OzVMX Forum

Clubroom => Twinshock Trials => Topic started by: David Lahey on April 19, 2009, 03:05:37 pm

Title: For Wombat Cota 172
Post by: David Lahey on April 19, 2009, 03:05:37 pm
In here there is a nice brochure photo of a 172 but it has round fork legs.

http://geocities.com/cotamontesa/

I don't think I've seen one before with square fork legs but I'll keep looking
Regards
David
Title: Re: For Wombat Cota 172
Post by: cappra on April 19, 2009, 07:32:51 pm
Post 1979 Cota 123/200's had square forklegs.  172 never did.
Title: Re: For Wombat Cota 172
Post by: Wombat on April 20, 2009, 06:30:27 am
Thanks for the site David, I've been Googling Montesa images and sites over the past few days.
I'm yet to locate any leads on workshop manuals - are they available (preferably in english...)?
And cappra, thanks for the tip on the forks. David directed me to your site - very tidy and informative by the way. 8)

I bought the bike on eBay and the blurb calls it a '1976 Cota 172 rare square-fork leg model' - which meant squat to me.
It's a mid 70's Spanish trials bike and that's what I'd been chasing for a while. I have no 'Trials' background.

But tell me, does having later model forks mean I'll have dramas with scrutineering at vintage/twin shock trials? :-\
And are these 'Factory Koni shocks'?
Title: Re: For Wombat Cota 172
Post by: cappra on April 20, 2009, 06:17:55 pm
There was no "rare square fork leg model" on the Cota 172.
I don't think you will have any problem passing tech, as the forks you have mounted
look to be from a 76' Cota 348, so your in the same time era, if that matters.
Not sure of your rules there, but in the states, this bike would have no problems
getting thru tech.  Sorry, but Koni's never came as standard on Cota's.  Again,
I don't think you should have any drama going thru tech with aftermarket shocks.
There are no official Montesa workshop manuals.  There are
Chilton and Clymer repair guides, but they are not model specific.  They still give
some good general information.
Title: Re: For Wombat Cota 172
Post by: Wombat on April 20, 2009, 06:29:00 pm
You're a wealth of information cappra, thank you!
I'm currently chasing one of the Clymer 'Vintage' series manuals as it claims to cover Montesas of that era.
'Chilton' I'm not familiar with - but when in doubt, Google it... ;)
Title: Re: For Wombat Cota 172
Post by: cappra on April 20, 2009, 07:18:30 pm
The Clymer guides are pretty easy to find on Ebay.  They did reprint the manual
but it's bundled in with the Bultaco and Ossa repair guide.
Title: Re: For Wombat Cota 172
Post by: David Lahey on April 23, 2009, 01:59:50 pm
Jared those forks on Wombat's 172 are not from a 348 - 348 forks have a leading axle. Don't ask me what they are off though.
Wombat, eligibility scrutineering for Twinshock class where you will be riding is based on peer pressure -you and your 172 will be welcomed with open arms.
Our MA rules say that the bike has to be a pre '87 twinshock model and have drum brakes and air cooling. There was a 1984 cut-off a while back but we wanted to allow people to ride TLR250s and late model Cota twinshocks so it was changed to 1987.
For an example of what would be frowned upon is Yamaha monos are air cooled and drum braked and came out in 1984, but are not allowed even if modded to be twinshock.
David
Title: Re: For Wombat Cota 172
Post by: JC on April 23, 2009, 05:46:08 pm
How reliable were the 172 motors? I read somewhere that they had fragile clutch/gear selector/kick starter issues. Is it true?
Title: Re: For Wombat Cota 172
Post by: Wombat on April 23, 2009, 06:41:42 pm
...eligibility scrutineering for Twinshock class where you will be riding is based on peer pressure -you and your 172 will be welcomed with open arms.
Our MA rules say that the bike has to be a pre '87 twinshock model and have drum brakes and air cooling. There was a 1984 cut-off a while back but we wanted to allow people to ride TLR250s and late model Cota twinshocks so it was changed to 1987...
David
How nice is that? Are you talking about OZ? That sounds like the Kiwi attitude to VMX. ;) :D ;D
But thanks for the tip.
And by the way I've also picked up a TY250A, though neither have arrived as yet.
Title: Re: For Wombat Cota 172
Post by: cappra on April 23, 2009, 06:42:30 pm
Your correct.  The 348's forks are leading axle. I checked all my data
and the only square fork legs with a non leading axle is the VA mx model!
so I'm not sure what they are off of.

JC,
The motor is reliable.  There is a problem with the kickstarting mechanism.
When starting the bike you have to feel the kicker engage the starter gear
before kicking.  If you just pounce on the kicklever, you can strip one or both
kick gears and finding these gears new is almost an impossible task.  You don't
want to treat this motor the way you would an mxer!
Title: Re: For Wombat Cota 172
Post by: Wombat on April 23, 2009, 06:51:53 pm
...the only square fork legs with a non leading axle is the VA mx model!
so I'm not sure what they are off of.

...There is a problem with the kickstarting mechanism.When starting the bike you have to feel the kicker engage the starter gear
before kicking.  If you just pounce on the kicklever, you can strip one or both
kick gears and finding these gears new is almost an impossible task.  You don't
want to treat this motor the way you would an mxer!

What year is the VA MXer? Any more 172 hints like the kick starter tip? :-\
Title: Re: For Wombat Cota 172
Post by: cappra on April 23, 2009, 11:40:25 pm
VA's were built in 1976.  No other tips for the 172 that I can think of.
Title: Re: For Wombat Cota 172
Post by: JC on April 24, 2009, 08:12:40 am
They don't look long enough to be VA fork-legs.

