The Tale of two ty250 Mono's - pic heavy

[thaiguzzi]

There. Now say that again, but faster. Bit of a mouthful...

This is the story of building two nice Yamaha ty250 mono's from a set of four i bought last year.

Air cooled monoshock trials bikes.

I've called them "Ol' Blu" and "Ol' Yeller".

Because one is painted in classic late Bultaco colours of white chassis with blue tank and seat unit, and the other is a  black chassis with classic Yamaha yellow tank and seat unit.

Both will have Yamaha speed block decals.

Both have had a bunch of money thrown at them, and a ton of hours (in excess of 200 hours the pair).
Hopefully finished in a couple of weeks.

 

[thaiguzzi]

The four photos above are the actual photos used in the ad that i spotted, several weeks or even months after it first appeared on here, TV Classifieds, and possibly B&S.

Rang the guy up, they were to be sold as a set of 4 only, not split up, plus several spares, advertised at 39k, located in CM. One was a good quiet runner, one was a rough runner, just, the rest were in various states of dis repair. One complete spare engine, new Made In Chang Mai fibreglass mudguards, spare monoshocks and linkeages, and other stuff not in those photos. Guy said he'd accept 35k for the lot, not a Satang less, and seemed genuine and knowledgeable.

 Time to borrow a cab 2 seater pick up truck (no way that lot would go in my 4 door Vigo) and hit the road to CM...

 

[thaiguzzi]

Left early  80 kms from the other side of Udon, , got there just as it's getting dark. Have'nt been to CM in a few years, Jeez the traffic is bad. Guy had booked us a decent guest house just up the road, but first to the business.

Guy was really nice, really knew his stuff regarding trials bikes, stunning house and workshop, marvelous collection of motorcycles and cars, large collection of Honda trials bikes through the years which he was slowly whittling down, plus the last of his 2 strokes - these Yamahas.

Deal was a deal, bought some extra new Vee Rubber trials tyres, loaded up, and  went out for a pizza with the guy. Beers, bed, and long slower journey back home.

This was February last year, 2016.

More to follow...

[thaiguzzi]

So i've got home and start seeing what i've actually got, and start doing my research, downloading parts and workshop manuals, putting them into print etc etc.

Turns out they are all 1984 Japanese Market only models, first year of production. Nice. Frames are numbered, but the motors have left the factory (all 5) un-stamped. The Yamaha motor number pad is still there, unblemished, but no number stamps.

3 are ty250S models (S for Street legal), 1 is a ty250R (R for race = competition only model).

Difference being the S models have a bunch of bracketry on them for legal stuff like lights, indicators, horn etc, and even an oil tank for 2 stroke oil. The R has none of this, ran pre-mix as std, no oil pump and had a magnesium clutch cover as std. Says so on the cover where the other 3 have the word "kickstarter". The R also had one bracket the others did'nt have - for the remote gas resevoir for the race shock.

All the bikes run magnesium brake plates, front and rear.

Interesting, the front drum has an INTERNAL brake lever, nothing on the outside.

Also these ty250 Mono's ran a unique rim/hub/spoke set up. Hubs have 16 holes, rims have 32 holes and there are 16 spokes and 32 nipples. Yeah, unusual and downright weird. Unique to these models, and they never changed the design till they went front disc in 1990. They are called Z spokes. They can't have set the world on fire, because when patents ran out, nobody ever copied them...

The three S model also have 5 litre steel petrol tanks, the R version running a 3.5 litre plastic tank.

More to follow...

 

[CMKiwi]

Interesting project(s) and I dare say will keep you busy for some time.. I hope your man cave is ready!

[taninthai]

interesting ,,, and looks like a mission and a half,,,,i take it they are finished now,,,,come on really wanna see this yellow and black one.sorry just see finished in a couple of weeks

[papa al]

...been waiting for this thread for a while....

[thaiguzzi]

Everything is prepped and painted. Just need final assembly.

Oh and the exhaust downpipes and mid boxes still need a good seeing to with the gas torch.

