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Author Topic: Front suspension rebound!?!  (Read 3641 times)

Alantris

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Re: Front suspension rebound!?!
« Reply #10 on: January 24, 2013, 09:21:51 PM »

We here have had similar issues and changing the rear shock fix that.
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aditya7297

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Re: Front suspension rebound!?!
« Reply #11 on: March 19, 2013, 06:37:05 AM »

We here have had similar issues and changing the rear shock fix that.

Interesting, i shall try that..
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Hylife

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Re: Front suspension rebound!?!
« Reply #12 on: April 23, 2013, 05:29:53 AM »

There should be a tyre pressure placard (sticker) on the left side of the swing arm. If this is missing/removed and your GT250R is using original sized tyres 110/70 17 on front and 150/70 17 on rear then the manufacturers recommended COLD tyre pressures are
Front 200 kpa /29 psi
Rear 225 kpa / 32 psi (solo)
Rear 250 kpa / 36 psi (2up)

Use a good quality tyre gauge. Never rely on the gauges you find on the end of the hose at your local gas station. The wall mounted digital type where you set a target pressure are much better or go buy your own from your local auto parts store for $10.

Under-inflated tyres make smooth cornering more difficult and over-inflated tyres decrease the amount of tyre in contact with the road leading to bouncing, skids and falls.

And, balance your wheels.

If you really want to check &/or replace your front fork oil, it is done by volume, which means you have to completely flush all the existing fork oil out first. The GT250 & GT250R capacity is 400cc +/- 2.5cc per side Use a large volume syringe available from your local pharmacy/drug store to measure the oil accurately. Use fork oil Shell Tellus #22 . The 22 is an ISO standard for hydraulic oil viscosity at 40 degrees Celsius. Specially branded for motorcycles it is called Shell Advance Fork 7.5 . Shell are generally recognised as the industry standard setters for hydraulic oils.
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stigger

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Re: Front suspension rebound!?!
« Reply #13 on: April 23, 2013, 06:59:14 AM »

You're probably one of the first people to actually WANT a steering damper  ::) ::)

Whether it be for road OR track , most riders have NO complaints with the way the Hyo steers  ??? ???

Maybe there's some under lying problem in the way your bike was set-up by your dealer  :-\

Bazza
I don't know MikeOnTheRock was pretty keen on them.

From a long time ago. --> http://korider.com/index.php?topic=5931.0

note the piccie in mikes sig
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bazzabear

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Re: Front suspension rebound!?!
« Reply #14 on: April 26, 2013, 05:30:54 PM »

Nice one mate ........... never noticed that before  ;)

Baz

aditya7297

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Re: Front suspension rebound!?!
« Reply #15 on: May 30, 2013, 01:39:07 PM »

There should be a tyre pressure placard (sticker) on the left side of the swing arm. If this is missing/removed and your GT250R is using original sized tyres 110/70 17 on front and 150/70 17 on rear then the manufacturers recommended COLD tyre pressures are
Front 200 kpa /29 psi
Rear 225 kpa / 32 psi (solo)
Rear 250 kpa / 36 psi (2up)

Use a good quality tyre gauge. Never rely on the gauges you find on the end of the hose at your local gas station. The wall mounted digital type where you set a target pressure are much better or go buy your own from your local auto parts store for $10.

Under-inflated tyres make smooth cornering more difficult and over-inflated tyres decrease the amount of tyre in contact with the road leading to bouncing, skids and falls.

And, balance your wheels.

If you really want to check &/or replace your front fork oil, it is done by volume, which means you have to completely flush all the existing fork oil out first. The GT250 & GT250R capacity is 400cc +/- 2.5cc per side Use a large volume syringe available from your local pharmacy/drug store to measure the oil accurately. Use fork oil Shell Tellus #22 . The 22 is an ISO standard for hydraulic oil viscosity at 40 degrees Celsius. Specially branded for motorcycles it is called Shell Advance Fork 7.5 . Shell are generally recognised as the industry standard setters for hydraulic oils.

