pmk

Firing up the laptop, pretty certain I saved the sales brochure that indicates increased compression, I think. If not it is something that was posted on the vast internet.

Interesting, mine takes a pretty good effort more than slippers would allow. I have read the later year versions did have increased compression. Maybe the USA or should more correctly say, the non UK versions have the higher compression that Scorpa advertised in the later models. I say this because those later models, in the sales brochure also indicated the lighter flywheel. Thanks for the reply. Need to do more homework now regarding how they increased compression.

Actually guys, it does start well. Timing is advanced. Most people consider these a high compression motor, and honestly, it requires a pretty good push of the kickstart to crank the motor through. No plans to add a decompression device. Just wanted to get it to spin slightly easier, so if it were to stall, it could possibly refired before putting a foot down. As is, it would be difficult. As I mentioned, some cylinders have a small bleed hole into the exhaust port. Drops the cranking pressure a bit for easy starting and is a non issue while running. Other times the manufacturers have cut key slots extending the port toward the head. Just another way to lessen cranking effort.

Agree, but Bondy does have about half a million very recent posts about that old Yamaha engine in the French chassis. Besides, is a modern Scorpa still truly a Scorpa, or rather a Sherco with different paint? He certainly did not ask about Shercos or their granddads, the Bultaco.

The drain on the Scorpa SY250 he is referencing, is nothing like a standard case bolt. Case bolts are typical Allen head style, while the drain is a hex head bolt style with built in flange to help seal the copper washer.

Agree on the manually operated cable actuated compression release, they would work too good for what I am suggesting. My 73 OSSA MAR has the cable operated type in the second spark plug hole. Some bikes though have a bleed hole, and it reduces cranking pressure to get it started. No mechanicl device or anything to operate, simply kick and go.

SY250r, has anyone made a compression release to let the engine be started easier. When I say made, some of the vintage open class MX machines came from the factory with a small hole drilled above the exhaust port. This bled off a portion of the compression pressure while kickstarting, but was a non issue while the engine was running. Granted the TY250Z engine used in the Scorpa starts pretty easily, but certainly has a bit of compression to kick through.

I believe, and can check next time I drain the oil, that is a second drain plug. If the Scorpa had a left side kickstand, you could remove that drain while on the kickstand, rather than use the lower one where the bike must be vertical to drain the oil. The parts manual shows it simply as a straight bolt / plug. No special detent or anything, just a plug.

After some tinkering around with engine tuning, and I won’t post my actual jetting since it can be varied for other parts of the world, I want to mention that the needle clip groove position is quite sensitive to jetting on the SY250r. I found that running in the middle groove, while not bad, was rich. The exhaust showed signs of spooge and a wet tailpipe. Also, the engine could be felt to be rich when riding. Not blubbering rich, just slightly rich and it showed in the transition from pilot jet to needle. I tested the next clip groove leaner. The engine ran clean, accelerated ok, but had a slightly soft exhaust note and soft accelleration. Also, you could faintly here the engine wanting to ping and ever so hinted at surging. To work within the two settings, I fabricated a 1/4 mm thick shim to provide a mid point between grooves. These are also easily purchased, but I opted to punch one from shim material rather than wait. The shim was installed under the clip, raising the needle 1/2 a groove. Essentially place the needle position at clip groove 2.5. In this setting, the engine runs absolutely clean, but is now crisp with a good exhaust note. No pinging or surging is there currently. The engine accellerates strong with no hesitations. Possibly the TK carb, the 26mm carb size, and the engine exhaust combo have made it this fine to adjust. I do not have any optional needle jet sizes, so possibly the next leaner brass needle jet is sized to be 1/2 steps of the clip groove. But I am not sure for a TK, plus the needle jet would need to have a trip from a Japan warehouse, to a UK Yamaha dealer, then sent to me in tne USA. Simply sharing.

Capacitor, the round cylinder shaped item, black in color with a rubber sleeve it sits within. Mounts onto the subframe tab. On my SY the subframe screw was in hard contact with the capacitor.

I spent a bunch of time on positioning the stuff. Assumed my bike was as delivered, and if so, I certainly changed it for an easier fit. Be sure to check and relocate the capacitor.

Bondy, you are not wrong or crazy about the CDI. My best advice, go to the ADVRider website, in the trials section I started a SY250R topic. In that topic I posted all sorts of photos, including repositioning all the electrics next to the carb. If you look close, the capacitor mount is wrong and the subframe bolt will be trashing the capacitor. Thes SY250R are a decent machine, but some stuff is really cobby unless you sort it out.

