Pre 81 MX class rules?

[Kwaka-Kid]

hey guys,
firstly is anyone racing in this class on here?

The biggest issue i have is my XR500 has a 23" front wheel. and its proving (online) hard to find any manufacturers that make any good rubber for it! i can only see that bridgestone make an enduro tyre for it but id need a proper MX style full knobbly as it will only be used in the sand and on the dirt.

so my main question is do the rules either let me drop a whole front end off a XR200 in or later model 250 or something, or can i at least just go get a 21" front wheel for it?

and if its the 21" wheel... anybody got a spare they are willing to sell?

any info on this class is much appreciated or links to sites which state the exact rules (though i know from circuit racing some of the rules are let slide like this for reasons like availability of parts etc)

cheers KB'ers!

[Firefight]

hey guys,
firstly is anyone racing in this class on here?

The biggest issue i have is my XR500 has a 23" front wheel. and its proving (online) hard to find any manufacturers that make any good rubber for it! i can only see that bridgestone make an enduro tyre for it but id need a proper MX style full knobbly as it will only be used in the sand and on the dirt.

so my main question is do the rules either let me drop a whole front end off a XR200 in or later model 250 or something, or can i at least just go get a 21" front wheel for it?

and if its the 21" wheel... anybody got a spare they are willing to sell?


when do you need the 21 incher by Logan ?I think I know where one is, also looking for my old MNZ rule book now can, t find it yet too much shit in shed of humble cottage, may pay to pm Oscar/ Motu or Merv I think they may be able to answer your question.Will be working at woodhill next saturday, pop out if you get a chance.

F/F

[Kwaka-Kid]

next saturday? im there. Surely wont have bike ready but ill come out on the streeter to remind myself where it is and say hi.

k, i dont need it in any big hurry, got a bald front tyre on the beast atm, good enough to get the bike going on and the engines still in getting a main mount welded back on. So sorry but i should have checked my book i have one somewhere too, completely forgot it covers dirt doesnt it? i have it on my PC somewhere too... damn just as disorganised

[NordieBoy]

Get your 23" hub laced into a 21" rim.
The 23" hub has better braking effect than the 21's (bigger diameter).
I think you can even get away with using for example a new Excel rim as it is a safety thing not performance but I just picked up a 21" from a kx125 off trademe and stripped the rim off it.

I have also made a new seat for my 250 that's 3cm taller and a lot firmer than the 25 year old foam in the original :shake:

Check out some of the rules at http://www.vmx.livewire.gen.nz/

Have fun :2thumbsup

[Kwaka-Kid]

your a legend nordie!

thanks for the link and the tip with the wheel - my dad says he has relaced rims loads before, not hard at all, but i still have the problem of not having a 21" rim and a limited budget which crosses out buying new... but hopefully if FF's contact or whatever works out i could relace the 21" rim to my hub if i find braking is bad (otherwise ill be lazy and leave the 2 seperate) So tell us nordie when you planning on racing ur 250? i used to have one of those too when i was about 12! awesome machine eh.

[NordieBoy]

So tell us nordie when you planning on racing ur 250? i used to have one of those too when i was about 12! awesome machine eh.

I had my 1st ever race at the North V South on the 10th.
http://www.classicmx.nelson.geek.nz/2004-10-10-NorthVSouthClassicMX/

I like the 250 as I can race in Smallbore, Pre 80 B, Pre 85 :done:

Unfortunatly I'm still using the 23" front and can't turn as tight as basically everyone else, that's my excuse and I'm sticking to it :devil2:
I've got all the bits to go to 21" but money and time...

I'm going to remove at least the front balancer, get the head cleaned up, compression raised and another pipe on it.
It's a bit slow revving for MX but perfect for trail riding at the moment.

