Technique Clinic

[johannvr]

Sounds like I'm not entirely alone then.

No, yer not. Anybody ever seen me & the DR trying to negotiate Muriwai Beach's sand dunes? Or the muddy slippery patches down south? (talking that 'Naki mud now that was the topic of one or 2 comments elsewhere recently)

If I don't bog & fall off I slide & fall off.

Still a mud load of fun tho'

[Oscar]

Ain't that the truth


I don't have too much trouble with dunes and flat beaches anymore. I think it was Offrd who said to me that 80 k was good and that 100 k was better. I'm no expert but I get by.
However, in Oz I would be blasting down some road at about 120 k and because everything is the same colour I would suddenly find myself in a rut in deep sand. Road level was suddenly axle height at times.
Everything seemed to be OK - like the bike was much easier to ride than it was at 10 or 20 k, but this is where the mind game thing came in. I kept thinking about how many extra pieces I could give my skeleton if I fucked up.
What really had me filling my pants was that it was just as chancey to slow down as it was to keep the power on. When the sides of the rut started to grab that front wheel, I was in deep doodoo.

Standing up helps, but is no guarantee.
I knew I was in the shit on Kawhia beach when I slowed so quickly sand off of the rear tyre started hitting my mirrors...

[warewolf]

What really had me filling my pants was that it was just as chancey to slow down as it was to keep the power on. When the sides of the rut started to grab that front wheel, I was in deep doodoo.

Woodhill bike park (now called The Sandpit) is a great place for Aucklanders to practice riding in sand.

Deep loose sand chews power, you need lots of it to get the bike "up on the 'plane" like a boat. The front needs to be up and floating, kinda just skimming the surface. Steer more with your footpegs than handlebars, don't worry if the bars flap around a bit. Shut the throttle and the bike stops pretty quickly, sans brakes. If the front starts to dig in and tends to tuck, you need to open the throttle to push the front up and out again. Shutting the throttle will bury the front and the result may not be pretty. Definitely a mind game / learned skill. (yeah, what oscar said.)

Similarly, in ruts, as with crossing the ridges of loose stuff on otherwise hard-pack gravel roads, you need to power on and lighten the front, driving it through the loose stuff. When you do this, the forks extend which gives you two more benefits: the forks are at their most compliant part of the suspension stroke; and the chassis is raked out, slowing the steering (less likely to tank-slap) and lengthening the wheelbase, increasing stability.

When the front hits the edge of a rut, you need to power on to maintain control/directional stability. Braking is only really an option once everything is together again; although sometimes you can brake hard with the back and get it to dig in and drag, keeping the bike raked out from the back end.

No, not nice on a big, heavily-laden bike at a good clip. Power on, weight up and back real quick!!

[Bass]

Deep loose sand chews power, you need lots of it to get the bike "up on the 'plane" like a boat. The front needs to be up and floating, kinda just skimming the surface. Steer more with your footpegs than handlebars, don't worry if the bars flap around a bit. Shut the throttle and the bike stops pretty quickly, sans brakes. If the front starts to dig in and tends to tuck, you need to open the throttle to push the front up and out again. Shutting the throttle will bury the front and the result may not be pretty. Definitely a mind game / learned skill. (yeah, what oscar said.)

Similarly, in ruts, as with crossing the ridges of loose stuff on otherwise hard-pack gravel roads, you need to power on and lighten the front, driving it through the loose stuff. When you do this, the forks extend which gives you two more benefits: the forks are at their most compliant part of the suspension stroke; and the chassis is raked out, slowing the steering (less likely to tank-slap) and lengthening the wheelbase, increasing stability.

When the front hits the edge of a rut, you need to power on to maintain control/directional stability. Braking is only really an option once everything is together again; although sometimes you can brake hard with the back and get it to dig in and drag, keeping the bike raked out from the back end.

No, not nice on a big, heavily-laden bike at a good clip. Power on, weight up and back real quick!!

