CB750 wallow on high speed sweepers or bumps

[SirFallalot]

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

[Shaft]

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

[jaffa90]

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

[MCN]

Spension/Head Bearings/Shite tyres/Wallowed road.
____________________
Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[SirFallalot]

[to v or not to v]

id try lifting the forks back up that 1cm, just to see how it affects the wobble.
____________________
current bike Yamaha Thunderace.
Moto Guzzi V7.

[Nobby the Bastard]

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."
Triumph Sprint ST 1050

[A100man]

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

[redeem ouzzer]

All steel framed bikes do this.
____________________
Be a REAL MAN!

[stevo123]

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.

[SirFallalot]

Thanks for advice
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
____________________
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

[sickpup]

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.

[MCN]

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.

[Bru]

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

[SirFallalot]

[Bhud]

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

[SirFallalot]

[chriscrane]

I suggest https://www.quotemeless.co.uk/funeral-plans
____________________
c crane

[jaffa90]

[Copycat73]

[xX-Alex-Xx]