this is a straight repost from BF, I may edit it later:
Blast Tips, Mods & Info (updaded 4/9/2009)
BASIC 9 - MODS TO INCREASE PERFORMANCE (Simple, Free, Inexpensive, Better-Than-Free):
1) Install Iridium Racing Spark Plug (IXU01-27) – Awesome – better mileage, performance and at least 1 extra horse for about $35 + shipping from sparkplugs.com. This improves combustion and will pay for itself in fuel savings and no replacement ever saves on future spark plug costs too. Better-Than-Free!
2) Do primary adjustment - preferably sound method - on the loose side - If this is too tight, it will rob you of hp & wear shoe - ride around for 1/2 hour then adjust primary by ear - warmed up, idling on level ground, block under kickstand so bike is nearly level - loosen jam nut a lot, then loosen adjuster bolt till you hear noise, then tighten till noise disappears, then tighten jam nut keeping adjuster in place - primary is now properly adjusted.
3) Install aftermarket exhaust or modify stock exhaust by drilling a 1 5/8" hole directly across from the first hole of the stock exhaust on the same side as the stock hole but all the way to the right of it. You will gain about 1 hp for drilling stock exhaust, 2 hp for a Vance & Hines aftermarket exhaust, 3 hp for a Jardine and as much as 5-6 hp for a custom Supertrapp exhaust with stepped constant radius eshaust header. See Custom Intake & Exhaust tread - http://www.buellforums.com/forum/showthread.php?t=4773
4) Shim Carb needle to .050 - better slightly under than over - 2 #6 machined brass washers from a model store is close - this removes low end hesitation. The model store in my area did not have them so I polished some punched brass #6 washers from the local hardware store with 600 grit wet/dry sandpaper until I got .049. Be careful when opening the top cover of carb to put shims under needle head as the spring can fly considerable distances!
5) You can do an air box mod and install a K & N air filter ($50+) but for the same or less money and less work, you can get a superior result by tossing the air box and filter and building a custom intake filter … see the Custom Intake & Exhaust thread http://www.buellforums.com/forum/showthread.php?t=4773 to see what other forum members have done. You can gain another horse here.
6) Drill Carb air-screw plug out and bottom air screw … then turn 2-2/3 turns out if you’ve done mod 3 & 4, 3 turns out if You’ve also done mod 5, 3-1/3 turns out if you have a Jardine or other superior free-flowing aftermarket or custom exhaust. The other mods have minimal effect.
7) Install a Yost CV-40 REV 1 Power Tube - unfortunately, you have to purchase the complete CV40 Master Kit, Rev 1 when only the Tube is needed. Expect 1-2 hp boost and smoother low to mid acceleration. You must have aftermarket exhaust and a free flowing intake for this to work well – the freer flowing your intake and exhaust, the better the result. Improves combustion and this can be very noticeable. You should NOT drill the slide in the carb as this only benefits twins. Installation is simple – remove your main jet and unscrew the tube under the jet and replace that tube with the Yost Power Tube – reinstall the jet as this does not impact your jetting. I got a bargain on eBay for $22 (retail $105). Make sure you get CV-40 carb Rev 1 and not the Rev L which is the older model.
8) Build a Carb Air Splitter or Purchase PowerNow – this mod is second only to shimming the needle and Yost Power Tube For effect and Improves bottom to mid acceleration. PowerNow Airflow Splitter for 40mm CV Keihen Carb (HD N56B / 27404-00YA). See Custom Intake & Exhaust tread - http://www.buellforums.com/forum/showthread.php?t=4773 for what some Forum members have done.
9) Rejet Carb to 45/170 if you’ve done mods 3 & 4 (later years have 170 stock – earlier years have 160) – rejet to 48/175 if you’ve also done mod 5 – rejet to 48/180 if you have a Jardine or other superior free-flowing aftermarket exhaust. The other mods should have minimal effect on jetting.
Tip: You can also add a Dial-A-Jet for CV-40 carb to give you adjustable jetting and this works well with the Yost Power Tube to better vaporize fuel - go down two jet sizes for Main jet and one size for Slow jet.
Note: 12 pounds = 1 horsepower … How many pounds can you remove from the bike? … How many pounds can you remove from the Handlebar Nut (a human who holds onto the handlebar while a motorcycle is underway)?
Note: When you've done the basic mods above and maxed-out the intake and exhaust, your Blast is breathing Twin style with 48/180 jetting, and Air-screw out 3 1/3rd turns on a stock Blast Motor. 48/175 with Vance & Hines or drilled stock exhaust.
Tip: If you do any of the mods to the carb, I suggest you replace the crappy bowl and top cover screws that easily strip with stainless steel cap screws – these are metric 4mm screws.
Oil Filter: Filter for 1988-2000 Toyota Celica/Corolla 1.5-1.8L fits Blast
**Don't use Fram #4967, they are Junk Filters
H D 63806-00Y is OK
Walmart - SuperTech #ST4967 (formerly same as OEM Buell) – quality low cost filter.
