feetupfun

Those old photos are fantastic fourex. It's exactly how I remember trials from the time and one of the locations looks quite familiar. That kid in the last photo sitting backwards talking to you looks familiar. Also no wonder so many old bikes have broken stand mounts. Look at you two sitting on the bikes on their stands. One friend of mine was a bit small for his TY250 in 1974 and had to have it on the stand to be able to start it. Luckily for him the stand was on the left on the A model. Your TY175B looks a lot like mine did, even where the top shockie mount was moved to and the black fork boots. Were they konis too?

I can say that the Majesty 200 motor as they were done back in the day had a bigger-sleeved TY175 cylinder using a TY250 twinshock piston with bushes in the piston to suit the smaller little end pin. As for the power developed, my hot rod TY175 is 210cc and I had to calm the motor down considerably after it was first built in 2005 before I was happy with the motor. The cylinder and head was done in a way that would provide strong response everywhere by the expert race engine builder who did it. I reduced the compression ratio and fitted an ignition I could set up to smooth out the low RPM response to make it gentle enough for me to comfortably ride the tight stuff. After my refining of the response it has a strong bottom end and very strong mid range and a nice top end that I never need to use and overall it suits my weight, strength and reflexes perfectly. A younger high level rider would probably have preferred it exactly as it came from the engine builder. It has exactly the bottom end power you would expect from a 210cc motor as in midway between a 175 and a 250. Highly-skilled trials riders who have had a go on it have preferred riding the hot-rod 210cc TY175 to riding one of my very nice TY250-based bikes. Some of these highly-skilled riders have commented that they would have liked the response to be sharper.

Tony, austini and I have been collaborating already in private. I would love to know more about the Godden Majesty TY175/200 but I've not ridden one. They are a vanishingly rare beast. I've ridden a Godden mini Majesty Ty175 owned by Paul McLeod in NZ and it was excellent but a quite different design to the bike austini has acquired.

Could be due to a few things and finding out what it is will probably require taking the cover off

Do you know if the one you want is made of steel or aluminium?

No reason at all Rod. That's what I do with most of my bikes that have the two compartments separated

I've got a mix of AMAL 80/200, Domino slow and Suzuki DS80 twistgrip assemblies on my twinshocks and they all work very well but have found that the AMAL and DS80 types are more easily broken in crashes

I also have used silent blocks for swingarm pivots and in Australia, individual silent blocks can be bought from Blackwoods

Yes they have been a good thing on every old two stroke trial-type motor I've put one on so far

For GasGas and Sherco, their 4 stroke development was driven by pressure from the FIM who were planning to ban 2 strokes. GasGas and Sherco development was dropped when the 2 stroke ban was dropped.

Left side. Nothing else fits. Right side. DT125/175 1974 to 1977 (ABCD models) fits. YZ125/175 C/X fits. Later DT175, IT175 and YZ125 don't fit without mods.

Quick answer. Yes

GasGas manual downloads available here https://www.thehellteam.com/technical-support/gas-gas-parts-and-service-manuals.html

Another interesting thing about the bike is that the swingarm looks non-standard. Maybe it's a stronger design to cope better with sidecar use

Hmmm that stamping looks a bit dodgy for a few reasons. They didn't make a bike model called a 51H. The number after the 51H is too low to be on a 349 motor. 51M series started in 1976 and there were many thousands of M51 Cota 348s made before your series 1 Cota 349 was made but yours is stamped number 00221. The appearance of the metal surface after the 51 is smoother than at the 51 meaning the original letter and number after the 51 could have been ground away and re-stamped with a different letter and number. Another possibility is that Montesa made trials sidecar-specific motors that had a different engine number series and this has not become widespread knowledge yet. What does the frame number stamping look like?

The reason you got all that 2T related feedback is because in your post you said you were interested in the Beta 300. Beta make a 2T 300 and a 4T 300 and some people assumed you meant the 2T 300 and were trying to steer you away from it

Wasn't the original poster asking about a 300 Beta 4 stroke?

It would help with reading the stamping of your engine number if you scraped the paint out of the stamping

Here's a photo I lifted from the North Atlantic Trials Assn webpage that shows a 349 motor up close and it has the engine number where yours is stamped

I've just noticed that the frame is also Cota 349 not Cota 348

It doesn't look like a 348 motor. Clues being the shape of the clutch cover and the bolt-on inlet connector. I'm thinking Cota 349 motor. That doesn't solve your mystery though because 349 is 51M too. Here is a photo of the engine number on one of my 348 motors and it is located on the top of the front engine mount lug. I don't know where 349 numbers are stamped but it might be worth a look at the front engine mount lug

Yep, should be M. How about a photo?

Spec sheets are not a good source of geometry information because they don't specify if the bike is laden or unladen or if there is any static sag or what pressure is in the tyres or what tyres. You will get real numbers by reassembling the important bits and measuring it yourself. If you are trying to copy a proper trials bike, measure the proper trials bike yourself so you are comparing apples with apples. Be aware that modern front and rear trials tyres are a fair bit taller than front and rear trials tyres of the past and the heights of the axles are very much affected by pressure.

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Motor parts are very expensive so make sure there is nothing wrong with the motor