how do i.d. which china motor i have?

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Smokey1981

New Member
Jul 9, 2010
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kansas city
i got a 2nd hand kit for free that im wanting to tinker with i know its one of the slant style head motors but i cannot seem to find any serial numbers denoting the displacement. sooooo how do i know which one i have 49cc 66cc or 80cc???? any help would be appreciated thanks in advance guys
 

JonnyR

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May 13, 2012
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ronkonkoma, new york
there are only 49cc and 66cc the 80cc is the 66cc
other than that i don't know how to tell the difference without taking the head off and measuring the cylinder
 

biknut

Well-Known Member
Sep 28, 2010
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What you're asking isn't easy to answer. There's a lot of different factory's in china that make these motors, and they all look very similar.

Post a couple of pictures of your motor, and someone may be able to help you.
 

MotorBicycleRacing

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Jul 28, 2010
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there are only 49cc and 66cc the 80cc is the 66cc
other than that i don't know how to tell the difference without taking the head off and measuring the cylinder
Yes, there is no 80 cc motor as it's really an exaggerated marketing
ploy for a 66 cc.
You don't need to pull the head off.
It's fairly easy to tell a 66 cc from a 49 cc by the size of the head
studs and the distance between them.
49 cc are always 6 mm
66 cc are mainly 8 mm with a few older motors having 6 mm

post a pic if you wanna know for sure.
 
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Smokey1981

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Jul 9, 2010
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kansas city
the motor looks like the typical cheap chinese kit, i just picked it up tonight and havent torn into it yet i can measure the cylinder diameter and piston thois week some time when i get back down to the garage. does anyone happen to have bore and piston diameter measurements that they can post up? im not sure of the age of the kit its a basket case right now lol ill measure the studs in the morning
 
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biknut

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Sep 28, 2010
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So far I've seen 3 different 47mm pistons, and I'm pretty sure there's more than that. The wrist pin is in different positions, and the piston skirt is a different length.
 

Smokey1981

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Jul 9, 2010
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kansas city
i checked the bore & piston this morning 47mm on both ill have to check the studs for the size when i hit the hard ware store later on this week they look to be 8mm by eyeballing them this thing is missing some hardware so i have some searching to do. thanks you guys for all your help in figuringout what motor i have dance1
 

Smokey1981

New Member
Jul 9, 2010
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kansas city
theres some carbon on the te top of the piston & the exhaust side of the piston has carmely tan look im guessing thats from the exhaust port the cylider bore looks nice and clean no scoreing theres the typical carbon ring at the top of the jug where the rings dont get high enough to clean it. the rings seem a lil bit snug in their lands (oil/carbony sludge) im also attributing this to it being a 2 stroke motor thats been run on mystery mix for god knows how many miles. all in all im thinkin fresh gaskets & rings and see how long before it gives up, oh it also has needle bearings on both ends of the connecting rod i peeked at them when i yanked the jug yesterday.
 

IlliniRider

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Jul 4, 2012
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Champaign IL.
I have an older engine that needs ID'd also. Can a positive identification be made from connecting rod markings? Would spare parts be available from vendors other than the unknown original? I am certain that the engine modifiers on this forum know all. Please help a guy out!
 

Smokey1981

New Member
Jul 9, 2010
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kansas city
I have an older engine that needs ID'd also. Can a positive identification be made from connecting rod markings? Would spare parts be available from vendors other than the unknown original? I am certain that the engine modifiers on this forum know all. Please help a guy out!
ok well help us a little , i knew mine was a chinese kit i looked up as much info as i could find and asked the fine folks here on the board for some specifics to i.d. mine. so if you have a 2nd hand CHINESE kit look at the same things i did. angle plug verses strait plug head, check the size of the piston, and the size of the head studs that should point you in the direction for most of the parts, the motors are kinda generic theres tons of variations even from the same manufacturer regarding bearings vs bushings on the connecting rod for the piston, different piston domes and combustion chambers on the cylinder head. research and measure what you have and im sure we as a group can help ya out dnut

if its not a chinese kit post pics maybe it can be i.d.'d by looking at it ????
 
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Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
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up north now
there are only 49cc and 66cc the 80cc is the 66cc
other than that i don't know how to tell the difference without taking the head off and measuring the cylinder
Just tpo throw a wrench in that observation, I have a 60cc engine (58cc) and a 70cc here for sale. There were a lot of different engines, and several different sizes.

I have measured 46cc, 47cc, 49cc, 58cc, 66cc, 68cc, and 70cc.
 

Smokey1981

New Member
Jul 9, 2010
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kansas city
thanks bikeguyjoe!!! im assuming the 66cc on up were the ones that biknut had mentioned with the different piston wrist pin heights and 47mm bores? do you happen to have a list of the wrist pin height measurements to help us further i.d these motors?
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,837
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up north now
No. I am not that fastidious.
I just used to measure bore and stroke when I had them apart new to clean them out.

Honestly, I have never had to replace anything inside an engine, so I just ran 'em, sold 'em, built another, ect.