The "BlowFly" Project

Discussion in 'Battle Scooters' started by driller, Nov 22, 2013.

  1. Yellow Jacket

    Yellow Jacket Been here awhile

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    As promised, the test results are in. Acceleration was 9.77 sec, averaged of 8 runs. The stock, baseline time was 10.51. Almost 3/4 second improvement. I was a little disappointed, hoping for a little better than that, but I may have had hopes that were a bit out of line with reality. That 9.77 sec. is almost identical to what I got with Drillers own 200 Vespa.
    Top speed results were more disappointing, 56.5 mph two way average using GPS. Speedo was indicating 61. This is right where we started with the stock bike. Many modern bike do have a rev limiter built into the ignition system. Don't know if the Fly has that or not. I did run the bike on a long downhill and got it to indicate 69MPH. This would seem to rule out a rev limiter, but, most bike use a "soft" rev limit. This retards the ignition to reduce power, not cut the ignition off. So, it may be the bike does have a rev limiter, but will still run higher rev's on a downhill. Does anyone have any knowledge on this? Really would like to know.
    I'm now getting even more backfire on deceleration than ever, it's really bad. Bike idles a bit rough and will not start when hot unless the throttle is opened. I did try to adjust the idle mixture but didn't seem to make much difference. Screw was out 2 turns to start with. Driller has the tool to do the adjustment, but it isn't very easy to get to so don't know exactly where it is now.
    #61
  2. Chillis

    Chillis Land Barge Pilot

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    Sounds like you need richer jetting. Don't burn up the the engine with a downhill run on a cylinder that is not broken in and running lean.

    Are there any threads on Modern Vespa that have used the same kit that you can get a litmus test?


    How does the plug look after a wot chop?
    #62
  3. Yellow Jacket

    Yellow Jacket Been here awhile

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    Driller also has a Honda PCH 125. At some point in time we will do a set of tests on it to compare. This bike has what seems to be typical Honda off line acceleration, ie, very good. It will be interesting to see what such a small bike can do. Wish I had done a set of tests on my old '87 Honda 150 Elite before I sold it.
    #63
  4. MODNROD

    MODNROD Decisions, decisions

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    Most of these Piaggio things seem to have a 2-stage limiter. The first is a soft limit that reduces advnace, then a full limit where it starts missing firing points to stop it.
    Plenty of info on advance curves on MV in the "hotrod" section, my own SC One 125 did it, as did a friends LX150, as does my X8 now.

    I know when these Liberty 200s came out they didn't have any more speed than a 125/150, just got there a bit quicker. The stock set up used low compression and was under carbed to reduce high rpm output (think VW Beetle). Lots of low and mid grunt.
    #64
  5. Yellow Jacket

    Yellow Jacket Been here awhile

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    I should have mentioned that in checking fuel milage, since the 200 top end job mileage is only 45MPG. I never did check milage before the change. Also, I've kept a log of any reliable performance data I can find on scooters. In Feb. '06, Cycle World did a full road test on a Vespa LX 150, which I believe is the same motor as the Fly. Bike dyno'ed at 8.7HP, top speed was 66MPH, and weighted 247# dry. That is over 10 MPH faster than the Fly. That and the 45 MPG makes me think all is not well with that motor. When time allows, I'll check ig. timing, making sure the advance is working, cam timing, although Driller and I checked cam timing at least 3 times. I'l take a look at the plug although I'm certain it will be very rich and I've never really mastered the art of reading plugs.
    #65
  6. driller

    driller Twist and Go

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    Yep,that was the problem. Wish this had surfaced earlier.
    http://modernvespa.com/forum/topic123697
    Good to know it was not just us!:huh

    Actually, the GT200 is rated at about 72-74mph by Vespa. Using the 10% optimistic rule of thumb, that seems about right according to the speedo.
    The older Fly 150's are rated at 61-62mph top. The newest model with the 3valve head and more power is rated lower at 59mph. Don't know how the ET4's andLX150 are getting more claimed top end with essentially the same engine.
    Some who have done150 Leader conversions have opted for an upgear change in the tranny for more top speed (65-66mph) to go with the increased power. Most have done this because they prefer the small frame scooter for light highway/touring as opposed to the large frame GT series.

