Topic: New Shocks came in

[mlinder]

Ordered some progressive rears, they came in today.
12 Series 13" - 12-1204B
Springs - 125/170lb

Will let you know how I like them, though to be honest, damn near ANYthing would be better than the (original, 38 year old?) stock parts I have on now.
Black spring, black shock, looks mean as hell.

Doing a fork seal change too this weekend. Should be a very nice difference, all told.


(by the way, Z1 again gave excellent service. Stuff got here damned quick.)

[Chris Liston]

based on my experience they really make a huge difference.  I wound up replacing for the fork springs with progressive a week later has the bike was a little mismatched between front to back.

[mlinder]

based on my experience they really make a huge difference.  I wound up replacing for the fork springs with progressive a week later has the bike was a little mismatched between front to back.

I've got fronts as well.
Just the seals are shot, so have to those too.

[EBCB]

How much were they?

[mlinder]

Eh, $240ish shipped?
And the fronts were, I dunno, 60 bucks shipped or something.

[mlinder]

The difference is farkin huge. I may have got overzealous on the spring strength, considering I'm in the process of lightening the bike. We will see.

[mlinder]

OK, difference is night and day.
It feels like a completely different motorcycle altogether.
While the 145/190s are a tiny bit stiff, I think it will suit my riding style. I'd recommend one or two stiffnesses down (the 105/150's or 125/170's) for the majority of people (the 105's being 'stock' for out 750's, the 125's being 'heavy duty'), but if you want really tight suspension, these 145's are the way to go (they are also listed as the 'heavy duty' springs for the 650 sohc.)

[mlinder]

Well, after some spirited riding yesterday, I've noticed that with progressive all around, and avons at both ends, the frame is decidedly 'flexible'.

The engine is going to come out this winter for some upgrades, and I was going to re-powdercoat the frame.
I'm thinking I may do some frame stiffening work while I'm at it.
Anyone have some pictures of where gussets and extra frame stiffening components have gone for 'racing' versions of my bike? (cb750).
I can prolly figure most of em out, but would just assume follow a 'proven' pattern.

[bwaller]

Probably best to do the obvious upgrades first. Swingarm bushings, change to brass and replace the pivot tube, wheel bearings and also tapered steering head bearings. Check spokes too.

It's your choice, but the idea with suspension is to be compliant enough to keep the tire surface in contact with the road as much as possible, but if you're sprung too heavily that contact may well be disrupted because of bounce and may be why the bike feels "flexible."

It's a given that those new shocks will be an improvement over stock which were just there to hold the springs in place!

Just a thought.

[mlinder]

No problem with traction. It's the amount of traction that is showing me just how flexible the frame and swingarm is.
Took some really heavy sweepers at some pretty high velocities yesterday, and the suspension and tires worked wonderfully.
And, it's true, the more load on the frame, the stiffer it got, but quick directional changes really showed some torsional flimseyness (i.e. the neck and and swingarm are NOT at 180 degree angles to each other in fast changes).
I've got new tapered steering head bearings on the way, and looking for a good supplier of bronze bushings.
I fear these will only exacerbate the frame-flex though.
I've been looking at this page:
http://www.tonyfoale.com/Articles/Frame.mod/KawaMods.htm

BMW also had a removable brace from headstock to swingarm on their r90s racer. Apparently this thing helped immensely (I had the pleasure of knowing one of the racers somewhat personally, and he said this improved rigidity immensely.
I may try something similar.

[rhinoracer]

It's just my opinion: Chassis flex isn't that bad unless you can't hold a line through a curve or you're trying to shave the last 1/10th of a second from your lap times on the track. In fact it's one of the benefits of steel frames vs aluminum.

You're right in changing steering head bearings and swingarm bushings first, that could be the reason of the loose feel of your frame.

If I was seeking to increase frame rigidity I'd go and build a new ChroMoly frame and shave a few pounds in the process rather than sinking money into strengthening a 38 year old fatigued steel frame.

My experience (in off-road racecars not bikes) is that if you try and reinforce a fatigued mild steel section of the frame, the new tubes are so rigid they would cause failure of the old tubes (crack them) during the first hours of the race.

...my 2 cents.

[mlinder]

As I said, it was the directional changes that got things fruity.
You make a good point about adding stiffness to a fatigued frame though.
I can either get used to the flex (I was used to it on my old beemers, actually, and it stopped bothering me after a short while), or, as you said, get some aftermarket frame.
But, who makes (basically) stock frames out of chromoly?

[bwaller]

Do you have any play in your swingarm?

I would contact Hondaman for this work, he started providing this service and can possibly save that tube and then machine bushings to fit. I recently had a set machined locally and I think it's likely you'll get a tighter fit. The problem with buying premade bushings is that they are machined with larger tolerances so as to fit everything. Hondaman can custom size em for you.

[750essess]

New bushing and bearings will help greatly.No one makes a frame any more to my knowledge. Seely and Dunstall made frames but are really hard to find. Chromoly isn't simple to build a frame out of it, your welding has to be top notch and needs to be heat treated afterwards to relieve stresses in the heat affected zone. Dom steel tubing is also an option, it doesn't require heat treating and is cheaper. I am having similiar problems. Although after tinkering with suspension settings it is much better, I still get some flexing in turns at higher speeds. Has a 600f4 fork with IKON shocks and new bushings bearings etc. I dont think I will mess around with the frame. You have to ask yourself just how much can be asked of a 35 year old motorcycle and when its time to stop modifying things and just ride it! LOL

[mlinder]

I am just riding it
But, I want to ride it faster...

bwaller, I'd love to have hondaman do that, but as it stands, the 750 is also my daily rider, so I can't really afford to be without it for any length of time.
I suppose I could rebuild the 350 engine... then do it....
Hell, I dunno.

[bwaller]

Maybe he offers an exchange, would save time.