Roger that.
I had already figured out most of this (with lotsa help) and of course, it works, mostly.
However, knowing what to do and having the balls to actually do it when it goes against all your survival instincts, are 2 different things. I guess that you can change what is instinctive if you practice enough.
Even so, I note that the carnage rate with guys trying to ride like this, going to and from the OCR in Oz recently, was appalling.

I was reading an article not so long ago, on suspension setup techniques for off road work. The guy who wrote it says that to set up for sand, you should wind your damping right up - like harden up the suspension as much as you can - no preload increase, just damping. He didn't explain the thinking behind this however.
This seems to be at odds with what you were saying about front end compliance.
Any comments?

The other thing that was tricky in Oz was getting the weight up and back because there was a bloody great bag in the way of moving the arse rearwards. It meant that we really had to get on the gas to lighten the front which started a major domestic with the survival instincts. There was the odd occasion when I had it completely tapped out at speed in the deep loose stuff. I only ever did it when I was dog tired and really sore. It was born of desperation - scary stuff and pretty stupid looking back.

[Bass]

Water crossing are interesting. I've a theory that hitting cold water with a hot bike fucks up the mixture and makes it stall. Cracking the choke slightly seems to help.

I've been thinking about this one and I can't decide whether I think that it's right or wrong. I don't doubt your observation that cracking the choke helps, I was just wondering why.

Could it be that it just brings up the idle speed. With a mechanical choke (non EFI) isn't that normally the first effect?

[Oscar]

I've been thinking about this one and I can't decide whether I think that it's right or wrong. I don't doubt your observation that cracking the choke helps, I was just wondering why.

Could it be that it just brings up the idle speed. With a mechanical choke (non EFI) isn't that normally the first effect?

It could be, but idle speed or mixture, it worked.
Actually on consideration the cold should make it rum rich, not lean, so the increase in idle was probably the answer.

Deep cold water at Ohakune was consistently stalling the BMW's.
The water was at about intake/injector level and the EFI couldn't cope...

[Bass]

Deep cold water at Ohakune was consistently stalling the BMW's.
The water was at about intake/injector level and the EFI couldn't cope...

I have often wondered about the detrimental effects on a hot motor, of plunging it suddenly into cold water - especially an air cooled one like my DR.

I would have thought that mistreating it like that would give rise to all sorts of nasties, like seizing it as the block suddenly contracts around a piston which remains at close to normal operating temperature. Even cracking the block seems like it would be quite likely and yet I have never seen anything like that happen. I have not been around the Adv riding traps for very long, but I have never even heard of it happening.

How do we get away with abusing them as we do?

[cooneyr]

I have often wondered about the detrimental effects on a hot motor....

Who knows - maybe alloy is more forgiving but thank god we don't have problems. Had a landcruiser with a 2LT motor (turboed 2.4 diesel hilux motor) that cracked the head and dropped the "inserts" (whatever they were) into the cylinders due to repeated dunkings. $4000 later for a new motor and labour - ouch. Apparently the 2LT motors have a very high tendency to cracking heads - I just accelerated it.

Cheers R

[warewolf]

However, knowing what to do and having the balls to actually do it when it goes against all your survival instincts, are 2 different things. I guess that you can change what is instinctive if you practice enough.

That's the premise behind a lot of Keith Code's work. Riding a motorcycle is not natural, it is a foreign learned skill. That, and understanding how your survival reactions work (and work against you) is what riding smarter is all about. The end result is that you ride in a manner that does not provoke the survival reactions.

(And it is why ppl often suggest getting a small, light, cheap bike to learn in the dirt, so that you don't need massive cojones to learn on the thing.)

Even so, I note that the carnage rate with guys trying to ride like this, going to and from the OCR in Oz recently, was appalling.

The learning process on a big heavily laden bike is just way too slow. The carnage on the Aussie BMW safaris got pretty bad there for a while, too, for obvious reasons.

I was reading an article not so long ago, on suspension setup techniques for off road work. The guy who wrote it says that to set up for sand, you should wind your damping right up - like harden up the suspension as much as you can - no preload increase, just damping. He didn't explain the thinking behind this however.
This seems to be at odds with what you were saying about front end compliance.

