Been looking at the GT6 Grubee engine just now but everything I find is being sold by one of the now 7 different businesses/websites by the guy that runs gasbikes.net. Jesus Christ how many shady businesses does this guy run. Must be how he keeps money rolling in but youd think the government would shut him down as that is shady as hell.
66cc, picking a starter engine
- Thread starter Rusty_S85
- Start date
gary55
Well-Known Member
The engine kit your showing is the same engine kit being sold by Gasbike and Kingsmotors only Kings is charging 30 dollars less. I believe the 4 hp is a bit high of a estimate as the only diff. between this engine and a bone stock engine is the head. This aftermarket head on the GT5 pro is a 8cc head where as a stock slant plug heat is 6cc so to get the same performance from the so called pro racing engine you need to deck the cyl. about .030" +=.
The GT6 they advertise for 10 bucks more has the 6cc aftermarket head so won't need decking to have equal compression as a stock engine, but if you plan on adjusting for squish clearances the GT6 has a larger squish band with a smaller chamber so more fuel will be caught in the quench space, and the comp. will be very high which I believe is hard on wrist pin bearings. Modifying the GT 5 for squish clearance will get you to a good place as far as comp. is concerned, and with the smaller squish band and larger chamber will have more fuel accessible to ignition.
I realized that after my post that the GT6 must be some house brand thing for Gasbike/Kingsmotor/Raw-motor and all four other websites that guy runs selling parts.
It seems officially the GT5 is the highest numbered engine that is offered as a true Skyhawk.
Ive been doing some thinking and really started thinking do I really need to invest this much money into an engine to be capable of 50 mph when I might find out I don't care to go much over 25 - 30 mph vs the 35 - 45 mph I was thinking of going.
My only big problem right now is finding a GT5 style engine that is the engine alone as I really don't need to spend the extra money for the extra gear I wont be using.
Hell I even though of buying the MPG-38 engine for $280 and just forget paying the extra $100 for balancing. At least that engine comes with a competition 5.0cc head recommended or option 5.5 - 6.0cc head if you are in a very hot climate (which it does not say what the definition of very hot climate is). That might be all I need as it does say in the description it is capable of up to 45 mph. Not to mention it also comes with a spark plug, NT carburetor, throttle cable and extra jets included in the $280 price. That would save me some cash by not having to spend $80 for the VM18mm carb I was looking at. But I might still have to as the NT carb might not accept a 1/4" fuel line which is what I based my fuel system on so far. But with a little wd40 or zep I could lube a smaller hose up and force it over the 1/4" barbs.
Right now my eyes have been opened up I took up this project to be a cheap project that I could do during the summer that I could get done compared to sinking a lot of money into the cars I'm restoring that require more time and more money. Well $1,200 invested in this bike now and its not finished yet and that money could have done a good amount on my restorations, given most of that money is shipping as Ive been ordering parts more than locally buying. So I am thinking maybe I need to stop reinventing the wheel and trying to make this some kind of race bike performace wise. The original "indian" motor bicycles had a top speed of around 30 mph in the teens. Would be more period to be capable of 30 mph in my eyes.
It seems officially the GT5 is the highest numbered engine that is offered as a true Skyhawk.
Ive been doing some thinking and really started thinking do I really need to invest this much money into an engine to be capable of 50 mph when I might find out I don't care to go much over 25 - 30 mph vs the 35 - 45 mph I was thinking of going.
My only big problem right now is finding a GT5 style engine that is the engine alone as I really don't need to spend the extra money for the extra gear I wont be using.
Hell I even though of buying the MPG-38 engine for $280 and just forget paying the extra $100 for balancing. At least that engine comes with a competition 5.0cc head recommended or option 5.5 - 6.0cc head if you are in a very hot climate (which it does not say what the definition of very hot climate is). That might be all I need as it does say in the description it is capable of up to 45 mph. Not to mention it also comes with a spark plug, NT carburetor, throttle cable and extra jets included in the $280 price. That would save me some cash by not having to spend $80 for the VM18mm carb I was looking at. But I might still have to as the NT carb might not accept a 1/4" fuel line which is what I based my fuel system on so far. But with a little wd40 or zep I could lube a smaller hose up and force it over the 1/4" barbs.