Thanks for the great detailed feedback on how to fix the problem.. i tried all of the above except changing the fork oil and my rebound is more or less gone. But now the moment i hit speeds in excess of 120km/h the steering gets into a wobble.. actually more of a vibration and i just cant seem to want to pull it faster than 130 km/h iv got both rims aligned and am yet to get the wheels balanced but i still feel that's not the problem. It could be the front tire is screwed coz once i had to ride the bike for about 25 odd km's till a fuel station coz i had a flat and no tools to repair the tire. So I think i'll replace the front tire and see if that fixes the issue and there after give you a detailed report of what went wrong.. Thanks again guys for all the assistance.  :D   
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Hylife

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Re: Front suspension rebound!?!
« Reply #16 on: June 02, 2013, 10:38:56 AM »

If the bounce is at speeds over 100kph in a straight line and you notice your instrument cluster moving up and down, it will be a tyre/wheel balance issue. It is easy fix it yourself for less than $5 or pay for a motorcycle repairer to do.

If you want to do it yourself, visit your local car tyre sales outlet and ask to purchase some self-adhesive (stick-on) lead balance strips. Approx $1 each. They are approx 1cm x 10cm with snap-off grooves making half a dozen little squares. Most car tyre outlets will happily sell you these weights if you explain why you need them because they generally don't do bike tyres.

1. Remove your front axel/wheel from your bike and re-insert your axel into the wheel hub.
2. Make 2 piles of something so that you can sit the axel on (I use 2 piles of old house bricks).
3. Slowly spin the wheel and wait until it comes to a stop.
4. Using a felt marker pen place a mark on the exact highest point on the wheel rim. This mark is the exact opposite of the heavy point. Repeat 2 or 3 times to get the exact light point.
5. Chop up one of your lead weight strips into single squares and using a very small blob of Blutack, stick 1 lead square on your wheel at the marked lightest point.
6. Repeat 3, 4, 5, until your wheel will stop at any random point. You may need peices smaller than 1 little square to get it perfect. It is now balanced.
7. Count up exactly how much weight you used and chop one strip to this exact amount.
8. After thorough cleaning of your rim with methylated spirits (at the stick-on point) to remove any and all traces of oil and dirt, cut that exact amount in half and place half on each side of the wheel (left/right) at the light point you have just cleaned. You may need to pre-bend the lead weights to match the profile of your rim.
9. Refit your wheel/axel to your bike. Test.
10 At half tyre wear re-balance your tyres.
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umop-ǝpisdn

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Re: Front suspension rebound!?!
« Reply #17 on: June 02, 2013, 10:52:05 AM »

I have two things to add:

1. With the pile of 'stuff' you use to put the axles on, they need to be perfectly level @ both ends. Fiddly, but not hard.

2. What ever weight you add, it's best to cut the weight in half and place the two pieces 10cms on either side of the lightest point, so 10cms to the left AND right from the TOP of the rim, when the wheel stops spinning. The idea being to average it out better.
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Hylife

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Re: Front suspension rebound!?!
« Reply #18 on: June 03, 2013, 02:35:21 PM »

Yep, try and get that axel as level as you can but it is not necessary to be perfectly level so long as the highest vertical point is within approx 20mm of centre it will not alter where the main heavy spot is. Of course this is all assuming that your wheel bearings are nicely free of lumps and bumps.

Most tyre manufacturers deliberately overlap the rubber strips/layers progressively around the tyre circumference in an attempt to minimise heavy spots but in reality this actually makes multiple heavy spots around the tyre which are supposed to equal out but rarely do and this self-serve static balance method cannot address that problem. You may end up with two balanced heavy spots and two other lighter spots and still get bounce although that would be at twice the bounce frequency so wouldn't be as severe.

Commercial balancing machines will pick up the multiple "wobble" points by spinning the wheel at speed and indicate to the operator exactly where and how much each weight is to be placed.
Unfortunately it is very difficult to find a bike shop that actually has a commercial motorcycle tyre balancing machine. Most bike shops themselves either use the static method or don't bother to balance at all and will try and tell you that the more expensive brand 'X' tyre they want to sell you doesn't need to be balanced, hogwash, all tyres do.

If you know anyone who does regular track work ask them where they get their tyres balanced. If you remove the wheels yourself and take them in it is fairly cheap to get done commecially and it makes a huge difference to how your bike feels at speed.

If you haven't got a commercial motorcycle tyre balancing machine in your area at least the static method is way better than no balancing at all.
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aditya7297

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Re: Front suspension rebound!?!
« Reply #19 on: June 07, 2013, 07:23:57 AM »

@Hylife. That's is exactly what happens!! :-\  Thanks for the DIY on how to balance my wheel. :D I shall try that out over the weekend, and let you know if its good or not..
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