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SL350K1 - saggy forks!

Mikepacific60

Veteran Member
Joined
Aug 6, 2021
Total Posts
266
Total likes
17
Location
Brisbane, Australia
Hi all,
I’ve just rebuilt the forks from my SL350K1 (mine is an early K1) - details are in my project build elsewhere on this forum.
Interestingly, the springs are not held in by the screw-in cap on the top of the forks - the springs are retained by a circlip.
Each fork had two springs, separated by a nylon joiner.
When I reassembled the forks (noting that I never rode this bike or even had a good bounce on it before I disassembled the forks), the springs are, what seems to me, pretty saggy. Specifically, the forks collapse about 5/8” or so before the springs are even engaged.
I’ve searched around and can’t find the specified length of these springs.
I know some sag is called for, but this seems excessive, particularly when there is no load on the forks.
Scratching my head about what to do….I could make up some 5/8” spacers to go on top of the springs - important to note that it would be very difficult to get the retaining circlip in place if the springs / spacer was taller than the circlip groove. Alternative I could look for new springs of the required capacity (I weigh about 93kg). Not sure if new springs to suit my forks (33mm tubes) are even available. The bottom couple of coils on the lower spring actually wind in a bit tighter than the main body of the spring…ie the measurement across the bottom of the spring is narrower than the rest of the spring).
Appreciate and thoughts or actions people gave done in this situation.
Cheers
Mike
 
Oil will not change the droop in the forks due to sacked springs. It's a difficult issue, as good springs will probably be pricey and adding a spacer (but maybe 1/2" instead of 5/8" to make it easier to reassemble) would work but how will it feel? Forks can't be expected to ride at the top of the travel all the time of the wheel would not have movement available to drop into low spots while riding, but you don't want excess loss of spring-controlled travel either.
 
The only number given is 6.7" of travel. So: assemble a fork w/o the springs and measure the total travel. assemble the forks w/springs and measure assembled length with the fork in contact with the spring. Subtract one number from the other and see what that answer is.
It would be very weird to have a free zone in the fork travel where there's no spring action but anything is possible.
I don't find any offerings for new springs in a quick check on Google so likely they would need to be custom made.
There's nothing wrong about using a spacer for setting sag but this doesn't sound like what you're dealing with. Measurements above will help.
 
the forks collapse about 5/8” or so before the springs are even engaged.

This sounds like the springs are not the correct length for this particular fork or somethings missing from the internals. There shouldn't be that gap there like that. Sorry if it was brought up in your build thread, but what is the history of the bike? Just wondering if a previous owner put in the wrong springs before you bought it or there is a internal part missing?
 
Hi all,
Thanks for the comments.
I’ve looked closely at the exploded diagram on CMSNL - all the parts that should be in my forks are there.
I have noted one thing though - maybe the fork stanchions have been replaced at some time. In the parts diagram the forks step down between the lower and upper triple tree, whereas my fork stanchions are parallel all the way down. All the new parts I purchased fit the stanchions as they should.
Maybe the stanchions have been replaced at some point and the replacement ones are a little bit longer?
I’ve circled where the forks step down on the CMSNL diagram.
20A46458-575B-41C4-9EAD-66ED89753433.jpg

I’ve attached a photo of my bike when I got it…no non-standard fork length issue there (at least not to my eye):

3E778F00-89CA-4F5C-9A32-CC829AB16FC6.jpeg

I’ll do some more research…..
Cheers
Mike
 
That is interesting about the top of the fork in the parts diagram. I just looked at the K2 diagram and they are just straight, I wonder if they have been switched out at one point in the bikes history? Anyone else on this site with an SL that could maybe know a bit more about it or take some measurements?
 
I've got my K1 on the lift and just looked again. Straight tubes top to bottom. Ser # 2047051.
You're front end looks correct. Wish mine looked more like your beginning point.
201_5121.jpg
Yeah, the mufflers are attached to the swingarm.
 
Very interesting that Jim’s forks are parallel…..my SL K1 is an early build 202***
As it turns out I have the wrecked forks off the bike where I got my “dirty” engine. That K1’s s/n is 302***. Interesting differences in those forks….35mm tubes and the axel mounts use four bolts per side. Contrast to my forks with 33mm tubes and two axel bolts per side (Jim’s looks to be a two bolt version as well).
I just hacksawed the tops off the wrecked (35mm) forks (the tubes are completely beyond saving) to extract the springs….only one spring per fork…
Perhaps Honda had a few iterations of K1 forks.
Cheers
Mike
 
Oh, wasn’t aware of that…I thought it was a K1 as it had a 19” front wheel.
Just to show what those forks look like (I commented above they were beyond help) - this is after I hacksawed the tops off to get the springs:
BF860710-FDB2-4C6F-94A5-21365D738D76.jpg

Now there is a example of forks beyond help!
Cheers
Mike
 
Yeah, bit of a polish up - I’d probably need new seals as well!
Haven’t checked the springs as yet, but I think you are correct in that they likely won’t fit.
Cheers
Mike
 
My SL350 has (had) a saggy front as well. When on the side stand the forks would fully extend, and when the bike was standing, the forks would compress about 1.5” under it’s own weight. I applied the old ‘air over hydraulic’ method by inserting a tyre valve stem in the fork cap and adding just enough pressure to extend the forks under the bikes weight.
There were a few bikes back in the day had that system.
 
Hi Gazzweld,
Yes, I remember that trick well from my trail riding days in the 70’s and 80’s.
I had been giving that option some thought as well….wouldn’t need much pressure…
Cheers
Mike
 
The CM400/450 and some other models used the air assist forks. 1 bar or 14 psi is the limit for those.
They also use an interconnect hose so the pressure is balanced between the 2 forks.
 
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