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Thread: Habana / Mojito 50 repair + tuning

  1. #1
    apriliaforum prov-nov raffaello's Avatar
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    Habana / Mojito 50 repair + tuning

    Hello Guys,

    I'm new to the forum, though I've read most of it looking for some information about the Habana / Mojito 50 reparation and tuning.

    I got my 2001 Habana (as they call it in Europe) / Mojito 50 last year. No restriction ring on the variator, the silencer was also tuned by the previous owner. I was riding it for a couple of months until end of August, when my silencer broke down. It just broke on one of the weldings... Investigating the cause I found that the lower mounting point bolt was gone (due to a broken thread) and the engine vibrations caused the welding to brake. Also the upper mounting point was broken. The old silencer was rusted and clogged, so I decided to buy a new one. I've bought a Tecnigas Silent Pro (the orifice is gone) as I use my moped daily commuting to work. The side effect of the silencer problem is I had to take apart the whole engine.

    And that's where it starts...

    Looking at the Haynes Manual I've found that I've got the Aprilia 50 cc engine, which is based on the Morini horizontal, I think one of the most popular ones, so a good starting point. The spare parts and tuning parts are easily available.

    After removing the cylinder I've found that the piston rings are not doing their job, there are marks of exhaust gases all around the piston. One of the rings seems not to expand properly to the cylinder diameter while placed on the piston... Took it to the workshop, the guys told me that at least the piston and rings have to be replaced and that some treatment has to be done to the cylinder itself. I decided that it could be a good moment to invest some money in a better cylinder kit, to get some more power / acceleration.

    The other thing that has to be repaired / replaced is the standard 12 mm carburetor. The mixture bolt is completely stuck, the engine runs very rich, the fuel consumption was around 5 l / 100 km (around 47 mpg!!!). It's the standard Keihin PWS carb, which I read is crap, not worth investing in. Going through this and lots of other forums I've decided to go for a 17,5 mm carb, which is a good start. And should be enough for my needs. I've found a Dellorto 17,5 mm PHVA carb for a reasonable price and I'm planning to invest in. The next decision to take is - which cylinder kit to choose?

    The most important thing for me is reliability. I do not need high top speed (although up to 10 mph more would be OK), only better acceleration and more power to manage occasionally an aditionnal weight of a small 2nd person behind.

    I'm not into any of the crappy chinese kits that can be bought in EU for some 25 USD, I want something that will last! And I think I prefer cast iron over aluminium I would prefer to stay with the stock crankshaft / rod / bearing, having in mind my requirements. What should I be looking at? What about the variator rollers and spring? I would say they are stock. Will they fit the setup?

    Thanks in advance for your suggestions

  2. #2
    apriliaforum expert
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    my buddy has a mojito.

    the 17.5mm carbs for sale new are setup for open airfilters. they are louder than a premium sport exhaust. better off finding a 17.5 off an aprilia but then it wont fit the bike at all.

    ----

    i think people use the keihin carbs on your bike.

    ----
    the cheapest and best bbk is the airsal sport with no head. runs smooth and strong....
    Last edited by sublunacy; 04-08-2017 at 01:38 PM.
    --- diploma for engine repair in 2012 ---

    derbi bullet 2006 - piaggio AC - malossi T.C. half - custom GPS dash - TPR 70CC - topperf crank - vl13 reed and spacer- yamaha rt180 kickstand - giannelli shotV4 - phbg 21mm - doppler mesh top venturi filter

    complete wtp volta bmx 2012 - sanko seamless japanese cromoly heat treated and blue printed frame - 21lbs

    1992 lt250r suzuki quadracer - maier plastics -chromed shearer pipe - chromed works suspension - ++++++++ - 220lbs

    previous vehicles - subaru legacy turbo 1991 - mazda mx6 turbo 1990.

  3. #3
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    what size keihin carb do you have? how about the reeds?

    ---
    the tecnigas silent pro is a great choice. i can see nothing out of place but the cylinder needing perhaps just a new tnt 20 dollar piston. i think the power you are trying to find with the carb is completly fruitless. tuning the carb and rollers and using the folowing. - champion ac sparkplugs and red synthetic oil like it says on the sticker. try to avoid the green ones marked dual purpose if the red stuff is right beside it.

