Tail end twitching on GSX750F

[sakean99]

I have recently acquired a '97 GSX750F with 18k on the clock. But it has some screen & clock surround damage so the mileage is not necessarily correct.
I notice that linear road repairs/ white lines etc cause the back end to twitch as I drift across them. Last time I felt anything like this was on a '55 250 Beezer C11 with knackered swinging arm bushes. That used to also pull sideways under acceleration (such as it could manage). Now the Suzi has a tad more power but accelerates as straight as a die.
Is it normal for modern bikes with their pointy profile tyres to be sensitive to longitudinal ruts or is something likely to be worn (besides the rider)? All suggestions, including the rude ones(provided they are funny) are welcome.
Does your bike stick to your chosen line like a train or can you feel it twitch slightly nervously across the reinstatements & road markings?

[Dom_]

I find that on my rs50, it runs 90 front and 100 rear, which is bloody skinny. Over white lines mine seems to do the same as you are describing, i just put it down to thin tyres and the white line. But i'm unsure now

[Scotsman37]

Have you tried the testing the back/front wheels for side ways movement while on say a paddock stand. If there's a sign of sideways movement or sound of grinding coming from the wheels and, if so, then it's a case of replacing the wheel bearings with a set of new ones.

Also, maybe the swing arm needs to be topped up with grease.

Here's a link for finding part no.'s so as to get the correct OEM replacement parts for your bike.

https://www.bikebandit.com/partsbandit/oem~submit_from_stage~1~section_dept_id~1.asp

Or you might like this site for 2nd hand parts;

https://www.cheshiremotorcyclesalvage.com/acatalog/

Yes, at times white lines particularly when you're filtering through traffic when the road is very wet along with cat eyes on road. I personally hate those road repairs done after laying cable for NTL because when you go around corners and the surface happens to be raised in the middle of the repair it's a freakin' nuisance!

[Kickstart]

Hi

They do tend to be sensitive to it. However check the tyre pressures carefully (and also check with the tyre maker as they might specify quite a different tyre pressure for that bike than the bike maker does). Check for play in the wheel bearings, steering head bearing and also the rear suspension linkages. Swinging arm bearings are possible, but they rarely seem to wear. Also have a play with the suspension settings, and probably best to set them back to standard as a good starting point.

All the best

Keith
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[BLOFLY 636]

what keith said my old ZZR 250 did that when I would tip it from one side to another, felt like the rear tyre was sliding out like Gary Macoy style but it turned out to be the rear wheel bearing on it's way out
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[sakean99]

Thanks everyone, lots of useful ideas there. I have tried to flex the rear suspension when on the main stand & it did all feel very solid. Tyre pressures seems a likely one & I will check them next.
I'm due an MOT soon (hence low price of bike!! ) so I'm trying to sus out problems before I get slammed by Mr Local Bike Shop.
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[bish777]

Make sure headrace bearings are tightened to the right torque!

Incorrectly torque headrace beaings can give the rear end a vague or twitchy feel.

[sakean99]

Well, I couldn't find anything wrong & neither did the local bike shop. I now have a new MOT Thanks for all your help. I guess I am just getting more sensitive & nervous as I get older & closer to the grim reaper! Sides of the tyres have hardly ever even got warm - yet!
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[Scotsman37]

Sometimes the wash off from fields that have been sprayed with chemicals/manure get washed out onto nearby roads making them slightly slippery to travel on.

Well done on the MOT !

[BLOFLY 636]

forgive me if this is a stupid question but what exactly is an MOT?
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[Scotsman37]

[Kickstart]

[BLOFLY 636]

oh ok then, here in Western Australia we don't have any of those tests. Just need to renew the license on the bike every 6 or 12 months. On the odd occasion if a traffic copper pulls a bike or car over they may want to inspect the vehicle for any problems such as tyre wear, oil leaks or any other simple to spot problems. If there is a problem, the officer places a Yellow sticker on the windscreen of the car ( I am not sure where the sticker goes on a bike ) and the owner has 3 weeks to rectify the problem/s and return it to a pit inspection for errr, inspection if the vehicle passes the yellow sticker is removed and the vehicle drives or rides away $50 short for the insection. If the vehicle fails then you may get an extension on the 3 weeks limit or you need to hand the plates in and take the vehicle home to fix at your own leisure, when you are ready to have another insection then you must tow the vehicle in and have it inspected and re-licensed
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[Scotsman37]

To get the MOT certificate here in the UK it's a yearly costs of £15 (about $24 aus dollars) starting from 3 years since the bike was new and it has to pass the MOT before the old one expires otherwise like you said take it there by trailer for inspection unless you can find a mechanic to come and inspect it!

On top of that our vehicles require a yearly road tax certificate (disc) to be always displayed on our vehicles and the cost of it depends on the cc of your vehicle can be as high as £60 ( about $96 aus dollars). You can only get the disc if you've got a valid MOT certificate.

Plus the on top of that again we require vehicle insurance which can be as little let say for average £130 ($208) to even as much as £1,000 ($1,600) depending on your personal circumstances and what vehicle you choose!

[Kickstart]

[Scotsman37]

The value of the Aussie dollar has jumped then because it's always usually sitting at about average $1.60 to the £1. Oh well, my Aussie relatives will be extremely happy !

Queensland and Melbourne

[BLOFLY 636]

[Kickstart]

Hi

My insurance in Melbourne on an GPX750 was half the price of the insurance I had on my FZ750 in the UK. That was despite full no claims on the FZ and none used on the GPX, plus not having an Aussy licence so the cheaper companies would not touch me, and the UK insurance being TPFT while the Aussy insurance was fully comp.

UK insurance is full of get out clauses.

Your insurance is working out at around £600. If that is fully comp then you would be very lucky to get it anywhere near that cheap over here. Mine is around £225 (~Aus$550) on a 1200 Bandit with full no claims and being 36, with a full licence for 16 years.

[BlueNinja]

Hey.

Check if your bike uses a cush drive! it may be worn, this will cause it to pull to one side under acceleration. Fit a new one, (around 20 squids) grease the bearings, axle etc, fit it the rear wheel back, replace split pin, and remember to pump the rear brake pedal before using it again!! this will take up the 'slack' in the brake lines and cylinder.

Should be an easy cheap job
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