Piaggio, low topspeed

Discussion in 'The Workshop' started by Deikoo, May 30, 2017.

  1. Deikoo

    Deikoo Member

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    44
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    Piaggio Engine
    I bought a scooter with a broken motor.
    Now I have fixed it, but the topspeed isnt there.

    Setup: (it was completly original before)
    Piaggio engine.
    70cc
    17.5 Dellorto PHVA, 88 mainjet, 38 idle and A22 needle.
    racing CDI.
    "sport"exhaust (no restriction)
    original airbox with filter.
    6,5g weights and no restriction on variator.

    The first run after this reparation was done yesterday. It only did 55-60km/h on the gauge.
    Did not hesitate or anything. Took it up for a hill, and it accelerated from 40km/h to 50km/h, so the power is there.
    I dont have a revcounter so I dont know the revs, but I think it should rev a lot more...
    What can it be? Any suggestions?

    Please forgive my bad english :p
     
  2. scubabiker

    scubabiker NITROJUNKIE

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    7,321
    Something dumb like loose plug maybe?
     
  3. Deikoo

    Deikoo Member

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    Piaggio Engine
    Changed the sparkplug just before, because the old one was bad.
    So sorry, no loose plug :)
     
  4. 328isport

    328isport Member

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    45
    aren't 6.5g rollers a little heavy for that spec? Whats acceleration like off the line? What 70cc kit/make exhaust is on it?
     
  5. Deikoo

    Deikoo Member

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    Piaggio Engine
    Yeah, Ive though if it is too much, but the acceleration is ok from start. Cant pop wheeles, but thats not what I want.
    Upp to 1/4 gas I have good respons, after that, its crappy...
    With too heavy rollers, shouldnt I deaccelerate when going up hills? Now I accelerate in steep hills (from 30-50km/h)
     
  6. Deikoo

    Deikoo Member

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    Piaggio Engine
    Had it out for a spin today after some adjustments. Had it on WOT almost all the time.
    The plug is now white as snow!!!
    Didnt think that 88 main should be too small!!
     
  7. Stevep

    Stevep Well-Known Member

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    5,895
    is the 70cc cylinder run in properly?
    May be getting too much air even with the standard air box on....................
     
  8. Deikoo

    Deikoo Member

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    Piaggio Engine
    How could it get too much air with original airbox if the mainjet have the correct size (and no airleaks) ?
    Dont know how many ours it should be run in...
    Maybe one our or soo (too little, I know, but the comp is good) Moment 22 actually... You need a good mixture to run the cylinder in, but you need to do the test to have a good mixture. If I run the cylinder in with a lean mixture, thats worse than drive with WOT for a couple of minutes...

    I cant rev it as much as it should and the plug gets white as snow (and some burns). Too me it looks like a very lean mixture. I can ofcourse move the needle, but WOT is telling me that this is NOT the problem (at least right now).
    Im trying to find some main jets today and we will see tonight, hopfully :)
     
  9. Deikoo

    Deikoo Member

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    Piaggio Engine
    Ok, some updates.
    I have changed to mainjet 92.
    Also Changed needle position. Finally got a good air/fuel mixture.
    Still going 55 km/h.
    Changed weights to 4,5grams. Topspeed 45.
    Changed to 5,5 grams. Topspeed 50.
    (Started with 6,5 grams. Topspeed 55.)
    Toprev are the same with different weights. (Unrestricted cdi)

    Wtf can it be?
     
  10. Deikoo

    Deikoo Member

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    Piaggio Engine
    Wondering... could it be the reeds ??
     
  11. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

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    1,850
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    Piaggio Skipper
    reeds could be.

    ok for top end running in. theres two ways to do it the way most will say and thats ride throught the rev range not overstressing the motor for around 300 miles , this allows the hardened surfaces to bed in. its what most shops will tell you because if they told you to ride balls to the wall and you had a smash then told mr police man " well the bike shop said i should be running it as hard as possible " they looking at a court case and you suing them.

    now the second way. you jump on the bike once its setup and has a good oil and fuel mix. you then ride it hard as hell through all the rpm range like you stole it ......... BUT BUT BUT i can hear you say .... well what your doing is forcing those piston rings into the hardened cylinder surface so they eat away at that surface quicker and that means bed in faster BUT and its a big BUT this comes at a risk of blowing the top end out its a risk one takes if you want to do a hard run in .

    thats the two ways to run your top end/new bike in both work but the later is better but comes at a risk ....... the top end needs to break in and as it does it will loosen up and a little extra power is gained to as things settle in fully, from the word go everything is tight as a nuns purse so you gotta allow it to relax and settle down then you see the money payout at the end.

    heres Jake telling you fact from fiction about a hard break in , be warned he does let loose some bad language so its at viewer descresion

     
    Last edited: Jun 4, 2017
  12. Deikoo

    Deikoo Member

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    Piaggio Engine
    Hard break in...
    Just my experience with Cars. Rental cars often has better peformance than a "private" car.
    Why? Hard break in :D
     
  13. Tamiyacowboy

    Tamiyacowboy Pippa's Owner

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    1,850
    Rides:
    Piaggio Skipper
    just let its settle buddy first its all gonna be tight like i said, it needs to wear a bit so dont go balls out 24/7 just let it have a little here and there to help set those surfaces. Jake is saying more about geared bikes , but for us scooter owners its a bit more harder due to the auto transmission we run .

