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Power Sports Tuning Community Blog List http://forums.pstuning.com/index.php?app=blog Community Blog List Syndication Sat, 26 Sep 2009 11:31:55 +0000 advance@powercom.net (Power Sports Tuning) IP.Blog 60 Improving the Aprilia SXV Supermoto - Second Engine Oil Analysis Attached Image

]]> Wed, 01 Oct 2008 00:41:05 +0000 Improving the Aprilia SXV Supermoto - Engine Oil Analysis http://www.oillab.com/cominfo.html

QUOTE

*Science is a way to teach how something gets to be known, what is not known, to what extent things are known (for nothing is known absolutely), how to handle doubt and uncertainty, what the rules of evidence are, how to think about things so that judgments can be made, how to distinguish truth from fraud, and from show.

- Richard P. Feynman

As mentioned previously, I use Castrol TWS (short for "Ten W Sixty") for three reasons:

1. It meets Aprilia's specifications for viscosity (10W60).
2. It is readily available (BMW car dealers stock it).
3. It is relatively inexpensive (roughly $10 per liter).

The oil sample I submitted for testing was used for 321 miles (about 40 miles of testing on the street, and 280 miles on a roadracing course). This was the first oil/filter change since the engine had been completely stripped and re-sealed over the winter. I will also mention that my air filtration is the standard OEM paper element, and the oil filtration is an aftermarket unit (HiFlo HF154). All venting is exactly as it came from Aprilia. Some "make-up" oil was added during those 321 miles but, unfortunately, I did not keep detailed records of the amounts.

Although you may find my results interesting (and perhaps even useful) I encourage you to submit a sample of your own oil for analysis. It will not only help you determine the health of your engine, but also what an appropriate drain interval is for *your* use of the bike.

Each test kit costs $21.50. There is a $5.00 shipping charge for, apparently, any number of test kits. Each kit comprises a screw-top sample container, some paperwork, and a return shipping box. Your oil sample may then be returned via U.S. mail quite inexpensively (less than $2.00). By the way, don't let a postal employee tell you that special handling (read extra $$$) is required. Up to 4 ounces of oil may be sent via regular parcel post. (If you do submit an oil sample for analysis, please mention that you learned about it in my blog. I'd like to know how effective this type of "advertising" is.)

Copyrighted test report posted with permission from Oil Analysis Lab, Inc.

Jim's Commentary...

Water: 0%, Zero, Nada, Zip, Naught, Bupkis. Hurray! This means that my re-seal job is holding up.

Viscosity: 18.2 centistokes as measured at 100 degrees C. According to a conversion table on the back of my analysis, this equates to an SAE 52-weight engine oil. Basically, my 10W60 oil had "degraded" to 52 weight oil due to fuel dilution and shearing. According to Oil Analysis Lab, Inc., viscosity is "the single most important property of a lubricating oil." This value was the only item on my test results that raised any sort of warning flag. Other sources say that, ideally, the viscosity should remain "in-grade" (there is a tolerance.) If the test sample's viscosity is outside spec. by 1 grade (thicker or thinner), it is considered "abnormal" and +/- 2 grades is considered "excessive". This really makes me question the wisdom of starting out with anything other than the grade specified by Aprilia (10W60).

In racing, the theory goes, using a lighter viscosity oil can reduce "windage" (frictional loss due to internal engine parts churning in oil) and thus put a bit more horsepower to the ground. The downside it that the lighter oil offers less "protection". But when you think about it, that trick is most effective in a "wet sump" system. Our dry-sump systems probably won't benefit much at all. Yes, it does take a bit more horsepower to pump the higher viscosity oil through the engine -- but I doubt you could even see that difference on a chassis dyno. (If anyone does do that dyno test, make sure the oil and coolant temperatures are the same for both tests, and the oil in both tests has seen the same usage.) It usually takes a long time for oil-related failures to surface. You won't necessarily see an immediate problem related to the use of oil with "insufficient" viscosity. Other than the fact that you can buy synthetic 10W40 much cheaper than 10W60, I don't see any point to using it in our engines.

