Author Topic: soft clutch after about 30 min of riding  (Read 1111 times)

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Offline jrB

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soft clutch after about 30 min of riding
« on: May 31, 2012, 08:20:08 PM »
hi all. search thing don't work for some reason for me. My problem... well started two weeks ago when I got cut off, down shifted to fast, locked up rear end but made it off highway. after I got my 1972 cb500 k home and inspected my lock up I found a broken clutch push rod, tore clutch rod seal, minor damage to left case, buckled chain on front sprocket, broken oil sensor and wire. After replacing all with new I fired up bike and clutch wasn't engaging. So I opened up right side and although seen no signs of damage to anything I went ahead and replaced the clutch disk but kept old springs and plates. in the process I drilled extra holes in the clutch basket hub. Reassembled everything and all works well with the exception of once the engine gets hot the clutch gets soft. by means of hot- I ride 30 miles to work, most on highway at about 80, last 3 miles through traffic lights at maybe 45. Hence when my problem begins. also I put new oil (the honda gn4) and filter. In the past I added a oil pressure gauge to watch my oil instead of dummy light. on highway I used to get about 70 psi of pressure once hot, now I'm at about 35 psi and my dummy light comes on.   
hope this is enough info, thanks in advance :)

Offline brooze72

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Re: soft clutch after about 30 min of riding
« Reply #1 on: May 31, 2012, 08:33:30 PM »
By soft, do you mean slipping? or something else?
2011, 2012 & 2013 Godzilla Relay Rally Rider
"Hold on loosely...don't let go
 If you cling too tightly...you're gonna lose control"
1972 CB500K1 - restored rider
1981 CB650C - new project

Offline jrB

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Re: soft clutch after about 30 min of riding
« Reply #2 on: May 31, 2012, 08:56:37 PM »
no it don't slip, although it's sometimes hard to get into 1st. the clutch lever is initially firm then just gets easier to where it feels like it isn't doing anything when it really is. also once in 1st it starts out spongy but still catches on at about 50%.

Offline brooze72

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Re: soft clutch after about 30 min of riding
« Reply #3 on: May 31, 2012, 09:05:08 PM »
That's interesting, I have never experienced a soft clutch.  Since we're (ultimately) moving springs mechanically with the lever, I can't figure out how a hot engine would change the feel like that.  Only thought that comes to mind, have you checked the cable to see if the outer housing is compressing near the engine when hot? (Just a wild ass guess here)
2011, 2012 & 2013 Godzilla Relay Rally Rider
"Hold on loosely...don't let go
 If you cling too tightly...you're gonna lose control"
1972 CB500K1 - restored rider
1981 CB650C - new project

Offline jrB

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Re: soft clutch after about 30 min of riding
« Reply #4 on: June 01, 2012, 10:50:01 PM »
cable rides high by tank but does drop down within an inch or so behind head and infront of carbs. wondering if (1 of 3 things here) 1st- the clutch I put in has slanted grooves. next payday i'm going back to the oem.  2nd- I reused the old springs. could I have weakened them?  and 3rd although new oil, is it too light for our summers here in phoenix, but good for our winters.

Offline andrewk

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Re: soft clutch after about 30 min of riding
« Reply #5 on: June 02, 2012, 04:39:38 AM »
cb500 clutch would have slanted grooves OEM.  only one that does to my knowledge.

It's weird that it's temperature sensitive.  My first suspect would be the cable, but it might be worth ensuring that everything is back together right.  I'd get new springs if you're getting a new clutch.

Also, is the adjuster cam/riser in good shape?