Kawasaki Sportsbike Riders Club - Australia - Online Forum

Hello Gents, this is a bit involed but still a learning experience......

I have Promecha modded forks in my REX and thought you might like some update info. It was modded along the lines of MCN project ZRX so 0.92 front springs and Promecha "revalve", shocks revalve only. I have done about 5k since mods done, my original complaint of the forks was bottoming,wallowing and harsh etc, after 5k my thought are still harsh, but big improvement on the bottoming (although i did raise the oil height 5mm), no wallowing, steers a lot better BUT still skips mid-corner when encountering multiple small mid-corner bumps (forks only, shocks are ok,just, but ok none the less). Now with reducing rebound the mid-corner skip improves, but, not enough and have run out of rebound adjust at FULL SOFT, so call Promecha with the thought of going to next lighter fork oil so as to have further adjustment, now, Promecha at time of revalve said using 10wt oil, NOW they say they used 2.5wt OIL !!!! ( i have never seen oil this light in convertional forks before!)

So, have any of you encountered any of this and have you found a "fix"? Backing off rebound is not causing anything dramatic in other areas, compression is still mid-adjustment. Promecha say they use 14mm fork spring preload (fitted) i am thinking too much with maybe too soft spring, although maybe they have found this is best compromise whilst still using the original Kawi (Showa) piston on this "sealed" cartridge.

Has anyone anything further info. on Racetech modded ZRX forks? did you do both compressions and rebound pistons and what springs?

Cheers to all,

Emmet

Mate I think you are a little confused. You dont get wollowing from the front, wollowing is a rear spring/shock issue.
I just cheacked mine, & I have 7 rings showing on the spring preload, & 10 clicks out from fully in on the rebound, I dont have any front end problems. Im 90kg geared up.
The wolloing I still get [in the rear] but I think Im expecting way to much out of the KYB shocks.
Put a cable tie on your fork leg & see exactly how much travel your using. I have never bottomed out , only on the rear when the Mrs is on & we are geared up, I can push pretty hard with her on the back, I do whoever run the rear spring preload 1 down from full hard. 2 down when Im on my own.
Addng fork fluid isnt a good thing as you will get hydrolic lock & loose fork travel..[bad move] If anything with my race bike we run 10mill less, so as the fluid gets hot its got room to expand. This bottoming out you speak of has me intreeged????

Thanks for the reply Sman, rear i am running same as you. Front i generally am at 10 out from full hard rebound and 8 out on comp, it bottoms (as measured at fitted zip tie on fork leg and you can feel it) on bigger bumps (BIG) at higher (160k) speeds, with fork oil height raised it acceptable, i only added 5ml, i didnt dissassemble to measure what Promecha already had. It skips on mid corner small multiple raised or dipped bumps,it doesnt let go (these are mainly tight downhill stop-go corners) but does try to run wide as you would imagine, it did the same thing on standard forks on these bumps (same corners although now at higher speed than before). I originally had rebound on fork at 8,went 9 better,went 10 better etc, Peter said he used 10 wt oil so i thought i might try 7.5 so i had some more rebound adjustment, i spoke to him a second time to run my thoughts by him, he now says used 2.5 wt oil......so what to do, live with it....pull apart and find out exactly what he did...if he is not accurate with the oil weight i am wondering what oil height he gave it. A common trick (apparently) with these is to run 15wt with stronger oil, you (apparently) end up with settings around where you and i (and Ken Wooton) have. At the moment i am riding my z900 a lot running in a new engine so not too concerned with the Rex, it s a lot better after Promecha than before but only really on the bgger stuff, its much the same on the small choppy stuff, i would liek to keep it good on big but improve the choppy small stuff. My background (100 years ago) is A grade motocrosser,bike & car mechanic, so i have some understanding of suspension,no expert by any means but some knowledge) the choppy stuff feels like too much rebound and/or soft spring with too much preload (apparently we have 14mm internal preload according to Promecha PLUS what you and i adjust in),either way just playing with it. Its worse with a bag on the back,its worse on down hill stop/go corners etc, maybe i am chasing something that is just design flaw in these forks,maybe expecting too much and just have to live with it OR maybe spend up and fit different cartridge or pistons via mods etc. In any case its really nice to be able to run all this by similar like minded RIDERS.

