pmk

Somewhere on the internet, there is a set of photos about accomplishing this. I thought they were linked on the laptop but apparently not. I searched quickly with no luck. I think the guy is from Italy that did the repack.

Always liked the looks of those bikes. Never seen one in person and not even sure if many made it to the USA. How do they compare to the production bikes of the same ERA, such as the TY and MAR, plus more.

Agree, the OSSA requires the cable be cleaned and lubed constantly, and typically. Most times this is done the day before an event.

If it matters, my friend uses these on his 72 OSSA MAR. Forget his setup, but thought he used the hot start to activate his compression release, with it on the clutch side. Pretty certain, after he stalled and could not refire the motor on a downhill, I think he listened and moved the compression release to the brake side. None the less, he runs these levers. My OSSA uses the oem Amal levers, not endorsing them, just saying. https://msracing.com/hard-parts/controls/levers-and-perches/aof-clutch-lever-assembly.html

No changes made yet. Thought this was interesting. Was asked to inspect cylinders of a friends RD Yamaha. Cylinders inspected good, but has a drilled hole above the exhaust port. Photo later after I resize it.

Your photos are accurate. Yes, it appears the split lockwasher has failed and broken into two halves. You should take the extra effort to replace the seal. My MAR had the original seals in it, and they slid out with little more than finger pressure. On these OSSA engines, what is confusing is that what appears to be a washer is not. The entire spline comes off the crankshaft. Most modern bikes have the spline machined as part of the crankshaft. The puller is reasonably priced and must be used to remove the short spline adapter shaft. From the washer as you call it to the top of the spline will come off.

Pretty much the same type tool we bought from Alex Snoop in New York

Agree, you must have the puller to even consider reusing the part. Even with the correct puller, the cush drive spline on my 73 MAR still broke during removal. The shaft and cush drive spline are a tapered fit with no keys or driving locks. Simply tne tapers press fit, by tensioning the bolt secures it on the crankshaft. As you go back together with it, proper torque is a must for not only the cush drive spline but also the flywheel, and clutch basket. My buddies MAR with a previous owner homebuilt engine overhaul died and would not run, after a bit of troubleshooting, I sorted out the flywheel had sheared the key. Essentially, the flywheel was not properly tightened. I explained to my friend, after seeing the flywheel issue, and several other issues, we needed to check the torque on other stuff. Sure enough, the cush drive was not tight, and tne chutch nut was finger tight.

Don’t like the bike or just trying to flip it? Recently, an SY250r was advertised for $3800 USD. Not sure if it sold, or what it sold for, but the price seemed agressively optimistic for the bike in the condition it was in. Mine is pretty well sorted out now and actually, as posts here and on other sites mention, these are a grat bike for new riders and most riders up into intermediate levels. While I enjoy wishing I had a new bike, reality is, this bike is far more capable than I am. Plus, they seem to be a good value. Currently, mine is getting new brake and clutch hoses, new throttle cable, had to replace a recently failed thermostat switch, so the new style is installed now. Planning to install a new super flexy rear mudguard, while sealing the airbox better against water, plus adding a quick drain incase I suspect water entered the airbox. It does run very good now that I dialed in the jetting, I want to measure the ignition timing setting. This is a USA SY250R and it seems the manuals timing spec is possibly for the UK bikes. Time will tell where the numbers come in at. Likely I may slight adjust the timing to retard it. Just to get less flameout that randomly happens while riding. As is though, super smooth, and very tractable with electric motor type power.

Looks very nice. Want to ask, did you tie wrap the rear mudguard at the bolt holes? Curious if you drilled the airbox as that lets in unfiltered air.

When are you planning to share photos of this masterpiece?????????

The countersink cutters angle must match the bolt heads angle, otherwise there will be only a small ring of surface contact between the bolts head and countersunk hole in the sprocket. You mentioned using a drill to accomplish countersinking the sprocket. Most drill bits are an angle of 118 degres and some being 135 degrees, but other odd angles may exist. Countersinks come in various angles also, typically 60, 82, 90, 100, 120 degree cutting angles. Pretty certain the proper cutter angle was 90 degrees, but did not run to the toolbox and check.

To properly countersink the holes, you must use a countersink in the drill press or milling machine. The countersink angle must match or the sprocket will work as you accellerate or decellerate, ultimatley ruining the hub.

Just dealt with this. No countersunk sprockets in 40t. Only counterbored. Considered swapping from flush head / countersunk style to the counterbored shallow dome stle heads. The Scorpa swingarm to bolthead clearance was pretty tight, and the countebored sprocket and that style bolt was marginal if any clearance. Ultimately, I countersunk the counterbored sprocket and used the original flush head bolts. Catch a look at the recent topic where I installed the Jitsie snails and 40t rear sprocket.