I'm building up 2 sets of wheels so I can have an off-road and an on-road set as I'm getting it road registered :soon:

I've already built up the seat to my 6' 2" spec - no more 25 year old foam and knees around ears :laugh:

http://motorsport.nelson.geek.nz/mybikes/dirt/xr250/

[Kwaka-Kid]

hmm.. interesting.. what is the downside of not runnnig the balancer shaft etc ? aside from more vibes, does it not ruin the engine anywhere quicker?

also what tyre are u running on the 23" and is it suited for motorcross?
going to the links to checkout now dude, you the man tho! good to hear u just had a race! i cant wait just to toodle about and have some good old fun - did you find like everybody was really really good?

[NordieBoy]

hmm.. interesting.. what is the downside of not runnnig the balancer shaft etc ? aside from more vibes, does it not ruin the engine anywhere quicker?

Revs pick up/drop off quicker = quicker shifting and better acceleration.
More vibes = rubber mount the exhaust.


also what tyre are u running on the 23" and is it suited for motorcross?

Some good knobblys but I have no idea what brand or anything.
The bike is stored in my brothers shed so I can't check.
They were 2nd hand when I got the wheel and don't have much in the way of nice clean edges on the knobs.
Coming out of hairpins I couldn't keep in the ruts that had formed as the bike just wanted to push wide across the damn things.

The 23" is brilliant for trail riding as it goes over/through anything without any twitchyness at all but isn't sharp/responsive enough for MX really.


going to the links to checkout now dude, you the man tho! good to hear u just had a race! i cant wait just to toodle about and have some good old fun - did you find like everybody was really really good?

It was great fun. I had some good battles and didn't come last.
After the first race I didn't even get lapped :D
Really really good? That's why I entered Pre 80 B Grade :D
Leave the A Graders to their own racing...

[laRIKin]

The 23" hub has better braking effect than the 21's (bigger diameter).

Sorry but I think that you are wrong on this one.
The 23" wheel has more leverage on the drum so that means less braking.
Also has more mass to stop.

I know with my van has trouble with 14" wheels to pass a WOF (hand brake),
until I put the 13" rear wheels back on (thats what it can out with stock).

[laRIKin]

When to 23" wheels came out we found that they were good over ruts.
But were not so good following them.
They seamed to rail the bike and you could not get back out off them.
I can not tell you why this is, but when I was riding with a mate that a
XR500 with 23" front wheel. And I had a XT500, when I turned a corner in the
bush my mate would go straight ahead, unless he could see the ground.
Are the 23" tires narrower?

I think that you are alright to race as long as your motor is on the era.
And you have drum brakes and are twin shocked.
Well that was the rules down here a while ago, any way.
Could of changed how, because of the rule police.

[NordieBoy]

Sorry but I think that you are wrong on this one.
The 23" wheel has more leverage on the drum so that means less braking.
Also has more mass to stop.

Not when you match the hub up with a 21" rim :D
The 21" brake drums are a smaller diameter than the 23" ones.
The braking effect is about the same with the 21's and the 23's but stick the 23" hub in a 21" rim and it's even better and you havn't even had to get a twin leading shoe setup (and you also have about 15mm square more braking surface as well) :sly:

[Kwaka-Kid]

choice info thanks guys!

hmm so nordie where are you? in aucks where would i race and what class would i enter the 1980 in, you say pre 80 class, that means id be in the next step?
i was under the impression there was a pre 81?

Either way should be fun just getting the beast out there, and excellent a B class, how about a C ? :D im going to do loads of woodhill and general riding before i come close to racing but for sure it is the eventual goal.

[NordieBoy]

You'd have to find out your local club rules as to what classes they run.
Down here in Nelson it's Pre 75, Pre 80 A, Pre 80 B, Smallbore (<250 4st, < 125 2st), Mid Bore (<350cc 4st), Open 4st, Open 2 st and usually All In.

Some clubs have small bore as <350.

The 1980 XR 500 had no changes from the 1979 one except the tank sticker so you should get away with it.

