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Thread: 2001 ditech to carb conversion, Total Cost $49

  1. #1
    apriliaforum Junkie mwlehman's Avatar
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    2001 ditech to carb conversion, Total Cost $49

    I posted the following on the Ditech side but figured I post it here also, sorry if I should not have

    I have been asked to post a little write-up here about my cheap ass conversion. I do not want to upset anyone by posting this so sorry if I do.....oh and sorry for the following ramble, not much of a writer but I will do my best

    I purchased a 2001 SR 50 Ditech for my wife it has 625 miles (she has many more ), it has ECU Remapped, 6.8g rollers, Leo Vince ZX Chrome, nice clean bike. It started right up and ran great but did not idle, it would shut off as soon as throttle was closed, The person I purchased it from had installed 2 new computers, new fuel and air injectors,new o-rings, new gaskets, new air pump, new piston and rings and it still did not idle. I bought it for $500 with all extra parts I checked for airleaks with soapy water and found none..I wasn`t going to spend much money on it because I am cheap LOL.

    I have a 2003 ditech that runs fine, idles fair but starts hard, I put a new piston and rings in it but in the meantime I had purchased on ebay this 1999 Aprilia SR50 carb for $21 shipped http://www.ebay.com/itm/330912098264 and had it sitting around incase I needed it.

    My wife loved the SR50 but could not deal with the non idle issue.....so this past sat I tore into it. I was going with the KISS method, keep it simple stupid ! I pulled the TPS off the rubber boot but left it plugged into bike wiring, I then cut a 3/8 rubber hose in half length wise and stuffed it in the TPS butterfly to keep it open all the way, next I put the carb into the intake boot the TPS was mounted in. The carb had the throttle cable and hand grip attached but I did not put them on the bike yet. I then pulled the return line off the fitting in the head and connected it to the inlet on carb, (I did not put a filter on yet as I was doing the minimal I had to in case I had to revert back to injected), I then unplugged the fuel pump. I pulled back the brake lever and wrapped it with tape to free up my hand to work the throttle I had in my lap, now I was ready to see if it started....................

    I turned key on, hit starter button and holy shit it fired up almost instantly, I almost shit my pants, I kept it running with throttle till I adjusted idle circuit..it sits and idles perfect!! Now I had to clean up the installation and make it permanent.

    I sat back and looked things over deciding how I wanted to run fuel lines ect. First thing I did was unhook throttle cable from twist grip on bike and carb, I decided to leave original injector throttle cable in bike still attached to TPS , I pulled it off grip, next I threaded the carb throttle cable through the frame up handle bars and connected it to the twist grip, made sure it worked fine and buttoned that up..on to fuel stuff
    I looked at the fuel line situation and decided the quickest easiest cheapest way for me was to use the injector return line and the carb feed line.

    I ran down the local auto store and bought 1/4 fuel filter, manual fuel shut-off valve, clear fuel line, fuel line clamps and a package of fuel safe rubber caps.. $20 and change....back home I removed the fuel pump and capped the outlet on tank, I made up the carb fuel line with filter and shut off and attached to fuel tank and carb. When I was done with that I gave some thought to the oiling system, I knew it was not designed for carb but I left it hooked up and running but added some oil to fuel..LOL I wasn`t very precise about it, just dumped about 3 ounces in tank and sloshed it around ( will be more precise in future, I may just remove oil tank and pump and go with premix),

    I then put all the plastic back on and took it for a short run up the street, it ran very nice the whole way up the rpm range..almost to crisp so I took the carb of and checked the main jet size with some small number drills, found size that fit and drilled jet out next drill size larger, slapped it all back together ......

    My wife and I ride downtown every sat for coffee and I figured it was a good test. My wife started her`s with the carb right up and then has to wait for me to get mine started LOL...then off we went, I kept an eye on her water temp but it never moved more than an 1/8" off peg, it put out a little smoke the whole ride, started perfect the whole day, ran and idle great. I checked the plug when we returnd home and it is a nice milk choc brown

    I unplugged the injector plug and that made no difference in the way it ran, but the injector light stays on in dash. Last night I removed the airpump from motor and put an aluminum plate I had made at work,

    I also have an extra head the I tapped the injector hole to 7/16-20. I am going to use a stainless steel bolt to seal the hole..I toyed with the idea of getting a bolt that was a little longer than needed , I was going to use multiple washers under head of bolt to get the threaded end of the bolt flush with inside combustion chamber and then try removing washers from under head to thread bolt into combustion chamber farther to raise compression.

