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I've been trying to get better clearance on my rear as I bottom out whenever my wife is on the back of the bike. I've changed the setting to the max clearance on the stock shocks but want to raise the back as I'm still bottoming out. Anyone know the maximum modified shock length for my CM400t? I know stock is usually 13". How much longer can I go?

Also, I've been told by a shop that I need to change my fork seals - but I have a feeling its the actual springs in the forks (bottoming out on bad bumps in the road). Only one side is leaking (mildly). Its apparently like a 3.5 hour job? Is this normal? Just got an answer back from our Honda dealers here in Toronto that they don't sell the OEM spring anymore. Do I have a choice and will the fork seal replacement help (given that there is the air pump on this model into the suspension)? Forgive my use of terminology - this is my first bike!

Any help would be great!
 

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I'd look at replacement, generic type shocks. Their springs are always too stiff. If you are riding 2up though, they may be the best bet. Longer shocks will alter geometry, but stronger spring rates will be better, as the height can be right, but not bottoming out.



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Moved to SOHC Suspension.
Weak/old springs with old shocks would be the source of bottoming. I'll refer you to Progressive Suspension for the shocks and they will advise you on the springs needed.
If there's a leaking fork seal then the fork will be low on oil. Time to replace the seals and fork oil with modern technology. The fork springs can be measured to see if they are out of spec, specs are in the FSM. Changing the seals isn't that big a deal, more time consuming than anything else. I'd suggest going to 10W fork oil, FSM calls for ATF which is @7-8W. All Balls Racing sells the fork seals and dust caps as a package.
 

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I'd look at replacement, generic type shocks. Their springs are always too stiff. If you are riding 2up though, they may be the best bet. Longer shocks will alter geometry, but stronger spring rates will be better, as the height can be right, but not bottoming out.



Sent from my SM-T800 using Tapatalk


If I wanted to make my bike a bit bigger since I'm fairly tall, 6'2, I'm considering a fork that is longer. The changed geometry of, say, 40mm height - does that come with any risk?
 

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If I wanted to make my bike a bit bigger since I'm fairly tall, 6'2, I'm considering a fork that is longer. The changed geometry of, say, 40mm height - does that come with any risk?
1979 CM400T, 1981 CB900F front end, CB750 rear shocks. Springs and shocks from Progressive Suspension.
414339_2809939442716_457878143_o.jpg vs. stock 100_0701.jpg
Or a front view of the road bike vs. an '81 CM400C
201_5011.JPG Note: the 400C front suspension is a bit lower than usual due to no air in the forks, 1/2" or so
 

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Hi everyone
I’m in the process of making some mods to my 400t and I wanted to go more on the scrambler side of things.
This is why I am dusting off this thread: what is in your experience the maximum length we can go for on the rear shocks and what’s been the effect on the handling?

thanks everyone
 

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The length of the shock should keep the bike level, raising the rear without doing the front will change rake and trail of the front end. The only way to lift the front is by using longer fork tubes or a different front end.
 

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The idea of a CB 750 rear shock is great!
But are those not a bit too stiff ?
What is your experience when riding solo?
 

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If I wanted to make my bike a bit bigger since I'm fairly tall, 6'2, I'm considering a fork that is longer. The changed geometry of, say, 40mm height - does that come with any risk?
You might be looking for a fork of a Honda CX 500 C, they are a bit longer.
Plus: you'll have a double discbrake if you like!
By the way: ATF-oil in a fork works just fine!
 

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The idea of a CB 750 rear shock is great!
But are those not a bit too stiff ?
What is your experience when riding solo?
The CB750 shocks are from Progressive Suspension so the spring rate was set to match the CM400 base and GVW max weights. They work great. Solo I set them to the softest position and loaded they're set on the 3rd of 5 positions. 2 up with a load would probably go to 4th or maybe 5th position.
Just taking stock CB750 shocks would be too stiff because of the bike weight difference.
 
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