[laRIKin]

Not when you match the hub up with a 21" rim :D
The 21" brake drums are a smaller diameter than the 23" ones.
The braking effect is about the same with the 21's and the 23's but stick the 23" hub in a 21" rim and it's even better and you havn't even had to get a twin leading shoe setup (and you also have about 15mm square more braking surface as well) :sly:

I stand corrected, I was not sure, or even thought that Honda up-ed the size
of the drum on the 23" wheel.

I was thinking after my post.
I can remember going to a Honda promo do, boy did I leave there with Honda
is the greatest, and the most innovative bike company for designing the 23" wheel ringing in my ears.
If they said it once. Hang on they didn't, they kept on saying every two
minute's until we all weakened and joined in, NOT.

The 23" front wheel stayed around long than the 20".
Boy that one did not last long at all.
Does any one know how long the 23" lasted for?

[NordieBoy]

XR's had 23's in 79 and 80 and the XL's had them in 80 and 81.
Then the XR went to 21" front and a 17" rear <_<

The brake drum diameter on the 21" is about 124mm and on the 23" it's about 137mm.

The actual braking surface on the shoes is only 3mm longer for the 23 over the 21.

I need to get out more :rolleyes:

[Motu]

The 20in front has been around a hell of a long time,had a ridgid BSA C11 with a 20,my 1967 Cheney had a 20,always trying the size inbetween,must be a reason.That 23 sure took some effort to change line.

The classic guys in Auck aren't part of MNZ,are adament about not having competition licences,they used to have ''demonstration rides'' with no flags.Not too sure what they do these days.Most of the guys running the show are Westies KK,so you should be able to find someone local to set you right.

[Kwaka-Kid]

Wicked motu my dirt brother!

Where are they at? are you one of them?

hmmmm. interesting no MNZ? strange. i have a race licence anyway.

[laRIKin]

XR's had 23's in 79 and 80 and the XL's had them in 80 and 81.
Then the XR went to 21" front and a 17" rear <_<
.................................................. ................................
.................................................. ................................
I need to get out more :rolleyes:


Thanks for that info.

It's funny really, how they some times play around with stuff on bikes.
And in the end after CADing it CAMing it and a room full of experts,
talking and deliberating about it.
They go back to the what was all ways their.
Makes me think that the old bike designers new what they were doing.

[laRIKin]

The 20in front has been around a hell of a long time,had a ridgid BSA C11 with a 20,my 1967 Cheney had a 20,always trying the size inbetween,must be a reason.That 23 sure took some effort to change line.


I was meaning on MX bikes.
They for you that may not know, tryed the 20" on MX bikes a few years ago.
You could buy one brand I know of (now not to sure Kawasaki) with the
option of the 20" front wheel.
It flopped and the wheel only work well on flat MX track's, from what I can
remember.

The bikes that you are talking about, were they Scrabblers or Street?

[Motu]

The Cheney was a hand built motocrosser,they are still made today - mine was built for Ivan Miller,the best Motocross rider in New Zealand in those days.It was actualy a 1968,I got that wrong.The C11 was a grasstracker,and the rear tyre I seem to recall was a Firestone Grasstrack.

KK,I was talking to Peter Groves a couple of weeks ago,he was involved at the very begining and is still riding in classic MX,in case you don't know who he is,he was the original owner of Mt Eden Motorcycles.Mike Fullerton is also very involved,last time I was speaking to him he was foaming at the mouth about MNZ and competion licences,I know some others out west too.

[Kwaka-Kid]

thankyou very much, know why does the name fullerton ring bells? strange.

anyways cheers again dude.

i now have another problem you might be able to help me with
the XR500 engine came with the right rear engine mount snapped off, like if you recall the engines (all the same those early honda singles) this was apparently not uncommon, and the top of the mount on the engine has pulled off.... what do i do, i cant be arsed pulling it to peices to split casings to hand my mate the case to weld... any other ideas? was just going to ride it the way it is... cant weld in place as all the rubber seals in the engine will melt. any advice really appreciated.