Fuel Dilution: 1% by volume. Oil Analysis Lab, Inc. says that fuel dilution is "the main cause of reduced viscosity." Fuel injected vehicles tend to exhibit considerably lower levels of fuel dilution than their carbureted counterparts. This is because the ECU is controlling the excess fuel required for a cold start. Not only can the computer add the minimum of excess fuel, it does so only as long as necessary (possibly unlike a manual choke controlled by the rider).

Silicon: 22 PPM (parts per million, by mass). This is usually considered a measure of how much "dirt" is in the oil (sand or silica is silicon dioxide). According to Oil Analysis Lab, the silicon measurement is "Used to determine the level of airborne dirt and abrasives." However, some oils contain silicon as a de-foaming agent. Similarly, freshly-rebuilt (fewer than 4 oil changes) engines sometimes exhibit high silicon numbers due to oil being in contact with silicone case sealants (silicone, the organosilicon polymer, is most commonly polydimethylsiloxane).]]> Sun, 29 Jun 2008 14:10:43 +0000 Improving the Aprilia SXV Supermoto - Quick Disconnect Fuel Coupler Tool
The other day I received a catalog that offered a set of quick-disconnect tools for air conditioning and fuel lines http://www.harborfreight.com/cpi/ctaf/disp...temnumber=97576 and the proverbial light bulb turned on!

My local auto parts store sold 4 different types of quick-disconnect tools, but none of them looked like they would work on my SXV.

I ordered a spare quick disconnect (Aprilia P/N AP9100494) for the amazingly low price of $1.99 just to take measurements.

This photo should give you an idea of what the tool looks like, and how to use it. Only one-half of the tool is shown (with a 5/16" gauge pin simulating the fuel pump fitting), but both halves are simultaneously inserted to disconnect the coupler.

I made the tool from 1-inch aluminum bar stock. The ID is 8mm and the OD is 11mm for about 1/4 inch. The "collar" is about 1/16" wide. I sawed the tool in half with a jeweler's saw.

The tool is not optimal, but does work. I had to pry lightly against one-half of the tool with a small screwdriver. The other half of the tool I could reach with my fingertips. The collar can't be too much larger in diameter, otherwise the bottom of the fuel tank would prevent its insertion. Perhaps starting with 1-1/4" stock, and making the collar a "D" shape would work better?

As long as the tank was up, I thought I'd show my added protection for the fuel pump wiring. The woven OEM sleeving was quickly becoming abraded from contact with the frame and tank. The fix was to cover the wires with a piece of clear plastic tubing, slit along its length to allow installation. I cut away the OEM sleeving prior to installing the tubing. Electrical tape ensures the tubing stays in place.]]> Sun, 18 May 2008 21:15:47 +0000 Improving the Aprilia SXV Supermoto - Clip-style Master Link
As near as I can tell, Aprilia uses a Regina 520 ORSBX chain on the SXVs. Parts Unlimited sells a Regina master link for that chain (part number 1225-0005, $6.95) which fit properly. The RXV's master link (Aprilia P/N AP9100533) may also work. I don't know.

Incidentally, you can make a nice clip removal/installation tool from a cheap pair of pliers. The pair shown in the photo are Chinese-made, 7" linesman pliers which cost me all of $4.00.

I used a belt sander to shorten one side. A bench grinder could work too, but would require a lot more care to ensure the metal removal is straight and even.

I usually safety-wire the clip in place, like this...

But my SXV did not like the safety wire and rejected the "transplant". After one trackday, the safety wire had vanished! Probably due to rubbing on the chain sliders.]]> Sat, 10 May 2008 13:11:43 +0000 Improving the Aprilia SXV Supermoto - Cold Starting Difficulties?
After a couple simple changes, my bike now spins over with such alacrity it just amazes me! It cold-starts instantly (after the 3-second prime period has expired) first time, every time.

The likely culprit is shown in the pic below. That is how the solenoid-end of my starter cable came from the factory. I'm pretty sure my bike was assembled by monkeys.

