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Thread: Low Compression - Scarabeo Ditech

  1. #1
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    Low Compression - Scarabeo Ditech

    2005 Scarabeo Ditech was running perfectly. Went to start it after a long ride the previous day and it started, ran rough for a couple seconds then died. Started a couple more times with the same result. I did a leak check (soapy water) around the air injector, air compressor and motor but didn't find anything. I proceeded to run a compression test. Result was low, 60psi, so I bought a set of rings/head & base gasket. After installing the new hardware, I reran the test which yielded the same results. Curious what to do from here. I'm a newbie when it comes to motors so I'm not sure if the piston needs to be replaced or the cylinder needs to get honed, please see photos... If the cylinder gets honed would replacement rings still generate a full seal?

    Thanks!
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  2. #2
    The Anal Intruder William the Third's Avatar
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    The cylinder looks ok, not great, but ok, but then it's really hard to tell from the photos. It's kind of one of those things you need to see in person unless it's blindingly obviously damaged. The cylinder is cast aluminum and nikasil (or similar) plated, so there are limits to what you can do to it.

    The piston looks bad. Lots of blow-by passed the rings. Speaking of rings, where are they in the picture? There is also some damage at the bottom of the piston skirt, that makes me wonder if there is matching damage to the cylinder walls.
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  3. #3
    apriliaforum expert NoNameForEver's Avatar
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    Need better pictures of the cylinder.. But it looks like you need a new cylinder. Very expensive $450 plus(comes with piston and rings)... Cheaper to order the Malossi big bore kit, and Malossi is the only ones that makes an aftermarket kit for Scarabeo Ditech... This is the kit..., you'll find the part number on that page so you can source it more locally, if you choose to go that way....
    Last edited by NoNameForEver; 08-17-2018 at 11:08 AM.

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    Will - Photos were taken during ring replacement. Thought the blow by may have been cause by damage to the alignment feature in the ring groove so I wanted them to be visible.

    NoName - Thanks for the input. I was considering a BBK instead of factory replacement. Would the linked also work, its $300 and stateside? I've upgraded the exhaust to the reverse and installed 7 gram rollers, would adding a BBK require additional upgrades beyond that? The link you provided claims that the primary gear requires replacement, I'm hoping that not the case...

    I will post more photos of the piston/cylinder to ensure they are the root cause of the issue, however I'm out for the country until September.

    Just to confirm, if the cylinder is damaged honing isn't an option due to limitations of the material?

    Thanks!!

  5. #5
    The Anal Intruder William the Third's Avatar
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    Quote Originally Posted by mattbig01 View Post
    Will - Photos were taken during ring replacement. Thought the blow by may have been cause by damage to the alignment feature in the ring groove so I wanted them to be visible.
    Understood. I don't see any problem with the alignment pins. The old rings were clearly not doing their job, and/or the piston/cylinder is in worse shape than the pictures would seem to show.

    Quote Originally Posted by mattbig01 View Post
    NoName - Thanks for the input. I was considering a BBK instead of factory replacement. Would the linked also work, its $300 and stateside? I've upgraded the exhaust to the reverse and installed 7 gram rollers, would adding a BBK require additional upgrades beyond that? The link you provided claims that the primary gear requires replacement, I'm hoping that not the case...
    The BBK is probably the best option price wise, but the BBK doesn't perform as well as most would like on the Scarabeo due to reusing the 50cc head. Never could figure out why Malossi would do something so stupid. You don't need to worry about gears unless you want a higher top speed. The exhaust and roller weights are pretty much perfect for the BBK (as well as stock), so no worries there. The BBK you linked to is the correct one.

    Quote Originally Posted by mattbig01 View Post
    I will post more photos of the piston/cylinder to ensure they are the root cause of the issue, however I'm out for the country until September.
    Sounds good.

    Quote Originally Posted by mattbig01 View Post
    Just to confirm, if the cylinder is damaged honing isn't an option due to limitations of the material?
    Nikasil (and similar) plating is very hard, but also very thin. It's harder than some hones, so they'll pretty much do nothing more than maybe "de-glaze" it. Due to it's thinness, any hone that is hard enough to actually cut into it may cut through it and expose the soft aluminum under it. Flexible hones also run the risk of getting caught on a port edge and flaking off the plating, again exposing the soft aluminum under it.
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  6. #6
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    Quote Originally Posted by William the Third View Post
    The BBK is probably the best option price wise, but the BBK doesn't perform as well as most would like on the Scarabeo due to reusing the 50cc head. Never could figure out why Malossi would do something so stupid. You don't need to worry about gears unless you want a higher top speed. The exhaust and roller weights are pretty much perfect for the BBK (as well as stock), so no worries there. The BBK you linked to is the correct one.
    Will - Just curious, are you aware of anyone that has had the cylinder repaired? I found this service. Considering you said the BBK wasn't great for the Scarabeo, I'm wondering if this would be a better option.

    Thanks again!

  7. #7
    The Anal Intruder William the Third's Avatar
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    Quote Originally Posted by mattbig01 View Post
    Will - Just curious, are you aware of anyone that has had the cylinder repaired? I found this service. Considering you said the BBK wasn't great for the Scarabeo, I'm wondering if this would be a better option.