    --

    let me know if you have more questions.
    --- diploma for engine repair in 2012 ---

    derbi bullet 2006 - piaggio AC - malossi T.C. half - custom GPS dash - TPR 70CC - topperf crank - vl13 reed and spacer- yamaha rt180 kickstand - giannelli shotV4 - phbg 21mm - doppler mesh top venturi filter

    complete wtp volta bmx 2012 - sanko seamless japanese cromoly heat treated and blue printed frame - 21lbs

    1992 lt250r suzuki quadracer - maier plastics -chromed shearer pipe - chromed works suspension - ++++++++ - 220lbs

    previous vehicles - subaru legacy turbo 1991 - mazda mx6 turbo 1990.

  4. #4
    apriliaforum prov-nov raffaello's Avatar
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    The carb is 12 mm, which is just below 1/2". I have no idea about the jet sizes, due to the stuck screws I decided not to take the carb apart and just replace with a new one which could be set up easier. The reed valve seems stock, the petal thickness is something around 0,02 mm. (1/1280"). The engine was running on a red oil, I've bought a new one, Castrol Power1 Racing I've got one concern about the spark plug - the one installed is NGK BPR7HS, though Haynes says it should be BPR8HS (which is colder). I'll look for a champion equivalent, thanks.

  5. #5
    apriliaforum expert
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    the reeds are maybe fine but these little reed cages are worth looking at....you can test it by mouth suction - blow out air then reverse flow/suck in...it should close all at the same time and not leak at all. done
    ---
    the carb is pretty small. you do need a larger carb if you go 70cc - but just a 50cc is fine for the mild exhaust pipe. the correct size is 12-14mm carb at 50cc. so yes a 14mm carb would be a nice upgrade.
    --- diploma for engine repair in 2012 ---

    derbi bullet 2006 - piaggio AC - malossi T.C. half - custom GPS dash - TPR 70CC - topperf crank - vl13 reed and spacer- yamaha rt180 kickstand - giannelli shotV4 - phbg 21mm - doppler mesh top venturi filter

    complete wtp volta bmx 2012 - sanko seamless japanese cromoly heat treated and blue printed frame - 21lbs

    1992 lt250r suzuki quadracer - maier plastics -chromed shearer pipe - chromed works suspension - ++++++++ - 220lbs

    previous vehicles - subaru legacy turbo 1991 - mazda mx6 turbo 1990.

  6. #6
    apriliaforum Member
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    I have a 50cc mojito retro...i ended up getting a malossi sport cylinder in 70cc....i will let you know how it works out.....broke my spark plug wire - waiting on that so i can begin break in...

    Im still using the stock 12mm carb...once i get the bbk set I will look into a larger carb
    2004 Aprilia Mojito Retro 50cc
    2003 Vespa ET2 50cc
    2001 Triumph TT600
    1993 Yamaha Razz 50cc

  7. #7
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    update...well im running in the Malossi 70cc cast iron sport cylinder....its real nice....has a neat gurgly/bubbly sound to it....very smooth...i am too early into the break in but i can feel the power pull...i accidently got on it too much at a stop light and it wanted to wheelie .....running the stock carb with an 80 main jet....im sure i will need to upgrade the carb eventually

    btw im running:

    stock rollers
    stock variator
    stock clutch and contra spring
    stock carb with 80 main
    leo vince touring pipe
    Last edited by jixaw; 04-13-2017 at 03:27 PM.
    2004 Aprilia Mojito Retro 50cc
    2003 Vespa ET2 50cc
    2001 Triumph TT600
    1993 Yamaha Razz 50cc

  8. #8
    apriliaforum prov-nov raffaello's Avatar
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    (waiting for mod's approval I've posted a new post below)
    Last edited by raffaello; 04-14-2017 at 01:45 PM.

