px timing problems

[bikerbob]

Hi guys Urgent help wanted. Have fitted px 125e engine into my 1966 sprint have converted all electrics . Engine was purchased rebuilt with DR 177  cylinder kit rebored to 180cc sip road 2 exhaust standard carb . After running in engine is quite rough to ride. Checked timing only to find it set at 56 BTDC? No wonder it is rough.  advanced  stator plate as far as it would go, now fires at 43BTDC but ran a bit better. After looking at my mates px noticed flywheel diferent so swapped flywheel for his now fires at 38BTDC. Am using strobe light, Used piston stopper for TDC , used dial on flywheel and my marks match  timing marks on fan cover. the only solution I can see is to elongate slots in stator plate but this can not be right. Any help would be appreciated as I am now lost for answers. Regards Bikerbobob

[henri]

your figures dont make much sense ,unless youve got ya advance/retard way back to front .fully advanced the screws will be in clockwise end of slots in stator .fully retarded anti clockwise end of slots . what about the static timing marks down at the 7 oclock position "a" an "it" . a 125 should be timed with the "it" to the mark . H

[pxguru]

The crank, stator plate and flywheel all have to match, like all parts made for a PX. You might have some PK parts mixed up or a dud crankshaft. Wouldn't be the first time

[bikerbob]

hi thanks for replies,  I agree these figures don't make sense. I cannot see how it even ran. Have done some 200 mile on this at slow speed as told to run it in. Kicks back a lot when starting and vibrates at 40 mph but smooths out at 45. I was told it has a new Mazzucchelli crank,  engine was built by someone who has built a few engines as a living but not known personaly but was very cheap. will rebuild in winter. Will take photos to download to see if I have done something silly. Am at present building the original sprint engine as well as another px engine converting to reed valve. Have  been building various engines mainly 4 stroke for some 40 years as a hobby  so not a beginner. Photos to follow ASAP 

[henri]

i'm surprised it even started that advanced ,never mind kicking back . an i'd not run it anymore til youve checked the piston crown ,that advanced i'd expect to see burning/pitting in crown ,if not a hole starting to form .use a magnifying glass to look at plug nose ,little silvery balls are a sign of pre-ignition/detonation ,which over advanced timing will give .
my 1st thought was your flywheel was a poets day 1 , (p*sh Off Early Tommorrows Saturday), had a mate recent who had a new fly with the centre rivetted one rivet rotated/out. that was fun , but your mates flywheel did pretty much the same .so am starting to think the new cranks a poets day one an keyways in wrong place ,as i cant think what else would move the timing so much .H

[bikerbob]

Hi Henri am I missing something. Firing at 38 btdc instead of 20 is to far retarded. But will check piston anyway

[henri]

the point you advance/retard to is the firing point ,19-18 btdc . advance from that is 20+ btdc,retarded is towards tdc . ok, least ways thats how ive always thought of it .H

[bikerbob]

Hi finally sorted took head of, clean as a whistle found few digs in head which would point to previous problem hence rebore and rebuild. Checked top dead centre marks on flywheel with marks on cases with piston at top dead centre, spot on. replaced stator plate from same unit as flywheel put it all back checked with strobe and spot on at 19deg as I wanted, problem fixed. So my cheap rebuilt engine is now an expensive project IE new ignition system as my mate wants his flywheel and stator plate back. Was going to upgrade in winter to a variable system, but will have to order this week, am looking at the new malossi ignition from sip or a good known kit from vespatronic, or parmakit. Has anyone got any thought on this

[henri]

look at avotechnica , there variable kits for smallies are half the money of parma's/vespatronics . £140 or there abouts ,i think they do a large frame one but not sure . or theres mappable cdi's which work on stock stators ,kryptonic's are known/good . H

[bikerbob]

Hi guys have ordered new malossi variable ignition, so will fit as soon as it arrives. Now timing sorted had good ride out, engine a lot smoother but now revs out at 55 mph and will pull away in third gear so gearing needs sorting, as a quick fix, if I change my clutch gear for a 20 tooth (22 at present) would this give me longer legs for motorway driving. all other gears are standard px125e with sip cnc race clutch. am fitting px200 primary in winter, but at present being left behind by 200s and race tuned small frames in club on long straights. B