CT-70HK1 Ignition (again, I know. Sorry)

ctbale

ctbale

Member
Hey Guy after seeing your pictures I have a question.

So it looks like you used an original 4 speed honda lower end. I have the same sitting on the bench trying to figure out what to do with it. Looking for a cylinder/piston/head combination that will work. Got some help coming my way but I am curious what piston did you use? Looks like you have a E22 head? Here is my thread. Maybe we can continue the Q&A over there to we dont muddy the subjects. Thanks for your help.
https://lilhonda.com/index.php?threads/china-top-end.21981/
 
6

69ST

Well-Known Member
If I've missed something, by all means say so. There's no difference between any CT70 top end made from 1969 to 1981, other than casting numbers...same 47mm bore, "short" rod and taller (compression height) piston combo, with the "old" dome configuration. 12v used a longer connecting rod with matching shorter (compression height) piston. If you use a 12v piston with a 6v (short rod) crank, the piston will sit too far below deck height, at TDC, and you'll have low compression.
 
ctbale

ctbale

Member
The issue I was worried about is when you have a short rod crank, with the original taller dome piston, and you try to put on a china head which (I think) has a shallow area/combustion chamber (post 1981 style) the old dome piston hits the valves?
 
R

Roy Chambers

Member
ctbale said:
The issue I was worried about is when you have a short rod crank, with the original taller dome piston, and you try to put on a china head which (I think) has a shallow area/combustion chamber (post 1981 style) the old dome piston hits the valves?
Click to expand...

Did you also notice that it say's 49 CC's on the Cylinder?
Thanks Roy.
 
ctbale

ctbale

Member

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kirrbby

kirrbby

Well-Known Member
ctbale said:
no I missed that. was that you way of saying that the 88cc kit will work under a china head? I have one of those sitting under a honda head on one of my 1977 CT70, works great.

What I am asking is will the orig dome piston clear under a china head.

post 42 says no.
https://lilhonda.com/index.php?threads/ct70-runs-wont-idle.21595/page-3
Click to expand...

Ya but post #38 says he bought a Zoomzoom complete kit...which is supposed to fit every CT70 ever made, and for only $54 .
I don't think that is the E22 head.
 
ctbale

ctbale

Member
yea, the zoomzoom kit has the flat top piston, will only give you 80psi when using a "short crank" motor. Then you will run into the same problems mk2davis did. then he said a domed piston hits the valves in the china head. I dont think this the zoomzoom kit has a E22 head. Not for $54

I have this kit coming but if I install it on my short rod motor, gunna have 80psi. Basically same as zoomzoom.

https://www.ebay.com/itm/Cylinder-Head-Piston-Gaskets-For-Honda-ATC70-CRF70-CT70-TRX70-XR70-S65-70CC-US/362397995714?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

The seller gave me $29 back to keep it. Seller knows it will be low compression, most likely has had many complaints.

Gunna use the kit, but gunna mill down the top of a domed piston so it wont hit the valves
 
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OLD CT

OLD CT

Well-Known Member
Looks like the cheap china head strikes again. :LOL: It's not a ignition problem! Check the compression TAWPTool.
Cheap isn't good and good isn't cheap. Doubt that ''grinding'' on it will work ctbale.
 
ctbale

ctbale

Member
I am gunna use that tool on my bench ..... round on each end .... says something about dont grind alum .... ???

.......or maybe a lathe :)

or put it in a vice and hit it with a 4" grinding wheel!
 
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