Exhaust Jag pipe on 66cc

Discussion in '2-Stroke Engines' started by wagel, Oct 6, 2016.

  1. wagel

    wagel New Member

    Tried Jaguars pipe design from his website. As I had to use what materials I could find locally then it is not 100% accurate. The ID of header pipe is 22mm and stinger is 14mm. Looks like this. [​IMG]
    Feels like I got some power gains down low as it seems to accelerate a bit better but top speed went from 40km/h to 42 so no apparent gains there. Hope some porting adjustment does the trick. Any ideas?
     
    FurryOnTheInside and AutOtaku like this.

  2. zippinaround

    zippinaround Active Member

    jags pipe is designed for torque i believe not top speed. looks pretty good although i would grind down the welds a bit is it loud?
     
  3. wagel

    wagel New Member

    I will grind the welds at some point if I will keep the pipe but have not decided yet. Also plan to paint it black but I didn't want to put in too much effort before I have tested that it actually works and performs. At the moment the whole bike is just a test platform for the engine. In near future I plan to get a decent MTB and then depending how stuff fits make a new pipe or adjust this one.
    It is really quiet at idle but makes some decent noise at speed so if someone wants to fly below radar and not piss off neighbors early morning or late in the evening then a silencer is needed.
     
    Last edited: Oct 6, 2016
  4. jaguar

    jaguar Well-Known Member

    Stock intake port duration is too little. Increase it to 120 degrees open.
    After that if you still want more speed then raise the exhaust port 1mm at a time till it's where you want.
    Make sure your main jet is optimized for speed. Too big or too little will limit speed. What color is the plug?
     
  5. wagel

    wagel New Member

    Will take the jug off next time when I have time to mess with the bike and measure current porting and start dremeling. The plug at the moment is black but its the same plug I used with a bit bigger jet and stock exhaust and then it was black and moist :D so might be that it hasn't burned clean. I have a mikuni VM18 with main jets from 55 to 95 if I remember correctly but haven't had time to fab an intake to use it. That's going to be on my list soon.
     
  6. jaguar

    jaguar Well-Known Member

    it doesn't take long to change the plug color with a jetting change
     
  7. wagel

    wagel New Member

    I thought so. Also its intermittently 4 stroking at max speed WOT. I'll try to fix it with the mikuni.
     
  8. butre

    butre Well-Known Member

    the fix is a smaller jet, not a new $80 carb
     
  9. wagel

    wagel New Member

    What I meant was that I'm not going to waste time on fixing the mixture issue of the stock carb as I have the mikuni with buch of spare jets on the shelf anyway and it would be more reasonable to spend the time on fabricating an intake for that one.
     
  10. Randall

    Randall Member

    Substitute "bike" for "pipe".

     
  11. wagel

    wagel New Member

    Picture of the plug. But it isn't too accurate as it is not from a WOT plug chop but just some messing around and maybe even idling.
    [​IMG]

    Also looks like I have some "nice" blowby
    [​IMG]
     
    Last edited: Oct 9, 2016
  12. jaguar

    jaguar Well-Known Member

    nice color plug.
    it's hard to get these fat rings to seat well, even if you use the right break-in method. (using more oil and taking it easy is the wrong method)
     
  13. wagel

    wagel New Member

    Haha.. Measured the porting on the black jug and almost pissed my pants.
    The measurements are not 100% accurate but I guess close enough.
    Deck .7mm
    Exhaust 27.66 which gives 152deg
    1st transfer 30.78 which gives 132deg
    2nd transfer 32.43 which gives 120deg
    Piston 44,5 and intake 56.2 which gives 110deg

    Thats the stock porting for this jug, exhaust might be rised .5mm or so as I gave it few strokes with a file at some point when I had the engine apart the previous time.
     
    Last edited: Oct 12, 2016
  14. wagel

    wagel New Member

    Anyway had some fun with da Dremel and some files so now it should be 160 ex, 120 in and didn't touch the transfers as I have to still figure out which is worse. Unequal transfers or too high transfers.
     
  15. wagel

    wagel New Member

    Naaah.. shiet. Top speed 45 and no noticeable difference in acceleration. Hits 40-42 quite fast and then like a wall. I think the header might be a bit long but would be hard to shorten as the pipe would be lower and hitting the ground soon. Also I have a offset "key" on magneto side so it retards timing and on top of that ignition that retards timing so might be too retarded as a result. Was too lazy to change it after fitting the custom CDI. Will flip the key around to advance or try a stock key. WOT plug chop added.
     

    Attached Files:

    Last edited: Oct 12, 2016
  16. jaguar

    jaguar Well-Known Member

    45 is enough.
    yes, that wall is due to pipe design.
    now think about putting a good carb on it.
     
  17. wagel

    wagel New Member

    Thanks for your input. I might manage to upgrade the carb later this month.

    As for 45kph top speed, I think I'm not going to settle for that. I did some calculations and if they were not way off then 2mm rings in this engine limit it to 8500rpm so with a small safety factor I'd like to go up to 8000rpm. Before that I'll try to balance the crank a bit more and maybe if I find the equipment try to true it better than it is atm. I guess I'll have to start looking for a piston with 1mm rings soon. Quite hard task, maybe fitting a scooter jug with its piston might be the easier route. Has anyone found a piston that would fit and rings that wouldn't destroy the chinasil coating?
     
  18. jaguar

    jaguar Well-Known Member

    look on my site for info on alternate piston and rings.
    45 is about the limit for moderately modified china girl engines. and if you port it to go faster then it sucks at low RPM.

    what did you use to calculate the max speed due to the thick rings?
     
  19. zippinaround

    zippinaround Active Member

    45 seems pretty slow , all I did was make a jag style pipe on my 48 cc and it goes 42 on flat everything else is stock except sparkplug wire and plug
     
  20. jaguar

    jaguar Well-Known Member

    maybe your speedo isn't calibrated right. It normally takes more than my pipe to get that kinda speed.

    and 45mph is the safe limit for a motorized bicycle. Any more should only be used on a drag strip or closed race course.
     
Loading...