85cc monkey bike upgrade to 110cc? Will it work

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Monkeysteve
Posts: 11
Joined: Fri Jan 29, 2021 11:50 pm
Rides:: Ktm 300

85cc monkey bike upgrade to 110cc? Will it work

Post by Monkeysteve » Fri Jan 29, 2021 11:55 pm

Any advice appreciated
Bike is a skyteam st90 monkey bike 85cc. Similar if not same as c90 I’ve had in the past?
Don’t want to buy parts and not fit
Thanks

cozi70
Posts: 593
Joined: Tue Nov 20, 2012 1:16 am
Rides:: Z50,cf70,msx and an auld german 1200gs
Location: Belfast, Northern Ireland

Re: 85cc monkey bike upgrade to 110cc? Will it work

Post by cozi70 » Sat Jan 30, 2021 1:46 pm

Hello Steve and welcome aboard.
With the 107cc kit fitting on the 85cc Honda cub 12v engine there is a strong chance it will work.
Early 12v cub engines need the casings opened up manually,but later ones are already wider to accept the 107 barrels bigger skirt,so I'll interested to know how yours appear.
Have you looked at the kit from petrolscooter?
Colin J

Monkeysteve
Posts: 11
Joined: Fri Jan 29, 2021 11:50 pm
Rides:: Ktm 300

Re: 85cc monkey bike upgrade to 110cc? Will it work

Post by Monkeysteve » Sat Jan 30, 2021 1:54 pm

Thanks for the reply
Yes I’ve seen the kit from petrolscooter on eBay and it’s cheap but unsure how good it will be? Have you had any experience with these kits reliability wise. I would like to know if it will fit before disassemble and buying parts ideally? Thanks again

cozi70
Posts: 593
Joined: Tue Nov 20, 2012 1:16 am
Rides:: Z50,cf70,msx and an auld german 1200gs
Location: Belfast, Northern Ireland

Re: 85cc monkey bike upgrade to 110cc? Will it work

Post by cozi70 » Sat Jan 30, 2021 2:51 pm

Monkeysteve wrote:
Sat Jan 30, 2021 1:54 pm
Thanks for the reply
Yes I’ve seen the kit from petrolscooter on eBay and it’s cheap but unsure how good it will be? Have you had any experience with these kits reliability wise. I would like to know if it will fit before disassemble and buying parts ideally? Thanks again
Yes,I have already done a 1988 motor,but only covered around 500 miles on it,and I'm about to do a 1996 engine, both using those kits.

Monkeysteve
Posts: 11
Joined: Fri Jan 29, 2021 11:50 pm
Rides:: Ktm 300

Re: 85cc monkey bike upgrade to 110cc? Will it work

Post by Monkeysteve » Sat Jan 30, 2021 7:57 pm

Just taken mine apart and measurements seem right. Do you upgrade the intake or jets? If to what sizes. Thanks

cozi70
Posts: 593
Joined: Tue Nov 20, 2012 1:16 am
Rides:: Z50,cf70,msx and an auld german 1200gs
Location: Belfast, Northern Ireland

Re: 85cc monkey bike upgrade to 110cc? Will it work

Post by cozi70 » Sat Jan 30, 2021 8:25 pm

Monkeysteve wrote:
Sat Jan 30, 2021 7:57 pm
Just taken mine apart and measurements seem right. Do you upgrade the intake or jets? If to what sizes. Thanks
I ran the standard issue 110/125cc pit bike 22mm carb and it was fine,but read others retained their standard cub carbs,19mm iirc,and upped the main jet slightly.

Monkeysteve
Posts: 11
Joined: Fri Jan 29, 2021 11:50 pm
Rides:: Ktm 300

Re: 85cc monkey bike upgrade to 110cc? Will it work

Post by Monkeysteve » Sat Jan 30, 2021 9:09 pm

Any idea what size jet to go to?

cozi70
Posts: 593
Joined: Tue Nov 20, 2012 1:16 am
Rides:: Z50,cf70,msx and an auld german 1200gs
Location: Belfast, Northern Ireland

Re: 85cc monkey bike upgrade to 110cc? Will it work

Post by cozi70 » Sun Jan 31, 2021 12:05 am

Monkeysteve wrote:
Sat Jan 30, 2021 9:09 pm
Any idea what size jet to go to?
There is guide in this forum that discusses this conversion, think they explain the jet sizes.

Monkeysteve
Posts: 11
Joined: Fri Jan 29, 2021 11:50 pm
Rides:: Ktm 300

Re: 85cc monkey bike upgrade to 110cc? Will it work

Post by Monkeysteve » Sun Jan 31, 2021 11:48 am

Did it you have to modify the crankcase- make wider for barrel skirt? Measurements of the skirt seem it will just fit but think it will be close

cozi70
Posts: 593
Joined: Tue Nov 20, 2012 1:16 am
Rides:: Z50,cf70,msx and an auld german 1200gs
Location: Belfast, Northern Ireland

Re: 85cc monkey bike upgrade to 110cc? Will it work

Post by cozi70 » Sun Jan 31, 2021 1:21 pm

Monkeysteve wrote:
Sun Jan 31, 2021 11:48 am
Did it you have to modify the crankcase- make wider for barrel skirt? Measurements of the skirt seem it will just fit but think it will be close
I've only experience with bigger Chinese engines,but the later Honda c90 engine I'm about to do doesn't need the around 2mm excess removed to fit the 107 kit,but the earlier honda did.

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