Phase One.

[Motu]

First thing was to get the handling sorted...now I can tick that box.

This might push the ideas of some of you lot here,but thinking outside the box is good for you.Dirt bikes are the best thing for gravel roads,we all know that,and that's what I've been riding mostly in the 21st century - however,they are not really that good.The weight distribution is wrong,and the CG too high - the rearward weight bias is offset by the more forward riding position,and I really like to get well forward.The high CG causes a lot of problems in corners - in power slides they step out too quick,and you need to keep the bike more upright.In the dreaded Off Camber Right Hander and other places turning at low speeds in thick gravel the front wheel wants to step out.

I wanted a bike with a more even weight distribution and lower CG....and I've been wanting to do a streettracker for many years.The R65 may seem an odd choice....but it covers a lot of other requirements for me too (simplicity,parts availability,parts adaptability for a start).First was tyres,I really wanted some K180's,but settled for 4.00 x 18 Dunlop K70's front and rear.Using tyres of the same size both ends is seldom done in the motorcycle world,but I've done it before (using K70's),and such a large front tyre is not the done thing either....but of course I've done it before.I can't run a front guard now....but gives it the streettracker cred anyway.

Next was the bars - I had dirt bars on the R65 before,but had to lean forward,and they were too narrow.These are genuine flattrack bars - Slideways from Omar.These put my hands in the perfect position,and at 33inches wide give plenty of leverage.

I had my first ride with this setup tonight - and I am SO SO impressed!!!! On the twisty sealed roads the bike is light,turns in and flip flops with practically no input - lovely to look down and see a cylinder head just inches from the road.The 100% cross section tyres give sharp handling,and surface regularities give no feed back to upset things.I don't notice that big front tyre.....but I can feel the power of it's contact patch.

In gravel it's 7th Heaven,total control with no surprises.The narrow section tyres cut through the gravel to the surface,and the super low CG gives unbelievable stability.I really had to push it to get the rear wheel into any action,and that front tyre has plenty of power in reserve.It was a bit of a gamble to choose the K70's,just going on my previous experience with them and the gut feeling they would do the job.

A proper streettracker seat is needed of course,and if Eurodave ever finds the time he might do me one to fit.It will be a work in progress....crash bars,sump guard,exhaust system....on and on.But now I know it's project worth the effort - goodbye dirt bikes....

http://img167.imageshack.us/img167/4456/slidewaysjm3.jpg

[Storm]

Thats a ..uh..original......... idea you have going on there. Full marks for originality.

[Ixion]

Tried a deep water crossing yet ?

Seriously , though , taht looks very much like many bikes from my younger days. Granted exact same sizes tyres front and rear were not so common (though I'm sure there were some ) but the difference between a 3.50 front and a 4.00 rear is pretty small. Is the CG really so much lower than a class Briddish big single? Especially if you factor in the difference with a rider sitting high on a dual seat amd a rider sitting on a single saddle low on a rigid frame .

[JATZ]

http://img167.imageshack.us/img167/4456/slidewaysjm3.jpg

HMMMMMM.

This is gunna be interesting :niceone:

:corn::corn:

[Motu]

Is the CG really so much lower than a class Briddish big single? Especially if you factor in the difference with a rider sitting high on a dual seat amd a rider sitting on a single saddle low on a rigid frame .

Not a lot I would say - but a BMW would have the lowest CG of any bike after 1980.I was looking for something with a ''classic'' set up...ie,a 50/50 weight balance,low CG,min 650cc,no more than 2 cyl etc.Not a lot that isn't over priced (W650,Sporty) or too old (XS650) or parts orphans (various Honda's).Add to that the simplicity and ease of working on an airhead,the parts availability,the support locally and on the internet.

I like the R65 because of the rev happy motor - no problem to be buried in the red on a gravel road,the 800 would be more strained in that situation.It still has plenty of power for me,is happy forever anywhere between 100 to 140kph.The mono R65 is not an orphan like the twinshock,it's the same as the other mono bikes,and has a version of the K forks.

[xwhatsit]

That's damned interesting. I suppose thinking about it -- well, dirt bikes are for dirt, right? Not roads made from stones. I mean which manufacturer has ever built a bike specifically targeted at gravel?

Kewl. So Phase 2 is just cosmetic stuff like the seat, or what else do you have in mind?

