You are here:

Motorcycle Repair/Trail 90 Carb & Clutch

Advertisement


Question
QUESTION: Hi Bill Silver, I've purchased a 1970 Honda CT-90 recently and am trying to work out a couple of issues. The first is in regard to the Carburetor float level adjustment height which I can't seem to get a definite answer.
My question is this, is the measurement location from the body base of the carburetor, "gasket surface", to the top of the float, which of course is now upside down when measuring, OR the partial flange that drops down approx. 1/4" from the carb body base?
Also, in regards to the clutch, which I know the prior owner replaced just prior to the sale. The clutch won't release at idle when in 1st gear, standing still. And the effort required when shifting up OR down is more than it should be.
Thank you so much, I will be most happy to donate.

ANSWER: Steve, the 1970 CT90 should be a K2 series machine. The float level shown in my tune-up books is 20.0mm.

Measure in the center of the carburetor body. I generally set the carburetor on its side, so the float can swing in/out just touching the spring-loaded float tip, then measure from there. Do NOT compress the tip during measurements. If there is a cutaway in the body at the middle, use that surface.

The clutch is centrifugal, releasing at idle speeds and also disengages when the shift pedal is moved in either direction. It is important to assemble the clutch release parts so the shifter arm (clutch lever) is centered up on the end of the shift plate (clutch plate) linkage.

http://www.cmsnl.com/honda-ct90-trail-1970-k2-usa_model621/partslist/E++07.html#  #5,6

It is easier to do when the engine is on the side. Once those parts are installed correctly, you have to turn the outer adjustment screw counter-clockwise until it stops, then back off just a little bit and lock the nut in place.

Hopefully, the clutch pack was assembled properly. If so, then the clutch adjustment procedure should allow the clutch to disengage when the shifter pedal is depressed up or down.

Be sure that the engine is tuned properly, so the engine idle speed is low (below 1,300 rpms). If the engine is struggling to idle properly and you turn up the idle speed excessively, the centrifugal weights start kicking in and the clutch will engage while the bike is sitting still.

Bill Silver

---------- FOLLOW-UP ----------

QUESTION: Thank You Bill for your response. I donated, but unsure if it finalized?
I do have a couple of follow-up questions;
In regard to your response," If there is a cutaway in the body at the middle, use that surface". You are referring to the gasket surface of the carb body?
Also, in regard to your response; "Hopefully, the clutch pack was assembled properly" If I ultimately remove & disassemble the "clutch Pack", I won't know if it's assembled "properly" Do you know of a VERY clear assembly procedure or video that I can use as a guide. Also regarding the friction discs, are all replacement discs the same, do all types need to be soaked in oil prior to assembly. The friction discs that are in my clutch pack now could be ruined as a result of improper assembly, OR, no oil soaking prior to assembly? And I can't assume that the spring have been replaced. Can you please advise. Thank You, Steve.

Answer
Q
If there is a cutaway in the body at the middle, use that surface". You are referring to the gasket surface of the carb body?   Yes
Q2
Also, in regard to your response; "Hopefully, the clutch pack was assembled properly" If I ultimately remove & disassemble the "clutch Pack", I won't know if it's assembled "properly" Do you know of a VERY clear assembly procedure or video that I can use as a guide.

http://forum.ih8mud.com/threads/honda-ct90-clutch-writeup.248270/

https://www.youtube.com/watch?v=rx3ph3VCFm0  5:06 shows shift lever installation setup

https://www.youtube.com/watch?v=UdPRSLbpW0g  more around this one on the youtube lists on the right side.

Q3
Also regarding the friction discs, are all replacement discs the same?
Q4
do all types need to be soaked in oil prior to assembly. It is a good idea, but not completely necessary.
Q5
The friction discs that are in my clutch pack now could be ruined as a result of improper assembly. Probably not....  it is hard to really damage them due to mis-assembly problems. It just won't work.
See Q4
no oil soaking prior to assembly? And I can't assume that the spring have been replaced.

Bill Silver

Motorcycle Repair

All Answers


Answers by Expert:


Ask Experts

Volunteer


Bill Silver

Expertise

Need help with vintage Hondas from the 1960s? I am an expert with 250-305cc bikes in particular and most all of the other pre-91 models, in general. I do NOT claim to have a great deal of experience on Gold Wings, Cruisers, ATC/ATVs and dirt bikes.

Experience

I have owned/ridden/maintained Honda motorcycles for 35 years. I have written five books on Honda repairs and collecting. I was a service manager for two Honda shops back in the 1980s.

Organizations
VJMC (Vintage Japanese Motorcycle Club) of North America

Publications
VJMC newsletter, as editor for two years and as contributing editor currently.

Education/Credentials
3 years auto shop in high school, teacher's aide in Automotive Technology in Jr. College, Diesel mechanic course in college, self-taught mechanic and automotive writer.

©2016 About.com. All rights reserved.