    We will be removing the evap system to see if that has any effect on the pop/backfire issue. Also, still need to check the plug and maybe change the jetting.
    #66
  7. driller

    driller Twist and Go

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    What MODNROD says fits into my expectations. Not looking for much if any increase in speed. Just get there a bit quicker.
    Disregarding rev limits, it appears the only reliable way to increase top speed is by changing gearing in the final drive providing you have the increased power to pull the higher ratio..
    I'm still wondering why the mileage seems so poor.
    #67
  8. Yellow Jacket

    Yellow Jacket Been here awhile

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    I've spent my free time for the last several days trying to find what's wrong with the Fly. Here is a list of what I've checked. If anyone has any suggestions for anything else I could look into I'd like to hear them.
    Rechecked cam timing.
    Checked ignition timing. It is running maybe 6 degrees advanced but there is no way to change it. Advance works but there are no marks for advance so don't know it full advance is correct.
    Checked gap between flywheel and pulse coil. Gap was only .006, spec's call for 14- 35 thousands. Set gap at .018. Not sure but doing this may change timing a small amount. Will check it when I get Fly running again.
    Valves set.
    Checked to make sure no obstructions in the intake, i.e., no shop towels, rats nests, etc. We did install a new air filter.
    Been through everything on the carb several times. Jets are all stock size and have not been drilled out. No blockage of either idle or main air bleed jets. Set carb up on bench with a test fuel supply to check float valve for leakage. Adjusted float height.
    Spark plug was sooty black and bike is only getting 45MPG.

    As of now, I'm trying to locate a 72 main jet which is the smallest available in this series. Once I have that installed will see how it runs. I have the tools to enlarge the jet in very small increments so will work on jetting trying to improve performance.
    #68
  9. Motovista

    Motovista Parts is Parts

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    The backfiring could be the SAS. 6 degrees of advance isn't a lot, and with a stock jet, the bike should be a little lean, and not overly rich, which the spark plug indicates. What you describe sounds like a bike that is bogging. Have you tried running it without the airbox? That will tell you if you're overjetted or not. And of course, you can use a ziptie to cut off some of the air getting in and see if that makes it run better too.
    My ET4 got about 49mpg with a big bore kit, so that's not too surprising, but it ran out well.
    How does the motor do when you are revving it up on the centerstand? Does it hit a rev limiter? Is it blowing smoke? You might need lighter rollers so it runs up into the powerband, but this does sound like it's in the top end. Are you getting a lot of blowby or oil in the airbox? On some of their air cooled engines, Piaggio says to set the valves at .15 and .25mm, which seems incredibly loose, but you might try that.
    if either of you are coming this way before March, bring it in and we'll throw a couple of hours at it on the house, to see if we can't figure out what's going on. Thing I hate about Flys is what it takes to get to the engine,
    Last but not least, are you using an e plug and not an h?
    #69
  10. driller

    driller Twist and Go

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    Thanks, George. The SAS filter foam was falling apart when we pulled the fan shroud off. We replaced it with some foam we had that is coarser than the OEM stuff. Just wondering if that is more free flowing would the backfire/pop be related. Or, could some of the broken down foam filter have gotten in the SAS and be partially blocking it? Did you get the rubber variator ring in for the GT200?

    Cold, cold cold. No testing right now.:vardy:vardy:vardy
    #70
  11. Motovista

    Motovista Parts is Parts

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    It's freezing here too. Yes, I did get the o-rings, and some exhaust gaskets. I'm not sure if I put them up yet or not. We're changing the look of the site, so I've been putting less on until it's done. This is the time of year when I can get my own work done, so I used one to put a CVT FR4 Variator and Malossi XK Belt in my GT. Even with this weather, I've managed to go through most of a tank of gas since the changeout, and I want to see if my mileage does improve from the variator. I switched out the Leo Vince for a PM Tuning pipe about a month ago, and that made a surprising amount of difference in performance, and after I put the new variator and belt on it, and it pulls solidly through the midrange and tops out about 4-5 mph faster. Also, maintains speed up the Ravenal better. I've got a friend with a couple of GTS 250s, and when the weather gets better, I want to see how the GT performs compared to a stock GTS.
    #71
  12. VanDiemenF2

    VanDiemenF2 Adventurer

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    Mike,
    Just got back from the Left Coast on Sunday. We took the scooters on the Versahaul to visit Carol's family over the Holidays. The RV park was 5.5 miles from her uncle's place in Long Beach and I was able to put 125 miles on the Fly 150 (with the Malossi 190 kit) over the last week. I alternated with my GTS300 everyday. The Fly modification is almost exactly what I wanted in that it keeps up with the GTS in traffic and at stop lights, etc. When I swapped bikes, the 30-45 MPH strength of the GTS is more apparent, but in take off they are close. The Fly has been flawless, mileage is down from 65 to 50MPG, but I have been pretty heavy on the throttle and riding all two up. The Hotel California was 70-79 F all week long. It was 6 F at work yesterday.