I imagine that at low ambient temperatures, the plastic sleeving contracted, changing the tension on the lug/fastener thus increasing its contact resistance. Of course, I trimmed the plastic back to allow full contact between the lug and the fastener. While I was working on that cable, I decided to solder the terminals to the cables as well. This reduced the electrical resistance of the completed assembly by about 50%. This is not a big gain in absolute terms because the cable's resistance is only milliohms. However, anything worth do is worth doing properly. I soldered the connectors on the high-current cables between the starter and the solenoid, and between the solenoid and the battery. (BTW If you don't already have experience soldering heavy connectors, I would not advise learning how on this one.)

I thought about soldering the engine's ground cable too, but on the advice of a U.K. supermoto racer decided to completely remove the cable instead! Of course the engine is already grounded by virtue of being bolted to the grounded chassis. Seems like a "belt and suspenders" approach to me. If the mounting bolts loosen and cause a bad ground, I would prefer to learn about it sooner rather than later, anyway.

I have one other important tip for cold-starting. Because I modified my twistgrip, the yellow button no longer has any affect. This always left me guessing exactly how far to open the throttle during a cold start. Changes to the 2008 model year include a different cold-start "choke" knob. On both the '08 and the '07 models, the throttle blades are simply held open farther than normal idling speed during cold-starting. On the '07 models the throttle was 9 to 11% open. On the '08 models, this was implemented as 10 to 12%. That might not seem like a big increase, but at small throttle-blade angles, a 1% change produces a noticeable change in airflow.

Prior to every cold start, I now turn the idle-speed adjuster until I see 1.2 volts on the TPS (Throttle Position Sensor) as measured between the white wire to the airbox connector and ground. As the bike quickly warms up, I back the idle down to an acceptable speed with the adjuster.

Incidentally, I still have the "old" starter gears, and see no reason to change. The new starter gears have a different ratio. They reduce the cranking speed by about 9%, but also provides about 9% more torque multiplication for the starter motor.

One final thought, make sure the fasteners are tight on all the high-current connection points: battery, solenoid, starter motor, chassis ground mecca, and engine mounting bolts.]]> Fri, 09 May 2008 15:15:38 +0000 Improving the Aprilia SXV Supermoto - Intermittent Rough Running Solved
I did have one minor problem at the track that was easily solved. The OEM push-on terminals for the ignition coils have caused trouble for many owners. Even though I knew this was a potential problem area, I had chosen to ignore it. When my engine finally started misfiring, I squeezed all four connections tight again with a pliers. (There's a separate coil for each spark plug). EDIT: Just realized there is one of the crappy terminals on the oil pressure sending switch as well.

A loose connection here can result in rough running or even cause a cylinder to cut-out completely. If you race the bike, may I suggest implementing this fix *before* having problems. My symptoms came on so suddenly and so severely that a DNF surely would have resulted.

Along the top row of the photo you can see the OEM connector and its plastic cover. Next to that is a standard crimp-style push-on terminal (available at any hardware, home improvement, or auto parts store.)

In a critical application like this, I prefer to solder the connector rather than crimping it. The bottom row of the photo shows two layers of heat-shrink tubing, and a standard connector with its red plastic sleeve removed. If you heat the red plastic sleeve with a hot-air gun (paint stripping gun) it comes off easily without bending the connector.

NOTE: The predominately orange wire should connect to the top terminal of the ignition coil. If you reverse the primary connections to the coil, the engine will still run but the ignition system will have to produce a higher voltage to jump the gap. (It takes perhaps 30% less voltage to fire a spark plug when its center terminal is negative than when it is positive.) Thus, with reversed primary polarity, under some conditions of cylinder pressure, temperature, A/F mixture, etc., the ignition system may not be able to produce enough voltage to jump the gap and a misfire will occur.

Here is a simple explanation of the importance of polarity written by the Champion Spark Plug Company... http://hometown.aol.com/bgahc/01_jwha_coil...sparkplugs.html]]> Fri, 09 May 2008 13:34:13 +0000 Improving the Aprilia SXV Supermoto - Oil Pressure Gauge
Salient features...