I don't know, but I suspect the damping is increased because the soft sand has some give, absorbing some of the impacts for you. It can be described as like surfing in molasses, very different behaviour. I can see how slowing/stiffening the suspension action could be useful in soft deep sand, but it's difficult to explain concisely. Also I was thinking about ruts in general, not necessarily sandy ones. There are always compromises.

In whooped-out sand, generally you want faster rebound, to avoid the suspension packing down through not rebounding fully before the next hit; and slower compression, to avoid the suspension packing down by being pushed further through its stroke. Bear in mind that dirt bikes tend to adjust compression as a priority, road bikes rebound. Witness the less fancy bikes in each style that only have one adjuster. So its possible (not having read it myself) your tuner only did mean to increase compression, and/or was not factoring in whoops or ruts.

Mud is another situation which seems illogical. Compression, rebound and preload all get increased for mud - because it sticks to the bike, increasing the laden weight. Much more important on a 90kg MXer than a 390kg adv tourer. You'd think in the soft, slick conditions you'd want to go softly, softly.

The other thing that was tricky in Oz was getting the weight up and back because there was a bloody great bag in the way of moving the arse rearwards. It meant that we really had to get on the gas to lighten the front which started a major domestic with the survival instincts. There was the odd occasion when I had it completely tapped out at speed in the deep loose stuff. I only ever did it when I was dog tired and really sore. It was born of desperation - scary stuff and pretty stupid looking back.

Yep, I don't like being constrained by luggage, either, so prefer a small backpack rather than tankbag or tailbag. But needs must, and in that case 'ride to the conditions'. I got no other answers to that one.

[warewolf]

I've a theory that hitting cold water with a hot bike fucks up the mixture and makes it stall. Cracking the choke slightly seems to help.

Could also be reduced spark efficiency via partial shorting of HT leads or whatever? A few more rpms helps avoid stalling on misfire, and ups the alternator output voltage. Might just be enough to keep the engine out of trouble?

Whatever the reason, I know I try to carry more than idle revs through water as an extra anti-stall measure. Also in case I have to dump the clutch suddenly to balance the bike, push it over a rock, etc etc.

[Bass]

the "inserts" (whatever they were)
Cheers R

Valve seat inserts.
They're common with alloy heads (and others) as the parent alloy is not up to the tough environment around the valve seat area.
When you crack a head, the cracks tend to start in the same area and can release the seat inserts to wreak havoc internally.

[Bass]

Bear in mind that dirt bikes tend to adjust compression as a priority, road bikes rebound. Witness the less fancy bikes in each style that only have one adjuster.

Thats useful. I didn't know that. Ta

But needs must, and in that case 'ride to the conditions'. I got no other answers to that one.

I was just saying to Jamie a day or so back, that we did 18,000 km on top heavy bikes, in totally unfamiliar conditions, without a single serious incident and only a few pucker moments.
So we must have got something right, even if it was only to realise how much we didn't know.
I note that in 6 years back riding, I have come off a road bike once, with moderately serious consequences for both me and the bike (broken ribs etc).
In one year adventure riding, I have lost track of the number of times I have come off the DR with virtually no consequences for either me or the bike.
So it seems that being as slow as a wet week does have some advantages.

[warewolf]

Yep, I have come off the dirt bike countless times with no ill effects, more often than not at a standstill or near to it!!

[Bass]

more often than not at a standstill or near to it!!

That's the big difference!

[NordieBoy]

I have often wondered about the detrimental effects on a hot motor, of plunging it suddenly into cold water - especially an air cooled one like my DR.

I would have thought that mistreating it like that would give rise to all sorts of nasties, like seizing it as the block suddenly contracts around a piston which remains at close to normal operating temperature. Even cracking the block seems like it would be quite likely and yet I have never seen anything like that happen. I have not been around the Adv riding traps for very long, but I have never even heard of it happening.

How do we get away with abusing them as we do?

How about in a 3-hour cross country race.
250's/450's etc being held on the limiter forever and then hitting creek/bog/whatever crossings - In winter.