Results 1 to 10 of 10

Thread: Need Some help with Ditech SR50 Morini engine

Hybrid View

Previous Post Previous Post   Next Post Next Post
  1. #1
    apriliaforum newb
    Join Date
    Jun 2012
    Location
    Vancouver BC
    Posts
    6

    Cool Need Some help with Ditech SR50 Morini engine

    Ok Ive read all the stickies and I am still stuck, if you can help pls do! Thanks

    So first off i had a compression issue with my SR50 which came with a 70cc Malossi Kit, I was only getting 90 PSI. I took the head off notice the rings were stuck to the piston, it was still starting but only for a few mins then not start again until enough fluid created a seal inside the piston. anyways i order a new gasket kit and piston and rings I had some leaks but fixed those with new o-rings. I am now testing with it all connected air hoses and all and I am only getting 70 PSI. My question is do I need to have the coolant filled up before testing?? Am I missing a step? I will look at the air compressor after this I dont hear anything. The reeds are good, all gaskets changed. any ideas??

    Thanks again!


  2. #2
    apriliaforum Junkie joelbo's Avatar
    Join Date
    Mar 2009
    Location
    Waterloo, Ontario
    Posts
    357
    Did you check the walls of the cylinder? It might need a quick re-bore. If the rings were off at all they could've nicked it up. How old is the fuel in it??

    Sent from my LG-H812 using Tapatalk

  3. #3
    apriliaforum expert
    Join Date
    Jul 2015
    Location
    ontario
    Posts
    1,815
    So it is carbureted, ok
    like I was saying I heard another guy complaining about the malossi morini rings a few years ago.
    --- diploma for engine repair in 2012
    --- custom parts and machining
    -2T&4T cylinder&engine prep,port,polish,balancing--------------------------

    -derbi bullet 2006 - piaggio AC

    https://www.apriliaforum.com/forums/...t-Tuning-Guide << Link

  4. #4
    apriliaforum Member Pinkscoot's Avatar
    Join Date
    Aug 2016
    Location
    NC
    Posts
    137
    Are you opening the throttle completely when you test?
    Italian scoots owned: 2003 Scarabeo 150, 1998 Italjet Velocifero, 2009 Vespa GTS 250, 2012 Vespa S50, 2007 BV 250, 2014 Aprilia SR50 Purejet, 1977 150 Sprint Veloce (future project) and Vespa ET2 (future project)

  5. #5
    apriliaforum newb
    Join Date
    Jun 2012
    Location
    Vancouver BC
    Posts
    6

    Ditech Morini

    The scoot is fuel injected, Ive drained all the gas it had a nice mix of water or something with gas, the jug was clean nice and smooth no scratches. When I check compression I have the throttle wide open. Funny thing is this the first time Ive ever worked on this scooter, this is kinda embarrassing Ive rebuilt 4 other carbureated scooters while my own scooter is still sitting on the lift....LOL sigh......Even if the seals of the injector are not sealing or completely off I still should be getting 95-110 psi.

    So annoying, The exhaust is off, wide open throttle the compression guage is verified and working I have both a snap on and cheap-o one and both read about the same. I am going to open up the compressor and have a look also.


    So does it need to have the coolant filled probably not right.....Im drawing straws. anyways I will take it apart and post some pictures

  6. #6
    apriliaforum newb
    Join Date
    Jun 2012
    Location
    Vancouver BC
    Posts
    6

    Ditech Morini

    The scoot is fuel injected, Ive drained all the gas it had a nice mix of water or something with gas, the jug was clean nice and smooth no scratches. When I check compression I have the throttle wide open. Funny thing is this the first time Ive ever worked on this scooter, this is kinda embarrassing Ive rebuilt 4 other carbureated scooters while my own scooter is still sitting on the lift....LOL sigh......Even if the seals of the injector are not sealing or completely off I still should be getting 95-110 psi.

    So annoying, The exhaust is off, wide open throttle the compression guage is verified and working I have both a snap on and cheap-o one and both read about the same. I am going to open up the compressor and have a look also.


    So does it need to have the coolant filled probably not right.....Im drawing straws. anyways I will take it apart and post some pictures


    Thanks !!!

