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Grubee GT5 80/66cc PistonHawk Bicycle Engine Kit, Thoughts?

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Old 08-21-2013, 02:38 AM
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Default Grubee GT5 80/66cc PistonHawk Bicycle Engine Kit, Thoughts?

Talked with Greg at Piston Bikes seems like a nice fellow and answered a ton of questions I had. However....I want to know if any of you have read, seen, used this GT5 configuration.

Another question I had is I just helped my buddy install a Arrow GT5 into his bike tonight and the gears in the clutch housing are different from his Ebay style motor. The Ebay motors gears are just straight toothed and the GT5 gears are helical (slanted). Is this a performance advantage or is the advantage having gears that produce less noise?

One last thing. I asked Greg if there was anything else that I needed to add before I installed this kit and we talked about an expansion pipe which he thought should be added later but he highly suggested the High Performance Round 66cc Head to add right away. Does this increase HP at all or is the effect of added HP from a cooler motor? Should I wait and just get the Cylinder and head from CR Machine at a later date like the beginning of spring?

This is the head from Piston Bikes (Made by CR)
http://www.pistonbikes.com/Grubee-Sk...1gru66phaf.htm

This is the Cylinder and head directly from CR.
http://www.shop.crmachine.com/Stage-...66cc-BTKS1.htm

If it helps to know Im 165 Lbs and live at over 5000 ft elevation so while being light is beneficial my elevation robs the horsepower.

Thank you for any replys,
Dan.

Last edited by Danschutz; 08-21-2013 at 03:41 AM.
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Old 08-21-2013, 10:41 AM
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Default Re: Grubee GT5 80/66cc PistonHawk Bicycle Engine Kit, Thoughts?

In regards to the gears, I think they might be stronger, but don't quote me on it. Automotive differentials have helical gears for durability, so I would think the same concept applies here as well.

As for the head and exhaust, break the engine in first, THEN mod the crap out of it.

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Old 08-21-2013, 11:33 AM
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Default Re: Grubee GT5 80/66cc PistonHawk Bicycle Engine Kit, Thoughts?

Dude,
That's good advice. Probably like most of us here Ive tinkered with stuff my entire life and its hard to resist add ons lol. Looks like I might have picked the wrong bike to start with so perhaps Ill use the extra cash for another donor bike and turn this current project into a E Bike for next spring.

Guess I'll build a cruiser.

Dan.
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Old 08-22-2013, 12:31 AM
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Default Re: Grubee GT5 80/66cc PistonHawk Bicycle Engine Kit, Thoughts?

I'm not so sure about adding a high compression head on a new engine (or at all). They raise compression which puts more wear on the bearings and internals. And bearings are the first thing to fail in your engine. An expansion chamber, on the other hand, is a pretty worry-free addon that adds a very noticeable amount of power. I would do that first and hold off until later on the head and maybe get a compression gauge for that.
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Old 08-22-2013, 01:18 PM
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Default Re: Grubee GT5 80/66cc PistonHawk Bicycle Engine Kit, Thoughts?

Quote:
Originally Posted by Will122391 View Post
I'm not so sure about adding a high compression head on a new engine (or at all). They raise compression which puts more wear on the bearings and internals. And bearings are the first thing to fail in your engine. An expansion chamber, on the other hand, is a pretty worry-free addon that adds a very noticeable amount of power. I would do that first and hold off until later on the head and maybe get a compression gauge for that.
That was actually my final decision. Held off on all mods, will break it in and then I'll be eyeing the CR cylinder/piston/head package. Motor has been shipped, now its waiting time! Oh and looking for another donor bike, doesn't look like my current rig will work.

Dan.
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