    I have to say I am very happy with the way it turned out..it really does start and run great. After seeing how it starts and runs I just purchased another carb and cable off ebay, should be here this week

    Now a little about me..lol

    I grew up in Pennsylvania in the middle of dirt track racing, sprintcars, modifieds, gokarts . I started racing karts when I was 15, we were not wealthy and my father and I (father mainly then) did all our own motor work, 2 and 4 stroke motors, my father is a genius and I am not saying that because he is my dad...the man is brilliant, we mainly raced yamaha piston port class, motors had to be "stock", they gave you a list of specs for everything..our motors were incredible, non of them stock but all within spec, so legal..won alot of races and decided to move on after 7 years.

    We were in the middle of sprint car country but I did not have the funds to play that game with 20-30k motors at the time..so I decided to go with micro sprints. they look like a small sprintcar but run anywhere from 125cc up to 500cc motorcycle motors. We raced the 270 2 stroke class which was most popular..and again my father was the guy, we won a ton of races, one for $5,000 to win..I owned my own car for a year and then was a paid driver, 50% of purse..these are the years where I learned all about 2 stroke motors, jetting, porting timing, squish bands , we split our own cranks and rebuilt them ourselves, used v-blocks, dial indicator and lead hammer to align them.we did all kinds things to those motors...

    I did that for 3 years and then decided to pull up my pants and get in way over my head , I bought a 410 sprintcar..for those of you who are not familiar with those cars..750-800hp in a 1400lb car on a half mile dirt track...better than sex...anyway my dad still doing the motors and chassis set-ups, we would buy used parts and do what we could, I ran my own car for about 1 and was offered a ride in someone else`s car.....paid driver again! I do have to amidt I never won a 410 race, finished third one night..that was all good until the owners son decided he wanted the ride..I was out.

    I was approached but a friend named Bill Henderson abut getting a 358 sprintcar, same car as a 410, just 358 ci motor...now Bill isn`t you normal type person, he has a way higher than normal IQ and is very introverted, works in a bowling center as a machine mechanic, lived at home with his mom at 45 (still does now), won`t leave the house sometimes, he was fanatical about proper preparation on the car, it had to be perfect, everything perfect, he kept notes on everything....but we had one hell of a car, crazy fast ..of course my dad is still doing my motors and chassis set-up..two years we finished first or second in 90% of our races..won 12 out of 14 at one track, 2 track championships one year..I finally stopped racing in 2007 ..we ended up with over 50 sprintcar wins

    ...but the main reason I won all those races was my father...he showed me how to look at thing and figure our how to do it myself and how to fix thing of make things without buying new...he always impressed on me not to follow the leader on doing thing...not be afraid to try different ideas. I just called him last week and ran the aprilia situation past him to see what he thought about it

    I could keep going on about racing for a while LOL..so many crazy stories...oh I did race motocross for 2 years

    sorry again for the ramble and off topic..
    Mike

    PS: I do have 2 chinese 50cc scooters that will eat both my aprilia sr for lunch..they are monsters LOL..just not as cool as the Aprilia SR

  2. #2
    apriliaforum newb
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    can you suggest any other carbs that might work...there are no sr50 carbs on ebay right now....how about from a Scarabeo Aprilia 50?
    http://www.ebay.com/itm/2000-Aprilia...8a38cb&vxp=mtr

  3. #3
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    dellorto 12 till 17.5 work awesome
    you can also easily swap it to a mikuni carb with even less to modify but dont go over 17.5 for the stock engine

  4. #4
    apriliaforum Junkie mwlehman's Avatar
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    ok..it has been 4 years and the SR50 has been flawless. It has about 5500 miles and still running great.

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    apriliaforum Junkie mwlehman's Avatar
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    still going
    Once you have ruined your reputation, you can live quite freely

  6. #6
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    PS: I do have 2 chinese 50cc scooters that will eat both my aprilia sr for lunch..they are monsters LOL..just not as cool as the Aprilia SR[/QUOTE]

    What engines do these Chinese scooters use, Gy6, or 2 stroke and are they the right shape to fit an Aprilia? - Chinese stuff is cheap in UK

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