About another couple of weeks. Been busy (Triumph, farm, farm machinery etc)

More posts and pics in the meantime...

[thaiguzzi]

59 minutes ago, taninthai said:

interesting ,,, and looks like a mission and a half,,,,i take it they are finished now,,,,come on really wanna see this yellow and black one.sorry just see finished in a couple of weeks

Both bikes when finished will be absolutely identical, bar the paint jobs.
Part of the reason for this project is to get my 11 y/o son into motorcycle sport. Once he can get both tip toes on the ground we are off practicing.

Ol' Yeller is his, Bumblebee (Transformers etc), kids like yellow/black paintjobs. I do too....

Ol' Blu is mine, i like Bultacos.

[MAZ3]

Can't wait to see them finished, your tempting me !. Cheers

[thaiguzzi]

Ok, quick recap on trials bikes and why the Yamaha monoshock was so important in the history of the sport.

# Pre 65.

Trials was pretty much a Bitish sport and dominated by English bikes. Anything and everything from 500cc four stroke singles to 125cc 2 strokes. Predominantly 4 strokes, ideal capacity 350cc thumpers. Most bikes were modified from road versions, there was not a purpose built from the ground up designed trials bike.

# Twinshocks, 1967-75.

At the same time as the Spanish decided to get involved, Bultaco, Montesa, Ossa, the FIM could see the potential in growth of a worldwide new discipline in motorcycle sport. the 3 Spanish manufacturers were looking for new markets for their 250 2 strokes which were selling in big numbers in the States as scramblers/enduro bikes. So they lured the best British riders away from the staid old fashioned and poorly managed English factories to help design from the ground up their new trials bikes. Sammy Miller to Bultaco, Mick Andrews to Ossa, Rathmell to Montesa etc etc. These were all immediate successes and made the heavy cumbersome Brit bikes obsolete overnight. Light weight 250 2 strokes designed just for trials was the new thing and way forward.

# Twinshocks, 75-85.

A market completely dominated by Spanish bikes selling in their droves for nearly a decade, the Japanese, and then the Italians wanted a piece of the action. All 4 Japanese manufacturers again, lured the top riders away (some of them the same riders that went from Brit to Spanish previously), this time from the Spanish bikes to Japanese and Italian.

The championships were still being won mainly by Spanish bikes, but Yamaha and Honda sold well, Kawasaki and Suzuki dropping out after a few years. And the Italian Fantic brand making fantastic bikes and selling in big numbers. Another Italian brand, SWM, made great bikes and won world championships. To this day, riders in the UK think the 156 and 200cc Fantics were the best twin shocks ever made, and have become a bit of a cult bike.

 This period of early '70s to the mid '80s was the heyday of trials sport, huge number of spectators at championship rounds, an explosion of rider numbers of all levels in Europe and manufacturers selling bikes by the bucket load. It never really took off in the States like the manufacturers hoped for, it was meant to be the next "big" thing but it never happened, the Americans preferring desert racing and moto cross starting to take off big time.

#Air cooled monoshocks, 1984-92

In '84 along came Yamaha with the TY250 Mono.
Every twin shock overnight became dead in the water and obsolete. One word - grip. It had grip and traction that no twinshock could get close too. It was'nt just the multi link shock, it was the design of the length of s/arm and positioning of motor, g/box sprocket etc which was so radical.

By 85/86 every manufacturer had followed suit and made their own. They had to.

Honda, Fantic, Aprillia all made great bikes that won championships, but it was the Yamaha that sold in droves and was so popular at clubman and grass roots level, because, basically the thing was indestructable.

# Liquid cooled bikes 89-94 on

Disc brakes front and rear, radiators and fans, slightly lighter, use of aluminium in frames and s/arms becoming popular, along with USD forks. Design and looks changing. Starting to look like the modern trials bike of today.

# Liquid cooled bikes 95-2001

 As above, but even more radical and lighter. Visible from side view petrol tanks gone, no seat, back to normal RWU forks. Trials is one of the few motorcycle sports where USD forks never took off.