Right now my eyes have been opened up I took up this project to be a cheap project that I could do during the summer that I could get done compared to sinking a lot of money into the cars I'm restoring that require more time and more money. Well $1,200 invested in this bike now and its not finished yet and that money could have done a good amount on my restorations, given most of that money is shipping as Ive been ordering parts more than locally buying. So I am thinking maybe I need to stop reinventing the wheel and trying to make this some kind of race bike performace wise. The original "indian" motor bicycles had a top speed of around 30 mph in the teens. Would be more period to be capable of 30 mph in my eyes.
CrazyDan
Well-Known Member
http://www.bicycle-engines.com/2-Stroke-AngleFire-Engine.html
Official Grubee skyhawk GT5A 66cc with slant head
https://www.grubee.net/collections/skyhawk-2-cycle-all/products/gt5a-es-2-stroke-engine
Same engine and same price but with the hole to start with a cordless drill.
Official Grubee skyhawk GT5A 66cc with slant head
https://www.grubee.net/collections/skyhawk-2-cycle-all/products/gt5a-es-2-stroke-engine
Same engine and same price but with the hole to start with a cordless drill.
Well today Ive been doing some reading and some searching I think I am going to go with a Zeda 80 engine. I can pick one up for the same price kit wise as the GT5 but it has a longer rod and longer stroke than the GT5 and its claimed to be a true 40mm all around motor.
So I am thinking of buying one of these for $130 and then working some magic on it myself post break in. But before I run it I think I am going to find out the CC of the current head and use some clay to measure the deck clearance from piston to the head surface for quench that way when I make a swap to a high compression head with a quench band I can set up quench to be the same.
So I am thinking of buying one of these for $130 and then working some magic on it myself post break in. But before I run it I think I am going to find out the CC of the current head and use some clay to measure the deck clearance from piston to the head surface for quench that way when I make a swap to a high compression head with a quench band I can set up quench to be the same.
CrazyDan
Well-Known Member
A longer stroke engine can't do as high of rpm as an engine of the same displacement but a shorter stroke.
Right, shorter stroke can rev higher faster. But for off the line acceleration lower end power is what I would need more than the ease of the engine winding up. Now if I were to go for high rpm spinning then I would probably be better off with the longer stroke. But thing is the difference in stroke between the Zeda 80 and the GT5 is only 2mm as the GT5 is 38mm stroke while the Zeda 80 is 40mm stroke. The 2mm increase in stroke will make more torque than the smaller stroke but with how minimal the stroke is I don't think it should effect what rpm the engine could safely handle.
Street Ryderz
Well-Known Member
When refering to large displacement engines that can be true but not allways it just requires better ballence to overcome the higher rotational mass and the longer stroke produces more torque generally,but in these engines your talking about 2mm extra stroke length and 5mm in rod length and a mass difference of under 10 grams so really not much to overcome,The advantage is the wrist pin location being more centered on the piston there is less thrust or torque side wear of the cylinder since the piston stays squared in the cylinder better they also tend to run a little smoother in the top end compared to the short stroke generics!
Longer rod also helps to prevent piston side loading. But thing that has grabbed my eye is that Zeda sells a Weekend Warrior kit that I can pick up for $120 that I have to assemble the cylinder and head. This allows me to double check it as well as to do some measurements before final assembly. I really want to find out what kind of deck clearance out of the box this engine would have between the piston and the quench band which I am assuming the slant head has. That will allow me a goal for when I swap over to a high compression head. I just have to find out exactly what CC the slant head is and compare it to the Jake diamond head might not even be worth wasting money on the swap other than for looks.
Street Ryderz
Well-Known Member
On average there used to be 2mm from piston crown to the deck but now it's closer to 1mm and that can vari from engine to engine,The Jake diamond head is around 7cc and the copy(clone)is simmular but protrudes into the bore and takes up some of the 1mm space yeilding a real tight squish clearence!
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