What is the difference in ATC90 and ATC110 points motors?

[thefox]

What is the difference between the atc90 motors and the early (79-80) atc110 motors? Is it just the bore size or is the stroke different too? How big can I bore an atc90 engine?

[fabiodriven]

Me thinks me senses an all-out lambasting coming on from the older members about using the "search" feature-:eek:

[thefox]

I am and older member… :lol: lol . A search resulted in some conflicting posts.

[oscarmayer]

i beleive it's just bore. i had an old 90 and we put the "big bore" kit in. it was jsut a 110 stocker piston that was higher in comp.

[greenhuman]

Bore and stroke are bigger on a 110. You can't use a 110 piston or 110 big bore on a 90 because the 90 has a 14mm gudgeon pin and the 110 has a 15mm pin

[Vealmonkey]

The cylinder spigot sizes are different also. You can't just bolt on a 110 cylinder on an atc90.

[200xman]

If you need a points 110 motor to build let me know. I have a few laying around that you could have but shipping might be a killer.

[peter250r]

just lookin through my service manual here for some differences:

the compression ratio is 7.5 to 1 for a 90 & 8.5 to 1 for a 110

up to 1980 the 90 & 110 were the same engine and transmission wise, only the bore/stroke were different. the 125 shared the same transmision

1981 the 110 and the 125 changed to CDI instead of points ignition.

hope that answers ya question mate

[SWIGIN]

just lookin through my service manual here for some differences:

the compression ratio is 7.5 to 1 for a 90 & 8.5 to 1 for a 110

up to 1980 the 90 & 110 were the same engine and transmission wise, only the bore/stroke were different. the 125 shared the same transmision

1981 the 110 and the 125 changed to CDI instead of points ignition.

hope that answers ya question mate


up to 80 eh??

they stoped makeing the 90 in 78....lol

but yeah, the main difference is the cly and crank

[oscarmayer]

so i guess that's why they had a "big bore" kit for the 90 instead of using the 110 piston even though it bored it to a estimated 110. interesting. i didn't knwo why we didn;'t use a 110 piston, but hey now i do. Thansk guys! ya tought me more knowledge!! SWEETNESS!!!!! i always like learning.

[thefox]

Lots of good info, thanks guys!

Todd, I might take you up on that offer. My thought was to but a 110 motor in my 70 roller, I found a complete atc90 but if I am going to do the work modding the 70 I want a 110 motor. I have to check what else I will be needing to see if it would be easier just getting a complete 110. I have another 110 that I can borrow the motor from for fitment but I don't want to permanently take that motor.

[trizilla]

since this thread is here..... does anyone know the rods lengths from each? also what is the stroke and piston compression height's for each? im not sure where to get this info from. does anyone know if these engine's would benefit from 3 angle valve seats?

[Vealmonkey]

Well, for the 90 and 110 engine you will have to redrill 2 holes in the 70 frame first of all. The chain sizes of the 90/110 are different from the 70 also. The 90/110 engine is heavier than the 70 engine. Also the 90/110 is slightly longer than the 70 engine. And those things are just for starters. Some people who put the 90/110 in the 70 also put the front engine mount in to try and relieve the stress on the rear of the frame. There are fitment issues with the carb and intake also. That is why alot of people just go with the lifan type engines since they are based on the z50/ct70/atc70 engine block, not the atc90/110 engine block.

[peter250r]

since this thread is here..... does anyone know the rods lengths from each? also what is the stroke and piston compression height's for each? im not sure where to get this info from. does anyone know if these engine's would benefit from 3 angle valve seats?

90: 50.0 X 45.6mm(1.97 x 1.79in)

110: 52.0 X 49.5mm(2.05 x 1.95in)

comp. ratio

90: 7.5:1

110: 8.2:1

comp. pressure

90: 142-170psi (10-12kg/cm3)

110: 156-198psi (11-14kg/cm3)


thats all i can find for ya sorry

[thefox]

Well, for the 90 and 110 engine you will have to redrill 2 holes in the 70 frame first of all. The chain sizes of the 90/110 are different from the 70 also. The 90/110 engine is heavier than the 70 engine. Also the 90/110 is slightly longer than the 70 engine. And those things are just for starters. Some people who put the 90/110 in the 70 also put the front engine mount in to try and relieve the stress on the rear of the frame. There are fitment issues with the carb and intake also. That is why alot of people just go with the lifan type engines since they are based on the z50/ct70/atc70 engine block, not the atc90/110 engine block.

I was thinking of the Lifan but this time I would like to keep it all Honda and I like how the 110 engine doesn't look much different then the stock 70 motor. I figure I will cut the frame and lengthen it about 2 inches as well as sleeve it for more strength. Still haven’t figured out the intake though.