  7. #7
    apriliaforum expert Louder North's Avatar
    Join Date
    Nov 2011
    Location
    Ottawa, ON Canada
    Posts
    988
    Quote Originally Posted by Murphy Chow View Post
    The scoot is fuel injected, Ive drained all the gas it had a nice mix of water or something with gas, the jug was clean nice and smooth no scratches. When I check compression I have the throttle wide open. Funny thing is this the first time Ive ever worked on this scooter, this is kinda embarrassing Ive rebuilt 4 other carbureated scooters while my own scooter is still sitting on the lift....LOL sigh......Even if the seals of the injector are not sealing or completely off I still should be getting 95-110 psi.

    So annoying, The exhaust is off, wide open throttle the compression guage is verified and working I have both a snap on and cheap-o one and both read about the same. I am going to open up the compressor and have a look also.


    So does it need to have the coolant filled probably not right.....Im drawing straws. anyways I will take it apart and post some pictures


    Thanks !!!
    Are you measuring cylinder compression with the air compressor disconnected? Cylinder compression of 90 psi should be enough for it to start unless what your are measuring is the sum of both cylinder and air compressor pressure.
    2007 SR 50 Ditech (Morini) 19,000 kms AND 2011 SR 50 Ditech (Piaggio) 2000 kms
    Buzzetti side stand 03/18/12
    Porter Cable water trap 06/19/12
    ECU completely derestricted ver 2.8.0 08/10/12)
    LV ZX-R 09/10/12 - repaired and painted 10/18/14
    Motul Scooter Power 2T oil
    NGK ZMR7AP spark plug, indexed, gapped to .030
    Malossi Multivar 2000 w. 7.5 gm Dr. Pulley sliders (13/06/15), Malossi Special Belt, White contrast spring @ 8000 km 11/12/12,
    Malossi X K belt, front brake pads @19,000 km 06/15/17
    8mm Mirror Riser Extender 05/12/2013
    Michelin Power Pure tires @ 9000 km 05/18/2013, replaced @19,000 07/19/2017
    HGT adjustable fuel pressure regulator 06/08/2013
    90 kph on slight down hill; 103 kph fastest ever going down hill

  8. #8
    The Anal Intruder William the Third's Avatar
    Join Date
    Oct 2003
    Location
    Asheville, NC
    Posts
    8,114
    The direct injection engines used in the Aprilia SR50 are low compression engines, so 90~110 PSI is ideal (even with the compressor attached, as the amount of air injected is trivial). Too low is a problem for obvious reasons (one you get below 75~80 PSI, it will be hard to get the engine to start), but too high (110+) is also a problem. The fuel/air mix is injected by the air injector at ~70 PSI (fuel pressure is ~105 PSI stock, but that is injected into the air injector, which is fed by the compressor ~70 PSI). So if cylinder compression is too high, rather than the fuel/air mix being injected into the combustion chamber when the air injector opens, there won't be a large enough pressure differential for proper injection to occur, or even worse air from the combustion chamber will be pushed into the injector. Since I know some of you will be curious as to how it's even possible to inject at ~70 PSI when cylinder compression is 90~110 PSI, this is because the air injector opens well before top dead center when peak compression happens. When the air injector opens pressure in the cylinder is still well below 70 PSI. However as you raise peak compression, so too do you raise the pressure in the cylinder when the injector opens. Get too close to, or exceed, 70 PSI, then you'll have problems.

    Mind you, not all compression testers are equal, so unless it's been recently calibrated, the number it reads is at best a good estimate.
    #1 Forum Loser

    1973 Harley-Davidson Aermacchi Z-90 - Restoration project
    1983 Kawasaki KZ750 Spectre - Fathers old bike
    1998 Kawasaki KE100 - My first bike at 14
    1998 Laverda Ghost Strike 668 - A fun little bike
    1999 Aprilia RS250 - Track bike
    2001 Aprilia RSV Mille - My first Aprilia
    2007 Aprilia SR50R Factory - My babe magnet
    2009 Aprilia SR50R Factory - My "help me I have a problem"

  9. #9
    The Anal Intruder William the Third's Avatar
    Join Date
    Oct 2003
    Location
    Asheville, NC
    Posts
    8,114
    Quote Originally Posted by Murphy Chow View Post
    Ok Ive read all the stickies and I am still stuck, if you can help pls do! Thanks

