes, so I'll take your advice and play with it some.

Learning from everyone here, thanks for starting the thread Bigbill.

I'm still learning some things too.

What are the specs on the case bolts on a '72 250 WR? Looking for example only: bolt's diameter is 8mm with a pitch of 1.25 and a length of 25mm.
The bolt size is a M8-1.25x25, I'd like to change mine out to some allen heads.

You may be able to get a complete engine set from DC Plastics. They have several sets for most Husqvarnas.