feetupfun

I've seen an M49 with a red Clarke plastic tank and it looked pretty good

Here is a photo that shows how the seat/tank unit rests on those lugs

Here is what the lugs would have looked like originally. My photo shows an M85 frame. My other M85 frame (the pretty one in the photo) has nothing there at all and a M80 frame on the other side has no lugs either. The lugs do line up with the side mounts on the airbox like in vintagenut's airbox photo but what purpose they are intended to serve I don't know. As far as I know both my M85s were sold new in Australia and came with fibreglass tanks.

The oil you see is probably condensed vapour/smoke from the combustion process. Modern two-stroke oils can be so good at resisting burning that they can cause what you are seeing. Once the sound absorbtion material in the exhaust is fully wet with this oil and it can't hold any more, it will start coming out wherever it can. It really doesn't do anything except make a mess so if you can manage the mess then you don't have to do anything. If you rode the bike hard enough the exhaust may get hot enough to stop the oil condensing inside the exhaust. Also if you ride it hard enough with oil already in there, it may clean it out to some degree. If you decide to clean out the exhaust by taking it off (it can be cleaned out a few ways when off the bike) but still continue to ride in the same manner, it will continue to fill up with oil. I've seen bikes with a drain line at the low point and when the bike is parked, they put a container under the drain line to catch what comes out.

The part John Cane sells for the TY250 is actually a DT swingarm protector and as he says on his web page, you will need to trim it to make it fit the TY250 swingarm. I just trimmed one for a TY250 swingarm a few weeks ago.

Yamaha TX500 also and many other 34mm tube diameter Japanese forks made by Kayaba in the mid 1970s

Wear grooves in the basket fingers can cause sudden engagement. You didn't mention removing the grooves. Where the lever is when the clutch engages is adjustable via the cam and cable. First set the cam to give 90 degrees angle between cable and cam arm at the point when the clutch starts to disengage. If you can't get 90 degrees then there is something wrong. Set the cable adjustments to put the release point where you want it. If there is not enough cable adjustment then there is something wrong.

A Reflex is probably similar in power output to a standard TY175, maybe even a bit more powerful, so if that was a reason you got rid of the Reflex then a standard TY175 will probably disappoint you. A standard TY175 will also be a fair bit less powerful than your GasGas 200 was. A standard TY175 handles far better than a standard RL250. All the RL250s I've ridden go like a train so if power and a seat are the most important criteria to YOU, then the RL would be the pick. If you like to modify things, the TY175 can be made more powerful and the handling of the RL250 can be improved. They are both good to ride sitting down unless you are over about 5'10" in which case the TY175 will feel camped and the RL250 will be great.

It sure looks like a 348 frame to me. It was a very distinctive series of frames with the removable pieces that go from the swingarm pivot to the cylinder head. All the 348s and the first two 349s had those struts like that. Yours has had extra plates fitted for the footpeg relocation but otherwise looks standard for a Cota 348. As for the engine number, do you know where to look but it has been erased or you just haven't found it? The tank graphics are 1978 model 348

Paul just a thought. I've seen a couple of M199B that have the taper top fork tubes, like a pre-74 Bultaco fork tube. I don't know enough about 198B to know if it's the same with some of them too. If yours is like that it might be a different thread to the tubes with the parallel top tubes. I'll check a taper top tube soon and post up the thread size

sounds normal in that recording

Less than one casing repair per year now, but I'm careful now compared to when I was a kid

Here is another early M49. I took these photos in the 1990s when it was for sale but I didn't buy it. I've posted these because it looks fairly original and also looks like it hasn't been ridden since the early 1970s. The seller had been fairly serious about trials competition in his youth. He even had a spare set of crank seal carriers and told me he would have the spare seal carriers ready fitted with new seals to make for a quick turnaround in his workshop between trials (crank seals didn't last as long back then as they do now) Location was Woorim (Bribie Island) Queensland

Here is my early M49 showing what I think are the original front guard mounting brackets. I can take close-ups when you are ready

Some racing ignitions for two strokes retard the ignition as the revs rise

Yes stuck clutch plates are a very common thing on any bike that has not been used for a while, not just Technos. It can even happen overnight if the conditions are right. If in the unlikely event that it doesn't release after riding around with the clutch pulled in, the friction plates may have become too well stuck to the steel plates from rust in which case you may have to take the clutch cover off and remove the plates one at a time to free them.