# 2002 on-

Gas Gas produce the TXT Pro which again revolutionizes the sport, and every manufacturer has to make their own version or be left behind. Basically a bike which lost 15 kgs in weight. So bikes went from 75-80 kgs to 65 kgs overnight. Big difference in trials. Pretty much been the same ever since.

 Today's sport is a world away from even the 70's and 80's, stop rules, no stop rules, ridiculous skills. Market is dominated by Spanish (Gas Gas, Montesa - owned by Honda, TRS) and Italian (Beta) bikes with a smattering of French(Sherco/Scorpa) .

Twinshocks is a big popular scene in Europe and the States for vintage bikes as is the pre 65 scene.
And this is where the air cooled monoshock splits the vintage/classic buffs. Some think they are proper bikes, the last of the air cooled proper engines, where bikes still look like real bikes, and others think they are the work of the devil, the invention of the multi link a design from Lucifer himself, making their twin shock bikes obsolete overnight and hence un-competitive in the same class. To this day, air cooled monoshocks cannot run in the same class as a twinshock.

 Here endeth today's lesson...

[Rhys]

Dude,  that is some project, should keep you tinkering about and around for a little bit.   Keep us updated on your creation...On the pegs mate...

[thaiguzzi]

So, i've bought 4 bikes, a bunch of spares inc another motor, another swing arm, another set of forks, another pair of hubs, and i want to build 2 nice ones from that lot and have a bunch of useful spares left over. Maybe even sell one left over cheap as a spares/repair kind of project. Spare engines are nice, but do i need two spare rolling chassis?

Time to sell the Yamilia as i don't need 3 trials bikes, and it will help fund parts needed for the resto.

 

[papa al]

deja vous

[thaiguzzi]

Yamaha ty250 monoshocks.

Came out in 1984, last made in 92, replaced by the liquid cooled, alloy perimeter framed TYZ in 93.

Early ones were red frame and white bodywork. Around 86/87 they went all white and by 89/90 they brought the Pinky out, which was basically a stock ty250 but with a disc front brake (competition by then were using discs front and rear), and, er, pink colour scheme on the mudguards with splashes of green and other hideous gaudy colour schemes. Hate that period of time when all the manufacturers where trying to out do each other in puke designed colour schemes.

6 speed box, 1-4 extremely close together (they will wheelie in 4th just on the throttle at a near walking pace), 5th with a fair gap, and again a big gap between 5th and 6th. 6th only used on the road or between fast sections.

Bottom end of the motor is based on a YZ 490 moto cross, and hence why Yamaha ty250 mono's are reknowned as being pretty bulletproof.

Flywheel has a HEAVY weight pressed on the diameter, and is one of the reasons these motors have ridiculous torque.

There's a saying for riding a stock one of these; rev it up, count 1-2. Cut the throttle back to idle, count 1-2-3-4...

Stock weight is 82-89 kgs depending on the model and spec.

[thaiguzzi]

The Yamilia has gone to it's new owner, time to see what i had.

All 3 spare motors had no pistons inside, just a conrod flapping about. Bottom ends on two were great, one a bit iffy. Bore sizes were useable ranging from stock to 1.5mm o/s.

Quiet runner did'nt need a lot, new spark plug, took the carb apart and stuck it in my hobby ultrasonic cleaner (looks like a toaster...), made up an air filter out of builder's foam (no air filters amongst all 4 bikes),  and rode it around as is. Ran well.

Rattley runner needed as above and a serious carb clean and temporary home made foam filter. Forks were completely shot. Bottoming out, no damping, sloppy. Leaking what little oil they had. So stripped 3 sets of forks out and made do with the best of 3 prs of everything to get one half decent set.

Bike would'nt rev out, carb off again, pretty much all good inside. Turned out that the mid box and end tailpipe were full of those beetle creatures that make their home in any orifice over here. Revving the tits off the thing at a stand still and all these beetles and parts of their home start flying out...

 Anyway, rode quiet one and rattley one round for a few months, making a list of stuff i needed to buy, mod, make, paint.

