Topic: Police CB650PZ

[TripleDeuce]

Hey hush and soos, If either of you get a chance could one of you measure the distance between your fork seal and the bottom of the tree? It seems like my forks are a lot lower (shorter) than they should be.






Sorry about the hijack.

[Hush]

morning triple, when I put my forks in I always just clear the top of the upper fork clamp (tree).
If your poke higher say up to the bottoms of your handle bars then you can just release the clamps and drop them back down about half an inch.
If you mean from the lower part of the triple tree, I'll get back to you after I have some sleep.

[Soos]

Hey hush and soos, If either of you get a chance could one of you measure the distance between your fork seal and the bottom of the tree? It seems like my forks are a lot lower (shorter) than they should be.

Sorry, can't tell you what the "stock" ones should be.
I'm not about to swap back to a single disk for a measurement... sorry.

I "upgraded" to dual disks using '79 cb650 fork tubes(and springs), and DOHC 750 lower legs with the dual caliper/disk setup.

So I cannot guarantee any measurement I gave would be accurate for what you are looking for.
Not to mention I have some 5/8 spacers on top of my springs......





l8r

[Hush]

OK Triple, you are in luck as I have my forks off for rebuild.
From very top to seals (so whole chrome part in picture) =380mil or 38 centimetres or 15" inches.
White parts are my lower tubes, from end to end without counting the lower studs=15"inches.
From top to centre middle (which is where middle of axle would be) =30"inches.
Hope that helps ya figure out if ya springs are shorter or what, measurements were taken fully assebled so my springs are in and compressed ready to fit.

[TripleDeuce]

I've got 12.5" from the top of the fork tubes to the seals while on the side stand. Me thinks my springs are weak. I really like the stance she has, and it has never bottomed out on me, so I may just leave her alone til something breaks. 

[scunny]

CB650Z  370mm with bike on side stand

[TripleDeuce]

Looks like I need to buy a metric tape measure 

[Soos]

370mm = 14.5669 inches.

(370 X 0.03937 = 14.5669)


Nah, just need to know the formula for converting metric to american"standard"...


standard my arse.
There is what.. 3? 4? countries IN THE WHOLE WORLD that use the american "standard" as their normal measurement?
Sad IMO.


But anyways, mabey your springs have been cut?
Are yours air assist forks?




BTW, mine measure 13.5" from the seal to the top of the fork tube with the bike on the sidestand.
12 3/4 inches with me sitting on the bike from the top of the seal to the top of the fork tube.
I have yet to bottom out either.



l8r

[Hush]

Wouldn't hurt to change out your fork oil, mine was like silver water but I only broke them open cos fork oil was running down the legs and getting all over my twin front discs, when seals go they don't come back.
Easy to do with them on the bike, just undo the wee nuts at the base and let that bad stuff go, replace wee screws back into forks, unscrew the tops and add about 3/4 cup of new fork oil to each, it's more important that you get the same in each than the amount which you can play with later.

That's quite a difference from my standard forks to yours so perhaps you are right and the PO cut them, no biggie if it works for you.

[Frankenkit]

so.... if I were wanting to go with shorter progressive springs, like -1" would I just put the bike up on a lift to support the front end, unscrew the caps in the top, pull the old springs, and drop in the new ones?  Is that really all there'd be to it? I'm just thinkin' bout this because I get some sizeable front-end dive when I hit the brakes anywhere above a slow drift-in stop, and it's kinda unnerving sometimes, esp. considering how firm the rear end feels with the new shocks I have there.

[Hush]

Probably have to remove (temporarily) your handle abrs cos they are straight above the fork tops, I tend to hang a rope or bungy from the roof and let em hang while I play with the forks.
I've never done shortened springs, probably as easy as finding a shorter spring, remove bars, undo tops, remove old springs, slide in shorties......well that's how I'd do it.
You wouldn't even be disturbing the fluids unless you really wanted to change that at same time.
If you look at Clymer manual page 270 there is a very good exploded view of my old 79 forks, you can see the main long spring is just the last thing you slide in.
Does your bike have air assisted front forks? my 82 Custom did, they would be a different beast alltogether I'd guess.
Page 267 gives instructions for all models and yours doesn't look much dif to mine, even might get away with leaving the bars on while you did it.

[MikeB]

so.... if I were wanting to go with shorter progressive springs, like -1" would I just put the bike up on a lift to support the front end, unscrew the caps in the top, pull the old springs, and drop in the new ones?  Is that really all there'd be to it? I'm just thinkin' bout this because I get some sizeable front-end dive when I hit the brakes anywhere above a slow drift-in stop, and it's kinda unnerving sometimes, esp. considering how firm the rear end feels with the new shocks I have there.