3/4" square aluminum bar, 2.25" long.
The oil pressure switch has an M10-1.0 thread.
M10-1.0 banjo bolt (I made one, but a double-hose brake banjo would work).
90-degree brass street elbow to pressure gauge.
1/8" NPT pipe plug (not visible in pics) seals the line-bore. Had a nice small one with an Allen head (like Aprilia uses on the engine cases).
I sealed all the pipe joints with green Loctite (for "sealing welds and porosities").

With 10W60 oil at 45 degrees F, the gauge showed 90 psi while cranking to prime the system. After a minute of running, I saw 75 - 80 psi at idle -- increasing as the engine was revved. With the engine up to operating temperature, my oil pressure is about 35 psi at a 2200-rpm idle.

Although the photo shows a 160-psi gauge with an ABS housing, I used a 200-psi metal gauge on the bike. They both have about 1.5" diameter faces. The 200-psi gauge came from a home improvement store (near the air compressor stuff). It was made in China and costs about $4.00. U.S. makers Wika and Ashcroft sell similar industrial gauges -- about $10 for brass, or $50 for stainless. Wika rates their brass gauges for a maximum temperature of 160 degrees F, and their stainless ones at 212 F.

Wika also recommends only using a gauge to 2/3 of its rated pressure if the pressure is fluctuation. You can go to 3/4 of rated if the pressure is steady. Since normal oil pressure can reach 125 psi, I erred on the safe side with a 200-psi gauge.

]]> Sat, 12 Apr 2008 14:56:48 +0000 Improving the Aprilia SXV Supermoto - Engine Assembly Tips
1. Liner/deck height. As mentioned previously, I lapped the liners so they extend less than 0.001" above the cases.

2. I replaced my decompresser screws (into cam) with hardened SHCSs (Allen screws). I felt the soft OEM screws yield excessively before reaching the prescribed torque.

3. Gearbox drain bolt torque spec. seemed much too high. I tightened it by feel. It is an aluminum bolt.

4. Degrease cam / sprocket and crank end / flywheel tapers with acetone prior to assembly. The tapers need to be clean in order not to slip. Many mechanics incorrectly think the Woodruff key prevents a flywheel from rotating. The key is needed only for locating. Friction across the taper allows torque to be transmitted.

5. The only gaskets I replaced were the head gaskets. All the others were fine to reuse.

6. The only circlip I replaced was the one that retains the oil pump drive gear. I did not disturb the piston pin circlips -- but if I had, I would have replaced them.

7. I replaced the cylinder sealing O-rings with ones made of Viton. They are the SAE -152 size I ordered 25 pieces and used the two with the greatest cross-section diameter.

8. I also replaced the O-ring for the gear position (neutral) switch. Elsewhere in this blog I mentioned that mine leaked. I tried to replace it with the -021 size called out in the parts book, but was unable to make it fit. On a whim, I bought the slightly smaller -020 size and was able to install it.

9. Rod bolts scare me. You are probably better off not to disassemble them. Aprilia's specs call for a special thread lubricant as well as an additional 48 to 50 degrees of rotation once the initial torque spec has been reached. I just made sure the bolts were not *loose* by exceeding the *initial* torque spec by a guesstimate amount (20 - 30%). Here is a good technical explanation of rod bolts: http://www.eaa1000.av.org/technicl/r...s/rodbolts.htm

10. There are two left-handed threads in the motor. The primary gear nut. The front cam-gear retaining screw.

11. I replaced the gearbox-to-airbox vent hose with clear plastic tubing to watch for signs of fluid flow. Clear plastic tubing does not withstand heat well. A clear plastic tube will likely have to be replaced often.

12. Replaced the throttle body vacuum synchronization hose with lighter, more flexible, hose. I used an alcohol-resistant fuel line sold by Aircraft Spruce and Specialty.

13. Replaced bolts that hold exhaust system to the head with M6-1.0 x 31 studs and flange nuts.

14. The needles for the RH side timing (water pump) shaft bearing are free to become dislodged. I used a heavy grease to hold mine in place during assembly.