Went to the UK for a couple of months, c/w a big shopping list. Unfortunately this was a list of two off everything...

[thaiguzzi]

Fast forward to December. Back in Los, suitcase full of parts.

New spares, crank seals, gaskets, s/end bearings, all genuine Yamaha.

New Renthal 6" rise handlebars, InMotion air filters, Talon sprockets, front and rear, s/steel screw sets for the covers, reed cages, carb float bowls, fork seals, chain tensioner pads, 1 x chainguard (important on trials bikes - keeps the mud flung off the tyre going on the chain), wider modern footrests c/w mounts etc etc.

I like the fact that because so many of these were sold, and they've become a bit of a cult bike in Europe and the UK, there is a great parts supply situation for them and a great aftermarket. It's easier to get stuff that breaks regularly like rear mudguards for a 33 y/o Yamaha ty250 mono than a 10-15 y/o Gas Gas or Beta. Also a choice of stators, CDI's etc from different shops.

Yamaha pistons are long gone, but Wiseco (USA) and Wossner (German) make top notch replacements.

 Bought 1500 bahts worth of stainless fasteners in Udon (that's a heavy small bag) for all the fasteners i could change, 2 x new lengths of 520 chain, 2 x new throttles c/w nice grips (300 baht a set - ya gotta love Thai bike shops), new Yamaha RXZ fuel taps @ 100 baht each (ya gotta love Thai bike shops 2.0), new h/bar levers which once modded will fit the stock Yamaha perches and some s/arm chain run protectors off something made for over here, suitably modified with a stanley knife.

[thaiguzzi]

Time to strip the bikes out. I am using two of the S frames, copying the brackets or lack of, off the R competition frame.

First job, cut the stock footrest mounts off, and throw the ridiculous narrow stock pegs in the bin. Buy some 8mm thick plate steel, make some cardboard templates, shape, and weld 1 and 3/4" down and 1/2" back from the std position. Me being a lanky 6'3" bar steward, the stock peg position always felt like i was standing on top of the bike rather than in it. Now has a much more modern feel to the footpegs, twice as wide and more comfortable.

 

 

[thaiguzzi]

[thaiguzzi]

Next was get the S road frames looking like an R competition frame - no brackets inc steering lock!!! Also to lose some weight, especially the weight i had just put back on in the above pics with those heavy footrest mount plates.

Photo below is all the brackets cut off two frames.

To be continued...

 

 

[papa al]

Smart mod with the pegs repositioning.

Much more comfortable & controllable even for shorter person.

Awesome Yamaha YT dirt bikes.

Imagine a 350cc version.

;-)

[CMKiwi]

Thats some pretty good looking welding you got going on there.....1000 times better than some of the Thai sparrow fart Ive seen recently!  Like your welding helmet too.

 

This project seems to be moving along at a steady clip. Well done

[thaiguzzi]

On 14/05/2017 at 0:51 PM, papa al said:

Smart mod with the pegs repositioning.

Much more comfortable & controllable even for shorter person.

Awesome Yamaha YT dirt bikes.

Imagine a 350cc version.

;-)

Indeed, pegs were so old skool...

I know you have a 350 in the States, and i believe it has been played with and breathed on.

The 350's were only sold in the States and Canada. Europe never got them, Canada got the 250 too, but 'Merica never did. Ca'nt beat cubes? Well you can actually.

Research the net and the trials forums, everybody says the 250 was a better bike than the 350. They are identical bar the top ends. The 250 worked straight out of the box, the 350 did not. All to do with poor squish, incorrect deck height, barrel cylinder porting wrong, piston crown - you name it, out of the box the 350 was a sales disaster. The 250 was made for 8 years, the 350 - two years -tells ya something.
250 can be rebored endlessly (7 o/sizes in 0.5mm steps), the 350 can't because it runs a nikasil liner. So these days, according to the stateside trials forums, there are some trick 350's running around, but they've had the BOTTOM cylinder barrel gasket face machined, porting mods, c/head  gasket face skimmed, squish set and either a very expensive re-chrome of the barrel , or an iron liner pressed in and a suitable non Yamaha modified piston inserted.

