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Old 08-20-2010, 04:07 PM   #1
longhorn717
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Default 1980 CB400 fork replacement

I would like to get a new cartridge style front fork for my 1980 honda cb400t. I talked to a service man at the honda dealer and he said it wasn't worth the effort. granted I don't think they've been serviced in forever. Are the stock forks any good? I'm not a small guy either. From what I've read only that makes a difference. I'm 6' and 255lbs. Right now I would like to take girls for a ride but don't feel comfortable with my suspension. The rear shocks also feel springy/spongy. what are good replacements?

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Old 08-20-2010, 04:44 PM   #2
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I'd just put new seals and fluid in the forks and check 'em out. The bike in the best of circumstances is no ball of fire. Trying to sport one up is sort of pointless.

It would improve things to get a pair of Works shocks for it though. Japanese shocks in the 70s were pretty much shyt.
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Old 08-20-2010, 07:35 PM   #3
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PVC can go along way with sached out springs. Along with new oil as Seru stated.
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Old 08-20-2010, 08:59 PM   #4
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PVC can go along way with sached out springs. Along with new oil as Seru stated.
But stiffer springs goes further. You're a trackday-junkie, Moke - you know that increasing preload is a piss-poor substitute for the proper spring rate, and springs don't cost that much. Especially compared to a set of cartridge forks (used or otherwise - "new" costs outright, "used" just means you've got to rebuild 'em sooner or later, probably sooner).

Shocking sacked springs to increase their free-length works better, anyway; just hold one end, and essentially "whip-lash" them against a sturdy workbench, or even a smooth piece of concrete-sidewalk with a piece of thin cardboard laid-down on it.
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Old 08-21-2010, 08:27 AM   #5
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My problem is the front end goes down by about 3 or 4 inches when i got on the bike. this essentially gives me pretty much a solid front end with basically no damping. True I'm learning to ride on this bike but I can't believe I could trash this fork in six months. I'm not bad on it. anyhow what spring rate should I be looking at? where do I find them?
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Old 08-21-2010, 11:15 AM   #6
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Quote:
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But stiffer springs goes further. You're a trackday-junkie, Moke - you know that increasing preload is a piss-poor substitute for the proper spring rate, and springs don't cost that much. Especially compared to a set of cartridge forks (used or otherwise - "new" costs outright, "used" just means you've got to rebuild 'em sooner or later, probably sooner).

Shocking sacked springs to increase their free-length works better, anyway; just hold one end, and essentially "whip-lash" them against a sturdy workbench, or even a smooth piece of concrete-sidewalk with a piece of thin cardboard laid-down on it.

Well obviously brand new springs would be better. Guess I'm thinking why spend the money on a bike that old, that'd be my concern. I'm picturing a lot of pitting who knows.

PVC was a cheap alternative back in the day and worked surprisingly well. The reason I know that is because of the track. And it's certainly not a piss poor way to do cheap mods when you don't have any money. It helped me more than once where the available preloaded range wasn't enough.

I'am interested in this shocking technique
little hard to believe but Iv got a few springs lying around? I think. How much extra length can one expect from this method? This is spring free length right?
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Old 08-21-2010, 12:23 PM   #7
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Well obviously brand new springs would be better. Guess I'm thinking why spend the money on a bike that old, that'd be my concern. I'm picturing a lot of pitting who knows.
I concede your point. But his problem really sounds like new springs are in his future, if he's serious about keeping the bike.

Quote:
PVC was a cheap alternative back in the day and worked surprisingly well. The reason I know that is because of the track. And it's certainly not a piss poor way to do cheap mods when you don't have any money. It helped me more than once where the available preloaded range wasn't enough.
It's still a good technique - if you're almost there - and certainly cheaper than adjustable end-caps, or aluminium or steel tubing for gettin' the preload down "right".

Quote:
I'am interested in this shocking technique
little hard to believe but Iv got a few springs lying around? I think. How much extra length can one expect from this method? This is spring free length right?
Yeah - free length. It varies, but if you've got springs that have sagged, you can get maybe another 5%-7% of free-length out of them (or if you've got two springs that are almost the same length you can bring the shorter one even with the other).

To make it "stick", you've got to anneal 'em in an oven at about 300deg F or so (mem'ry - temp might be a bit higher) for 6-8 hours or so afterward.

I'm actually quite surprised you've never heard of it. I know you've done suspension work before.
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Old 08-21-2010, 12:36 PM   #8
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Quote:
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My problem is the front end goes down by about 3 or 4 inches when i got on the bike. this essentially gives me pretty much a solid front end with basically no damping. True I'm learning to ride on this bike but I can't believe I could trash this fork in six months. I'm not bad on it. anyhow what spring rate should I be looking at? where do I find them?
You're beyond the range of the springs in the front end - I've used Racetech springs and emulators for years - Good Stuff. Vintage Pavement

Bikes tended to be undersprung/under-damped when they were NEW all the way through the late-'90s even, so it's not really surprising to me that you're bottoming-out the bike.

They don't have a direct application for your bike on their website, you'll have to contact them.

Springs will run you probably $100-125, Emulators another $200-250 IIRC. They might even be able to help you with rebuild parts for the forks, and they've got some good (but more spendy!) shocks for the rear, they can definitely give you advice on how to proceed.
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Old 08-21-2010, 02:21 PM   #9
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well airhawk its either fix this one or get a new bike. and being young and underpaid. I don't see that happening in the immediate future. I'm also looking at resale value. I would like to make this into a nice little back-country burner. Its got good bones and was well taken care of until I got it. I paid 300 for it and have 50 in a chain, plus new blinkers with new wiring, and I modified the fuseblock to accept mini-max fuses. I'm aiming for a resale of 1200-1800. I know that's high for the age of the but I think with the upgrades and mods i'm planning it will be a good deal for someone. My goal is to make it similar in appearance to the Triumph Thruxton.
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Old 08-22-2010, 11:07 AM   #10
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No matter what you do to it it won't be worth squat. The bike was totally pedestrian when new. It was sold as a cheap commuter and had poor suspension and the power output set no records. In fact an earlier model CB450 would hand it its hat every time despite the fact that the CB450 was heavier.

IMHO you will never get more than 4-500 bucks unless it was perfectly restored AND someone was looking to collect one.

You can get a set of springs and shocks for it that will make it a competent commuter again without breaking the bank. If you want to do some painting and stuff for your own amusement well, that's up to you. But it'd be worth most entirely stock.
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