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Discussion Starter · #1 ·
Hi there,

I just recently bought a 1980 Honda Cm400t and I love it; however, I am 6'2" 190lbs and want to make it more into a brat style bike that is also tall enough to fit my size. I am a new rider and am a beginner in all things motorcycle, but I have been looking into suspension raising and building a custom seat to increase height. I was just wondering if anyone has any recommendations for how to go about that? Is it possible to interchange suspension from a taller bike onto the cm400t to increase the height and would I need a new swing arm to do that? Should I only use honda suspension or is it possible to use parts from different brands? Any suggestions?

thanks for taking the time, I appreciate your insight!

-Bow

IMG_4143.jpg IMG_4144.jpg
 

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Welcome to the forum, Bow. Great to see another 400 series here. Browse through the project logs and you'll get some ideas.
 
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Discussion Starter · #3 ·
Thank you,

I've been looking through the project logs. Should I have posted in there instead?

-Bow
 

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Nice looking bike. I'm 6'3" and I too ride a CM400. I don't find the height an issue, esp after replacing the handlebars with less "pull back". It looks like someone already did that to some extent on your bike. I'd vote to keep it stock for a while and see if you get used to it as you're new and changing the geometry/handling came come later. Besides, classic looks better than brat IMHO.
 

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That is a good looking bike! I am 6'1" and love my CM400. +1 on the keeping it stock for a while, you may grow to like it. Changing the stance and height of the bike will change things like handling and braking. Too bad someone ditched the cones for cut off pipes or it would be cherry! How does it run?
 

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Discussion Starter · #6 ·
Thanks for the Advice Everyone! I was planning on Riding the Bike through the season and then making modifications come winter anyway. The Bike runs well. a little bit of backfiring in the lower rpms and when rolling off the throttle sometimes, but other than that the engine sounds smooth and I love the feel of the ride. only 13000 miles on the bike and it has been kept in good condition as far as I can see. The lights and electric start all work perfectly so I'm not complaining yet! I think a carb clean is probably in order since the previous owner didn't clean them for the past two years. will that take care of the back firing or is the back firing pretty normal? I was reading in another forum that adjusting idle speed and carb cleaning will do wonders.

As far as the reason for raising suspension, I just want the bike to have a more aggressive fit to it and be more customized for my height, but thats just me.
 

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You may be running a bit lean. I had some deceleration back fire but after a new set of air cut valves, it is nice and quiet. Best bet is to clean the carbs and see what jets are in there, sync the carbs, set the valves, and set your air fuel mixture. You will have to do some plug chops after that to see where you are at. It sounds like a bunch of work but I really enjoy tinkering with this stuff at it really pays off. There are plenty of other things to check besides that though, do you have the FSM?

Is that a hose clamp holding the right pipe on? How are they attached to the bike? If they are just hanging off of the power chamber, you may want to look at supporting them somehow.
 

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Discussion Starter · #8 ·
Will be taking that on this weekend EazyDr. Thank you for your help!

The Pipes are attached to the frame as well as the power chamber, I think the previous owner just put those hose clamps on for some reinforcement.
 

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All good advice to follow so far.
To raise the bike will require a longer/different front end as well as longer rear shocks. It can be done safely as I have with mine. Here's some comparison shots of my 79 CM400T vs. a stock 81 CM400C
201_5011.JPG 201_5007.JPG 201_5010.JPG
with a proper paint job 2014.jpg
The front end is an 81 CB900F which gives you 39mm forks, air adjust forks, dual disc brakes and 19" front wheel. Rear shocks are 1" longer CB750/900 shocks. Only negative to the setup is I wish the turn in was a bit slower for response on the street, it's fine on dirt. It's very quick and light on 'turn in' but hasn't presented any problems in the last 60K miles
 

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CM450Cnewseat.jpg I got an old seat from ebay , removed the cover and shaved the foam so I could sit farther back. I'm 6'3" 230 lbs and this helped a lot. I made the new cover from material on ebay.
 

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Great job. Looks good. How does it feel? I want to increase the foam in the pilot part of the seat and the rear section has always looked too high to me. I happen to have long legs (torso was 'shortened' in a car wreck) and have just 'acquired' an old seat and want to do a similar mod. I get cramps in my hips with the present posture.
 

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Barney, another option is replacing your bars with a set with less "pull back". This made a big difference for me in both comfort and handling. Simple to do too, now I just have extra long cables, but it all works!
 

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+1 on changing those pull back 'buckhorns' for some nice CB bars. It made a big difference in the control of the bike, but my knees are still bent too much .
 

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I replaced the suspension on my cm200 in order to even up the lines and give it the brat look. it worked in terms of making the bike much bigger, but be warned: this will result in the chain grinding against the frame. You will need to find a way to bring the chain up a bit, or put a piece of plastic in there for it to grind against so you don't ruin your chain.
 

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That chain can also act as a saw and weaken the swing arm. It just isn't safe.
 
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