[thaiguzzi]

On 14/05/2017 at 2:09 PM, CMKiwi said:

Thats some pretty good looking welding you got going on there.....1000 times better than some of the Thai sparrow fart Ive seen recently!  Like your welding helmet too.

 

This project seems to be moving along at a steady clip. Well done

Er, not really. Acceptable i'd call it, but not pretty.

I'm a fitter/turner by trade, ie a machinist/mechanic. Lathes, mills etc, engine building etc. Not a fabricator. I can weld, but it's like sticking 2 bits of metal together. Putting brackets on etc ok, but anything super pretty or structural, i'll pay someone else to do it.

 Just put 2 new skids on the farm tractor's grass cutting box. 3" wide, 6mm thick, 120 cms long. 6mm to 6mm flat plate welded together. Now they were pretty welds...

Welder is a 1982/83 Danish Migatronic mig welder. My dad bought it for me new as a birthday present, expensive at the time. No electronics, just old fashioned board with resisters and thyroidister thingies, mechanical switches, just keeps going. It went tits up a few years ago, would have been binned in England - no spares, nobody prepared to repair the board, took it to the local electronics/tv/stereo repair man, and for 1500 baht, he chased and located all faults and re-soldered the whole board. God i love this country...

Welding mask is a cheapo £35ish quid Chinese auto dark helmet off UK Ebay. Works a treat.

[CMKiwi]

Hell I wish my dad had a mig welder when I was a young un.  We had a heavy duty Youngs arc welder and all I managed to do was burn holes in my bicycle plus my older brother played a trick on me which resulted in giving me one hell of a shock.

 

To this day even if someone offered me $1000 I would never want a shock of that machine again.... cars, lawnmowers, motorbikes and even 240 mains, not a problem but that arc welder gives a damn good boot (Probably to do with the amperage/current)

 

When I refer to sparrow fart, we had a local guy here that did the welding on my workshop/man cave.  I was too impressed (Read rather pist off).  His butt joints didnt and where he had a gap he just welded a nail ti cover up the mess!  I mentioned all this to the missus as it was her project, fat lot of use that was....too much loss of face etc.

 

Well I wonder whats going to happen after a few years when the whole lot falls down around ones ears?

 

But anyways... great looking project.  A fellow school friend had a Bultaco years ago.  Rich parents but he was pretty good at trials...cant remember if it was a 370 but I do recall it had a decompression lever and boy you could hear that when he pulled it in on his way to visiting our place in the country.  Damn nice bike but you had to be careful when kicking it over...if you got it wrong it would throw you over the handlebars.

[papa al]

2 hours ago, thaiguzzi said:

 

I know you have a 350 in the States, and i believe it has been played with and breathed on.

The 350's were only sold in the States and Canada. Europe never got them, Canada got the 250 too, but 'Merica never did. Ca'nt beat cubes? Well you can actually.

 

Research the net and the trials forums, everybody says the 250 was a better bike than the 350. They are identical bar the top ends. The 250 worked straight out of the box, the 350 did not. All to do with poor squish, incorrect deck height, barrel cylinder porting wrong, piston crown - you name it, out of the box the 350 was a sales disaster. The 250 was made for 8 years, the 350 - two years -tells ya something.

250 can be rebored endlessly (7 o/sizes in 0.5mm steps), the 350 can't because it runs a nikasil liner. So these days, according to the stateside trials forums, there are some trick 350's running around, but they've had the BOTTOM cylinder barrel gasket face machined, porting mods, c/head  gasket face skimmed, squish set and either a very expensive re-chrome of the barrel , or an iron liner pressed in and a suitable non Yamaha modified piston inserted.

1.  Yup. papa has 2two TY350s there.

One stock, one heavily modified for competition.

Except for the pegs, they don't perform appreciably different.

Both perform great.

2. I read those forums, and never read anyone saying the 250 performs better than the 350.

A reference would be appreciated.

