How does the clutch work on a honda st90

danny n

danny n

Member
#1
#1
Can any body explain to me how the clutch work on a 73 st90 3 speed centrifugal clutch, i know the arm on the shifter moves something in to release the plates and also you can adjust it on the outside but what moves, the outer drum or the inside it would nice to see it work in a cutaway view or tell me me or send me to a thread that would tell me .
 
minibikedude

minibikedude

Active Member
#2
#2
Shift lever disengages the clutch as you shift up or down a gear, It a great design that still being used today. That's probably one reason why Honda bikes are the best on the plant.
 
danny n

danny n

Member
#3
#3
I understand the basic operation of the clutch how the shifter disengages the clutch but step by step what happens inside of the clutch what moves ,and when like when you crank it up it disengages and then it engages when you gas it until you shift and then release the leaver, mine works fine but i just would like some input from somebody that has more info, i called some of the honda shops and the ones that have worked on them are gone. Thanks
 
minibikedude

minibikedude

Active Member
#4
#4
The shift lever pushes the clutch plates open and that's how it is disengages from the transmission and reengaged! There are 3 clutch plates and some metal disc that are in between the clutch disc.
I have rebuilt many of the Auto Clutches on my Honda CT70, ST90, CT90, ATC110's.There not that complicated.
Buy a service manual and it will show you how they work.
 
minibikedude

minibikedude

Active Member
#5
#5
Here is a rebuild of a CT90 engine on youtube, it is similar to the ST90 engine. They are all the same family of engine even the newer AT110 and CT110 engine is based of the original S90 engine. Thanks to DRATV. Good place to buy from also.

CT90 Tech Day 2011 Engine Build #1.m4v - YouTube

CT90 Tech Day 2011 Engine Build #2.m4v - YouTube

CT90 Tech Day 2011 Engine Build #3.m4v - YouTube

CT90 Tech Day 2011 Engine Build #4.m4v - YouTube

CT90 Tech Day 2011 Engine Build #5.m4v - YouTube

CT90 Tech Day 2011 Engine Build #6.m4v - YouTube
 
danny n

danny n

Member
#6
#6
With the motor off the clutch is locked up and when you crank it up it disengages the outer and inter hub with the weights I guess and as you gas it it pushes the plates together an takes off and when you shift the clutch cam pushes the outer hub in or the inter in which disengages the clutch ,sorry to be detailed on how it works:doah: but i just would like to know, thanks for the info so far i have taking the clutch apart and cleaned it and replaced some of the springs but i did not look at it close enough to see how it works ,to big of a hurry to get it going, i have rebuilt the whole motor with new top end, the trans shifter forks and low gear was replaced , also the clips on the rebuild i have watch all of them and picked up a few thing when i went through the rebuild, i like the low and high gear box, i would like to fix one of my two motor to incorporate one, not sure maybe it would work looks like the same block . thanks guys :thumbsup:
 
minibikegi

minibikegi

New Member
#10
#10
I own an st90, 1975 no clutch lever. year dated model might have still had variable tranny? my 79 ct90 has low gear tans, lever buy the foot shifter, its a no go if not in proper position,?
 
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