Resend my activation email : Register : Log in 
BCF: Bike Chat Forums


CB750 wallow on high speed sweepers or bumps

Reply to topic
Bike Chat Forums Index -> The Workshop
View previous topic : View next topic  
Author Message

SirFallalot
Trackday Trickster



Joined: 25 Oct 2018
Karma :

PostPosted: 22:14 - 27 Sep 2021    Post subject: CB750 wallow on high speed sweepers or bumps Reply with quote

On my 96 CB750...
On high speed turns (100+) the bike tends to develop what I believe is called wallow,wherim the rear end seems to lean up and down, although sometimes looking at the front end it looks it it's the culprit weaving left and right slightly.

First I thought it was the square tyres and old shocks, now replaced with BT32 and mid range YSS with default preload and rebound in the center. Forks are from a CBR F3 dropped 1cm as they were longer than stock, the bike turns quite sharply and it was a big improvement compared to stock.

At the same time I refit the useless screen due to a cross country trip.

The wallow is still there, either when leaning at high speeds, or at lower speeds (80-90) if a slight bump is hit (those shallow things going across motorways for e.g.).

It's not an uncontrollable tank slapper, but it's not confidence inspiring and a bit butt clenching. I am going to try removing the screen before my next run but do you recon it's just a limitation of the bike/twin shock, bad setup or the screen?
____________________
Lexmoto Valiant 125; 94 CB400; 96 CB750F2; 81 CB750 (restoring, lol not gonna happen); 2001 ZX9R(It's about to go :c); 2012 R1200R; 2015 R1200RS
 Back to top
View user's profile Send private message You must be logged in to rate posts

Shaft
World Chat Champion



Joined: 27 Dec 2010
Karma :

PostPosted: 23:39 - 27 Sep 2021    Post subject: Reply with quote

It's a 25 year old UJM, which was probably based on very similar underpinnings to your '81 CB, how good do you expect it to be?

It certainly won't be a patch on your Kwak, but it was never designed to be, it was meant to be a cheap allrounder and the passage of a quarter of a century won't have improved things.

If you want to go mad, replace every chassis bearing and bush you can think of, but you will still be left with a relatively flexible frame and swing arm.

Or just live with it and enjoy the excitement of high speed wobbles, just like we all did back then.
____________________
Things get better with age; I'm close to being magnificent........
20 RE Interceptor, 83 Z1100A3, 83 GS650 Katana
WooHoo, I'm a Man Point Millionaire! https://www.bikechatforums.com/viewtopic.php?t=234035
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts

jaffa90
World Chat Champion



Joined: 06 Apr 2016
Karma :

PostPosted: 00:55 - 28 Sep 2021    Post subject: Reply with quote

I suggest,
https://funerals.reassured.co.uk/funeral-4?product_id=2&channel_id=3&advertiser_id=9497ff66-d65e-4275-8dc4-a5dce624b280&campaignid=2037998309&adgroupid=77348804815&creative=377949831986&keyword=funeral%20cover&matchtype=e&targetid=kwd-2710391916&gclid=Cj0KCQjw18WKBhCUARIsAFiW7Jx2zMA0oRbAXQosLjF1hM2HrnJjbukynVKnMHbxiiU1w59iaAG4HkkaAs4bEALw_wcB
 Back to top
View user's profile Send private message You must be logged in to rate posts

MCN
Super Spammer



Joined: 22 Jul 2015
Karma :

PostPosted: 04:15 - 28 Sep 2021    Post subject: Reply with quote

Spension/Head Bearings/Shite tyres/Wallowed road.
____________________
Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts

SirFallalot
Trackday Trickster



Joined: 25 Oct 2018
Karma :

PostPosted: 09:21 - 28 Sep 2021    Post subject: Reply with quote

Shaft wrote:
It's a 25 year old UJM, which was probably based on very similar underpinnings to your '81 CB, how good do you expect it to be?

It certainly won't be a patch on your Kwak, but it was never designed to be, it was meant to be a cheap allrounder and the passage of a quarter of a century won't have improved things.

If you want to go mad, replace every chassis bearing and bush you can think of, but you will still be left with a relatively flexible frame and swing arm.

Or just live with it and enjoy the excitement of high speed wobbles, just like we all did back then.


