Handling woes GSX750 ET

[Rncv]

Hi All, 

I’m looking for some help with a handling issue I’ve been struggling with with a GSX750. 
It’s fairly well modified, R6 front end, b12 mono, gsxr oil engine. 
 

The trouble I have is it requires a lot of pressure on the handle bar to stop the front end from folding in. I’ve had the bike with a B12 front end and setup like a dream.

The R6 front end has a stepped yoke, the front ride height is set the same as the old B12 front end. Rear ride height set the same as another ET (which handles like a dream with a B12 front end). 
 

What should I be looking at? I’ve checked headstock bearings and they are good. 
apart from playing with ride heights I’m lost? 
 

Cheers,

Rob

[Muddy]

Others will know better, but I'd try dropping the forks lower in the triples until it wants to stop tucking.  Worked for my SV1000 with different front end.

[gsxwill]

Sounds like your bike hates yamaha parts 

Seriously though as already said, if you can raise or drop the forks through the yokes you should find the point it stops folding in 

 

[Rncv]

What I don’t understand is why when set to the same ride height as previous has it started this?… 

[dago]

The off set on the yokes might be different than before

[Rncv]

33 minutes ago, dago said:

The off set on the yokes might be different than before

From stem to fork position? 
 

that will increase the wheel base length? 

[Muddy]

1 hour ago, Rncv said:

What I don’t understand is why when set to the same ride height as previous has it started this?… 

Ride height is not the only bit of geometry in play here.  In my application the fork length from the top of the triple to the axle was identical, but it wanted to tuck in.  Lowering the forks in the triples by about 15 mm fixed everything - so much more confidence.

[dago]

Yes the position of forks in relation to the stem. The off set increases or decrease trail affect the turning

[no class]

have a gander at some Dave Moss suspension tuning videos on youtube

[Dezza]

Have the springs and damping of the R6 forks been adjusted or modified? An R6 will probably weigh several tonnes less than a modified ancient Suzuki 750, so it's not surprising if they don't work that well on a completely different bike. My guess is the R6 yokes will have less offset than the Blandit yokes too, which won't be helping. What R6 forks are they? Early RWU or later USD?

[Rncv]

54 minutes ago, Dezza said:

Have the springs and damping of the R6 forks been adjusted or modified? An R6 will probably weigh several tonnes less than a modified ancient Suzuki 750, so it's not surprising if they don't work that well on a completely different bike. My guess is the R6 yokes will have less offset than the Blandit yokes too, which won't be helping. What R6 forks are they? Early RWU or later USD?

No they are the standard stuff. They are 13s USD forks. Weight wise my bike is 10kg heavier than the R6 so not miles out. 

The yoke has the same stem/fork offset as a B12. 

[TonyGee]

Have you thought about the tyre ?  is it worn ? is it the right size ? would a different size make a difference ?  

[no class]

there are many factors here to set up suspension for your application .....did you check the rake / trail dimension ? rear dogbones will change geometry as well as the length of the forks/ spring rates .....  static sag for front and rear suspension .... tires / pressure ...etc etc 

[wraith]

As above, meany things can/do change the handling. 10kg may not seem much but if your new forks are shorter than the old one less spring etc to component for that wight, are the now yokes at the same rack? Is the front tyre the same 60,65,70 profile? 

Start with moving the forks up/down through the yokes and see what the difference is and take it from there.