kings motors gt 80

Discussion in 'High Performance Bicycle Engine Tips and Motorized' started by mike carter 2, May 17, 2016.

  1. brywink04

    brywink04 New Member

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    ive got a bike with the expansion chamber and silencer and im running a gt80 reed valve with keihin 16mm carb little bit of port cleaning. when i installed the reed valves i lost a lot of top end but gained a lot of bottom end power. What can i do to gain back some of the top end. im also running the sbp shifter kit and have done 45mph before installing reed valves. i also noticed that the base gasket has blew... motor only has about 200 miles on it.
     
  2. salorr33cc

    salorr33cc New Member

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    did you put windows in your piston after installing reeds,, and also a third port from bottom of intake port , up thru intake port and into cylinder and stop at the side transfer ports height,,,????

    you need to have either one or the other or both to get your top end back and or improve,, one mod will give you good low end and regular top end ,, and by doing both mods you get the best of both worlds low and high

    where did the base gasket blow at ??? you need to coat on both sides of base gasket and head gasket with permatex copper gasket seal,, i have been building car engines and motor cycle, ATV, Dirt Bike engines for over 22 years and never ever had a gasket leak or blow using this copper coat stuff,,, i swear by it !!!
     
  3. brywink04

    brywink04 New Member

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    on intake side. seeps a little. and i usually dont like using a sealant on a cylinder or head because id worry about it blowing out from the compression.
     
  4. mike carter 2

    mike carter 2 Member

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    allrite, i would like to see some updates.my gt 80 bike runs great,pulls real hard from about1/2 mph to about 35ish.pulls hard up hills also. i realy like this kit. i have ridden it as my only transport for months now and its faster every day,
     
  5. mike carter 2

    mike carter 2 Member

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    wheres Mikey ,wheres Sam90lx
     
  6. Neptunati

    Neptunati New Member

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    I'm dialing in the cns on mine. I'm definitely feeling some engine sealing going on. It's already feeling much more powerful than the grubee starfire kit I first bought in 08-2009.
     
  7. streak

    streak New Member

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    Its called four stroking
     
  8. bradnbikes

    bradnbikes New Member

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    I have installed the GT80 on my bike as well with the shift kit and SBP expansion chamber .. it has way more bottom end torque compared to the stock motor but it seems to have little top end , and no peek power like it did stock( on the pipe feel) ,, it does 35 with my 220 lb body on it .. but the old engine also did 35.
    I am putting a 40 tooth on the right side drive so I will probly increase top speed on that before running out of rpms

    I was wondering if you can link the specific port mods you did to the group or to me personally
     
  9. mike carter 2

    mike carter 2 Member

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    i removed the spacer from between the reed valve and the intake,port matched the intake and exaust,port matched the transfers between the jug and the cases,modded a x chamber from a 1979 suziki rm 60 using a header kit from fred c.i also ported the piston.if you havent ported your piston you are missing out on a lot of top end power .if you dont want to port your own piston ,appolo motors is where you want to go to find one. bike pulls from about 1/2 mph to about 38 and has enough tork to pull hard up some pretty big hills. gt 80 on a shwinn blackwell frame 26x3 tiresdance1
     
  10. Sam90lx

    Sam90lx New Member

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    I'm here, been busy with work. GT 80 is still running but still "four stroking" I think. Still feels like it is running out of steam on the top end, running a 40 tooth rear.

    Sounds like your bike is running great if you hitting 38. I am pretty sure I have not even broke 30 mph. It does get out of the hole good though.
     
    #90 Sam90lx, Oct 22, 2016
    Last edited: Oct 22, 2016
  11. Sam90lx

    Sam90lx New Member

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    Think mine has this issue as well. May be time to put a KTM 50 in there.
     
  12. Neptunati

    Neptunati New Member

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    I got my gt80 up to 35 mph, GPS verified. That was with the crappie flex pipe exhaust and 41 tooth sprocket. I got a kx80 exp chamber lined up to be welded on next. Looking to get to 40 mph and beyond.
     
  13. mike carter 2

    mike carter 2 Member

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    well, ive ridden all spring through summer,at least 1000 miles.this bike has been my only transportation.absolutly no trouble with the gt80 engine.runs better now than it ever has.i realy like this little engine! if you have folowed this thread you know what i have done to it. i would realy like to hear about your builds and mods that you have done, o yea,almost forgot ,bike pulls from about 2 or 3 mph to around 40 !!! thanks and i just hope that you have had as much fun as i have
     
  14. Mikey_

    Mikey_ New Member

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    Nice! I'm just getting back into this now-- About a year later. I'm glad to know that the GT80 works. I think that I might not order it in a kit but just get the motor and add the parts that matter for performance.

    I will likely build on a Slugo frame and use a jackshaft.
     
  15. turbobike

    turbobike New Member

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    My GT80 has just the reed, no spacer, ported cylinder from Kings, modded stock pipe on a Schwinn Dodger 40 tooth on 700 series wheels... 65 keihin main jet... Stock unmarked jet mic'd at 70 jet size. I'm 220lbs it has gps'd at 44 mph on a slight downhill 38 on a flat. Pulls no peddling from 2-3 mph. Couldn't be happier...
     
    #95 turbobike, Feb 24, 2017
    Last edited: Feb 25, 2017
  16. mike carter 2

    mike carter 2 Member

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    sounds like it runs great,are you still running the flex exaust?my bike couldnt breath through it.it was way to small.i even tried porting the mounting flang and building exaust from 1 inch conduit.still not good.found a suziki rm 60 x pipe on line and ordered a header pipe from fred c.in my opinion its the best lookin, best made header to use when useing a factory style pipe.the pipe realy woke my bike up!
     
  17. turbobike

    turbobike New Member

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    That's my next consideration. I do like how the stock pipe fits my setup though. I did have a concern a real expansion chamber might be to loud. If I lived in a free state (not NY) it wouldn't be a second thought. Have you seen a nice small silencer that fits your pipe?
     
  18. mike carter 2

    mike carter 2 Member

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    i just made one.it works pretty good
     
  19. mike carter 2

    mike carter 2 Member

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    i think i just cut the one off the pipe that came with the kit and modded it to fit
     
  20. mike carter 2

    mike carter 2 Member

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