[Ixion]

What's the front wheel diameter on an R65?

[vifferman]

Well done, Mr Motu, Sir!

[cooneyr]

What's the front wheel diameter on an R65?

Hate to point out the obvious, but 18" seems like a good answer :D


......First was tyres,I really wanted some K180's,but settled for 4.00 x 18 Dunlop K70's front and rear.Using tyres of the same size both ends is seldom done in the motorcycle world....

Alternatively you could have ment width???

Cheers R

[98tls]

Great choice Motu,fwiw here's a pic of a mates old beemer which just keeps on keeping on,only problem hes had was coming back from the Bert Munroe one of the carb diaphragms blew itself to bits resulting in a slow trip home,hes got some good contacts for parts if you get stuck.

[warewolf]

Nice one, seems like a primo project and great result. :yes:

[riffer]

Thats a ..uh..original......... idea you have going on there. Full marks for originality.


Don't knock it mate. I seem to recall that Douglas had a pretty successful horiz opposed trials/scrambler back in the 50s.

Nice project Motu. I shall be subscribing to this thread.

[Kickaha]

.First was tyres,I really wanted some K180's,but settled for 4.00 x 18 Dunlop K70's front and rear.Using tyres of the same size both ends is seldom done in the motorcycle world,but I've done it before (using K70's),and such a large front tyre is not the done thing either...

What advantage is there over running the smaller standard front size

[Motu]

That's damned interesting. I suppose thinking about it -- well, dirt bikes are for dirt, right? Not roads made from stones. I mean which manufacturer has ever built a bike specifically targeted at gravel?

Kewl. So Phase 2 is just cosmetic stuff like the seat, or what else do you have in mind?

Older...say, ''classic'' bikes for want of a better word were good on gravel as there was a lot around back then....and the tyres from that era were also good on gravel.Hence my choice of a ''classic'' bike,and ''vintage'' tyres.

I want the bike to be dual purpose....in this case a day tripper for use around local twisty and gravel roads,and a tourer...a bike for longer rides around the country.Just a shift in focus,we need to do that at times to keep lives fresh.To be swapped out in one night in the shed - wheels,rear subframe and seat,exhaust,maybe a screen....panniers etc.

Some personal theories - To have a well balanced bike,you need to be well balanced yourself.So you need to sit on the bike in a relaxed manner - all your chakra's in a row Grasshopper.Any strain you will transfer into the bike,you need to move around freely,putting forces into the bike at the appropriate places.Leverage,you need leverage to shift that bulk effortlessly.Slideways bars.....sideways at 160kph,good enough for me.

Hooning around gravel roads in cars as a lad,I preferred narrow crossply tyres - they had stiff sidewalls and a sharp edge to the tread,this swept away the gravel and made the tyre dig in.Radial tyres were dangerous as they have a soft sidewall and a round edge - this allows the gravel to get under the tyre and lift it off the surface.Motorcycle tyres - these days they have a different profile,and the curvature of the tread is far larger than the tyre cross section.The contact patch moves out to the side in corners....in imperfect conditions this can apply leverage into the bike.For example tar snakes...they make the bike snake.On gravel roads the stones get under the curvature of the tread,lifting it and not allowing full traction.

So if we have 100% cross section tyres like these K70's,we have a tyre 4 inches high,and 4 inches wide - I made a hemisphere with a 2in radius,not quite the profile,but close.They cut down through the gravel to the base and give traction.There is less input out from the centreline,so the bike doesn't move around - it crosses the centre hump without a twitch.Tar snakes,gravel on corners....whatever,the tyre is not affected.The 4.00x 18 K70 fits a 2.50 rim,that's what these wheels are,so it has the desired profile.Whatever....it's just what I think,and it works for me in my world.

[tri boy]

Nice start mate.:cool:
The beemer's doughy suspension will be a + for soaking up the corrugations too.
Carying capacity, fuel range all sweet also. Gear up for an sthern adventure me thinks.:headbang:

[bart]

Intriguing Grasshopper. Interesting theories. Give me more.:corn:

[Motu]

Nice start mate.:cool:
The beemer's doughy suspension will be a + for soaking up the corrugations too.
Carying capacity, fuel range all sweet also. Gear up for an sthern adventure me thinks.:headbang:

After soft long travel suspension it's a bit short travel and hard.Only a pre load adjustment on the rear,that's all I get.Not well balanced between front and rear,sometimes it's too soft in the rear,sometimes it kicks up,the front is slow to react at times too - but hey,it's better than an XS650.