AC/DELCO / PF1233
MOTORCRAFT / FL836
PUROLATOR / L14476
STP / S4967
BOSCH / 3311
MOBIL / M1-103
K&N / HP-1003
BECK/ARNLEY / 041-8066
WIX / 51394
Napa / 1394
FLEETGUARD / HF6158
AMSOIL / EA009
Oil: Mobil 1 oil for motorcycles, in 20w50 (V-Twin formula) is one of the best but hard to find.
Mobil 1 (Auto Formula) in 15w50 - very close, readily found & what most use.
Amsoil is the best by a very small margin.
Any Name Brand of Synthetic or Semi-Synthetic oil in 20w50 or 15w50 is good choice.
Oil Check Secrets: Ride for ½ hour to warm oil. Find a transparent drinking straw. With an indelible marker, put two marks on the straw, one at 5/16 inches from the end and the second at 15/16 inches from the same end. Now, remove the dip stick and set aside. Put marked end of the straw into tank, keeping it and your Blast vertical, UNTIL IT TOUCHES BOTTOM. Put your finger over the other end of straw and pull out of the tank. The two lines on the straw correspond to the marks on the dip stick and the oil trapped inside the straw shows the level of oil in the tank. Check level and lift your finger off the straw to let trapped oil drain back into tank. You can put a funnel in oil tank opening to add a oil without making a mess, then use the tool through the funnel to recheck level.
Transmission Fluid: It's safe to use ANY (*Motorcycle) quality 20w50 or 15w50 Motor oil in transmission and use of the Superior Synthetics will even aid in shifting. Just use the same oil you use in the crankcase and keep it simple..
Shortcut to Change: Drain when hot. You might want to put a block of wood under the kickstand to get it a little more level to drain it all out. To fill, remove the transmission vent hose from inside of frame next to left side of battery and fill from there using a small funnel. Fill with exactly 1 quart. Replace the trans vent back into the frame channel and you’re done.
Fuel: Manual says 87 octane - decal on my 02 Blast says 91 octane – I use 93 octane (premium) because of octane dilution - prior user probably pumped 87 and you could get 1/2 gallon or more of 87 before pump hose clears previous selection and starts delivering yours.
Front Forks: When you change front fork oil, change to 7.5 oil for improved handling.
Spark Plug: Standard "NGK" Spark Plug is #DPR9EA-9.
Tip: get a Denso Iridium Racing Plug (IXU01-27) - increases output and mileage, maintenance free, self-cleaning, lasts the life of your Blast, pays for itself in savings – At least a 1 horsepower gain - About $35 plus shipping from sparkplugs.com.
Tip: For plugs that don't have a "Fixed" top cap on the stud, red loctite the center threads to the threaded top stud before installing or it could vibrate loose - includes the Denso Iridium Racing Plug.
Air Filter Element Alternative: K & N makes a Drop-in for the Blast for $50+. However, you will be much better served for the same or less money by tossing the air box and air filter and building a custom stack intake filter - see the “Custom Intake & Exhaust” thread to see what other forum members have done. At least a 1 horsepower gain! http://www.buellforums.com/forum/showthread.php?t=4773
OEM Parts: Chicago Harley gives a 20% discount on Internet orders - ChicagoHarley.com
Shop Manual and Parts Manual: These are available in PDF format in this Forum - get a hard copy if you’re doing engine work. 02 Shop Manual http://www.buellforums.com/forum/showthread.php?t=584. O7 Parts Manual http://www.buellforums.com/forum/showthread.php?t=3527.
Oil leak/seep problem: Rocker Box Paper Gasket (infamous paper gasket leak on 01 to mid O2): Replace with new H-D/Buell (one piece) gasket or aftermarket Cometic.
Caution: Oil (breather) line and wire harness rubs through on air box sharp edge. Grind off sharp edge and protect or tape to prevent further damage - better yet, build a stack air filter and get rid of the air box.
Diagnosing Problems / Causes / Intake Boot (Das Boot): The Blasts carburetor is basically suspended by the intake boot and the air filter box. It is subjected to a large amount of vibration, and as it ages, it starts to crack, allowing the vacuum to escape and robbing your carburetor of the proper air & fuel mixture. DAS BOOT is responsible for most performance and starting problems on a Blast and is a common failure – get a spare or two or get a SUPER DAS BOOT from Thump-e in this Forum. Replacement is not a difficult.
Intake Boot Symptoms (Smallest to Largest):
1) Power Loss - loss of power while riding flat, not under load, not going uphill or steep grade
2) Small increases in fuel efficiency - you normally get 65-70 miles per gallon, and now you are getting 70-75
3) Random power loss followed by backfire, then a regain in power
4) Bike will turn over but will not start
5) Will idle but dies when you apply throttle.