    Thanks again!
    I've not known anyone to do it for a Scarabeo di-tech (sadly Scarabeo di-tech are pretty rare), but I've known of plenty of people, my self included, who's had it done with other cylinders. Your cylinder doesn't look like it has any serious damage, so it would probably be a good candidate for re-plating. I've never held a Scarabeo di-tech cylinder, but from the pictures it looks like it would also be possible to sleeve it, so that's another option.

    I've also wondered about if it would be possible to machine out the head a bit to give a combustion chamber volume more appropriate for a 70cc (actually 64.88cc on the Morini) BBK. I've never held a Scarabeo di-tech head, so there may or may not be enough material to work with. Some piston work may also help, as the stock Scarabeo di-tech piston has a little recess in the crown as I recall. I'm not sure 100% why that's there, it may be for clearance with the plug/injector, or it may play some role in combustion efficiency. Probably wouldn't hurt for that same feature to also be in the BBK piston, which it isn't.
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  8. #8
    apriliaforum expert NoNameForEver's Avatar
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    Although this Malossi kit doesn't give the same performance gain as other 70 kit does, it still gives a gain over the stock cylinder... so if you wanna just bolt on and be done with it, it's doing the job.

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    Sadly, my Scarabeo 50 Ditech sat over the winter collecting dust. This past weekend I finally took the time to install the Malossi BBK. Before I did, I rechecked the compression which again topped out at 60psi. After the BBK was installed compression was rechecked and is now at 90psi. Figuring that was enough to get the scoot started I reassembled enough to give it a shot. It still won't start.....

    Is 90psi cold crank with the new setup an expected reading? If so, I'm curious what the next step is for troubleshooting. I checked spark, it looked good (blue/purple arcing from electrode), I loosened hose clamps downstream of the air compressor and fuel pump, both had enough pressure the spray out. Should I gauge them. If so, what is the expected pressure? Could it be an injector issue? If so, whats the best way to test?

    Thanks!!

  10. #10
    The Anal Intruder William the Third's Avatar
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    Quote Originally Posted by mattbig01 View Post
    Sadly, my Scarabeo 50 Ditech sat over the winter collecting dust. This past weekend I finally took the time to install the Malossi BBK. Before I did, I rechecked the compression which again topped out at 60psi. After the BBK was installed compression was rechecked and is now at 90psi. Figuring that was enough to get the scoot started I reassembled enough to give it a shot. It still won't start.....

    Is 90psi cold crank with the new setup an expected reading? If so, I'm curious what the next step is for troubleshooting. I checked spark, it looked good (blue/purple arcing from electrode), I loosened hose clamps downstream of the air compressor and fuel pump, both had enough pressure the spray out. Should I gauge them. If so, what is the expected pressure? Could it be an injector issue? If so, whats the best way to test?

    Thanks!!
    90 PSI is acceptable, and around what you should expect. I'd get a check of fuel and air pressures (fuel without air should be ~35 PSI (key on without engine running or cranking), with air ~105 PSI (engine running or cranking), and the air while running/cranking should be ~70 PSI). Also confirm that the reeds are functioning/sealing correctly. Once we rule these out, you can start looking for problems elsewhere.

    Out of curiosity, have you tried to see if it will run, at least briefly (don't use too much, or damage may occur), on starter fluid sprayed down the throttle body?
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  11. #11
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    I haven't tried starter fluid, is it worth trying? Figured if it wont start naturally then there's likely something that needs to be addressed. I'll get numbers for air/fuel pressure on Saturday and report back.

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    Recorded air pressure, max cold cranking was 22psi, but sometimes there was no pressure at all... I connected my shop compressor and supplied 70psi. The system held constant pressure after shop air was removed. The scooter was cracked (need to buy fuel pressure pump so couldn't gauge it) but it still wouldn't start.

    Before the end of last season I removed the air compressor and did a leak test with gas and shop air pressurizing the outlet. It leaked, but it didn't seem too bad. I cleaned the seal between the orifice and the body but the leak remains...

    I also observed orange fuel inside the aftermarket inline fuel filter. Assuming the brass fitting corroded, whoops. I reduced down the stock 1/2 fuel line to 3/8 with brass reducers. Is there a better way? I hate the in tank filter, it never stays on and I cant find a 1/2 inline... What are some other options??

    Thanks

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    The fuel pressure gauge arrived so I tested during prime, 30 psi, and cracking, 90 psi. Air pressure was far higher than previous test maxing at 50 psi. Not only that, but the scoot started!!! Can't figure out what changed but it started. So, i took it for a spin. At higher speeds, anything past thirty, it would was hesitating. I'm assuming it needs more air/fuel, not sure which. Therefore, I was thinking of reinstalling the gauges and recording the pressure while riding. What numbers pressure should I expect when at 30+ mph? Thanks!!

  14. #14
    apriliaforum expert NoNameForEver's Avatar
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    Quote Originally Posted by mattbig01 View Post
    So, i took it for a spin. At higher speeds, anything past thirty, it would was hesitating.
    So... did you do a tps-reset?

  15. #15
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    Quote Originally Posted by NoNameForEver View Post
    So... did you do a tps-reset?
    No I didn't. Mind walking me through how to reset and rationale behind the suggestion? Is it because I installed a new map for the BBK?

    Thanks

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