66cc Flying Horse Tear Down

Discussion in 'General Questions' started by Fast Shag, Nov 7, 2014.

  1. Fast Shag

    Fast Shag Member

    So I torn my top end apart last night to test out my new dremel tool on it....The stock jug looked amazing compared to most of the pics I've seen on here! There were no casting burrs on the ports or transfers! The transfer ports were lined up(mapped out on paper), had a good forward angle and the piston opened completely on intake and exhaust ports. All i did was blueprint, or round off all corners, matched header flange and intake tube. The SBP expansion flange was horrible! I roughened up the intake and tube for better atomizing, and sanded jug for a little more compression. I ran it good and hard today, finding little performance increase but low end throttle response was quicker. I worked on the head when I first got the motor. Going over to bro's house tomorrow to use his compression gauge. Hoping for 120-130psi. I'm very pleased with the quality of this motor! Looks like I got a good one!:whistling:
    , PB070022.jpg PA300008.jpg
    66cc Flying Horse
    SBP expansion chamber
    41 tooth sprocket
    33.4 mph on flats, climbs steep hills with ease
    Last edited: Nov 7, 2014

  2. Purple Haze

    Purple Haze Active Member

    The newer engines coming out seem to have corrected port matching, plus the transfer ports are angled much better, so we don't have to do Jaguars JB Weld fix any more. Nice job on the chain tensioner! If you haven't done it already, you'll want to remove the clutch shaft housing and clearance the inside, you'll see where the chain rubs on it. This mod greatly reduces those annoying pinging noises that sound like problems, but are just the cover echoing when the chain rubs on it.
  3. Fast Shag

    Fast Shag Member

    That chain tensioner set me back about $4 at ace hardware! Thanks for the tip on the clutch housing. When I cold start it sometimes the rear wheel will lock up on me. Just a little backward push fixes it... But it did happen to me at an intersection once that really messed up my game. I'm using a #41 tractor chain and I think it's hanging up inside the housing when starting. Just another fun project with my new $10 Dremel!

    I tested my compression today and it came out to 126 psi. Not too bad and still not a pain in the butt to start.
  4. Fabian

    Fabian Well-Known Member

    That's the way it is with these engines: sometimes (on the rare occasion) you get a """really""" good one, and other times you just get a very ordinary one.
  5. Zen builder

    Zen builder Member

    Purple, Explain " clearance the inside". I don't have a full gallon run through my 66 flying horse yet,so break in is still in process, but I hear all kinds of noices . As this is my first bike, i'm not sure what is normal ( in the typical sound perimeters ) for them. I understand that they may have some piston lateral movement sound, and the normal chain noise, so if I can eliminate any noices, that would be nice. Also if I could isolate "outside the engine" sounds, I could hear whats going on inside a bit better. Thanks for your input .
  6. Fast Shag

    Fast Shag Member

    Million dollar question is how are you guys getting 40mph and up on these?!
  7. butre

    butre Well-Known Member

    lots of time and money for some, miscalibrated speedometers for others

    for me it's lots of compression (172 PSI), lots of port work, a 19mm carb, ram air, cold intake, a 5 digit redline, and a very strong ignition with an aggressive timing curve
  8. Fast Shag

    Fast Shag Member

    A good CDI is next for me but $80 for one is outrageous compared to the same price for a brand new motor! I'm trying to make this Ducati cdi work I got off my Piaggio Grande, but can't seem to get it going...
  9. Fabian

    Fabian Well-Known Member

    By recalibrating the speedo to a larger tyre diameter :shifty2:
  10. Fabian

    Fabian Well-Known Member

    You are wasting your time, because the Jaguar CDI gives you the option of using 4 different ignition curves, as well as ambient temperature compensation.
    The Jaguar CDI is well worth it's money. If it wasn't it wouldn't be fitted to my bike.
  11. Fast Shag

    Fast Shag Member

    I despise the idea of an unproporly calibrated speedo!:rolleyes7:

    I have been sold on the idea of Jag's CDI already, just waiting on some funds...I guess that when I ever see anything with the Ducati name on it I get all fuzzy in the brain! With 3 projects on my table now (Cranbrook bike, girlfriend's bike, and the non running Vespa Piaggio), snow coming soon, and winter money stowed away, I have to juggle my project funds a little. The CDI might just have to wait till spring.
  12. Fabian

    Fabian Well-Known Member

    Riding your bike down a steep hill with a GoPro camera (or similar) pointing towards the front wheel so you can't see the horizon (fooling people into thinking that the hill is flat ground) is another way to get 40+ MPH speeds.