15. Some owners advocate replacing the OEM exhaust gaskets with ones from a Yamaha TTR-125 (P/N 4BR-14613-00-00). The problem is that the Aprilia gaskets are fairly thin, and thus allow the header flange to contact the cylinder head. If there is not sufficient compression of the gasket, it can leak.

Although the TTR gaskets are very nice, about 2mm must be removed from their OD. Aprilia gasket: 38mm OD, 30.8mm ID, 1.55mm thick. Yamaha gasket: 39.87 mm OD, 30mm ID, 3.20 thick.

The Yamaha gasket's core is a matrix of fine stainless steel wires. I tried to reduce its OD using a belt sander, but this just exposed lots of sharp wires. A bench grinder worked better, but was not worth the effort. I think a better solution is to simply use two stock Aprilia gaskets in each head. I now have the Yamaha gasket in the front head, and two Aprilia gaskets in the rear head.

I probably made other changes. As I think of them, I'll add to this list.

16. Most of the heads on the seven M7-1.0 case bolts were out-of-round. There is not much clearance to the sides of the recessed pockets into which they fit. This can cause them to drag against the cases during torquing, and thus prevent them from achieving their designed clamping force. I machined each of the bolt heads just enough to "clean-up to round" in a lathe.

17. I hand-chamfered all the bolt-holes on the inside mating surfaces of both case halves. Any small imperfections from the manufacturing process (drilling / tapping) or assembly (installation of the fasteners can raise "high spots") won't allow the case halves to make perfect contact with one another.

18. Replaced the plastic oil filter cap with a cast aluminum one (Aprilia part number 851295). Although this is a recall (service notice number 010-2007) item, the dealer has to pyhsically have your bike -- they won't just hand you a new cap. It may be less trouble to simply buy the new cap outright.]]> Sat, 12 Apr 2008 14:26:32 +0000 <![CDATA[Improving the Aprilia SXV Supermoto - Engine Rebuilding: Tools & Chemicals]]>
I WOULD NEVER TRUST THIS WORK TO A RUN-OF-THE-MILL APRILIA DEALER. A friend has a saying regarding this sort of thing, "You know just as much as they do, and you'll be more careful!" On the other hand, if the dealership supports an Aprilia racer or has done several rebuilds already, you are probably safe trusting them to do the work.

In addition to normal mechanics' tools, you will need:

0. Engine Workshop Manual! Read it several times. Memorize it. Annotate the appropriate pages with torque and Loctite specs. Make lots of notes in it.

1. Aprilia Flywheel Puller, P/N 9100839 about $70. I e-mailed Motion Pro to see if they planned to offer a puller, but they never responded. The puller is something I could have made in the lathe, but an M33 tap costs about $80. I could have single-pointed the thread, but the only male thread I had to test against was the flywheel itself. (A bit of a "Catch 22" situation when you have to first remove the flywheel in order to use it to test the thread!)

2. M16-2.0 x 45 bolt for flywheel puller (does not come with the above).

3. Aprilia Primary Gear Locking Tool, P/N 9100843 $50. On all my 2-strokes I just jam aluminum between the primary gear and the clutch gear. But on the Aprilia, I wanted to be able to tighten the primary nut and/or alternator nut with the clutch removed. That, and the primary nut is *really* tight (118 ft-lbs). I want this motor to be as perfect as I can make it, so I decided to spring for the locking tool. It appears to have been laser or water-jet machined -- would not have been cost-effective for me to manufacture.

4. Three M6-1.0 x 25 screws to attach above.

5. Aprilia Crankshaft Locking Tool, P/N 9100844. (Mine was homemade -- simply an 8mm bolt with a 0.156" reamed hole and a 0.156" gage pin).

6. 6mm (exactly) steel rod for cam timing (I used one from a set of metric transfer punches. Enco model #831-0103, about $22. Must be 6mm, any smaller and the cam timing will be inaccurate.)

