Handling quirk

**Mental Trousers** · 8th February 2006, 19:07

Just wondering what people think the reason for this little problem is.

When I'm cranked right over (pegs aren't down cos a YZF 750 SP has more ground clearance than an NBL players arm pit) the front end gets a slight judder in it. Nothing major and it doesn't even scare me when it happens (everytime I'm over that far) but it does concern me that it shouldn't happen if I want to stay attached to the bike and be totally confident of doing so. I'm not sure whether it's tire pressure (33 as per manual), tyre it's self (Pilot Power) or suspension (slightly firmer than default on preload, compression and rebound).

Any ideas?

**Fishy** · 8th February 2006, 19:14

Do you notice it on any particular road surface? Rough smooth bumpy? all of the above? Possibly be from having the front set up slighty to firm maybe?

**Mental Trousers** · 8th February 2006, 20:06

Happened at Taupo racetrack on the Track day and also happens on varying surfaces on the road.

I've been thinking of backing off on the front settings for a little while. I get the feeling it'd suit me better if it's slightly softer. Gonna play around with the front settings soon. But I'd like to know opinions on whats causing this before I start to play.

**FROSTY:Me** · 8th February 2006, 20:26

try softening up the front end a tadd

**SPman** · 8th February 2006, 20:46

Originally Posted by Mental-Trousers

Happened at Taupo racetrack on the Track day

In the esses in particular? It used to happen to me as well - could be a bit stiff in the front - never worried about it - was more worried about the tyre skittering across the track.
And waddaya mean you cant get the pegs down - did it a coupla times at the kink at the end of the back straight at Taupo

**Mental Trousers** · 9th February 2006, 13:25

I'd only had the bike for 2.5 weeks after being bikeless for 6 years. Gimme a little leeway mate!! Be different next time though

It was mainly in the new sweeper on the old Taupo track. Could get it a long way over and stay there for quite a while on that part. Good fun. Although it felt like I was lying down on the job but that's not an entirely new feeling for me

**R1madness** · 9th February 2006, 13:49

Sounds like the front end is packing down on the ripples. Take off 2 clicks of front rebound and see how it feels.

**F5 Dave** · 9th February 2006, 16:29

The high speed compression is too stiff in these & the fork springs too soft so it feels too stiff, strange but true. Comp adjuster (bottom) may help, but really only adjusts low speed. I went for the fork valve option which was better.

Harder springs make it ride higher in the stroke in softer area. I've backed off preload a bit now. Think I went to .85kg, I'd have to check the box I still have the old ones in. I only really realised the springs were too soft after the valving, but they are (I'm ~77kg).

Dropping the forks down so 8mm showing + a 5mm trimmed washer under the rear shock helps turn-in a heap.

I'd try running more pressure on the road & as was for track.

**Mental Trousers** · 9th February 2006, 22:03

Thanks guys. Some ideas to play around with.

Might pm you about that lot sometime F5Dave

**R1madness** · 10th February 2006, 07:29

Originally Posted by F5 Dave

The high speed compression is too stiff in these & the fork springs too soft so it feels too stiff, strange but true. Comp adjuster (bottom) may help, but really only adjusts low speed. I went for the fork valve option which was better.

Harder springs make it ride higher in the stroke in softer area. I've backed off preload a bit now. Think I went to .85kg, I'd have to check the box I still have the old ones in. I only really realised the springs were too soft after the valving, but they are (I'm ~77kg).

Dropping the forks down so 8mm showing + a 5mm trimmed washer under the rear shock helps turn-in a heap.

I'd try running more pressure on the road & as was for track.

This is a common problem with late model JAP sports bikes. They are designed with a 65kg rider on board and they need to be able to ride their bikes streight off gutters and survive ham fisted wheelstands. (They park on the footpath in Japan). The extra comp dampining helps.
Early R1s (like mine) were shit because of this. I did the front springs and had a play with the oil and what a difference. Do the springs first as they are cheap and offer great results.

**Mental Trousers** · 10th February 2006, 08:26

Ah ok. Me being 95kg probably causes a bit of a problem then.

Got any names/urls for pricing etc on springs and valving for a '94 YZF 750 SP ???

**F5 Dave** · 10th February 2006, 09:22

Racetech.com has some good info & a spring calculator. They do seem to calculate slightly high spring rates. Watch the kg/lbs selection or you may get funny results.

I got my forks & shock revalved by Mark Patterson (Patterson O’Conner MC in Rotoruatorofa). The forks are a bit odd & required a comp & rebound kit so got quite pricey. Used competitor kits to Racetech, (Pacific something or other). + did another mod to reduce the bump stops holding the forks down too long.

The shock required some machining as the shims couldn’t move on high speed (high speed meaning shock movement, sharp edges etc, nothing to do with bike velocity) & then he looked up the Ohlins spec shims & used that. Took the kick out of the rear. You may almost need a stiffer rear spring, but I wouldn't worry about it.

Ended up costing erm ~ $1100 for both including labour, kits, oil, bushes & seals (then I got the fork springs after). I only regret not doing it sooner.

**R1madness** · 10th February 2006, 13:03

Give Ray Clee at Ray Clee motorcycle performance a call He is in Keumu but dont yell at me because i spelt it wrong). If he doesn't have the bits on the shelf he will get them for ya. He does the suspension for Andrew Stroud so he knows his stuff.
Oh yea the bits are not too dear but cant remember the price sorry.

**Mental Trousers** · 12th February 2006, 00:31

Well I played around a bit with Compression damping today. Found that it was wound up to max which is what would've been causing the problem. So I wound it out to almost factory standard (7 clicks but I went to 5). That was too soft though cos it started a very slight front end weave on high speed sweepers and gave a tiny shake on bumps. So I dialled it to 4 and it was perfect. Not sure if that's cured the slight judder when way over but I'll find out.