  9. #9
    apriliaforum prov-nov raffaello's Avatar
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    Hmm... I wonder where's my yesterday's post... (finally it appeared on the forum - will delete its content not to bring confusion)

    sublunacy, jixaw, thanks for your replies I've read some more, spoke to a couple of guys locally and the decision is taken - Malossi sport 70 cc, Dellorto PHVA 17,5 or 19 mm carb (+ new inlet from the carb to the engine... how do you call it in English?), new set of bearings and gaskets, new champion spark plug, and furthermore, perhaps in May / June, a Malossi Multivar

    Unless I'll find a crank at a good price, as suggested by one of the guys in a workshop here. He also suggested a new clutch for this set.

    And my own need - new front breaking pads

    jixaw, what carb were you thinking about?
    Last edited by raffaello; 04-15-2017 at 04:51 AM.

  10. #10
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    If i were you i would try to use the same intake (english word) with the new carb....unless its the same profile you might have issues with fitment....I'm not sure which carb i will get but to be honest i'm very happy with how it rides as it stands...i know you said you have to get a new carb anyways....maybe together we can figure out the best one.....

    I like this Malossi 70cc kit a lot..it really pulls...i hope its going to be reliable..
    2004 Aprilia Mojito Retro 50cc
    2003 Vespa ET2 50cc
    2001 Triumph TT600
    1993 Yamaha Razz 50cc

  11. #11
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    you dont need a clutch anyway for sure. you need a 70cc cylinder to fill the pipe then takeoff will be great with the stock clutch and stock springs.

    a variator upgrade with that pipe will be a waste of time and money i believe.

    ---
    i would focus on 70cc now/ the rest of the bike is fine. your held back with the cylinder and carb size.

    ---
    if you are going with an openfilter then get a 14mm-16mm aftermarket carb. they are setup for open filters so its easy to jet if you use it ALL. the polini cp carbs seem the best choice lately. the 17mm polini cp carb is getting a little too big for both you guys but not crazey big.
    @ if you measure the exhaust pipe manifold and cylinder outlet to calculate the cfm then subtract 20 percent/ this is the carb size you need. it works everytime because its based on air mass. the idea behind it is that hot air is 20 percent larger than cold air.

    im sorry if this sounds childish and incorrect based on what you have heard concerning bigger is better etc. but i can assure you the bonus power a larger carb brings is tiny and can be duplicated by reducing the vacuum pumping losses like better filters/intakes/reeds/pipe or any number of things.
    Last edited by sublunacy; 04-14-2017 at 02:47 PM. Reason: correction
    --- diploma for engine repair in 2012 ---

    derbi bullet 2006 - piaggio AC - malossi T.C. half - custom GPS dash - TPR 70CC - topperf crank - vl13 reed and spacer- yamaha rt180 kickstand - giannelli shotV4 - phbg 21mm - doppler mesh top venturi filter

    complete wtp volta bmx 2012 - sanko seamless japanese cromoly heat treated and blue printed frame - 21lbs

    1992 lt250r suzuki quadracer - maier plastics -chromed shearer pipe - chromed works suspension - ++++++++ - 220lbs

    previous vehicles - subaru legacy turbo 1991 - mazda mx6 turbo 1990.

  12. #12
    apriliaforum prov-nov raffaello's Avatar
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    Intake... thanks jixaw I've read / heard that the Malossi Sport cylinders have a very good and repetitive quality and thus are reliable and a very good choice for everyday use... We'll see What was your fuel consumption with the stock cylinder?

    At the connection point the diameter of the Dellorto carb is 25% bigger than the stock intake As I can imagine putting a bigger carb on a smaller intake would act as some kind of bottleneck for the air/fuel mixture. Am I right? As for now I managed to find one (!) intake that will fit the engine on the bottom and the Dellorto on the top side.

    sublunacy, I totally agree with you that bigger isn't better Contrary I'd go for the 90 cc kit My only concern is durability - the stock parts were engineered for stock performance (i.e. RPMs / power / load), I understand that there is some margin they can take. But how much and for how long? Changing a burnt or worn clutch won't be a problem if it happenss some time in the future, but I'd prefer not to see the result of a broken crank... Hope I won't have to

    The derestricted exaust manifold diameter of the tecnigas silent pro is slightly over 26 mm, so the carb should be 21 mm... Hmm... Really?

