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50cc to 110cc conversion, help needed!

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ghost_Shark

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Hi, i have a 50cc pit bike and i want to get more power, can i put a 110cc cylinder on without changing the crankshaft or the clutch? i have another engine but i want gears and a manual clutch.
 

my67xr

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Welcome to Miniriders,

You can take it out to a 70cc by fitting a 47mm piston, cylinder and head to it from a 70cc or 90cc.
https://www.ooracing.com/store/big-bore-kit-convert-50cc-to-72cc-big-valve-head.html
Or fitting a 52.4mm piston, cylinder head will take it out to 88cc
Classic Honda 50's Australia - TB Stock Head, 88cc Bore Kit, 20mm Carb Kit, Cam - 92-13 Models [TBW0930]
You would need another carby if your's cant be jetted to suit, and a better camshaft is recommended too
Classic Honda 50's Australia - 20mm Performance Carb - Fits a variety of Hondas [TBW0125]
 

ghost_Shark

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Welcome to Miniriders,

You can take it out to a 70cc by fitting a 47mm piston, cylinder and head to it from a 70cc or 90cc.
https://www.ooracing.com/store/big-bore-kit-convert-50cc-to-72cc-big-valve-head.html
Or fitting a 52.4mm piston, cylinder head will take it out to 88cc
Classic Honda 50's Australia - TB Stock Head, 88cc Bore Kit, 20mm Carb Kit, Cam - 92-13 Models [TBW0930]
You would need another carby if your's cant be jetted to suit, and a better camshaft is recommended too
Classic Honda 50's Australia - 20mm Performance Carb - Fits a variety of Hondas [TBW0125]
I was hoping i could just put a 110cc cylinder on as i already have one, but it seems no one has done this, do i don't know if the engine could handle so much more power. would it even fit without boring out the block?

Thanks for the quick reply.

P.S. i have another engine from a pit bike that is 110cc but it has a centrifugal clutch and no gears, i also have an engine that has gears but still a centrifugal clutch, so i was thinking if it isn't possible to make the 50cc engine 110cc, i cacn take the manual clutch and put it on the 110cc engine with gears, so it would be the same as taking the 50cc and changing the cylinder.
 

my67xr

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if you pull down your 110cc engine , you'll find it has a 52.4mm cylinder and piston, if the gudgeon pin is 13mm then it should all go together onto the 50cc bottom end
But due to the short stroke of the 50cc crankshaft it only adds up to 88cc's.
 

ghost_Shark

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Ok, then i'll just use the 110cc geared engine that i have, and change the clutch to a manual one.
Another thing i was wondering about is, performance cdi unit's and coil's do they make a difference? i have a cdi unit that has no restriction so does it still make a difference? and the coil's what's so special about them?

Also, what size carburettor is best for a 107cc engine? i had a 26mm carb from a 2 stroke on at 1 point but it died everytime i would throttle hard, was that due to too big/small carb or incorrect size jet?
 

my67xr

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Performance cdis aren't worth the trouble of fitting (especially the cheap) alloy china ones.
They have different timing advance settings, and are made from cheap componants.
Some of them work for a while, others wont work from new, also a lot fail prematurely when you're out riding and can leave you stranded.
You can upgrade the stator flywheel to a better kit, a lighter flywheel helps the engine rev faster, and you can get adjustable digitial timing stator kits like the Daytona 125/ Lifan 150 uses.
TB and OORacing sells a few cdi's too that are better quality.
One of our site sponsors sells them here in australia, give Jaimie a call to discuss what you want, he is very helpfull
Classic Honda 50's Australia

Most of the pit bike cdi's dont have a rev limiter in them, the valves usually bounce before you can get any where near the limit of the cdis' sparking capablity's
But as i mentioned before, they are available at an extra cost.