First question before i make any suggestions is what is your rider sag set at?

Strika wrote:First question before i make any suggestions is what is your rider sag set at?

Hi mate, 30mm front 20mm rear, 88k rider with gear on.

Ok, i am unsure what has been done internally, but with 30mm front rider sag, what % of the available pre-load is used. Eg,if it is half avail pre liad used the spring is too light. If you are using 5% of avail preliad the soring us too heavy. Udeal is about 1/3 of avaulable preliad.
Pls forgive typing, i am wonky ATM.

Angry Emmet wrote:

Strika wrote:First question before i make any suggestions is what is your rider sag set at?

Hi mate, 30mm front 20mm rear, 88k rider with gear on.

I have always set my sag to be the same, front to rear........

I normally set mine close too. But, i think the ZRX has perhaps less travel, as i had mine at about 20mm to get it feeling right.

Thanks Guys.

Front preload adjust is around 5 rings showing, dont forget Mr Promecha says he sets it up with 14mm internal anyway, so if i understand him we need to have our original adjusters full out to have only 14mm, any further in means we are adding more.
Preload on rear is on pos 2, works ok, bottoms now and again but soaks up the choppy stuff decently, comp and rebound on shocks are on pos 2 as well, comp on shocks makes very little of no differenct from what i feel. Comp and rebound on forks makes a lot of difference but seems like only in low speed shaft speeds, what i am thinking is less rebound to improve on the choppy stuff, currently pos 10 out from full hard, comp is also on 10 out from full hard, i also would be likeing less preload and stronger spring in forks,maybe a 0.95 BUT Promecha have probably already tried it and found you need different valving and/or pistons,not sure. Like i say he has told me 10wt fork oil when revalved, then told me he used 2.5wt this week, i am wondering what he did now. Forks are ok most places BUT are harsh on sharp edged bumps, skip on multiple small bumps in mid-corner (these are stop/go low speed but high lean angle corners), bumps like you find in the down hill tight corners over the top of Thredbo/Alpine Way and down the North side of Hotham. I could always slow it down but you dont find the bump til mid corner so is a bit late to slow! My original intention was (may still be) to go Promecha, ride 5k then go Racetech to see how much i can improve it, i love the learning experience with it all, ALMOST as much fun as riding it! If i can get the forks good enough i might motivate myself to invest in better rear shocks. Oh, i reckon the rear might have too hard a spring also, feels like soft-ish spring with too much preload as well. Bare in mind my experience with all this is dirtbike related so the harder spring with less preload might be a dirt bike trick and not roady stuff, although dirtbike knowledge had got me around E.C. in a 1.445-1.46 on a '04 Blade with similar times on last bike (1098 Duc), but i dont reckon i could get under 1.55 on the Rex, not likely to try either as i have one eye less these days!

Not knowing what has been done, it souunds like it lacks low speed rebojnd and compresion and has too much high speed compression.

Strika wrote:Not knowing what has been done, it souunds like it lacks low speed rebojnd and compresion and has too much high speed compression.

Ah, but if i add a click or two of either the skipping is worse...

That only adds support to my comment.

Strika wrote:That only adds support to my comment.

I'm confused, you think sounds like a lack of comp/rebound, if i add some the problem is worse, wouldnt that then mean less is needed? I mean the more i add the worse it skips...

No, not oil levels or weights just sounds like the valving is too little on the low speed circuit while too much on the high speed circuit. Revalve being the solution.

Strika wrote:No, not oil levels or weights just sounds like the valving is too little on the low speed circuit while too much on the high speed circuit. Revalve being the solution.

thanks mate, yep, sounds like valving might be it. But i wondered if it not inherent etc.