GT90 Conversion Kit...

pharside

New Member
Feb 7, 2013
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Pennsylvania
Hey guys, I was wondering if anyone has tried the GasBike/KingsMotorBikes GT90 Conversion Kit...
Is it any good? (..does it live up to it's claim of "up to 10 horsepower"?) Anyone know where to get the parts to complete it? ...I have a Grubee SkyHawk GT5... Could I take the crank, connecting rod, clutch, and misc hardware out of that to put the GT90 together?
Thank guys!
 

waynesdata

Active Member
Jul 10, 2017
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"If" it makes 9 or 10 hp the engine would be VERY short lived. Look at dirt bike 2 stroke for that kind of power.
 

indian22

Well-Known Member
Dec 31, 2014
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Oklahoma
Pharside I took some time to carefully examine the scant information provided by the "kit" vendor & "if" the photos and description are accurate I'm led to believe that your Gt-5 (38 mm) stroke engine bottom end and clutch/drive train components can be used with the cases and cylinder provided. The vendor states that case bearings are installed & all gaskets are included.

I'm also quite familiar with "reed type" engines & also the various vendor hp claims; from stock to highly modified & I think most oversell their wares. Especially import distributors who often pay others to reverse engineer the design work of dedicated engine builders/tuners who are often a part of actual race efforts, as well as provide complete engines & parts to hardcore racers. Engine builders who can and do wring out the 10 hp or more from 66 cc, but very few of us are going to duplicate that kind of output. Real race engines put to work on the street are typically a pain to ride & require constant tuning and tweaking to keep them creating top hp. A fresh engine that "actually" dynos 7 hp might drop off to 5 or 6 hp in just a few hours of normal street riding...just reality.

I'm not trying to talk you down from buying the kit, heck I'd buy the cases by themselves if I didn't have to buy the other unknown components that are included. Just to play with, but I'd buy an actual Arrow reed, carb & jug and use the GT-5 components to complete it. Same with the head. I won't buy a head from a vendor that won't because they can't at least tell me what the combustion chamber volume is.

Pharside chasing high hp really begins with well balanced rotating assembly's & good parts clearances or the high output engine may be fast but won't last.

Best of luck, Rick C.
 

John420jones

New Member
Jun 5, 2018
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Hey guys, I was wondering if anyone has tried the GasBike/KingsMotorBikes GT90 Conversion Kit...
Is it any good? (..does it live up to it's claim of "up to 10 horsepower"?) Anyone know where to get the parts to complete it? ...I have a Grubee SkyHawk GT5... Could I take the crank, connecting rod, clutch, and misc hardware out of that to put the GT90 together?
Thank guys!
Yes i have the gt90 kit my only problem was the piston from the kit would hit the crank so i used my old piston and made it look the same as the piston just pit a hole in it to match the other one
 
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Tocats121

New Member
Dec 7, 2018
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I've bought the same GT90 kit and have a GT7 for parts. How difficult was it to change the parts over? Is there a manual that I can use to break down and rebuild a motor.
 
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Rampage80cc

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Jul 8, 2019
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So with the gt90 kit did it actually make as much power as they say because I run ideal Reed system with race fuel and I shaved head the high compression set up and I still only making about 8
 

Tocats121

New Member
Dec 7, 2018
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I haven't gone that far in building my GT90. I have to order more parts to build mine and those parts are on hold for now.

There is guy in another feed that is using a GT5 part and some parts to a machine show to have the part cleaned up and changed the angle of the cam by 5%.