What dia are the fork tubes Wombat? 35mm? They look smaller than that.
Std 172 tubes were 30.5mm I think.
Title: Re: For Wombat Cota 172
Post by: Wombat on April 24, 2009, 07:52:34 pm
Hmmm, I'll measure and let you know - when it arrives.
The body work looks quite faded in the photos. Is that fibreglass or a plastic?
Would 'cut & polish' (Bling in a tube ;)) bring it up?

and while I think of it, do you think maybe the high sitting rear mudguard is the result of looping it?
I haven't seen any other 172's with a guard that high. :-\
Title: Re: For Wombat Cota 172
Post by: JC on April 25, 2009, 09:21:42 am
W,

yes the rear loop is definitely bent up way hi-er than std. Tank is fibreglass & would probably benefit from cut & polish.

I seem to recall that 172s originally came w 20" fr & 17" rear wheels, tho later models may have come w 21/18".


Jared, can these engines be safely taken out to 175cc w a larger (64mm) piston? (or thereabouts?)
Title: Re: For Wombat Cota 172
Post by: David Lahey on April 25, 2009, 09:54:16 am
Wombat what's that about Kiwi VMX rules and changing eligibility dates?
JC I thought that it was only the 123 that had the small wheels.
I'll post a nice picture of a little Monty from the Hunter Valley
Title: Re: For Wombat Cota 172
Post by: cappra on April 25, 2009, 09:56:18 am
The Cota 172 engine is nothing more than an over bored 123.  The 123 had a
54mm bore, and the 172 was 60.93mm bore size.  Both had 54mm strokes.
Oddly, the 172 was actually a 157cc displacement.  Don't think there is enough
material to be taken out to 64mm.  Another strange thing is that the 123 used
a 25mm carb and the 172 used a 20mm carb.  I remember that Bultaco did something
like that, using a smaller carb on the 325 than the 250, perhaps for lowend response.
Title: Re: For Wombat Cota 172
Post by: JC on April 25, 2009, 10:47:32 am
Yes, but I seem to recall reading that the bike's development started as a full 175 & was downsized from there. Also seem to recall that there's a fair bit of 'meat' in there for boring out, but I could be wrong.

Dave, how good were they in competition? (There's a chap up here w one for sale fairly cheaply, so I'm considering it, sort of)
Title: Re: For Wombat Cota 172
Post by: David Lahey on April 25, 2009, 04:07:02 pm
I think how well they go depends on how big you are. Not because of the motor performance, which is quite good, but because they are a bit smaller than other trials bikes in length. The TY175 suffers a bit from this too, but the Cota 172 feels a little bit smaller again.
Have a read of the TY175 vs Cota 172 comparo in T&T magazine. I think it was by Ken McIntyre. I think there might have been a comparo in ADB too but can't remember too much about it.
I'm 5'10" and found my mate's 172 a bit cramped (in 1976) but he was a bit shorter and it suited him fine. The main place I noticed it was in the fore-aft distance between the handgrips and the footpegs.
There was a bloke (Chris Lyons) who rode one in SE Qld trials at quite a high level back then and he didn't seem to have any issues doing well on his.
Title: Re: For Wombat Cota 172
Post by: cappra on April 25, 2009, 06:10:27 pm
I agree.  If your over 180 lbs (at the max) you should not be riding a Cota 123 or 172.
They were very light and nimble for a lightweight rider! 
Title: Re: For Wombat Cota 172
Post by: Wombat on April 26, 2009, 01:24:06 am
Wombat what's that about Kiwi VMX rules and changing eligibility dates?
It's just a comment about the Kiwi flexibility with their VMX rules and regulations in general.
And now I'm stuck trying to think of a good example...

You may have noticed many of our threads can go for page after page lamenting the Aussie over-regulation and hair splitting opinions on the eligibility of certain models.
Complaints of MA riding roughshod over the interests of the Members... accusations of a small 'power group' controlling our sport and not always for the best etc, etc.
DJ & Bill often mention the 'turn up and ride' attitude to the Kiwi VMX in general.
Probably how ours was intended before committees got involved. :-\
Nothing dodgy though! I'm sure they have enough rules in place to keep things tidy. ;)

From the outside looking in it appears (to me) to be a bunch of enthusiasts agreeing to ride/ race without getting 'buried in red tape'.
So, when you said "we wanted to allow people to ride..." I saw that as common sense flexibility - for the good of the sport... how it should be.
Title: Re: For Wombat Cota 172
Post by: David Lahey on April 26, 2009, 08:16:49 am
Thanks Wombat
Yes I reckon we fit the NZ model in twinshock here. The only bike I know of that has been stopped at machinery because of it not being within the spirit of the rules was a special that was built in the late 1990s. The frame was a (geometry and appearance) copy of the then current GasGas frame (twin spar perimeter frame). It did have two shockies and drum brakes and an air-cooled (DT250D) motor and was a credit to the bloke who made it, but didn't even resemble anything that had been made in the twinshock era.
Frames (and anything else) here in OZ can be modified in any way the owner fancies and still be eligible. Common changes people make on 1970s bikes are to change the steering geometry on bikes that had slow steering, to lower the footpegs on bikes that had them quite high, and to move shockie mounts to increase rear wheel travel a bit. Bikes from the 1980s are rarely modified as they are pretty good in those areas already. The footpeg mods are mostly driven by the current rules that allow stopping without penalty.