Ahah yeah that's the kind of answer I was looking for, I wanted to know if there's something that might need fixing, or if it's just a limitation of design, which is fine.It is quite exciting Laughing
____________________
Lexmoto Valiant 125; 94 CB400; 96 CB750F2; 81 CB750 (restoring, lol not gonna happen); 2001 ZX9R(It's about to go :c); 2012 R1200R; 2015 R1200RS
 Back to top
View user's profile Send private message You must be logged in to rate posts

to v or not to v
World Chat Champion



Joined: 24 Nov 2020
Karma :

PostPosted: 19:32 - 28 Sep 2021    Post subject: Reply with quote

id try lifting the forks back up that 1cm, just to see how it affects the wobble.
____________________
current bike Yamaha Thunderace.
its old and fat, but its a damned good ride. the bikes not bad either.
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts

Nobby the Bastard
Harley Gaydar



Joined: 16 Aug 2013
Karma :

PostPosted: 19:43 - 28 Sep 2021    Post subject: Reply with quote

I know that if you go under the bridge on the Keynsham bypass at 145 then the bike will pogo round the bend but that's because of the big dip in the road.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050
 Back to top
View user's profile Send private message You must be logged in to rate posts

A100man
World Chat Champion



Joined: 19 Aug 2013
Karma :

PostPosted: 19:47 - 28 Sep 2021    Post subject: Reply with quote

Recent MoT ? If not I'd check wheel bearings and S/A bushes..

mind you not sure how many 100mph corners I tackle these days..
____________________
Now: A100, GT250A, XJ598, FZ750

Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600
 Back to top
View user's profile Send private message You must be logged in to rate posts

redeem ouzzer
World Chat Champion



Joined: 06 Oct 2015
Karma :

PostPosted: 20:36 - 28 Sep 2021    Post subject: Reply with quote

All steel framed bikes do this.
____________________
Be a REAL MAN!
 Back to top
View user's profile Send private message You must be logged in to rate posts

stevo123
Nitrous Nuisance



Joined: 10 Aug 2004
Karma :

PostPosted: 12:39 - 29 Sep 2021    Post subject: Reply with quote

As mentioned already there will be some frame flex to blame. You could adjust rear rebound damping a bit higher and see if it helps you as well if you have luxury.
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts

SirFallalot
Trackday Trickster



Joined: 25 Oct 2018
Karma :

PostPosted: 08:14 - 02 Oct 2021    Post subject: Reply with quote

Thanks for advice Very Happy
Mot a month ago, I had bearings checked too and no play.
I think removing the screen helped it, not sure if because it was applying pressure to the handlebars...or because without it I go much slower. B roads are much better but A and M, damn pain in the neck Laughing
____________________
Lexmoto Valiant 125; 94 CB400; 96 CB750F2; 81 CB750 (restoring, lol not gonna happen); 2001 ZX9R(It's about to go :c); 2012 R1200R; 2015 R1200RS
 Back to top
View user's profile Send private message You must be logged in to rate posts

sickpup
Old Timer



Joined: 21 Apr 2004
Karma :

PostPosted: 10:55 - 04 Oct 2021    Post subject: Reply with quote

Was the springing and damping modified on the forks when fitted, I imagine the CB750 is a bit heavier?

If not this could be amplified by the rear end working correctly with the new tyres and YSS shock.
 Back to top
View user's profile Send private message You must be logged in to rate posts

MCN
Super Spammer



Joined: 22 Jul 2015
Karma :

PostPosted: 18:05 - 04 Oct 2021    Post subject: Reply with quote

I had the use of a 1990s Suzuki 750 in South Africa.
Tons of grunt but hopeless in a corner.
Auld bikes were only made for straight roads I think.
____________________
Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.
 Back to top
View user's profile Send private message Send e-mail You must be logged in to rate posts

Bru
Trackday Trickster



Joined: 01 Feb 2007
Karma :

PostPosted: 16:51 - 07 Oct 2021    Post subject: Reply with quote

My GPX600 makes its own bends, the twitchy little bastard.
 Back to top
View user's profile Send private message You must be logged in to rate posts

SirFallalot
Trackday Trickster



Joined: 25 Oct 2018
Karma :

PostPosted: 23:34 - 10 Oct 2021    Post subject: Reply with quote

sickpup wrote:
Was the springing and damping modified on the forks when fitted, I imagine the CB750 is a bit heavier?

If not this could be amplified by the rear end working correctly with the new tyres and YSS shock.


Yeah 30kg heavier, I thought the CBR forks would require new springs too, but after the conversion the forks became similar to my CB400 with aftermarket springs, my assumption was it had heavier springs in already.

Bru wrote:
My GPX600 makes its own bends, the twitchy little bastard.