Performance Ignition coils are available, AWR, Takegawa, Splitfire, Piranha and Ngk make a few.
The quality of the big name coils is a lot better than the generic china made coils, they last a lot longer and can give you a much better spark.
I use the Cheap china performance coils on my bikes and haven't had a problem with them yet.
Performance Racing Ignition Coil 110cc 125cc 140cc PIT Quad Dirt Bike ATV Buggy | eBay
http://www.ebay.com.au/itm/Racing-I...orcycle_Parts_Accessories&hash=item19eecb0351


Even just fitting a better spark plug lead can help, i use the Splitfire leads on my bikes and there is a noticable difference in the spark output.
Ngk sell a good quality lead too


Carby wise, something around a 20mm would be the best,
and run a decent foam filter on it too like a Uni Filter, and make sure it's oiled up too.
2 stroke carbs are set up differently inside to mix the fuel air, and generally use bigger jets too


To swap it over to a manual clutch is easy enough.
You'll need the manual clutch kit, manual gear shift shaft, manual clutch cover with arm, pusher/actuator etc, a clutch cable and lever
 

ghost_Shark

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Performance cdis aren't worth the trouble of fitting (especially the cheap) alloy china ones.
They have different timing advance settings, and are made from cheap componants.
Some of them work for a while, others wont work from new, also a lot fail prematurely when you're out riding and can leave you stranded.
You can upgrade the stator flywheel to a better kit, a lighter flywheel helps the engine rev faster, and you can get adjustable digitial timing stator kits like the Daytona 125/ Lifan 150 uses.
TB and OORacing sells a few cdi's too that are better quality.
One of our site sponsors sells them here in australia, give Jaimie a call to discuss what you want, he is very helpfull
Classic Honda 50's Australia

Most of the pit bike cdi's dont have a rev limiter in them, the valves usually bounce before you can get any where near the limit of the cdis' sparking capablity's
But as i mentioned before, they are available at an extra cost.

Performance Ignition coils are available, AWR, Takegawa, Splitfire, Piranha and Ngk make a few.
The quality of the big name coils is a lot better than the generic china made coils, they last a lot longer and can give you a much better spark.
I use the Cheap china performance coils on my bikes and haven't had a problem with them yet.
Performance Racing Ignition Coil 110cc 125cc 140cc PIT Quad Dirt Bike ATV Buggy | eBay
http://www.ebay.com.au/itm/Racing-I...orcycle_Parts_Accessories&hash=item19eecb0351


Even just fitting a better spark plug lead can help, i use the Splitfire leads on my bikes and there is a noticable difference in the spark output.
Ngk sell a good quality lead too


Carby wise, something around a 20mm would be the best,
and run a decent foam filter on it too like a Uni Filter, and make sure it's oiled up too.
2 stroke carbs are set up differently inside to mix the fuel air, and generally use bigger jets too


To swap it over to a manual clutch is easy enough.
You'll need the manual clutch kit, manual gear shift shaft, manual clutch cover with arm, pusher/actuator etc, a clutch cable and lever
Alright, i'll get a coil, lead and cap from a good brand, and get a mikuni 20mm carb, with an uni air filter. I'm not sure i wan't to change the flywheel just yet as it's a bit of a hassle to change, but eventually i'll probably do it.
Could i just take the clutch assembly from the 50cc engine and put it on the 110cc? that would be a lot cheaper if i could, but would the clutch hold?

So there's nothing i can do to stop it from diying if i yank the throttle all the way? i google it and it seems to be a common issue, but nothing seems to help it, some say it's the CDI, others the coil, personally i would put it down to incorrect carb settings but i'm new to 4 stroke's, i've been using 2 stroke's all my life.

Also if there a good instruction manual to follow in order to adjust the valve's? the man i bought my bike from said the valve needed adjusting as it has been sitting for a few years.
 

my67xr

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The 50cc clutch might fit, but you'll need to try it out?
I reckon it would be the same as the normal 110/125 manual 3 plate clutch.

Watch this, it explains how to set the valve clearances, but use .003" for the inlet, and .004" for the exhaust

[video=youtube;QJciyJRJh8Q]https://www.youtube.com/watch?v=QJciyJRJh8Q[/video]


To tune your carby to work nice with a 110cc will take a bit of time playing around rejetting, tuning, and a handfull of jets @ $5-$12ea might need 4 pilot jets and 4 main jets if you are lucky?
Even once tuned the bore of the carb is still pretty big, you'll lose bottom end due to the pressure drop when you open the throttle.
It is do-able,
but seeing as you can buy a smaller 20mm carby for $25 that is suited to a 110cc engine, it's not worth all the trouble's/cost.
 
D

Dewieprowler

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I did mine it was easy just had to dremmel out the block a lil bit but yes it does work
just adjust your screws like quarter turn higher it ripped after putting on a 110 head had it for 3 years and eventualy sold it guy still rips it no problems
 

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