    So first off i had a compression issue with my SR50 which came with a 70cc Malossi Kit, I was only getting 90 PSI. I took the head off notice the rings were stuck to the piston, it was still starting but only for a few mins then not start again until enough fluid created a seal inside the piston. anyways i order a new gasket kit and piston and rings I had some leaks but fixed those with new o-rings. I am now testing with it all connected air hoses and all and I am only getting 70 PSI. My question is do I need to have the coolant filled up before testing?? Am I missing a step? I will look at the air compressor after this I dont hear anything. The reeds are good, all gaskets changed. any ideas??

    Thanks again!

    I've highlighted the coolant question because I wouldn't be surprised if this is a/the source of your problem. Without coolant, you really shouldn't be running the engine very long. I know on two-stroke PWC with open-circuit cooling systems the general rule of thumb is 10~15 seconds if not in water or being supplied with cooling water using a flush kit. I can tell you that the engine gets quite warm in those 10~15 seconds. The SR50 engine (be it Piaggio or Morini) is a cast iron cylinder with aluminum piston, and a fairly tight wall clearance. Running it for any significant amount of time without coolant is quite risky. The thermal properties of aluminum will allow it to absorb heat and expand faster/greater (I believe the pistons used in SR50's to be hypereutectic, so thermal expansion will be less than a normal cast/forged aluminum piston) than cast iron. Since you mentioned running it for minutes without coolant, I wouldn't be surprised if you soft-seized the engine, which could explain the loss of compression. That would also explain the reason why it would start again after waiting a bit (gave it time to cool). It's also possible you tripped the overheating protection. I know from experience with the 2005+ scooters, if the engine gets too hot, the ECU will kill the engine, and not let it start until it cools down (never tested with the 2004 and older models).
    #1 Forum Loser

    1973 Harley-Davidson Aermacchi Z-90 - Restoration project
    1983 Kawasaki KZ750 Spectre - Fathers old bike
    1998 Kawasaki KE100 - My first bike at 14
    1998 Laverda Ghost Strike 668 - A fun little bike
    1999 Aprilia RS250 - Track bike
    2001 Aprilia RSV Mille - My first Aprilia
    2007 Aprilia SR50R Factory - My babe magnet
    2009 Aprilia SR50R Factory - My "help me I have a problem"

  10. #10
    apriliaforum newb
    Join Date
    Jun 2012
    Location
    Vancouver BC
    Posts
    6

    Ughhh

    OK so today I ripped it all apart, rechecked and redid everything I put in new o-rings on the injector seemed a tighter fit. No air bubbles when I soaped it down. Im sure I wasn't clear about this but I only cranked it over I didn't actually start it. I checked compression and I got 90psi. Ya!! I will add coolant now.

    When I checked compression, I had the throttle wide open
    The air hose was off and compression was 90psi, even with it on it was 90psi. Good or bad I'm not sure.

    It has new gaskets, reeds, piston and rings.

    Wish me luck

Similar Threads

  1. Need Some help with my old Ditech 2002
    By viper in forum Scarabeo 50 Ditech, SR 50 Ditech, SR Factory
    Replies: 26
    Last Post: 01-04-2008, 06:52 PM
  2. OK seriously need some help with the 70cc kit for the Ditech 07
    By krisnet in forum Scarabeo 50 Ditech, SR 50 Ditech, SR Factory
    Replies: 12
    Last Post: 10-21-2007, 03:27 PM
  3. Getting a 2006 SR50 R Factory...need some help with hop ups
    By lemondpoprad in forum Scarabeo 50 Ditech, SR 50 Ditech, SR Factory
    Replies: 5
    Last Post: 05-14-2007, 08:47 PM
  4. Need Serious Help with Sr 2001 morini
    By mattyg50 in forum Scarabeo 50, SR50, Mojito 50, Rally, Fly 50
    Replies: 3
    Last Post: 05-14-2004, 03:06 PM
  5. Need some help with part sizes and torque specs.
    By Chief in forum SL1000 Falco Forum (all years)
    Replies: 2
    Last Post: 07-07-2003, 10:10 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •