Here in sundrenched Australia, Betas come without the additional flywheel weight that is apparently standard in the UK. No one in my (mostly Beta riders) club even knew such a thing was available until recently. One day during a bike swapping session it was discovered that one of the Rev 3 250s felt much nicer than the others to ride and by process of elimination it was discovered that the cause of the difference was that the one that felt so much better had an additional flywheel weight.
Not long afterwards most of the 250 and 270 Betas in the club had the additional flywheel weight fitted and all was well with the world again.
We feel that even in our high traction riding conditions the heavier flywheel makes the bigger Rev 3s less demanding to ride. I have just bought a 2003 Rev 3 200 and am even considering adding flywheel mass to it.
I suspect that young riders who enjoy the thrill? of quick engine response and have excess energy to burn may not think along the same lines as the "mature" riders in our club.
The 175 forks are a smaller diameter than the 250 but are up to the job. They can be a little soft on the spring rate and damping but it is easy enough to experiment with different oil grades and spacers to pre-load the springs. To change to 250 forks you will have to bore out your yolks to take the larger diameter 250 legs, or fit 250 yolks also. They should fit straight in as the 175/250 use the same head bearings I believe. Although yours is a Godden frame I think they still retained the Yamaha head bearings which are ball race (and a ball-ache to fit....) However, the standard 250 forks are also under damped and have softish springs so there is not really any point changing. On works or supported rider Majesties, they were revalved to firm up the damping.
There are benefits from using the forks from a TY250 twinshock in your Godden Majesty.
I tried every possible combination of fork oil weight and quantity, preload variation and front end height, even tried (single rate) springs from a 1974 TM 125 motocrosser in my TY175 forks but was never happy with the action on mid to large obstacles. You could set them up for large obstacles but then they were not very good for small obstacles. Possibly if I was lighter than my 89kg the standard forks may have been OK.
I recently fitted TY250B forks with purpose made springs from B&J Racing in the USA to my TY175 and found that I could get the front end working well on large dry boulders and during heavy landings yet was still nice on small stuff.
Yes both steering stems and steering head tubes are the same but the TY250 tubes being a larger (34mm) diameter come closer to the fuel tank on the TY175 than the standard forks on full lock. Both sets of triple clamps share the same offset geometry. TY250 clamps are simply TY175 clamps with bigger holes. Aftermarket tapered needle roller bearings for top and bottom are the modern remedy to the standard Yamaha steering head bearings. I use the same brand of tapered needle roller bearings in both a TY175 and TY250B and have found that this allows rapidly front end swaps between bikes if needed (ie no need to move bearings from seats).
I don't know about where you live, but forks and triple clamps from TY250 twinshock bikes are readily available from bike wreckers here in OZ.
I just measured the original Telesco shocks from my 1976 Cota 348. They are 360mm eye to eye.
Axle travel to the point where the shock body just touches the bump rubber is 114mm.
Axle travel to compressing the bump rubber 10mm is 129mm.
You asked what the shockie length "should be". All I know is what works for me. I have 1980's vintage Marzocchi shocks on my 348. They are 352mm eye to eye and still work great.
If I needed new shocks for the 348, I would buy Falcon Classic Trials shocks without hesitation.
The two stroke decompressor as on that Cota 247 works by opening only a small hole between the combustion chamber and the outside air. The small hole allows air to flow in and out in a controlled manner dissipating energy just like fork oil moving through the orifices in the damper rods also creates a drag which dissipates energy.
A big hole in the head (as in taking the spark plug out) doesn't restrict the flow as much so doesn't provide as much braking effect.
On a 4 stroke, the decompressor is there to allow the motor to turn over easier for starting so it works by opening a large hole between the combustion chamber and the exhaust header. In the case of a 4 stroke, an exhaust valve is held open continuously to provide the big hole.
Please be aware that in dusty conditions, with the type of decompressor shown on that Cota 247 it is possible for dust to enter the combustion chamber via the decompressor hole (unless it has a filter), increasing ring, bore and piston wear rates.
You are spot on about the benefits of the pulsing effect on traction in marginal conditions.
Modern (2-stroke) trials bike manufacturers design their engines to provide a strong pulsing effect at low RPM to maximise traction in slippery conditions.
Being a regular rider of 1970s trials bikes since they were new, one of the things that is very obvious to me when riding a modern trials 2 stroke is the strong pulsing effect at low RPM compared with almost electric motor smoothness of the 1970s 2 stroke trials bikes.
The physics is quite simple of why the pulsing helps. A tyre slipping on a muddy rock has less grip than a tyre that has the tread stationary relative to the rock ie static friction is greater than sliding friction. When drive is on the verge of being lost due to low traction, the part of the engine cycle when no drive is occurring (between when the exhaust port opens and when the next power stroke starts) allows the tyre to regain the benefits of static friction in time for the next power pulse. A four stroke engine simply has a stronger version of this effect because it has a longer period between power strokes for the same RPM.
The effect is only a benefit when the tyre is on the verge of slipping. Once a tyre is spinning on a slippery rock, there is no benefit from the pulsing effect.
The same effect is being used in MotoGP bike engine development. These bikes also operate at the margins of traction during acceleration and are being developed to maximise static tyre friction by optimising the pulsing effect.
Another example is ABS braking systems on cars. They are are designed to pulse the braking to maximise tyre friction during emergency braking.
Hmm, havent checked the stator plate.. but now when you guys mention it... Althou i need to get an magneto puller. So you are sure it isnt the cdi box? Also noted compared to my montesa that the spark is weak. I fail to see it would be the woodruff key, as the magneto sits _firmly_ in place and timing at idle is ok.
It may indeed be the CDI box. If you have another Rev 3 there to use a test parts why don't you swap the CDI box first if you don't have a flywheel puller yet?
London to a brick it's the stator coil though.
Yes if the timing is right at idle it's not a sheared flywheel locating key.
One thing is for sure (to me). Montesas are by FAR the best looking!
Good to hear. I totally agree. I love riding my Cota 348 and OSSA MAR because in my eyes they are the coolest looking bikes I have ever seen. I suspect that the bike that someone likes the look of most has something to do with their association with that bike when they were at a certain age.
I've found that unless a bike was made between 1972 and 1976, it really doesn't rate in the looks dept for me.
That means that I was 13 to 17 years old when the strong impressions were made.
How old were you guys when the bikes you love were made?
Well done checking with a strobe. Yes whet you are probably seeing is what MarkyG has suggested. To prove to yourself that it is the stator before you shell out for a new one, can you swap just the rotor with another Rev3 to see if the problem goes away? About half the early Rev3s in my club have suffered this failure so we are geting pretty good at diagnosing it now.
The bike in the avatar, my overachieving '72 123 Cota has still got it's original piston and bore. I know it's original because the bike was near new when I bought it. I rebuilt everything in the cases, except the piston, bore and crank, it was all in spec and looked good. That was 4 seasons ago and it still pulls like day one. Can anyone beat that?
Dear Vintage Cota
I can't beat your Cota 123 story because I don't have a bike that old but this story must come close.
I discovered after taking the head off my 1976 Cota 348 for it's first ever decoke a few months ago that it still has the crosshatch pattern bore finish put there by the factory. The fork tube surfaces also have the original crosshatch pattern. Those Montesa fork gaiters do a good job protecting the forks.
My 1974 Yamaha TY250A has never had the head off and still runs perfectly and is quiet mechanically. I guess one day it will also need a decoke? The speedo read 3000km and was still working when I took it off the bike nine years ago.
Hey Feetup, the last item I need for a restoration of a 123 is an original set of handlebars with welded-on perches for the levers. I don't even know how to figure out the time zones in Aus, so would you be so kind as to contact the gentleman, find out if it has them, and get back to me on the board or via e-mail shaun_mcgarvey@shaw.ca ? Or just find out if he has e-mail too, please.
thank you, vintageCota
I have only got Ross' message machine so far so don't know for sure but I wouldn't hold out much hope for original 123 handlebars.
Time zones are easy. If you are in the USA or the UK just phone Australia in the middle of your night and you'll be pretty close.
He probably has an email address but I don't know it yet.
Will the carb and front forks from a 349 work on a 348.
Beware about front ends on 348s and 349s.
Yes the forks legs are interchangable but the triple clamps put the fork tubes at different centres. The 349 had the tubes closer together. If you are using the 349 triple clamps in a 348 consider the front wheel width and fuel tank clearance.
There was a bit of chat about someone looking for Cota 123 parts a few days ago.
On my last visit to a bike wrecker at Tiaro, Queensland, Australia, the owner had most of a Cota 123 for sale. If anyone is interested in it, please contact the owner (Ross) on +61 (0) 7 4129 2771.
Please consider the time zone before you phone Ross.
I'm just about to do a pre-purchase inspection and test ride on a 2001 REV3 200. Is there anything special to look out for with this bike? I am familiar with 2001 REV3 270 and the well known Beta problems with ignition stators and carby connector failures. What I'm after is any problems particular to the 200.
I'm told that the bike has recently had new rings fitted and that the reed land needed trimming to remove a bump.
The long wheelbase Montesa you were warned about is the red tanked model Cota 349. It was from around 1980 and has a longer swingarm than the later white tanked 349. If you don't ride in competition (need to turn tight) the longer swingarm of the red tank 349 makes for better steep terrain riding.
The 348 series (76 to 79) handle and turn well, have good power and are all red. However the only light weight red Montesas of the 1970s are the ones with the small motors ie 123 and 172. The 247s are the same weight as the 348s. Depending on how tall you are, you may find the 123 and 172 a bit small.
rite i am ridding a 2004 250 scorpa racing from vince (haven) now. I am about to swap it for the 2005 scorpa racing (2-stroke durrr !!! do they even do a 250 4??) and want some more power, as it is only a 250 at the end of the day just with a little bit more compression to the comp 1 with the diff gaskets. Dont see the point in doin it to ma old scorpa so have been waiting for a new one, just not sure what you can get for them.
thanks.
Don't have a cow, Luke.
Have a look at your first post again. It doesn't say you are getting a 250, just a Scorpa so it was pretty hard to work out what you were on about. They do make 125 4 stroke Scorpas too which are the bikes people usually want more power from.
Im looking to get a bit more power out of my new scorpa when i get it, has anyone got any links to UK bike shops which does like higher cc heads, High compression head, Ignitions, Carbs etc.....
thanks.
Luke
Are you getting a two stroke Scorpa SY250 or a four stroke? I suspect there is a bit of confusion about what Scorpa you are talking about.
Interesting thing... If you look at the latest TodoTrial posting on the 4T, and send it through the Spanish to English interpreter, you can pick up on their comments about the rear fender, down near the end of the article. While the language conversion is rough, you can gleen that they like the rear fender in that it is unique and adds an "aggressive" touch. Sort of like we would say that something looks like it is moving, even when it is standing still.
I have to admit that the rear fender is my least favorite aspect of the bike. If you look at the Scorpa.fr website, and check the accessories catalog, you will see an optional "competition" fender for the 4T. The angle of the picture makes it tough to tell much about it, but the verbal information I was able to get my hands on reports that the bend and curvature of the edges is defferent than previously offered. While it is still not the SY250 fender, it is supposedly a more attractive piece than the original. We will have to wait and see what the SY175 actually shows up with.
Doesn't the photo of new Scorpas lined up outside the Scorpa factory posted by Ben R in this string show the latest SY175 including the rear mudguard?
We don't get IRC here in OZ so I don't know about them.
We do get IRC tyres in Oz, I run one on the GG300ec of mine in the summer. The importer is located in Victoria, Bruce Collins used to import them.
Thanks Splint.
I haven't seen an IRC trials tyre yet but will now be on the lookout. From the sounds of what our friends from overseas are saying though the IRC probably isn't ideal for the dry riding seasons where I live.
Dunlops are better than Mitas and Pirelli but not quite as good as Michelin. We don't get IRC here in OZ so I don't know about them.
It's pretty simple as someone else said: You get what you pay for. If you want rim protectors buy a cheap tyre. If you want to win in competition, buy the best. When the others start making tyres as good as Michelin, their price will go up to suit.
The white framed model was introduced in 1988, there were no ty monoshock models before 1984, (they were twinshocks)
I think the "pinky" pink framed models were introduced around 1991 ish, i stand to be corrected on this point though.
"Pinky" TY250 Yamahas don't have pink frames. The pink bit is the seat/rear mudguard. The fork legs are blue. They also were the only air cooled monoshock TY250 model to have a front disk brake. They were the last air cooled TY250 model made and were sold here in OZ from 1991 to 1993. The watercooled TY250Z came here in 1994.
The only parts shared in common between the Pinky and the TY250Z are the front wheel.
If you have a set of bathroom scales you can weigh it one wheel at a time and add the two weights together to get the total weight.
My guess would be that the steel tank air-cooled monoshock TY250 in competition trim ready to ride would weigh between 88kg and 92kg. With indicators and lights, speedo and mirrors it would be a few kg more.
On the frame plate it says 220kg, although the measurments are in japanese i think. Are there jap kgs and english kgs?
But it definatly says 220kg, i was suprised when i say it but thats what it says...