[Motu]

No 8 is a good Kiwi standby.The cases could still be welded by a brave welder with the gears still in - Graham Gordon used to weld Austin Maxi gearboxes for us with the gearbox still together...but he's a nut case,and they never leaked either.Don't know if you could find someone that crazy these days...unless you talked to Graham,but I doubt he does that sort of thing now.

[laRIKin]

[QUOTE=Motu]The Cheney was a hand built motocrosser,they are still made today - mine was built for Ivan Miller,the best Motocross rider in New Zealand in those days.It was actualy a 1968,I got that wrong.The C11 was a grasstracker,QUOTE]

Well there you go you learn something every day.
I new that some of the older bikes had 19's but did not know about the 20's.

I will have to do a seach on both now.

Cheney Racing (http://www.cheneyracing.co.uk/)

Ivan Miller (http://www.motorcyclingnz.co.nz/news2.aspx?SectionID=29&ArticleID=604)

[Motu]

Good on ya - I know I got some tall stories...but they have a foundation in truth...somewhere....

[Firefight]

ma mates got a 21 inch complete wheel off an 80 XR500 A, havn,t seen it, but hes pretty good, he sorted Sudeep out on heaps of stuff , they want NZ$110.00 for it, left a message on your celly, but I know your too much of a tight arse to pay to get ya message, so let me know what ya wanna do

F/F :eek:

[Kwaka-Kid]

not only did i get ur msg but i left one on YOUR celly! :P


heh! baby davey banana boy

[Firefight]

not only did i get ur msg but i left one on YOUR celly! :P


heh! baby davey banana boy


sorry My Bad !! :doh: , will check my messages now !!

F/F :thud:

[Motu]

The 20in front rim may be one reason I didn't like the Cheney,I just made it a runner with a rough engine,took it for a few blats and couldn't be bothered again.I prefered the handling of my Rickman - this was made for natural terrain,the soft loam under grass and pine trees...made for sitting down feet up full lock slides on the deep soft berms that built up naturaly on corners,and the low but long jumps that aren't manmade,I just loved the feet up powerslides and standing on the pegs power stands.I never raced this bike,it was my street bike,but of course took it off road as well.

The Cheney I think was made for a different era - the begining of 2 strokes and man made tracks,it may of even been a one off for a specific type of track,it was short,light and quick steering,and the 20in wheel may have been part of the parcel,it was certainly a nervous bike to ride.

[pete376403]

If you're really desperate for a tyre for a 23" rim, speedway bikes since the year dot have used that size on the front. Might be a bit narrow for an XR at 2.75", but they are a reasonably blocky type tyre, bigger knobs than a trials universal but not as big as a full knobbly.
Also they used to use a 23" on the rear back in the '20's and '30s, the rear size was a 3.50" but the tread pattern was a bit weird - knobs arranged in a sort of "S" acrros the width of the tyre. "leapahead" was a favoured brand. However the rubber might be getting a bit hard, if you could still find one these days

[Kwaka-Kid]

yeah :S i would quite happily strugle around with the 23" on the front, but like i said availability of rubber, can anybody help s out and name any models of any brands that come in 23" to fit a 1.60 rim?

Also what are the rules on dates? i was fairly confident if i wanted to be in pre 81 the latest model part had to be pre 81, which is a shame because i also own a XR200R 1984 which has a 21" drum on the front, i think it would pop quite well into the 500 and i could just shove the 23" on the front of the 200 for when i needed the 21. But im worried the scutineers will know the diff and or pull me up for it. hmm what to do.

[NordieBoy]

Usually you can get away with "follow on" models.
This is where the bike hasn't changed between years.

http://100megsfree4.com/honda/h0500/xr.htm

The only difference between the '79 and '80 models was a smaller exhaust and a different tank sticker.

In '81 it went to mono-shock.

The 200 would be a bit too new.
You would have to race it in Evolution class (pre 85).