    Another effective way is to video a GPS speed reading, that's being taken on a motorbike and splice that video into the motorised bicycle video, showing that they are going 40, 50 and in some cases, trying to fool people that they are going 60+ MPH on their motorised bicycle.

    Lots of sneaky ways that people try and cheat the system.
  13. KCvale

    KCvale Motorized Bicycle Vendor

    The YD engines (flying horse and Skyhawk) were originally designed for 410 chain and they put a 415 chain sprocket on them.
    The issue is the chain hitting the front (straight part) of rear left cover plate.
    With 41 chain this will even be worse.

    Just pull that cover at look, you'll see the scaring.
    You can dremmel it but I just cut a 2" wide chunk out of the plate.

    Why the heck did you put a spring loaded tensioner on it?
    Did you not get your rear sprocket true and your chain gets loose and tight, loose and tight?
    Poor fix, the proper fix is to get the sprocket true on both the vertical and horizontal planes.

    Have you put an NGK 5944 (BPR7HIX) Iridium plug in yet?
    That my friend is something you will actually feel.

    AS for the 'clean' look inside that why YD is all I use for 2-strokes, they build a nice engine.
    Try the front page kit on the front page of gasbike.net sometime, it comes with the cylinder and piston in a different box so you don't have to take it apart to see the quality.
  14. Fast Shag

    Fast Shag Member

    I'll work on the housing today... My alignment is perfect from both sprockets and fits perfect on the outer hub. No wobble side to side or front to back. The spring tensioner kills a lot of vibration, makes the chain run more smoothly, and makes adjusting a snap! Why do some people pay up to $100 for a spring loaded tensioner? I also believe that a smooth running chain will prevent any loosening of the tensioner into the wheel, even though my tensioner is more solidly mounted than most by engraving the frame and clamp sides plus the use of red lock tight and double nutting (giggitty). Unlike making it a job and money maker for me, this is a hobby. Working on them, improving on design and handling gives me pleasure. Some things work, others don't; that's the fun in these! If I can improve design for $4, so be it. I made it, it works awesome, and someone else might benefit from it. You should see what I did with the scrap iron left over......

    I will try the double prong spark plug...I know that when I switched out the stock plug wire to a bosch it worked better.
    Last edited: Nov 9, 2014
  15. Fast Shag

    Fast Shag Member

    PB090040.jpg I added a 3rd motor mount using the bottle holder and chain guard screws. It now prevents the motor shifting over little by little by cold starts. (No matter how tight my mounts are) And I know motor mount screws never snap and knowing it's not a pain to heli coil motor mounts, It adds an extra safe guard mount if anything like that would ever happen on a long distance ride.:goofy: Plus, the decrease in overall vibration was HUGE. Cost....Free. Time....30 min. Killing two birds with one stone....Priceless.
    Last edited: Nov 9, 2014
  16. Fast Shag

    Fast Shag Member

    So I was able to get in there and see the scaring... I dremeled out where the gouges were and smoothed them out on the cover and inside housing. Couldn't remove sprocket after taking nut off, so I carefully worked around it and got everything ground down, nice and smooth. Thanks for the tips guys!
  17. KCvale

    KCvale Motorized Bicycle Vendor

    You are welcome ;-}
  18. Purple Haze

    Purple Haze Active Member

    OK, they say a pic is worth a thousand words:


    Attached Files:

  19. crassius

    crassius Well-Known Member

    if you have no dremel, you can use a hacksaw to make a cut just above and just below the scored area, then grab the place in the middle with your pliers and just snap it off

    leaves a nice, square gap for chain clearance
  20. Purple Haze

    Purple Haze Active Member

    Oops! I got the pics in the wrong order; but you get the idea.