7. Brass drift (3/8" diameter x 6" long) to remove cam gears.

8. Aluminum button to be used with flywheel puller. (Homemade. Protects the crank end from being damaged by the puller bolt. Obviously not required, but a trick I learned from 2-strokes.)

9. Two M6-1.0 x 55mm studs (Alignment tool for alternator cover. I just sawed the heads off some old screws. When you install the alternator cover, strong magnets tend to pull the cover out of your grasp. There is a seal in the alternator cover for the crankshaft. Do not damage this seal! The rod bearings are lubricated via the alternator cover.)

10. 14mm crowsfoot wrench needed to torque 1 headbolt. (From a set sold by Harbor Freight, item number 47928-3VGA, about $15. Needs to be ground down to fit. If this tool was not the flarenut style, it would not need to be ground down. When torquing this bolt, you need to compensate for the added length of the crowsfoot wrench. Here is a good link to a calculator http://www.belknaptools.com/extcalc.asp)

11. 16.9mm diameter rod a.k.a. "Jim's Engine Installation Tool". Because the swingarm pivot is also a motor mount bolt, removal/installation of the engine is somewhat of a challenge. When I removed my engine from the chassis, I was not smart enough to make this tool first. Instead, I "hung" the chassis from an engine hoist -- very cumbersome. The 16.9mm rod only needs to be long enough to go through the left side of the swingarm/chassis. Partially install the pivot bolt on the right side of the swingarm/chassis. Support the bike on a track stand via rear spools. Rest the engine on a floor jack. I put cardboard between the jack and the engine to accommodate any unevenness. It could not be any easier!

12. Snap-on A173 "Pick, Radiator Hose". Nice but not required. Just about makes the OEM hose clamps jump off.

13. Bailing wire (or safety wire) to make a puller for the cylinder liners. Instead of Aprilia tool 9100897.

14. Any M6-1.0 bolt to extract exhaust rocker shafts.

15. Two pieces of 2x4 wood about 10" long. (Used to support right-hand side of engine cases during assembly because shafts protrude.)

16. 17mm Allen wrench to remove piston pin access plugs. (If you are going to split the cases or *not* replace the pistons, this tool is probably not required.)

17. Small 2-arm gear puller (Might be needed to remove primary gear. Mine was very tight).

18. Motion-Pro clutch basket holding tool. Instead of Aprilia tool 9100896.

19. Strap Wrench to install water pump impeller. Instead of Aprilia special tool 9100938. You can remove the water pump impeller with a small block of wood and a light hammer tap. Using the strap wrench instead of the special Aprilia tool for assembly means having to estimate the applied torque.

20. Machinist's granite surface plate. (For correcting head warp and lapping liners to "zero deck". I duct-taped a sheet of 3M 220-grit wet/dry sandpaper to the surface plate.)

21. Torque wrenches: 0 - 50 ft-lbs, and 0 - 150 ft-lbs. I like having two torque wrenches. A small Snap-on dial-type for high precision on small fasteners. A large cheap Craftsman deflecting-beam type for large nuts.

22. Metric taps: M5-0.8, M6-1.0, M7-1.0 to clean old sealant and Loctite from threaded holes.

23. Quart and gallon Ziploc plastic bags. Keep all parts for front and rear cylinders separate as there are often subtle differences. Also, the cover screws have a variety of lengths and nowhere does the service manual explicitly state what goes where. The parts book is some help, but it is easier just not to mix them in the first place.

24. Access to SXV/RXV parts book (either on-line or printed from .PDF)

25. Camera. Take pictures of anything not clearly shown in the workshop manual. Especially hose and wire routing, etc.

26. HotCams valve shim set (9.48mm diameter shims. Fits most 450cc MX bikes). http://www.hotcamsinc.com/index.cfm?fuseac...p;productid=509 Best price I found ($66) was Yamaha of Troy on eBay. Note: Aprilia only uses shims in the range 1.40mm to 2.30mm thickness.

27. 5/8" steel rod 3 - 4 feet long. Place this through the rear motor mount bolt-hole and have a helper hold it while torquing the head bolts.