[Kwaka-Kid]

yeh dude - sorry i cant have explained myself properly, and yeah i already googled that site out :P

i mean still race the 500 - but can i put my 84 XR200 front wheel in? god its still crappy drum brake and id still use original forks. Secondly what can i do in terms of exhaust? as it came with a home made (back in mid eighteys) rolled can muffler, as the original rusted out - surely they cant expect it to be stock?... and if not hten how far can i go? buy a brand new system ? (not that i would) but get the old man to make a better system

[NordieBoy]

Exhaust shouldn't be any problem at all.
I'm sticking one of these on :cool2:
http://fran.orcon.net.nz/ids2.jpg

Most of the serious guys stick modified period type pipes on because they look the part. Imagine a 1979 XR500 with a T4 hanging off the side :eek:

Hmmm. Not MNZ affiliated, no noise restrictions?

This bike (http://motorsport.nelson.geek.nz/dirt/2003-11-30-Glenhope/mvc-181f.jpg) is straight headers and is the sweetest sounding thing you've ever heard.

The only problem with sticking the 200 wheel in (if it fits) is it's probably going to have bugger all (ok ok even buggerer all than normal) brakes as the 500 is quite a bit heavier than the 200.
But if it's just to have a play type of thing then go for it.

[Motu]

The next VMX is on dec 5th at Kiwitahi rd - that's on the right off SH16,just after the first Woodhill Forest entance sign,go to the top of the hill and turn right,it'll be a couple of km or so along there.

We had a Northern Trials Group trial up there today - Derick Hamm runs the NTG and also does VMX,so he has got this property for the VMX.One of the best things about trials and VMX is that you get to ride where others aren't allowd,on private property.Kiwitahi rd is fantastic...it sits at the top of the ridge,looks over to the forest,360deg views,stunning.

The NTG trials are hard for twin shocks,but they make an easy line for us - didn't help me today,I DNFd.On one section with a very steep climb I sat down and the bike started to loop - I stepped off the back and brought it around in a perfect 180...but it landed hard,my forks are tweaked and I think the front axle is bent.I have some shit in the carb and it kept stalling - I was absolutly knackered,so after the 2nd round put the bike on the trailer and rehersed my excuses.

Hope you can make it KK,I'll be there - as a spectator of course.

[Kwaka-Kid]

WICKED!
cheers dude!
i JUST GOT the XR500 going fully today.. all good cept when i take her off choke to ride up and down the road it wont idle? yet i have to blip throttle up a fair bit to keep her revving, and she does smoke a fair bit but not as serious as my 200. Hopefully will be there if i finish designing my own exhaust/muffler, my headers are SHOT and braised together rust is about all they are now.

[NordieBoy]

Carb clean?
Rings?
Traditional crack between plug and exhaust valve (or is that just the 250's)?


My 250 is a bit low on compression but I really really need to lose the counter balancers 'cause it just revs up and down so lazily it's not funny.
Perfect for trail riding as it'll go anywhere but I want a bit of snap to it.

[Kwaka-Kid]

is this your beast nordie?

was my old xr250, brother is on it, he woulda been 15.

[NordieBoy]

Looks somewhat like it.

Mine is the XR in front of my brothers gut...

http://motorsport.nelson.geek.nz/dirt/2004-10-10-NorthVSouthClassicMX/20041010-115253.jpg

The overbored Nifty with knobblies was fun as well :blink:

[Muzz67]

After riding B Daniels XR 250 with the Bshaft removed, my advice would be to LEAVE EM IN THERE!!!!! It was awfull and a 10 minute race gave me the worst arm pump I have ever had.
The tyre choice for a 23" rim is not good, and its probably best to relace a 21" rim onto the hub as suggested. No other front wheel slips into the forks without modifications, so stick with the original hub.
As for the 500 not running well, this is probably caused by the leaking exhaust, as I know when the header on my 500 crapped out it started backfiring on over-run and would not idle.And it was only a small hole near the head!