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Post by kippstakes on Jun 20, 2016 2:49:54 GMT -5
I have been doing some research on installing a 100 big bore kit on my 50. The kit includes the jug, rings, piston, wrist pin, clips, and gaskets. It looks like many have done it in the past with good results. My motor is a typical gy6. I am running stock exhaust and air filtration... though I do have a few spare pods sitting around.
My question is this: will I need a new head to accommodate the larger piston?--- I don't want to start bending valves. Also, my current main is an 85 (stock, so it's probably lean as-is) which will need to be jetted up, the question is how much larger? I was thinking around a 10% increase which would put me at about 94. Also, I am at 1500 elevation, so that should be considered (I figured a reduction by 1 or 2 should suffice). So ultimately came to a figure of around 92. Does this sound sensible?
Thanks!
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Post by arkie on Jun 20, 2016 3:10:26 GMT -5
Normally your stock head will be just fine. As far as jetting goes, your supposed 92 sounds about right. at least as a place to start. Remember that there will be a tuning process involved. I recommend getting a set of jets to work with.
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Post by arkie on Jun 20, 2016 3:11:13 GMT -5
Almost forgot  |
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Post by katastroff on Jun 20, 2016 8:17:35 GMT -5
When tuning a carb, always start big and go down. This way you will avoid running lean and overheating.
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Post by Deleted on Jun 20, 2016 9:37:05 GMT -5
I have been doing some research on installing a 100 big bore kit on my 50. The kit includes the jug, rings, piston, wrist pin, clips, and gaskets. It looks like many have done it in the past with good results. My motor is a typical gy6. I am running stock exhaust and air filtration... though I do have a few spare pods sitting around. My question is this: will I need a new head to accommodate the larger piston?--- I don't want to start bending valves. Also, my current main is an 85 (stock, so it's probably lean as-is) which will need to be jetted up, the question is how much larger? I was thinking around a 10% increase which would put me at about 94. Also, I am at 1500 elevation, so that should be considered (I figured a reduction by 1 or 2 should suffice). So ultimately came to a figure of around 92. Does this sound sensible? Thanks! Are you replacing the crank with a stronger one? If not, it is better to stay at the 72cc size. (which is marketed as 80cc) According to what I have read on this forum, the stock cranks can not really handle much more. Just a thought.
Bill
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Post by arkie on Jun 20, 2016 11:29:25 GMT -5
+1 on what Bill said ^^^^^^^^^^^^^ the 47mm bore size is reputedly the best for power/longevity. I didn't listen and I'm on my second crank now with my 50mm bore  There are very respected members here that have both the 50mm and the 47mm and I do recall one saying that he thought the 47 was not only easier on the engine but faster also. |
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Post by kippstakes on Jun 20, 2016 11:35:24 GMT -5
Almost forgot Thank you!  |
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Post by kippstakes on Jun 20, 2016 11:41:03 GMT -5
So an 80 might be a safer option then? I have seen information about the 100 upgrade being a bit too torquey for the factory 50 crank. I was planning on just taking it easy while starting off the line-- no WOT takeoffs/burnouts/wheelies/etc  . However, if there are few power gains to be had from the additional 20ccs then maybe 80 would be the way to go. Thanks for the quick replies, this is a great forum! |
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Post by kippstakes on Jun 20, 2016 11:41:30 GMT -5
Almost forgot Thank you |
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Post by arkie on Jun 20, 2016 11:57:17 GMT -5
Almost any question you might have has already been answered here in this forum. Poke around,spend some time in the tech section. And when all else fails one of us will be here to give an answer or opinion.  |
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Post by dachurchpcguy on Jul 7, 2016 13:05:45 GMT -5
One of my scoots has the 47mm kit with replacement head and high lift cam. The power difference is huge. I'm around 210 lbs. and I have trouble keeping it under 35mph. My 110 lb. daughter can't keep up with her 50cc scoot.
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Post by humanshield on Jul 7, 2016 15:38:00 GMT -5
One of my scoots has the 47mm kit with replacement head and high lift cam. The power difference is huge. I'm around 210 lbs. and I have trouble keeping it under 35mph. My 110 lb. daughter can't keep up with her 50cc scoot. lol. "Trouble keeping it under 35" Some of you folks say the damndest things.  |
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There are very respected members here that have both the 50mm and the 47mm and I do recall one saying that he thought the 47 was not only easier on the engine but faster also.
. However, if there are few power gains to be had from the additional 20ccs then maybe 80 would be the way to go. 