    so yep let it settle then we can start to see why its holding back.

    one note you say sport exhaust and no restriction are you very sure on that ? restictors are NOT just in the manifold end, some companys place a small cone in the tail pipe for restriction, its all to do with what pipe you have, leo vince tt and the technigas trek both have a single restriction cone in the manifold, but other companys pass that and restricted the pipe outlet.

    some companys go even deeper and when building the pipe insert a washer inside the manifold pipe way down deep ( seen this on older dep pipes for dt 125s and kmx 125s in old days) and the only way to get those out is to cut the pipe and reweld once its knocked out.
    do a little research on the pipe make sure it does not have multi restriction devices fitted or a stealth restriction in the end can outlet
     
  14. Deikoo

    Deikoo Member

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    Piaggio Engine
    Ok, I hear what u say. I want to go nuts on it, but i will take it for sunday tours aswell :(
    Should only try one more thing before sunday ;) Tjats drilling a hole in my airbox.

    Its Technigas, and they said it was just in the manifold (that I removed)
     
  15. Deikoo

    Deikoo Member

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    Piaggio Engine
    Update:
    Drilled a small hole in the airbox and that made a differens. Not so much that I wanted, but still in the right direction. Doing 60 km/h on the gps so its getting better (not satisfied until Im reaching 90)

    Also checked the reeds. Not a beatiful look. 1mm gap at one side :(
    Need to get better airflow to the carb. It feels like Im not using 50% of the carb...
    Also need to get some reeds...
     
  16. Deikoo

    Deikoo Member

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    Piaggio Engine
    Ok, now I really, REALLY need your help!!

    Today I have put on new malossi reeds, tried different mains after talking to Dellorto. They said that the capacaty for this carb is around 100. 98 works best for me (carb getting as much air as possible).
    I have tried 2 CDIs.

    Ok, positivs, it runs smoother and doesnt die at idle.
    It accelerates up to 50km/h in pretty steep hills, so it has power!

    Bad things: I cant get it over 60km/h!!!

    Anyone pleaase?!?!?
     
  17. 328isport

    328isport Member

    Messages:
    45
    This is an odd one.. a genuine 60km would be 37mph.. way down on where it should be, how does it feel up to this speed? Does it pull hard and then stop dead or is it tailing off at 50-55? I have a similar spec bike with a gear up kit and it is very strong around this speed, so I'd expect a bike without a gear up kit to be even more lively. How does it rev? with 4.5gr rollers it should be revving high even to the ear, there should of been a big difference in this regard between the 6.5 and 4.5gr, was there?

    Have you replaced the drive belt? Have you made any other changes to the transmission other than rollers?

    My feeling given it sounds like you've got your motor running OK is that something is wrong on the transmission side which isn't allowing you the revs you need. Ideally I'd do a compression test to further rule out the engine itself and try to get your hands on a rev counter as will then be easy to see whats happening..

    Also hows the plug looking now with the 98 main?
     
  18. Deikoo

    Deikoo Member

    Messages:
    44
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    Piaggio Engine
    Yeah, its really odd.
    It takes off quite ok. cannot do wheeles, so it isnt so good. it accelerates quite good up to 50-55km/h (10-12 sec tops), then it slowly comes to a stop at 58-59km/h
    With 4,5g rollers it reved just a little bit more (almost the same rev to my ear) than with 6,5g. The big differens was the speed. 45km/h with 4,5g and 55-60 with 6,5g.

    I have not replaced the drivebelt. It looked good, and its a standard belt.
    I have not made any changes to the clutch, transmission or the variator. It looks like its original.
    The plug looks like milkchoklate with 98 main (white as sugar with 88 and a bit wet with 102)
    Airbox is opened up as much as possible, even drilled one more hole in it so it could take in enough air.

    I havent done two things that I think needs to be checked.
    Dont know if the english name is the same, but here in sweden we call it "squish measure" (space between piston and header)
    The other thing is to try a different exhaust. The problem is that no exhaust in the world fits without some cutting and welding :(
     
  19. Deikoo

    Deikoo Member

    Messages:
    44
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    Piaggio Engine
    Here is some updates.

    Im waiting for a new exhaust. I belive that this exhaust is too small. My exhaustport is 28mm in diameter. My exhaust has 26mm near the engine. IF this exhaust should be fine, the endpipe should be 26*0,6=15,6mm (at least), this has 12mm.

    I checked the squish clearance yesterday and notice that the clearance was 0.00mm!!! I have small marks in the pistons.
    But in more gaskets and made one more from a beer can :cool:. Now it runs a little bit better (65km/h), but should run better.
    Nakaru says that the original head can be used. This was the problem. The original head is no good.
    I will order a 70cc head aswell.
     
  20. Deikoo

    Deikoo Member

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    Piaggio Engine
    Ok. Didnt want to wait for a new head...
    Took the dremel and a good stone and started to modify My head. Looks really nice now when Im done!
    Checked the squish and adjusted it to 0,7mm.
    Fired her up and it started so quickly! Great!!
    Went out for a spin. Fuck... 50km/h and I smelled fuel.
    Went down from 100 to 92 main and Went out again.
    65km/h!!! Wtf??? :mad::mad::mad:
    If that isnt enough, a 50cc passed me with a sick speed :oops::oops::mad:

    Anyone?? Wtf is wrong???
     

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