Laughing
____________________
Lexmoto Valiant 125; 94 CB400; 96 CB750F2; 81 CB750 (restoring, lol not gonna happen); 2001 ZX9R(It's about to go :c); 2012 R1200R; 2015 R1200RS
 Back to top
View user's profile Send private message You must be logged in to rate posts

Bhud
World Chat Champion



Joined: 11 Oct 2018
Karma :

PostPosted: 01:50 - 11 Oct 2021    Post subject: Reply with quote

I think you will have to change that default setting on your new shocks. Do they have enough travel to be able to do their job, is the spring rate suitable and available to you, and what about rebound damping. Cornering at over 100mph is asking a lot. Dave Moss has a lot of material on this stuff. Personally, I would just play with it, set preload so there's 30-ish cm static sag, then see if there's an improvement 2 clicks in or 2 clicks out on the rebound adjuster(s). From there, fine tune
 Back to top
View user's profile Send private message You must be logged in to rate posts

SirFallalot
Trackday Trickster



Joined: 25 Oct 2018
Karma :

PostPosted: 08:59 - 11 Oct 2021    Post subject: Reply with quote

Bhud wrote:
I think you will have to change that default setting on your new shocks. Do they have enough travel to be able to do their job, is the spring rate suitable and available to you, and what about rebound damping. Cornering at over 100mph is asking a lot. Dave Moss has a lot of material on this stuff. Personally, I would just play with it, set preload so there's 30-ish cm static sag, then see if there's an improvement 2 clicks in or 2 clicks out on the rebound adjuster(s). From there, fine tune


Thanks, the bike felt so much better than stock in the twisties that I didn't bother with settings beyond def or sag Rolling Eyes , I'll try measuring it and playing with the settings a bit next time I take it out Very Happy
____________________
Lexmoto Valiant 125; 94 CB400; 96 CB750F2; 81 CB750 (restoring, lol not gonna happen); 2001 ZX9R(It's about to go :c); 2012 R1200R; 2015 R1200RS
 Back to top
View user's profile Send private message You must be logged in to rate posts

chriscrane
L Plate Warrior



Joined: 23 Oct 2021
Karma :

PostPosted: 13:46 - 23 Oct 2021    Post subject: Reply with quote

I suggest https://www.quotemeless.co.uk/funeral-plans
____________________
c crane
 Back to top
View user's profile Send private message You must be logged in to rate posts

jaffa90
World Chat Champion



Joined: 06 Apr 2016
Karma :

PostPosted: 17:31 - 23 Oct 2021    Post subject: Reply with quote

chriscrane wrote:


Copy cat Rolling Eyes Read the script / replies.
 Back to top
View user's profile Send private message You must be logged in to rate posts

Copycat73
World Chat Champion



Joined: 11 Jan 2013
Karma :

PostPosted: 20:57 - 23 Oct 2021    Post subject: Reply with quote

SirFallalot wrote:


Thanks, the bike felt so much better than stock in the twisties that I didn't bother with settings beyond def or sag Rolling Eyes , I'll try measuring it and playing with the settings a bit next time I take it out Very Happy


been there done that ..... took the honda to some one who knows what he is doin.. cost £50 .. but stopped it wallowing round corners and sweepers with undulations...
____________________
Whatever I post I have no citation and no intention of providing one..
caveat emptor
 Back to top
View user's profile Send private message You must be logged in to rate posts

xX-Alex-Xx
World Chat Champion



Joined: 12 Sep 2019
Karma :

PostPosted: 21:27 - 23 Oct 2021    Post subject: Reply with quote

jaffa90 wrote:
chriscrane wrote:


Copy cat Rolling Eyes Read the script / replies.


It takes a lot of reading to get to the third post Laughing
____________________
DILLIGAF
 Back to top
View user's profile Send private message You must be logged in to rate posts
Old Thread Alert!

The last post was made 2 years, 156 days ago. Instead of replying here, would creating a new thread be more useful?
  Display posts from previous:   
This page may contain affiliate links, which means we may earn a small commission if a visitor clicks through and makes a purchase. By clicking on an affiliate link, you accept that third-party cookies will be set.

Post new topic   Reply to topic    Bike Chat Forums Index -> The Workshop All times are GMT + 1 Hour
Page 1 of 1

 
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum

Read the Terms of Use! - Powered by phpBB © phpBB Group
 

Debug Mode: ON - Server: birks (www) - Page Generation Time: 0.10 Sec - Server Load: 0.46 - MySQL Queries: 17 - Page Size: 115.02 Kb