CY 29CC 2-bolt motor w/ Fuelie 30.5CC 4-bolt piston/head, will it work?

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Bryan K.

Bryan K.

Well-Known Member
Messages
268
Location
Richmond Hill, Ontario
Hey guys.

Just building a spare motor out of parts I have laying around. I have a CY 29CC bottom end, it's a 2 bolt, and I have a 4 bolt fuelie 30.5cc piston/ring and head. After putting it all together, the gasket seals, the piston moves inside freely and there's lots of compression. Do I need to check for anything else? Does it matter how much clearance is between the spark plug and the piston head? There's no contact between them. The 4 bolt head kit I have is listed to work with 29cc and 30.5cc motors. I was surprised it all lined up properly with the exception of the 2 bolts that aren't being used on the head. The gasket seals perfectly around the head. Just want to make sure everything is ok before I attempt to fire it up. The CY's 2-bolt head replacement is just way too much money and isn't worth it imo, so if this doesn't work I'm just going to toss the motor.

thanks,

Bry
 
Bryan K. said:
Hey guys.

Just building a spare motor out of parts I have laying around. I have a CY 29CC bottom end, it's a 2 bolt, and I have a 4 bolt fuelie 30.5cc piston/ring and head. After putting it all together, the gasket seals, the piston moves inside freely and there's lots of compression. Do I need to check for anything else? Does it matter how much clearance is between the spark plug and the piston head? There's no contact between them. The 4 bolt head kit I have is listed to work with 29cc and 30.5cc motors. I was surprised it all lined up properly with the exception of the 2 bolts that aren't being used on the head. The gasket seals perfectly around the head. Just want to make sure everything is ok before I attempt to fire it up. The CY's 2-bolt head replacement is just way too much money and isn't worth it imo, so if this doesn't work I'm just going to toss the motor.

thanks,

Bry
Click to expand...
check squish clearance. I forgot the spec but @Seandonato73 ran 0.022" on his g320. you will need solder and accurate digital calipers (not the ebay $7 crap like I have lol)
 
Does it matter that the 2 bolt head is a 29cc and the 4 bolt head is a 30.5cc, or it's just negligible? I guess if the larger displacement is from bore, it should be ok as the piston kit was rated for both 29cc and 30.5cc. However, if the larger displacement means a longer stroke, that could affect rod length or the "squish" as well I'm assuming? What would be the result of having too much squish clearance?
 
Bryan K. said:
Does it matter that the 2 bolt head is a 29cc and the 4 bolt head is a 30.5cc, or it's just negligible? I guess if the larger displacement is from bore, it should be ok as the piston kit was rated for both 29cc and 30.5cc. However, if the larger displacement means a longer stroke, that could affect rod length or the "squish" as well I'm assuming? What would be the result of having too much squish clearance?
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if the piston is rated for 29 and 30cc then that means u need a longer stroke crank (not a longer rod. stroke is the position, vertically, of the crank pin) and you will have too much squish resulting in low compression which equals low performance (if the compression is low enuff it might not even start cuz its not compressing the fuel mixture)
 
Z.hb71 said:
measure the 30.5 and 29cc pistons, if they r the same then they use different stroke crank, if they r different then they use the same crank most likely = Best scenario
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28.5- 30.5cc piston is 36mm.
If Bryan's engine runs good or not will depend how it was made 30.5 if the head has been milled out for clearance for insurance like obr does then the squish or rather lack of will be to high?
If it was 30.5 by just adding a +2 stroker crank and a thick gasket then he will be golden??
Give it a try Bryan, you have nothing to lose. ??
 
Cheers. Thanks guys ?
mark35 said:
28.5- 30.5cc piston is 36mm.
If Bryan's engine runs good or not will depend how it was made 30.5 if the head has been milled out for clearance for insurance like obr does then the squish or rather lack of will be to high?
If it was 30.5 by just adding a +2 stroker crank and a thick gasket then he will be golden??
Give it a try Bryan, you have nothing to lose. ??
Click to expand...


Will do.. will report back with results
 
Z.hb71 said:
Well yeah. Except fuelie don't make a 30.5cc, which means it's either a rovan or a ddm big bore upgrade kit.
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I just assumed that Fuelie was all Rovan/KM stuff anyways. The 30cc Fuelie that comes stock on the Redcat Rampage is also a clone motor with a clone carb but all branded Fuelie. No idea what you're getting these days unless you buy from a reputable dealer.
 
Bryan K. said:
I just assumed that Fuelie was all Rovan/KM stuff anyways. The 30cc Fuelie that comes stock on the Redcat Rampage is also a clone motor with a clone carb but all branded Fuelie. No idea what you're getting these days unless you buy from a reputable dealer.
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That's why I only buy from reputable stuff. Fuelie only makes a 23cc to a 28.5-29cc, and are sold on ddm. eBay motors, no matter what they say can't be trusted. 90% of the time they are cheap crap rovans they say fuelie to sucker people in, none of their motors are authentic.
But im not trying to discourage you, have a go at it! Nothing to lose ?
 
Z.hb71 said:
That's why I only buy from reputable stuff. Fuelie only makes a 23cc to a 28.5-29cc, and are sold on ddm. eBay motors, no matter what they say can't be trusted. 90% of the time they are cheap crap rovans they say fuelie to sucker people in, none of their motors are authentic.
But im not trying to discourage you, have a go at it! Nothing to lose ?
Click to expand...
You mean from now on you will only be buying reputable stuff?
, ?
 
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