6) Fast Idling
Tests
1) Make sure it is not a gas tank vacuum issue, try to start your bike with the gas cap off (If no continue)
2) Have you checked your fuel is on, the fuel filter &main line into your carburetor? (If yes continue)
3) Are you getting consistent spark from your plug? (If yes continue)
4) Place hand over carburetor while attempting to start - you should feel strong suction, (If not continue)
5) Replace intake boot
Note: You may have smaller issues for a month or more before the boot gets to the point where the bike will not start. It has also been suggested that you regularly change the intake boot at least every 2 years. Replacement at a garage will run you just under $170, 2 hours labor + part, the boot is about $11.00 and easy to replace. Following Service Manual instructions for checking fuel filter and removing carburetor will get you the disassembly and reassembly instructions. Be sure you have the boot seated in the grooves correctly, and that the clamps are in the correct grooves and tighten sufficiently.
Replacement: DON'T just Yank it out! Loosen both sides of the airbox then pull the airbox with the carb attached a little bit away - THEN you can pop out the Boot! On the left side of the airbox lower down, locate and remove the TWO bolts that hold the airbox to the triangular bracket that bolts to the block- But DO NOT remove that Third Bolt that holds the bracket to the engine block- that one remains intact! Then on the right side of the airbox, remove the one bolt that goes thru that small metal tab on the underside of the airbox - that attaches it to the engine block - the box and carb are free to move enough to pop off the intake boot (manifold connector). When you're done tightening the boot clamps (don't over tighten), use Blue loctite on the CLEANED threads on the right side bolt and tighten snugly (there is a Torque value to that bolt- so don't strip the aluminum threads in the block). On the left side, the bolts insert into a threaded insert in the airbox- just use ONE tiny drop of blue loctite on THOSE cleaned threads and snug them up really good but don't strip by over tightening. That’s all folks
Super Das Boot from Thump-e: This is a boot that has been completely sheathed in a full length stainless clamp rather than a hose clamp on each end - still being tested but could be the last boot you ever need!
Tires: Stock size is 100/80-16(Front) & 120/80-16(Rear).These companies make tires for the Blast:
Worst – Dunlop K330 - older OEM tires, the rear last 2,500-3,500(?) miles. Tires belong in trash!
Best Handling - Pirelli MT75 - current OEM tires - rear last 2,000-2,500 miles, front lasts 4,000(?)
Best Mileage and Rain Tire - Avon AM51 & AM52 - rear tires last 3,500-4k miles, with 7,000+ for front.
Wider Tires - AVON VIPER STRYKE AM63 - 140/70-16 (rear) - 110/70-16 (front)
PIRELLI DIABLO Scooter Tire in same sizes as AVON - best construction, handling & mileage - the winner!
Note: The wider tires are built for a scooter that weighs 200 pounds more than a Blast so they are strong and give great mileage - especially the Pirelli.
Tip: For extended mileage and smoother ride from front tire (this tip WON'T slow steering to any noticeable degree). Replace front tire with a taller size from any quality tire manufacturer, but use the 100/90-16 size INSTEAD of the OEM 100/80 series. The 90 series fronts will last a few 1000 more miles and soften the bumps a slight bit more.
Tire Pressure: Front 28-32 PSI – Rear 30-36 PSI (lower pressure for solo rider – higher pressure for loaded to GVWR). Check your tire pressure frequently as an underinflated tire will rob you of horsepower, performance and safety.
Warm-up: When your Blast comes off "fast idle", you’re ready to ride but take it easy for the first 10 minutes as the engine continues to warm-up. If you idle for 10 minutes you can over heat because it is an air-cooled engine and needs to be moving to cool properly. Also, engine is not making optimal oil pressure at idle.
Headlight Upgrade: 7" round Candlepower or Diamond - I went from 55/60 watt quartz to 90/130 Xenon HID 6000 H4 bulb without melting wiring because Xenon HID gives 90/130 watt result from 55/60 input and is street legal - Awesome! More than 55/65 watt power consumption by the bulb is not street legal so please do not go there – just get a superior Xenon HID bulb. My Candlepower is Motorcycle specific rather than a generic automobile lens - not sure about the Diamond.
Ignition key: can be made with Volvo key blank VL6 by HY-K or Triumph blank (not readily available) - I had to go to a Locksmith.
Brake pads: Galfer Sintered Kevlar Brake Pads are the best - FD112 G1532 (front) - one finger braking. These pads are a great replacement for sport and utility use. They have the extra mechanical strength of a sintered pad and are good for use in sandy and wet, general purpose conditions of riding. Most of your braking is done by the front as weight is thrown forward when stopping … the harder you break the less effect the rear brake has and the more likely you will lock rear up and skid the back around. FD103 (rear).
Fork Brace: http://www.superbrace.com - Price polished $143.95, Black is $168.95. A fork brace will improve handling and braking. This is the only source right now.
By: Capt David