Chassis torsion

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ManuelSans

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Sep 6, 2017
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Hello all,


I have a Vmax '86 and a the father of a friend (he lives in Thailand) sent me through her some steel bars which supposedly should be used to rectify the chassis of the motorcycle since according to him the chassis is too weak to handle the power of the bike and gets twisted.


I have noticed that the backside mudguard is not parallel to the weel and therefore the back looks assymetrical... is this related to that?


Can anybody confirm the story of the chassis torsion and maybe help me find out how to install those chassis bars??


Thanks a lot


Manuel
 
The frame and suspension of the V Max is typical of bikes of the period where frames were not yet considered a high priority in terms of being equal to the power of the engine.

Adding frame braces will increase the torsional rigidity of the frame.
Whilst this may (in theory) allow you to corner faster this will put additional stresses of front and rear suspension.
If this is still OE it is now some thirty two years old and probably will benefit from upgrading.
Have a look at these steps that can be taken to improve the handling.

Regarding the rear wheel, do you mean that the mudguard is not parallel to the centre-line of the frame or is offset from it?
Alternatively is it the wheel that is offset which make the mudguard appear wrong?

It is normal for the rear wheel to be slightly offset from the centre-line of the frame; a feature often seen on bikes with shaft drive (I have been told).
Provided the wheel is parallel to the centre-line this does not affect the handling although you may notice it is slightly easier to turn one way verses the other.
Should this bother you it is possible to change the fixed pivot with the adjustable one as found on the RH side. This allows a small movement of the rear wheel over tote right.
 
Unless the frame is tweaked, from an accident, it's probably nothing to worry-about. Pictures showing the amount of offset could help us to understand your situation.

Most frame stiffeners either bolt-in diagonally between the front and rear chassis frame members, or weld-in, one popular system uses a weld-in on one side, and then bolts-in on the other. It's removable for engine work.
 
The frame and suspension of the V Max is typical of bikes of the period where frames were not yet considered a high priority in terms of being equal to the power of the engine.

Adding frame braces will increase the torsional rigidity of the frame.
Whilst this may (in theory) allow you to corner faster this will put additional stresses of front and rear suspension.
If this is still OE it is now some thirty two years old and probably will benefit from upgrading.
Have a look at these steps that can be taken to improve the handling.

Regarding the rear wheel, do you mean that the mudguard is not parallel to the centre-line of the frame or is offset from it?
Alternatively is it the wheel that is offset which make the mudguard appear wrong?

It is normal for the rear wheel to be slightly offset from the centre-line of the frame; a feature often seen on bikes with shaft drive (I have been told).
Provided the wheel is parallel to the centre-line this does not affect the handling although you may notice it is slightly easier to turn one way verses the other.
Should this bother you it is possible to change the fixed pivot with the adjustable one as found on the RH side. This allows a small movement of the rear wheel over tote right.

Thanks for the great information! I will have a deep look at it and will let you know how it goes... Right now I am struggling with a way more basic issue with the fuel pump, so I feel like I have to solve that before I improve the cornering capacities of this old lady :p
 
Unless the frame is tweaked, from an accident, it's probably nothing to worry-about. Pictures showing the amount of offset could help us to understand your situation.

Most frame stiffeners either bolt-in diagonally between the front and rear chassis frame members, or weld-in, one popular system uses a weld-in on one side, and then bolts-in on the other. It's removable for engine work.

So I guess in any case I will have to modify the current frame to accomodate the frame bars? I am not sure I am ready for such a complex operation. I am still a mechanics newbie...
 
Some frame braces bolt-in on both sides; some have one end which is welded, while the other is bolt-in, which is yours?
 
Seems like you didn't get the entire package, if you can't find-out the original manufacturer, you may need to fabricate something. Post some pics of what you have, and where you believe they will fit on the chassis, and we can probably figure out whose manufacture they are, and if you will need to fabricate tabs for getting the reinforcing bars mounted, either welded or bolted.
 

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