I've been very dismissive in the past about riders who complain about SH22,but after my first couple of times on the airhead I had to eat my words.I was a total mess - overshooting corners,ducking and diving mid corner,braking too late,too early,mid corner....I even got into trouble with just a few pebbles in a corner.But it wasn't me...I still know how to ride.And it wasn't the bike,it's a good handling machine.It was the set up,I had to set it up for my preference and the roads I wanted to ride.

I've been caged in for 20 years - 10 years trapped on Waiheke Island,and then 10 years trapped in my own business.Now I have 4 weeks holiday a year (thanks Labour,I hope Mr Key leaves that one in place) and I intend to do more than just day rides in the future.

So I'm setting it up as a day tripper - duh......

[tri boy]

I'm guessing the forks are dampening rod design only. Some race tech emulators and uprated springs should be on Santa's "give me you old c**t" list.
I've finally dialled the scramblers ones in, to what is a nice plush ride, but very controlled over high velocity square edged bumps. Only thing is there is no external adjustment, but since they only sit on top of the dampening tube, (and held down by the spring), they are easy to pluck out with a long parts probe, and then a simple turn of the tension screw to adjust shim opening pressure.

As for the rear...............:scratch:

[Motu]

What advantage is there over running the smaller standard front size

It comes from flattrack (this is going to be a streettracker remember) where they go into the turns with no brakes and scrub off speed with the tyres.The front tyre (sorry,they use tires in the USA) gets pushed very hard,and they use bigger tyres to take the load.If this site wasn't so petty about images I could show you some good photos of front and rear tyre loadings and fork compressions to show how they transfer weight with just the throttle.I have done some flattrack,and used to run a 3.75 x 19 speedway rear tyre on the front....I've also used that tyre on a couple of bikes on gravel.It takes a bit of getting used to,but a fat front tyre is good on gravel.

There is also a sidecar sitting in the shed......longer term there is another add on to the R65 project.

[Tony W]

It comes from flattrack (this is going to be a streettracker remember) where they go into the turns with no brakes and scrub off speed with the tyres.The front tyre (sorry,they use tires in the USA) gets pushed very hard,and they use bigger tyres to take the load.If this site wasn't so petty about images I could show you some good photos of front and rear tyre loadings and fork compressions to show how they transfer weight with just the throttle.I have done some flattrack,and used to run a 3.75 x 19 speedway rear tyre on the front....I've also used that tyre on a couple of bikes on gravel.It takes a bit of getting used to,but a fat front tyre is good on gravel.

There is also a sidecar sitting in the shed......longer term there is another add on to the R65 project.


I like your logic.

Looking forward to further developments.

[Motu]

Put a few more kms on it today - the Kaiaua loop,from the bottom,so get a few more interesting roads to fit into the ride,just a few small sections of gravel.This shot shows better the bend of the bars and size of the front tyre.

http://img166.imageshack.us/img166/8018/r65nk0.jpg

I'm relieved to now know I wasn't looking through heavy rose tinted glasses at bikes I have previously ridden,I really was better than I am.I still had my 1971 Yamaha XS1 when I had the XLV750 and XT400E - and I was puzzled as to why I felt so much more confident in gravel on this worn out shitter with street tyres than on my built for the purpose later model bikes.Now I know why,this is the set up for gravel.

Another interesting thing is the lack of wheelspin,I have to work hard to get the rear wheel to light up.The R65 has about 3 or 4 more HP than the XT600 (now 621cc),but the R65 feels much more powerful on the road....so surprising then that it just drives forward without drama where the XT600 would just break out in wild wheelspin in the same situation,on what all would believe to be far better tyres.A twin should wheelspin more than a single.A lot would be because of the tyres,but not all....I'll have to experiment more here.When it does get sideways it's just so controlable,no drama like a high CG bike,it just goes out,then comes back in when it hooks up...nice.As for the front - I can't get it to do anything,I just ignore it and get on with the road.