    I wasn't considering an open filter yet, was rather planning to use the stock box with oiled foam filter but I understand the engine could suffocate I'll bring the stock box from the garage to look how it's built to try to figure out the solution. As I remember, there is a 90 degrees elbow (?) air intake to the box, which can be turned around. I'll mesure its diameter, perhaps putting a bigger one will be enough. I was already wandering last year about the best position of the intake. To the front? To the back? Upwards? Downwards?

    Should the rubber hose between the air filter and the carb be bigger by 75% (for the 21 mm carb)?

    I know it's not a perfect tuning scooter so there might be problems getting it perfectly set up with available parts / accessories, but it's so beautiful and stylish And I'm a perfectionist, so I want it to be the best possible
    Last edited by raffaello; 04-14-2017 at 01:36 PM.
    Bella 2wheels - 2001 Aprilia Habana / Mojito 50
    Bella 4wheels - 2001 Alfa Romeo 156 Sportwagon 2.0 TS

    Italians know how to make it beautiful

  13. #13
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    good post. you came to the right place. -- i just edited to above to include the cyl outlet size when measuring the hot side cfm. cheers


    ---
    the 90cc bbk will have likely a 19mm exhaust outlet aswell so no change in carb size is needed from a 70-90cc. its that simple.

    ---
    im worried your intake and reed cage are to small from the factory to complete your build. if you want to measure both we can get to the bottom of it.

    ---
    the tecnigas trek/triops have 24mm ex manifolds but yours is super mild so im guessing its 19mm. if its 21mm then forgive me but my point still stands because there are no cylinders with 21mm outlets. i have not seen or heard of any.
    @ regardless try to get the hot side all matched up cfm wise then choose a carb based on that diameter/cfm. and by hot side i mean both the cyl outlet and the pipe inlet/manifold
    Last edited by sublunacy; 04-14-2017 at 03:08 PM. Reason: ok
    --- diploma for engine repair in 2012 ---

    derbi bullet 2006 - piaggio AC - malossi T.C. half - custom GPS dash - TPR 70CC - topperf crank - vl13 reed and spacer- yamaha rt180 kickstand - giannelli shotV4 - phbg 21mm - doppler mesh top venturi filter

    complete wtp volta bmx 2012 - sanko seamless japanese cromoly heat treated and blue printed frame - 21lbs

    1992 lt250r suzuki quadracer - maier plastics -chromed shearer pipe - chromed works suspension - ++++++++ - 220lbs

    previous vehicles - subaru legacy turbo 1991 - mazda mx6 turbo 1990.

  14. #14
    apriliaforum prov-nov raffaello's Avatar
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    sublunacy,
    the inside exhaust manifold diameter is really slightly above 26 mm, have a look youself:

    https://www.dropbox.com/s/3dspdnho8w...2021.49.12.jpg

    Edit: of course it's the pipe internal diameter for the moment no idea what's the diameter of the exhaust manifold on the cylinder, I'll try to find it online
    Last edited by raffaello; 04-14-2017 at 03:06 PM.
    Bella 2wheels - 2001 Aprilia Habana / Mojito 50
    Bella 4wheels - 2001 Alfa Romeo 156 Sportwagon 2.0 TS

    Italians know how to make it beautiful

  15. #15
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    im not a 90cc expert at all. if you want to tell me about them im willing to listen.

    ---

    ok the exhaust outlet on the cylinder wil be the limiting factor then if the pipe is as free flowing as it is. no problem and good luck. im sure alot of tuners will be jealous when its complete.
    Last edited by sublunacy; 04-14-2017 at 03:12 PM.
    --- diploma for engine repair in 2012 ---

    derbi bullet 2006 - piaggio AC - malossi T.C. half - custom GPS dash - TPR 70CC - topperf crank - vl13 reed and spacer- yamaha rt180 kickstand - giannelli shotV4 - phbg 21mm - doppler mesh top venturi filter

    complete wtp volta bmx 2012 - sanko seamless japanese cromoly heat treated and blue printed frame - 21lbs

    1992 lt250r suzuki quadracer - maier plastics -chromed shearer pipe - chromed works suspension - ++++++++ - 220lbs

    previous vehicles - subaru legacy turbo 1991 - mazda mx6 turbo 1990.

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