General mechanic's tools that not everyone may have:

1. 13mm deep socket

2. 8mm, 12-point socket for connecting rod bolts

3. 27mm, 6-point socket

4. 24mm, 6-point socket

5. 21mm box wrench for oil pressure switch

6. Various sizes of internal and external circlip (aka snap-ring) pliers

7. 1/2" drive pneumatic impact wrench. Not required, but nice to break large nuts loose.

8. Micrometers, etc. to measure parts. Your motor probably needs to come apart to remedy factory assembly defects, not because it is worn out. Although measuring instruments are initially not needed, I measured everything anyway.

9. Blind bearing pullers (if you need to replace any ball bearings).

10. Special bearing drivers, if needed. (Aprilia sells these, but it is much cheaper to make them if you have access to a metal lathe).

11. Metric Feeler Gauges. Preferable to Imperial gauges because they eliminate rounding and conversion errors when measuring valve clearance.

Chemicals:

0. Three-Bond 1207B to seal case halves (black). Replaces the bad Loctite 501 (The bad sealant is initially red, but fades to orange on the outside of the motor and pink where it contacts water.). I used an "acid brush" for fluxing copper plumbing to paint the cases with the sealant. The only place I've found to buy 1207B in the US is Rick Merhar's Accu-Products http://www.accu-products.com/oem-honda-par...prod_20254.html

1. Red Loctite (Aprilia specifies #243)

2. Blue Loctite (Aprilia specifies #270)

3. Permatex Copper Spray-a-Gasket. Dressing for the head gaskets.

4. Anti-Seize Compound for case bolts.

5. Grease.

6. Engine oil.

7. Acetone to super-clean mating surfaces.

8. Mineral spirits for general cleaning of parts.

9. Simple Green (a water-soluble cleaning product).]]> Sat, 12 Apr 2008 13:51:11 +0000 Improving the Aprilia SXV Supermoto - Excessive Coolant Consumption Fix

My liners actually extended about 0.002" to about 0.003" above the cases (exact dimension varied by location).

I used a machinist's granite surface plate to "lap" the liners and heads flat. I duct-taped a sheet of 3M 220-grit wet/dry sandpaper to the surface plate and measured my progress with a micrometer. I had to remove 0.0005" from the front liner before it would "clean up". I ended up taking off about 0.0015" and finished both liners at 1.980" (Note: the 450s have a different dimension here).

In the end, my liners extended less than 0.001" above the cases. I was careful not to "go negative", as this would have allowed the liners to move up and down and they would get hammered! Also, note that the liners "shrank" about 0.0002" as they cooled back to room temperature. The heat from my hands and, especially, the lapping friction, had caused them to expand slightly.

I think the reason Aprilia made the liners protrude is because they *should* protrude -- but only very, very slightly. Even with modern manufacturing techniques, it must be difficult (costly) to achieve exactly the right dimensions. I guess they assume the "compliant" portion of the head gasket must be able to accommodate some deformation?

I found the heads were also significantly warped. I had to remove material from the cam chain area and the perimeter of both heads. The heads were warped in a pattern that could be explained by the deflection needed to accommodate the too-high liner.

I don't expect to know the outcome of this "fix" until the end of the season. After all, it took nearly 1000 miles of use on a roadracing course for the original problem to become apparent.

BTW: I got zero help from my dealer or Piaggio (Aprilia's parent company) with this problem. They would not even acknowledge that I had a problem -- saying that transfer of coolant between the radiator and the expansion reservoir was "normal". Well, I did the calculations. It turns out that 1.1 liters of water expands by about 7% (77 ml) with a 100-degree C rise in temperature. Yes, a small migration due to expansion/contraction is to be expected -- losing half your coolant is not!

I would, however, like to thank the folks at AF1 Racing. They are the source for all my Aprilia parts. AF1 is the best thing about Aprilia! Visit: http://www.af1racing.com/store/Scripts/default.asp]]> Sat, 12 Apr 2008 13:25:31 +0000