Big Bore kit Question

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dweb4

Active Member
Messages
36
Location
Bowie, MD
I bought a big bore kit for my 2-bolt Zenoah the (25.4cc) one. I've torn done the top end of the motor and after taking the old piston off the crank and con-rod I notice the original piston is way bigger then the piston on the new bore up kit I just bought. I measured the original pistion it's about 34mm and the new bore kit one is like 30. Does anyone have a clue which bore kit I already have in my motor original owner can't remember what was done. I bought the FG Monster Beetle used this summer and it runs strong with jet-pro pipe, I just wanted to upgrade the motor to run insane. BTW it does have the original crank in it I want to put another crank in it also but don't know which one??? Any help would be appreciated.
 
32mm bore is for a g230 (22.5cc), 34mm is for a g260 (25.4cc), and a 36mm bore is for a 27.2cc. it kinda sounds like you get a 32mm bore kit.

when you go with stroker cranks you need to start playing with gasket thicknesses to achive the correct compression/clearance. it may be better for you to get a complete kit such as this 30.5cc from ddm http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.4757/.f or a race ported kit http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.4754/.f as it will be simpler to assemble and there is less chance of things not working as planned
 
ok thanks so the bore kit in the motor now is a 22.5cc so how does that measure up in performance to the 25.4cc that i purchased to put in? i'll look up the complete upgrades, again thanks for the help.
 
i couldnt really tell you how much of a difference it makes. here is a dyno chart courtesy of ddm
http://www.davesmotors.com/c.885035/site/images/g230rcdyno.gif[img]

the chart shows the g260 has a flatter torque curve, a slight bit more torque and horsepower, and the powerband is slightly lower with the g260.

mabey someone else will have experience with going from a g230 to a g260 in an offroad vehicle
 
look at the side of the cylinder.

give us the numbers on both the topends you have


be sure to indicate which is the new one, and which is the old.

sounds like you have a 26cc, and the topend you bought is a 23cc.
 
dweb4 said:
ok thanks so the bore kit in the motor now is a 22.5cc so how does that measure up in performance to the 25.4cc that i purchased to put in? i'll look up the complete upgrades, again thanks for the help.
Click to expand...

the new one you just bought (the smaller one) is the 23cc
 
ok looked at both top ends the original one (larger piston) number is 2070.

the new kit with the (smaller piston) top end has the same number 2070.
the top of the box on the new kit reads "bore up (25.4cc) kit for G230RC kit NR:GR23199"

so i'm not quite sure quess i maybe i have a g26cc original motor now the question is if i bore it up what can i bore it up to and also should i put another crank in????? :helpsmilie::helpsmilie:
 
looking at several top end kits, bot hthe 32mm and 34mm bore top end have the number "2070" cast into them. id guess thats just a casting number, the finished bore is the only difference.

the best way to tell what was in the motor and what you bought would be to get a pair of calipers (or a large micrometer) and measure the diameter of the piston. measure it just bellow the ring land.
 
i've had a 23,26,and now a 28 and i found that the 23 had the most top end but the 26 was the better one cause it was close in the top end department but had more bottom then the 23. the 28 i have now is just a torque machine but the lowest in the top end department. but since my firehammer has been slitely modified(nudge nudge wink wink) and weighs a tun i needed more power.
 
ok measured both old top-end and piston as well as new kit bore kit.

old top end and piston measure 34mm

new top end and piston measure 32mm

so i think i got as mentioned earlier an original g26 is in the truck and got a
g23 bore kit. i'll do some research and check into stroker cranks. does anyone have any good results with switching the stock carb out for a moded walbro one? i'm very green to 1/5th gas motors, ran nitro motors for years but this is new to me no doubt!
 
dweb4 said:
ok measured both old top-end and piston as well as new kit bore kit.

old top end and piston measure 34mm

new top end and piston measure 32mm

so i think i got as mentioned earlier an original g26 is in the truck and got a
g23 bore kit. i'll do some research and check into stroker cranks. does anyone have any good results with switching the stock carb out for a moded walbro one? i'm very green to 1/5th gas motors, ran nitro motors for years but this is new to me no doubt!
Click to expand...

if you get a +2mm longer crank you will need the thicker base gasket :no:

which then on a 2 bolt head ...it becomes more unreliable....
 
thanks trebor how bout if i got a 1mm crank would it still need a thicker gasket and how would relieablity be. what about walbro switching that out what benefit would come from that?
 
dweb4 said:
thanks trebor how bout if i got a 1mm crank would it still need a thicker gasket and how would relieablity be. what about walbro switching that out what benefit would come from that?
Click to expand...

if you go for any longer crank :boat:you will need extra gaskets as you need the correct clearance for the spark plug and piston also the squish band

http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.4754/.f

try this link it will show you all you need to know:helpsmilie:

:no: point in my thinking going for a +1mm crank

as for swapping carbs this is the one to go for a little harder

to use i:e tune and engine start as it does not have a choke:clown:

http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.4103/.f

i have this carb fitted on my ESP 27.2 zenoah

newpicsofmarderleopard025.jpg

dweb you need to update your location........................:)
 
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O'Neil bro's 27.2 race port

We'll after lookn on line and reviewing past threads/posts I picked an O'Neil bro's 27.2 race ported kit with 2mm stuffed stroker for my FG Monster Beetle. With Jetpro pipe already installed, I'm just getting through break-in and I'm SATISFIED!!!! Oh my I've seen sizeable performance gain just finishing the break-in I highly recommed this to anyone looking to upgrade there stock powerplant. Rebuild was a piece of cake also. Thanks Sean and crew at ONB....:)
 
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