I have replaced springs in a few of my dirt bikes over the years and that's all I had to do
would think most forks would be the same ?

probably a stupid ques. but why shorter springs would they be stiffer ? couldn't you just go with a stiffer rate spring ?
only reason I ask is wouldn't you need a spacer with the shorter spring ?

[TripleDeuce]

Hush, your bike came with dual rotors? Lucky cops, my front brake is like squeezing a hand full of grapes. 

[Hush]

Mine aint that hot right now Triple, but once the fork fluid stops dribbling all over them I expect a significant improvement.
Yes it was a requirement for the cop bikes, gave them an edge and the Officers a little insurance, if you want a set hunt for an old Police bike.

[Frankenkit]

MikeB, shorter springs cuz I'm shorter and I'm thinking (?) I can slip the tubes down further in the fork bottoms then, instead of trying to have my forks up through the triple trees like I do.  Then again, the fork tubes up thru the trip. trees is working for me ok right now, maybe I should just stick with stock spring size, but progressives or whatever anyway.  I'm a light little thing, but I still need my suspension smooth.

[Hush]

Fitting shorter springs will lower the front, and that would be the only thing you would need to change out....the springs.
Not sure if you can just cut your old springs like the boy-racers do here on their cars, one of the chopper making companies or perhaps a bike customising shop could tell you if they can cut yours down, if they could you would need to keep the bottom of the spring stock as they taper there, the top looks just same size most of the way down.

[MikeB]

Hey Hush
is this a safe condition to have your springs shorter than the fork tube ?
if the front wheel became unloaded wouldn't you have X" of freeplay in your suspension ?

I'm kinda curious how this might effect handeling ? I would also like to lower my front but with the air asist forks they don't push up through the triples very much at all

all my dirt bikes had springs that had to be compressed slightly to get the fork cap back on
but I guess these bikes dont do too much off roading to get the front wheel off the ground 

[Frankenkit]

yeah, I'm thinkin' I'll just go with the solution I have now.

BTW, MickeyX and I rode ALL DAY today and it was GREAT! 

[Hush]

I know stop skiting .
OK I had a pretty good day myself, not sure weather it was Scunny tipping me to rebuild and grease my advancer or if when I put it all back together I moved the pulse generators ever so slightly forward and got it in the sweet spot?
Anyhow I'm giving the credit to my Southern mate Scunny, good call brother good call, the bike is just unrecognisable speed wise, twist and go......very very quickly!
The rebuilt forks performed well with no bucketting in the corners and I'm actually getting to drop the bike a bit further over on corners.
Still can't get over her improved performance....ZOOOOOOOOOOOOOOMMMMMMMMMM.
Of course I wouldn't be Hush without a small down side, bike developed a noise, sounds like I got a leak at one of my headers, but small price to pay for such a great day riding at decent speed for a change, I seriously did not realise how retarded her performance was, now it's like twist and hang on ha ha ha...........wish it hadn't been so windy as getting to top speed wasn't an option today with gale force winds about.
Oh yeah do you know what happens when you hit a false neutral at 70mph? yep that's right RED LINE!! HA HA HA LOVIN IT.

[Frankenkit]

Maybe I should check out my advancer and see if I'm retarded, too.

[MickeyX]

I know better than to reply to that one. I gotta live with her. 

[Soos]

Good choice MickeyX!!




And as for "too advanced or retarded" you can do it by ear(if you have a good ear for subtle rythms)

Advance it(turn the plate counterclockwise) until it tops out on RPM, then back it off a bit.
It will put you on the edge of useful, but you should notice a power increase.
But if it's running and running good, mabey you don't want to mess with it.

I do it just to eek out the max power I can.
But I love tweaking the fine details.





l8r

[Frankenkit]

I dunno, if it qualifies as 'quick and easy' I could probably do it in an afternoon.

[Hush]

Your 650 is probably running OK anyway Kit, mine was lacking top end power and now it has that and a Hell of a lot of pick-up on acceleration, man this thing is zippy as, I'm in love all over again.
Took it easily to 70mph today even with evil cross wind threatening to dump me into the ditch but she had plenty left after that just I couldn't hold her in straight line against wind.
Oh yeah bike fired right up even though she has been sitting in shed minus forks for a few days so battery probelms are dare I say it....................GONE!
With tires bedded in and forks finally working I've actually got some handling, I used to feel like the juggler at the circus trying to balance a bike made of jello and slowing to near stall speed on corners cos she wouldn't go round them.
Just in time for Winter too, ah well we have plenty of nice Winter days here in NZ so not too worried about getting no road time.
Will concentrate on getting Jaffas' bike dialed in now so she can learn to ride it for next spring, not keen to have her wobbling around in winter on something that feels a light as a pushbike but has kick of a GSX1100 up to 50 mph.

[Frankenkit]

oh yeah, 65 is easy and sweeeet!