The K70 is a soft tyre,so much more than the ''vintage'' tyre it is marketed as.Check this out - 200km on them.The side lugs are really scuffed up,and you can see how much the tyre is bending and the lugs touching each other.I'm running what I think they should be - 20psi front,25 rear....maybe I'll go up to standard pressures later.

http://img166.imageshack.us/img166/2103/k70ah9.jpg

[warewolf]

If this site wasn't so petty about images I could show you some good photos of front and rear tyre loadings and fork compressions to show how they transfer weight with just the throttle.I'd like to see that... can you put them up on advrider.com?

[Motu]

I'll the images off my computer...it's just a messy way to do it.

I like this one of Nicky Hayden on the RS750 - the forks are fully compressed and the front tyre flattened with a huge contact patch,the rear wheel only lightly loaded and just stepped out 6 inches or so,perfect.He has done this by shutting the throttle and loading up the front tyre.Grrrrr,this is a dumb way to do it - Hayden is now the last image!

Kenny Coolbeth has his bike pretty neutral here,but check out the tyre loadings and how narrow the blue groove is.

Chris Carr is just making the transition to loading up the rear tyre more,but by the look of his right arm the throttle is still shut....getting ready to turn it with the throttle.A narrow groove again,so most likely a mile track.

Dunno who this guy is,but a fantastic shot of the rear tyre loaded up,check out the contact patch and sidewall flex....front tyre is only just on the track.

New Zealand flattrackers used either competition trials tyres in 18in,or speedway rear tyres in 19in - both tyres would flex and lay down a big foot print like the K180 flattrack tyres.

If you look at the close up photo of my front K70 you can see the same thing.Most people look at the K70 and say there isn't much tread on the side,it won't be good in corners.But you can see it flexes,and on large lean angles,it's not just on the small side lugs,but has flattened out and on both rows of lug,and they are touching.This might freak out people used to running high pressures on modern tyres.....but I'm used to it and feel pretty confident with my tyres flexing and working on the road.

[warewolf]

Awesome stuff!:clap:

[BMWST?]

never had a airhead,but when i had my k100rs i was amazed at the rear wheel traction,realy noticeable in the wet...i put this down to two things.The lightsh sring and damping rates allowed the wheel to follow every bump,and i reckon the shaft drive reaction had the effect of pushing the rear wheel down ...All my big road bikes fron the early eighties were pretty good on gravel...the front and rear tyres used to be more the same size and i used to run a slightly bigger front than std...

[Motu]

I would say the traction is a result of the tyre compound.I have found out on ADVrider that the K70 is available in race compound....and I was hoping that,y'know....But after testing out tyres in my shed with the end of a butter knife,they are not as soft as trials or speedway tyres which leave an impression for several minutes,but much softer than a Battleaxe.So maybe they will be good in the wet as well,which is what I always remember the K70 as,the best wet weather tyre ever.

[Motu]

These K70's are soft alright,they are getting destroyed! After 2,000km the rear tyre has gone from 7mm to 3mm,the front to 5mm.As you can see the rear tyre is being stressed quite hard,I didn't expect them to wear this much,I'll be going through these faster than any adv tyre I've used.

Anyway,it certainly proves the traction comes from the compound.After a bit more time on the bike I'm even more impressed,it just doesn't move off line at all.I have even cornered in the thick stuff between wheel tracks,applied power mid corner - the bike just stays planted where I put it.I'll have to save these tyres for gravel only,for road rides I'll be going back to the street tyres.

[NordieBoy]

These K70's are soft alright,they are getting destroyed! After 2,000km the rear tyre has gone from 7mm to 3mm,the front to 5mm.As you can see the rear tyre is being stressed quite hard,I didn't expect them to wear this much,I'll be going through these faster than any adv tyre I've used.

The front may have done 2000km but the rear has probably done 2500km :D

[Motu]

The speedo is driven from the gearbox,so maybe the front has only done 1,500km! If I've lost 4mm in 2,000km,I won't get another 1,000km out of it. Bugger,the price you pay for grip eh? $150 isn't too bad for a tyre these days I guess,but the whole point of this bike for me was to be able to clock more kms.I'll only be using these tyres now if I'm going on gravel,for a seal only ride I'll swap to my road wheels and tyres.....good to have a spare set.I'll have to look for some other tyres with the same performance....wish they had those K180's in stock....but how would they wear?