750SF cam timing is off

Those whitish stripes are odd looking and there's lots of pitting and assorted dark scratches. Both cylinders are definitely firing, I did strobe the timing and it's accurate and have gone up to 142 main jets and plugs are burning clean after checking them during a 50 mph test
 
Rip off the head and barrels and check it all out. Cross hatching could have been from a hone done on worn bores. Measure it all up properly. Isd it just me or do the bores look particularly dry? And have you checked TDC is aligning perfectly with PM (punto meridionale ... or midday, as a translation) - on the crank freewheel?
 
Piranha- That makes perfect sense since I've fixed several ham-fisted things the PO did to the bike. The center edge of the cylinder somehow got gouged up, and the collar around the oil relief valve is cracked. Those white "streaks" look like wear marks to me. I'm getting a friend to help keep the timing chain in place in order to remove the cylinder head which will show the condition of the barrels, and I'll let you know when that happens.
 
A thousand pardons if my nomenclature is incorrect, but I'm referring to this collar on top of the cam chain cover that houses an internal plastic ball for oil pressure relief. It appears the PO forced the fitting and cracked the base.
 

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Pirahana,
I removed the cylinders today and feel only the slightest/smallest wear marks on the cylinders, and you were right- the honing was done over those white "streaks", but there is no wear as a finger glides over them. The timing marks on the case/flywheel align to the cam sprocket mark, all w both pistons at TDC. Checked the advance mechanism on the points lobe, and it snaps back in place as it should. I might replace the 50 yr old condensers, and increase the main jet size yet again as suggested by a Laverda mechanic who feels it's running too lean. From what I can see, the valve springs are intact and there's only very slight wear on the valve tappet adjusters and valves.
Again, the bike instantly starts, holds a steady idle and revs freely at idle w no stumbles or flat spots, but the engine strains past 50 mph. I've heard different opinions about the header mid pipe affecting mid range- mine has no mid pipe. I'm using DNA pod air filters but there's no change w/ them on or off.
 
Do all your testing without air filters, it should run the same with or without. As long as the exhaust pipes are not blocked they are fine (the talk of lost mid range is talk of a few percent if any). All jetting is dependent on throttle position. Stick bits of tape on grip and housing for quarter, half, three quarter open slides (for transition through cutaway/pilot, middle of needle, and above 3/4 for main jet so that you know what you are checking. Change to your main jet only affects above 3/4. I did half throttle plug chops on my SF2 and it was at 150km/h, at 120 I am well under 1/4 throttle, so your bike struggling over 100kmh should not be main jet.
Can you get the bike to a dyno when you get it back together?
 
I am going with Greg T, but will elaborate a bit more, the tiny springs in the mechanical auto advance/retard unit may be knackered and not allowing accurate control of the ignition advance, which for a four stroke is actually quite a lot, addin rusty or seized parts and you are in business (or not) very simple and cheap fix?
keep in touch
CLEM
 
Thanks again guys,
I poked holes in the gas cap gasket and know its venting since it doesn't "pop" when the latch is released, but I'll try releasing the cap next time its running. I rotated the cam lobe on the ignition slightly clockwise, and it "snapped" back into position and have been told that indicates the advance is working, but Clem please advise if otherwise. Tippie, getting the bike onto a dyno is probably the ultimate test procedure. Scott Potter who worked on this engine has advised me to try 145/148 main jets since he feels its running lean, but this is only based on phone calls and he hasn't seen the actual bike. So I'm going to put the bike back together and try this jetting-
 
I'd be surprised if you advance unit was malfunctioning - the bike doesn't look to have had a dodgy enough life for it to be compromised. Mine lasted hundreds of thousands of miles without problem. if the points cam rotates fully to its stop and springs back it can't be causing the issues you're chasing.

I seriously doubt upping the main jet will have any effect on your lack of power above 50mph. A venting blockage issue will only occur if the engine is running and under power and then only once it has sufficient vacuum in the tank to prevent fuel flowing into the carbs.

I reckon this is gonna be a simple issue hiding in plain sight - but it's a really good idea to be going over the whole bike thoroughly, barrels off next.

BTW, don't freak out if you drop the cam chain down the gizzards - with the oil strainer plate removed and the motor chocked so the cylinders are vertical it's a breeze to insert wire down front and back of crank cam chain sprocket, attach wires to each end of the cam chain and pull it up front and back - then just secure loosely to the rear engine mount and genny stud ... or anywhere convenient.
 
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