Assume you are looking for the flat bottom bash plate. Not sure if there is truth to this, but supposedly the flat type can give fits while perched on a log that is not level. The curved type does not force rhe bike to be imbalanced. If you do not find one, consider building one, and in the design, you can add protection for the ignition cover and water pump.

Planned to be riveted if this works well. Need to find some #3 monel solid rivets to attach the clamp to the carbon. Putting the silicone sheet between the clamp and pipe should keep it from loosening.

Practice helps. If it were something I needed many of, say a production run, it would be more involved as I would make a mold. The mold would allow easier fabrication and a more glossy finish, plus repeatable edge trims. This morning I helped a friend rebuild his leaky MAR fuel tank. Pretty much reskinned the original fibreglass with new materials. More work than the exhaust guard, but worthwhile. Next for the Scorpa SY will be a carbon guard / access cover for the silencer. Going for the carbon appearance, but will not dent, and should allow repacking without welding.

Wanted to add, the white line in the carbon is a tracer. Tracers are an option in some carbon fabrics and are an indicator of the fabrics direction in regards to what is known as the warp. In critical repairs, fabric direction is called out. Bummer the tracer is there, but I was not too concerned, just saving the pants from burning.

Mark, as an aircraft repair tech with specialized in composites I cheated and was lazy building it, knowing what I could get away with. The headpipe was washed and scrubbed clean with Simple Green soap and Scotchbrite to remove residue from the burnt pants. Next I placed masking tape over the metal surface and drew lines of about the shape and location I wanted. Over the masking tape I placed a layer of high temp very flexible silicone rubber sheet, 1/8” thick. A helper positioned and held the rubber sheet in place while rolling it also around the curves, as this was done, the entire rubber sheet was wrapped in black plastic electrical tape. The tape was wrapped tightly. The silicone sheet provided the uniform air gap between the metal pipe and the carbon guard. I rough cut three sections of carbon cloth approximately to size but adequately oversize. On plastic sheet, I drew the actual cut boundaries for the carbon cloth. Epoxy was mixed, then the three plies were stacked while pouring epoxy between the layers. This epoxy / carbon stack was worked while between two layers of plastic film sheet. Using a Bondo squeegy, the epoxy was worked into the carbon fabric, and all the air was removed. Once ready, the entire stack of wet carbon was cut between the plastic film sheets on the previously drawn template lines. The lower plastic film was peeled away, and the entire stack of carbon was positioned onto the headpipe that was positioned in a vice by clamping the flange, but was over a trash bucket to limit the mesh if drips happened. Once positioned, the upper plastic film was peeled off while carfully draping the wetted carbon. Once positioned, the entire carbon layup was covered in peel ply, then worked by hand to comform to the shape. Then cured. The headpipe was not mold release waxed, I very carfully cut through the cured carbon into the 1/8” silicone sheet with a curting wheel, then the carbon guard came off with black tape stuck on the inside. This tape easily peeled off and the tape on the headpipe removed easily. The edges were final trimmed, then everything was wet sanded with 600. Total time spent, maybe an hour.

I was working on building a burnt pants heatshield also. Was not sure the cost of pants was justified so I made this. As for neat and tidy, thanks.

When I got this SY, there was evidence of the previous owner burning traces of riding gear onto the exhaust headpipe. During my informal dismantle and reassembly, I scrubbed that headpipe to remove all traces of burnt on gear, oil spooge stains and carbon builup at the headpipe slip joint into the exhaust mid box. After several hours of riding the SY, it was apparent that even I was leaving burnt riding gear traces onto the headpipe. Being frugal, I waited on some leftover high temp epoxy, then rounded up some scraps of carbon cloth. In a short bit of time, I fabricated my copycat heatshield. Mounting is simple, two high temp silicone bands between the carbon and stainless headpipe, everything held secure with two worm clamps. Hope it lasts a while and gets the job done.

FWIW, I did take a minute and flipped the master link so the clip is on the tire side of the chain.

Do a google search for Jim Snell showing how to install the pump seal on a Gas Gas.

Avgas and Maxima Formula K2 in both the 73 OSSA MAR and the Scorpa SY250R. I take a beating about mixing and running 50:1, but have no spooge with proper jetting, and after talking with Maxima, opted away from anything less oil than 50:1. Yamaha and Scorpa wanted 40:1 in the SY.