    Jim
    #72
  13. driller

    driller Twist and Go

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    Welcome back to the sunny South, Jim. Sounds like the Fly is "Just Right".
    We are almost there. We have some jets to install and test if the weather breaks in our favor.
    One question. Was the air intake left stock on your Fly?
    Hoping to move towards the prize soon.
    Cheers!
    Mike
    #73
  14. VanDiemenF2

    VanDiemenF2 Adventurer

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    Yes, the air intake is still stock. No riding today. RAIN!
    #74
  15. Yellow Jacket

    Yellow Jacket Been here awhile

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    After another boondoggle, this one my own fault, I finally got a couple #72 main jets. These are after market and not made with the same degree of precision as OEM jets are. However they will work for my testing. Jet numbers run very close to the actual hole size in MM. So the stock #82 jet is only .004 larger hole size than the #72 I have now.
    With no other changes since the last test, I got 9.79 sec. and 57.5 MPH. I didn't expect the bike to run that well with jetting that is 4 sizes smaller than stock.
    Weather permitting, tomorrow I will open that jet up very slightly to maybe a #75 and do another set of tests.
    I have a full set of jet reamers from my days a Ford Motor Co. These reamers have a very slight taper to them. The deeper you go with the reamer, the larger you make the jet. That is how I know that these after market jets are not as precise as OEM's are. These jets have a straight hole threw them, not tapered as are all OEM's. FoMoCo could control the size of their jets to within a couple .0001th's of an inch.
    More tomorrow, I hope.
    Just got off the phone with Driller. He's planning to ride his 200 Vespa to my house tomorrow. If so, we may have a side by side test run to report on.
    #75
  16. driller

    driller Twist and Go

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    Vic and I got out to the measured course to test the latest jetting on the BlowFly yesterday. Yet again, the acceleration times dropped but the original top speed is eluding us! :ddog Gradually working up in size on the main jet (started at 72/stock is 82) yields quicker acceleration. Max speed averaged only 55 and we are stumped as to why the loss. After I left for home, he reamed the jet out some more and the top speed did improve to 57mph.
    Perhaps things are still too lean.
    The roller weights we are running are 10.5 gms more than stock of 60gms. I was sure the increase in power would compensate for the higher roller weight.
    Plans are to mark the variator faces to see how high the belt is riding.

    Vic will post the latest numbers soon. An interesting note is the BlowFly is now running the course only about .25 sec slower than my GT200.:clap So, as far as acceleration goes we are getting closer to the original goals.
    A slight error in installing the diaphragm in the carb on the GT was recently found and was slowing the bike down. Now after being corrected, the Vespa has never ran better.:deal
    #76
  17. VanDiemenF2

    VanDiemenF2 Adventurer

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    Excellent news, Mike.
    #77
  18. Yellow Jacket

    Yellow Jacket Been here awhile

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    Has anyone here noticed that when I post test numbers it takes me a lot longer to get them up when the numbers are just so-so than when I can show good progress?
    With that in mind, here are some more so-so numbers.
    With that #72 jet reamed out, the time was 9.72 and 56 MPH top speed. Best time yet! Not much of a change since the 9.79 and 57.5 MPH with the #72 jet. This #72 jet does not have a tapered hole thru it so quite likely I didn't increase fuel flow much if at all. All I did was make the straight hole into a tapered one with the original size hole at the small end.
    I did open the jet again to what would be about a 75 and retested. It was late so I didn't do the acceleration test, just a top end run which was up slightly to 57.5. The wind was calm on this run where it was a bit breezy on the previous run.
    I'm now ready to try again when weather permits with the jet at about a #77. BTW, I'm getting pretty good at this jet cahnge thing. Got it done in 22 minutes this last time.
    Now, if any one is still reading this, here are some really good #'s from Drillers GT200. Months ago when he first left the bike with me to fix a rough idle I tested it at 9.74 sec. Bad idle was caused by an intake air leak between the head and the manifold. During the fix, I unknowingly failed to get the carb diaphragm seated correctly. Tested at only 10.29 sec. I've scratched my head over this ever since. Driller has ridden the bike like this for over a thousand miles. We finally got the diaphragm problem fixed. On retesting we got down to 9.29 sec., over 1/2 sec better than when he bought the bike. Now the bike is a joy to ride. I love it when a plan comes together.
    #78
  19. Yellow Jacket

    Yellow Jacket Been here awhile

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    Since I've tested the bike with and without the Evap system and found no change we've decided to remove it just to clean up the bike a little.
    Here's a couple shots for before:
    [​IMG]

    [​IMG]

    And after.
    [​IMG]

    [​IMG]

    This is what came off. Foot is there only for size comparison.
    [​IMG]
    #79
  20. Yellow Jacket

    Yellow Jacket Been here awhile

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    Sorry folks, I still haven't figured out how to reduce the size of my pictures. Tried but all I got was a white border on two sides.

    I'm begining to wonder if maybe the small size of the intake is the reason we just can't seem to get past the 56-57 MPH barrier. Ok, I may have fat fingers but look at this, I can't even get my pinky finger into the intake. It actually measures about 7/10 th's of an inch. Much smaller than the carb throat. When I'm done with this stage of jetting, I'll see what happens without the intake tube. The incoming air has to make a 45* bend, then a 180* bend before doing a couple more turns just to get to the air filter. Sure looks choked to me.

    [​IMG]

    Here's the little reamer I've been talking about that I use to take just a very tiny bit out of the jet at a time.
    [​IMG]
    #80