Topic: CB400 Four to XR400 Four

[Pezz]

G'day all,

Yep that’s right I’m building me a little 4 cylinder adventure bike.

I am organising a fundraiser for the Down Syndrome Association of NSW (AUSTRALIA) called:

Scrapheap Adventure Ride 2010
Riding to a place called Wanaaring NSW 200k's west of Bourke.
Link: <http://maps.google.com.au/maps?f=q&source=s_q&hl=en&geocode=&q=wanaaring+NSW&sll=-25.335448,135.745076&sspn=56.486015,78.486328&ie=UTF8&ll=-30.42973,148.359375&spn=13.904131,19.621582&t=h&z=6>
Rules:
Have to buy a Bike for less than $500.00.
Can be any road registered motorcycle.
You are allowed to spend additional sums on the bike to make it run and roadworthy, all machines participating must be registered.


Above is the donor bike.

A mate, Shane, give me this little beauty for $0.00. Thanks Buddy

I want to splice on a XR4/5/600 front end, wheel and swing arm rear wheel.
Still wondering what fuel tank, seat and guards to run. Need to build it as cheap as possible. I will not be butchering this bike as will be able to return it to CB400Four at the end if I wanted too.

When I first looked at it, it is very small. And quite light.

I havent even started to look at gearing ect. I have to pull the carbies out and overhaul. the motor has good compression with the kick starter. I will do a full comp test and post results when I get them.

I will keep posting as I progress.

[Zaipai]

Yes keep us updated with pics also. I like the idea. Good cause also. That tank is pretty durable, I have one on my 550 at the moment because my 550 tank sprung a leak. That tank can take a pounding..

[Pezz]

Tank looks good but only holds 14 litres . . . . I would like about 20 litres.

May just have to carry a rear rack tank http://www.nomadtanks.com/

I have a line on a set of XR650 forks for the right price. Just need some measurements as they may be too big.

[Zaipai]

Tank looks good but only holds 14 litres . . . . I would like about 20 litres.

May just have to carry a rear rack tank http://www.nomadtanks.com/

I have a line on a set of XR650 forks for the right price. Just need some measurements as they may be too big.

Yes very good point. You don't want to run out during the race. Love your Atom Ant avatar.. watched that cartoon all the time as a child. Ah.. the good old days..

[Pezz]

Im a bit torn really, whether to go for modern set up or period scrapheap setup?
Old XL500S swingarm and front end . . . . I have a line on some XR650R forks ect but I like the old school idea and it would be a lot funnier

 I have decided to name the bike 'Yajyuu'

Yajyuu is Japanese for beast

[Zaipai]

Im a bit torn really, whether to go for modern set up or period scrapheap setup?
Old XL500S swingarm and front end . . . . I have a line on some XR650R forks ect but I like the old school idea and it would be a lot funnier

 I have decided to name the bike 'Yajyuu'

Yajyuu is Japanese for beast

I love the name, it fits perfectly.

[obrut]

Pezz,

I'm in Sydney and have a 76 CB400F that I'm modding in a sort of heiwa/gravel crew inspired japanese minimilist style.  As a result, I have a few left over parts.  Let me know if you need any bits and pieces and I'll see what I can find to help the cause.

Cheers, Ryan

[Tim2005]

Sounds a great and worthwhile project. What sort of terrain are you going to be riding over- the XR stuff indicate it's off-road- is this serious rough stuff or reasonable quality dirt roads?

As far as choice of swingarm goes, bear in mind that the 400f swingarm pivot is very close to the crankcases and some swingarms may be physically too big to fit in, so check that before buying. For forks, I'd go for some off the heaviest dirtbike you can find, the 400 engine is much heavier than an XL's etc and you want to avoid using much of your budget buying stiffer springs too!

[Pezz]

Tim

I am organising a fundraiser for the Down Syndrome Association in 2010.

We re going to ride to a place called Wanaaring which is 200K west of Bourke NSW, Australia. Click Google maps for the location.

There will be some rough dirt roads during the trip as we will loop down in Western NSW.

Also looking at XL500S front end. Want to try to keep it Honda and not butcher the donor bike, appreciate you advice regarding the size of the swing arm.

[Pezz]

Well over the weekend I got to do a little surgery on the little 400/4.
As it is not running I decided to pull the carbies out and give them a thorough clean and service.



A broken manifold will need to be replaced.



A quick look inside the Carb’s shows number 1 opens a long time after 3 & 4 and 2 doesn't move at all. I will post the carbie rebuild photo’s as I go.

I will be doing a compression test but from the look of it a head gasket might be on order too. Or is this normal weepage on one of these?
 I am just weighing up how far to go with this as it is not a full restoration. I will know once I have the comp test numbers.



I am still looking for a  XL or XR front end, so if anyone on Oz is reading this can help?

[Ecosse]

this will be one unique beast! 

[Pezz]

I have found a great deal on a 460cc piston kit for the 400/4. $360 landed in Sydney. 

Anyone done one of these rebores?

Now I have to do a Compression Test to see if it needs the rebore.


MMMMM XR460 Four 

[rachet]

Interesting  build and worth following.

[Pezz]

Well I have just completed the compression test tonight 

1- 55 then 73 psi
2- 54 then 68 psi
3- 70 psi
4- 65 psi

A little bit of oil in No:1 and 170 psi

Looks like a 460cc kit is on the way.

Have also been looking at the air filtering system, looks like a lot of places for leaks, so I will have to have a good look at that as well. Im not a fan of pod filters but I will be riding over 600k's of dirt and gravel when its finished, so any suggestions 

[Pezz]

A little package arrived last Friday and when I opened it look what greeted me 

Im will pull the top end off this week and get the barrel bored.

Does anyone have the piston to bore clearance suitable for this engine??

[Ecosse]

dunno but that piston is too pretty to hide in a motor.

[Zaipai]

dunno but that piston is too pretty to hide in a motor.

I agree, why do you think they make em so pretty if they are just going in a motor?

[Ecosse]

dunno but that piston is too pretty to hide in a motor.

I agree, why do you think they make em so pretty if they are just going in a motor?

well, from an artists point of view everything that is good is inherently beautiful.

[Pezz]

Started to pull it down last night. Easy to work on.

I may have an oil leak to fix



Here is the rocker cover. A little pitting on 2 of the cam followers.


Pretty clean inside

[Pezz]

Progress has been a little slow.

I have the Barrell getting bored out to take the 460 pistons.

I recently picked up an XL250R with an XR Disc brake front for $362 off ebay 

I am working through the possibilities of fabricating a new airbox to accomodate the Prolink rear end. I would have to run vpod filters and build a box around them. . . . . I worry about the stock airbox sealing out the dust when off road

So it will be a busy Christmas period building an XR460Four

[c91x]

i can't wait to see the finished product....  are you concerned with being undersprung with the forks and shock off that 250

[Zaipai]

Good point. Perhaps stiffer springs?

[Pezz]

i can't wait to see the finished product....  are you concerned with being undersprung with the forks and shock off that 250

I am aware of that, the 400 is pretty light and with out the guards ect will come up light. I will wait until I get it together and see how it works. I have a few old valve springs I could slip in if needed

Kidding about the valve springs. Until its all together I wont know.

Also looking at fuel tank options too.

[Ecosse]

I am aware of that, the 400 is pretty light and with out the guards ect will come up light.

cb's weigh quite a bit more than the thumpers though.

Also looking at fuel tank options too.

as for the tank how about one from the old 1970's xr?

[Ecosse]

this is what i was thinking. it's a dirt bike tank and kinda sorta period correct. sorry about the crappy picture.