One of the guys that restored his KTM tank, photos and some info. http://www.ktm495.mxbikes.com/index.htm?REF=other37777.htm

Tank Skin, for reference only as they are not available for the Scorpa. https://www.dcvmx.com/xcart/product.php?productid=17991

Bondy, you have several topics going regarding the paint to use on the tank, the decals and more. Curious, how bad is your tank currently? A photo would maybe offer insight. Also, are you keeping the tank the original color, or doing a color change? i have a vintage KTM also. That bike came new with a white fuel tank. The gasoline / premix causes these tanks to yellow. Some owners have decided to not go crazy, and leave the yellowing as is knowing that the plastic is saturated with volatiles that may cause adhesion problems for paint. Others though have done as you plan to do, and painted the tanks. The best solution for the KTM turns out to be, a tank skin. This is a cover of sorts, that is white plastic and molded to match the oem tank. Since no fuel contacts the tank skin, unless you spill while refueling, the bright white color remains. Search for 1981 KTM 495 fuel tank and some info should be found. if your Scorpa tank is in good condition, you might consider, and I mentioned this before, perforating the graphics to allow them to vent. Below is one tool made specifically to perforate plastic films on model airplanes. Might be worth researching. On my 73 OSSA MAR, new it had a fibreglass fuel tank. As I did the resto-mod to the bike, I installed a white Clarke plastic fuel tank. The green stripes I made from MX background material. Even with draining the fuel tank completely after each ride, storing the machine with no fuel in it, the decals still bubble. My solution, prior to each event, I spray glass cleaner onto the decal, then carefully push the bubbles out with a plastic bondo spreader. Takes 5 minutes. That said, yesterday, I peeled all the graphics off the Scorpa fuel tank, except the Scorpa logo near the fuel filler cap. Check the link below for a perforating roller. As mentioned, read about restoring the white KTM fuel tanks. Those bikes need to look really good, and with a value being what a new Scorpa costs, the owners most times want the bikes super nice. https://www.towerhobbies.com/cgi-bin/wti0001p?&I=LXHZ26&P=0

ATF can be a fine choice to use in both a fork and rear shocks, however, other times it is less than good. FWIW, in my KTM,I run Mobil 1 ATF, with great results. This is in the fork only. On the 73 OSSA MAR, as I did the rebuild, I used Mobil 1 ATF in both the forks and the Curnutt rear shocks. After a few rides, it was apparent that both ends of the MAR were overdamped. Ridable but not lively. In the forks I switched to Maxima 5 wt fork oil. They work well with that setup. The rear shocks, originally specified running Ford ATF. Consider these were state of the art in the early 70s. Keeping this short, I swapped the rear shock fluid in the Curnutts to the same Maxima 5wt. Noticeably improved, but still no spring in its step. Ultimately, I had to make changes to the pistons bleed holes to get it sorted out. All that said, use caution when going to a different fluid, it may make a drastic change, or may be fine. This link is for Peter Verdones suspension fluid info he published a long while back. Good info to keep things consistent when changing brands or viscosity of fluids. http://www.peterverdone.com/suspension-fluids/

I could be wrong, but thought the main jet was seated against a washer.

Almost all plastics will tend to have some portion of the gasoline chemistry permeate through the plastic. You can try painting, it may work well or not. In an effort to minimize decals from lifting, most longterm decals come with small holes punched in the decals to allow the decals to vent, rather than bubble.

The airboot is a TY250Z part carryover onto the Scorpa. Disregard the tab, and ensure the airboot is oriented correctly so the offset does not strain the carb and intake rubber manifold. Also, ensure you do not secure the clamps too tightly. It can crush the airbox spigot or force the airboot off the carb spigot. Either would allow unfiltered air to enter the carb. If it matters, my SY has the tab at approximately straight downward on the airbox spigot.

Proper orientation of carb slide and needle assembly details.

My bike, likely all original. Fronts are button head, m8x16, lowers are flush head, m8x16

Shortly I will measure, Yesterday was crazy and I fell asleep before checking. Check back in two hours. The exhaust mid box is a slip fit onto the head pipe. Mine was a bear to get apart as carbon had built up on the head pipe where it sits inside the mid box. Took some silicone spray so as not to trash or swell the o rings, then carefully, and patiently was able to seperate the two. Once apart, use Scotchbrite and solvent to completely remove built up carbon. Then on reassembly, I use silicone grease, also known as Di Electric grease at tne auto parts store. I also use the silicone grease for the silencer to mid box joint. Taht allows easier removal of the entire subframe with silencer still attached.

I am in the USA. Since you have the curved bash plate, later today, I can measure my own bikes front bolts for you. Yes, the number would be M8x??

Interesting, how certain are you that yours is a 2007? The 06 shows a curved bash plate while the 07 is the flat type. Also, I thought, but could be wrong, 07 was the first year of the yellow spring.

If you have a 2007 with the yellow spring on the rear, could you be kind enough to measure the springs wire diameter accurately and if possible, the springs free length. Thanks