Jim Snell won the US National championship on a TY350 about then.

[What major competitions were won by TY250 mono?]

3. I don't know what, if any, mods his [or other 350 competitors] machine had,

but would like to.

A reference would be appreciated.

FApK, Yamaha quit marketing trials bikes altogether in USA after '86.

The 350 is under-tuned

Peak torque comes at 2500.

Compression is like 7:1.

Pretty hard to ruin a bore or piston under those parameters, 

[unless you forget the oil or something,]

and the chrome bore is more durable than iron.

papa not worried about getting hit in the head by a meteorite,

either.

 

.

[thaiguzzi]

Adv rider forum, trials section. Search Yamaha Mono. Tons on there. EVERYBODY says the 250 was a better bike. EVERYBODY says the 350 needs top end mods to run sweet. Me, i don't know, i've not ridden the 350, just like you aint ridden the 250...

I'll check tomorrow, 7:1 CR i think is the 250. The 350 may run something ridiculous like 5.5:1...

[taninthai]

10 hours ago, thaiguzzi said:

Welding mask is a cheapo £35ish quid Chinese auto dark helmet off UK Ebay. Works a treat.

was gonna say love the welding mask

[thaiguzzi]

21 hours ago, papa al said:

1.  Yup. papa has 2two TY350s there.

One stock, one heavily modified for competition.

Except for the pegs, they don't perform appreciably different.

Both perform great.

2. I read those forums, and never read anyone saying the 250 performs better than the 350.

A reference would be appreciated.

Jim Snell won the US National championship on a TY350 about then.

[What major competitions were won by TY250 mono?]

3. I don't know what, if any, mods his [or other 350 competitors] machine had,

but would like to.

A reference would be appreciated.

FApK, Yamaha quit marketing trials bikes altogether in USA after '86.

The 350 is under-tuned

Peak torque comes at 2500.

Compression is like 7:1.

Pretty hard to ruin a bore or piston under those parameters, 

[unless you forget the oil or something,]

and the chrome bore is more durable than iron.

papa not worried about getting hit in the head by a meteorite,

either.

 

.

 

I'm not getting in a pi$$ing contest...

# How do you know the stock one is stock? Looked inside it? Previous owner the original owner from new?

# Compression ratio's;

TY350 mono 5.3:1

TY250 mono, anywhere from 7.0:1 to 7.8:1, depending on model and year, most common being 7.6:1.

TYZ 250, water cooled, '93 on, 8.4:1.

 Just a tad of difference....

# Have a TY350 genuine Yamaha workshop manual to confirm the above figures.

# Snell would have won the US Championship at that time no what bike he was riding. Probably could have won it on a twinshock.

# Sport of trials is one of the few motorsports, where the vehicle does not make that much of a difference, they are so close and similar, it is the rider that makes the difference.

 Look at Tony Bou, 11 world championships on the trot, nobody close to him. he could win that on any bike. Ditto, a lot of people say that the Montesa/Honda is not even the best bike out there, but Bou keeps on winning.

 Bultaco won pretty much most world championships between 67 -83, but they were'nt that much a better  bike than the competition, they were mostly same same ish, they just had the top better riders.

# Yamaha have never won a world championship.

[papa al]

Bought from the second owner who says,

head has never been off.

Second owner put the vast majority of the

~400 [indicated] miles on the bike

when papa bought her.

Not competition, just fooling around

during annual elk hunting camps,

&c.

1st owner [family] runs Faye Meyers, the biggest MC dealership in Denver.

I didn't verify this info.

Maybe they lying.

Been lied to before.

All papa knows is that she charges up steep climbs,

[like mine-tailings dumps,]

like a boss.

2nd gear, 3rd gear...

1st is selected for boulder crawls.

Tested at over 12,500' AGL. !!

I think they went back to 250 because 350cc power-plant was

almost over-kill

at common elevations.

Jap bean-counters realised

that fancy chrome bore was an unneccesary expense.

Hell, the Brits would never know the difference.

They would buy them

even if pink!