The 220kg on the Japanese frame plate is probably the maximum legal all-up weight of the bike including rider/s. The usual abbreviation is GVM (gross vehicle mass).
29er suggested greasing the mating parts when you reinstall the flywheel. I hope that doesn't mean the taper? Mechanical drive tapers should be assembled dry and clean ie no water-dispersant, oil or grease. You are increasing the chance of another sheared key if you put grease on the taper.
The suggestion to use lapping paste on a damaged taper can be helpful once any high spots caused by the key failure are carefully removed. If the damage has cut up the surfaces too much and key failures recur even when the flywheel is re-installed properly, loctite can be used as charliechitlins suggested but the flywheel may need heating to release the loctite next time it needs to come off.
These are two of my favourite bikes and I often have trouble deciding which to ride.
First the differences in geometry and weight:
The TY175 has a 48.5 inch wheelbase. The TY250 is 50.5 inches.
The TY175 has a more raked steering head angle (less steep) but with the same triple clamp offset so it has slower steering than the TY250.
Both wheels, brakes and the front ends are interchangable (except for the dished sprocket on the TY250). The TY175 forks have skinnier tubes and have lighter springs than the TY250.
The TY175 (83kg) is 10 kg (22.4 pounds) lighter than the TY250 (93kg). About 8kg of this difference in weight is in the engine.
Riding them:
Chalk and cheese. In sections, the TY175 feels much lighter than the TY250 and because of this can be ridden much longer without taxing the rider's endurance. However the TY175 has a unique feel to the front end that I've never come across on other trials bikes of the same era. The front end never feels totally confidence inspiring on obstacles. There are a few possible reasons for this:
The forks flex noticably in rocks with an adult size rider.
The steering rake is more like an MX bike of the era.
The handlebars always seem too far back even when they are rotated well forward in the clamps. I am only 1740mm (5 foot 10 inches) tall.
On my competition TY175, I've moved the pegs down and back to give more room and have fitted the front end from a TY250. This improves things a lot but the front end is still not as good as say a Cota or OSSA or the TY250 of the same era.
The TY250 front end is more refined than the TY175 but one is always conscious of the TY250's weight when in sections. Both bikes are capable of turning as tightly or even more tightly than most of the other bikes probably due to their relatively short wheelbases. If there was a forte for both of them, I'd say it was in tight turns.
The first TY250 had a motor that was not as forgiving at low revs as later model 250 motors but they are all are very competent and run very evenly and smoothly with standard settings. The first model TY250 flywheel was lighter than the later models and the porting was different too. The B and later TY250 motors all lug and rev out with magnificent gusto.
The TY175 motor has noticably less grunt than the TY250 as you would expect but has the widest usable rev range I have ever witnessed on an old trials bike. It runs strongly right down to the point wher you could count the strokes yet will rev out far higher than other similar era bikes. This proves to be very important in competiton because you can run gearing that provides great clutch-out control at low ground speed yet the bike can also get to a usefully high speed in the same gear.
The TY175 would usually be the bike to choose if you wanted to score the least points at a trial but because of the front end and cramped riding position does not feel as satisfying to ride for me as the TY250.
In case you are a bit of a hoon, both are fantastic for pulling extended wheelies on.
The TY175 makes the better trailbike ie the handling is quite good at higher speeds and when sitting down. I don't know why but suspect it is because of the slower steering.
The bike in the avatar, my overachieving '72 123 Cota has still got it's original piston and bore. I know it's original because the bike was near new when I bought it. I rebuilt everything in the cases, except the piston, bore and crank, it was all in spec and looked good. That was 4 seasons ago and it still pulls like day one. Can anyone beat that? 
Flywheel Weight On Bike ?
in General Trials Talk
Posted
Here in sundrenched Australia, Betas come without the additional flywheel weight that is apparently standard in the UK. No one in my (mostly Beta riders) club even knew such a thing was available until recently. One day during a bike swapping session it was discovered that one of the Rev 3 250s felt much nicer than the others to ride and by process of elimination it was discovered that the cause of the difference was that the one that felt so much better had an additional flywheel weight.
Not long afterwards most of the 250 and 270 Betas in the club had the additional flywheel weight fitted and all was well with the world again.
We feel that even in our high traction riding conditions the heavier flywheel makes the bigger Rev 3s less demanding to ride. I have just bought a 2003 Rev 3 200 and am even considering adding flywheel mass to it.
I suspect that young riders who enjoy the thrill? of quick engine response and have excess energy to burn may not think along the same lines as the "mature" riders in our club.