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....

[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]

HMMMMMM.

This is gunna be interesting

[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

......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.

[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.
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.