There are two different rear hub types used on M49 and the early type is rare. The difference between the outers to the inners is the shape of the spoke on the end so the outer can wrap around as you suggest. The original spokes are "double-butted" which means that the hook end is a larger diameter than the rest of the spoke. It is possible to get spokes made like this if you want it to look totally original but most modern spoke kits have spokes that are the same diameter everywhere. I also have the gearbox shaft that is a size that In Motion don't have bushes for and found that the bush OD is a standard size and was able to get some sintered bronze bushes easily that were a bit small on the ID and machine them to size once fitted in the output shaft.

What was the carby that didn't fit?

To work out the spring rate the coil diameter and number of active coils are also required. If they were well sized at the time for the ROKON they will be in the ballpark for rate for that bike for trials. If the pistons aren't worn and you tidy up the tube bores without losing metal then you don't need to put rings on the pistons. I've got a few Spanish bikes with Betors that look like yours inside with not a huge number of hours and those forks work brilliantly. It's only worn tube bores and pistons that benefit noticeably from having rings. But if it makes you feel good, do it! Teflon sheet cut into a strip works well for rings. I don't know what micarta is.

There are countless different ways to modify a TY175 frame. There are copies of the first 175 Majesty frame but otherwise there is no generic name for any variation. If you want to make one you need to work out what you want to achieve and decide how to get there. TY175s have been getting frame mods since they were released in 1975 so there is no "year". There is also a very wide range of opinion for what the ideal TY175 mods are. I'll have a go at some safe generalisations. The Ty175 wheelbase is very short standard so lots of people make the bike longer. The steering rake is large standard (which suits the short standard wheelbase) so it's common to reduce the rake, in many different ways, to get a better trail dimension that will suit a lengthened wheelbase. The TY175 is short between the footpegs and the steering head so it's common to move the pegs back but there are other ways to fix this too. The pegs are high too so it's also common to make them lower. The forks are quite skinny so they flex a bit unless you are a light person. Most twinshock forks are 34, 35 or 36mm diameter and it is fairly common for the original TY175 forks to be replaced with something bigger. The TY250 twinshock triples and forks fit on without modification and can be set up to work very well. The swingarm pivot is a long way from the back of the motor so it is fairly common to move the pivot forwards which allows the use of a longer swingarm to improves handling and rear suspension action. The rear suspension travel is a bit short when compared to much later twinshocks like TLRs and Fantics and it is fairly common for one or both shock mounts to be relocated to increase the axle travel. The swingarm is fairly flexy so handling is improved by using something that resists twisting better.

Sorry Simon I'm not a Honda person. I just had a test ride on that one many years ago

Not sure what you are calling the spray tube cutaway. If you've got a semicircular shield that sticks up into the airstream where the needle comes out of the needle jet, the open side of the shield always faces the engine. No idea about that new type of slide. Your main jet holder looks like what was in the MK2 AMAL concentric on my M198. Having a bigger float needle and orifice doesn't matter but make sure the fuel height setting is not affected by the change. I figure you must be pretty keen on originality to be asking all these questions and you may well know already that this carby has a reputation for rapid wear of the moving bits. You didn't mention wear of the slide bore but they are well known for that. The fastest wearing bits are the needle and needle jet. There are many excellent alternative carburetors available.

I was thinking about that afterwards. I reckon it would be prudent if using 2 single lip seals to fit them so they were the same setup as a dual lip seal, which I think is springs out, but I haven't looked at a crank seal lately

They get very heavy due to the oil soaking the sound absorbing material and the buildup of carbon deposits. I've reduced the weight of a main chamber by over 1kg by cleaning it out. The sound absorbing material in the main chamber stops absorbing sound when it gets oily and when the mesh holes get blocked. On some exhausts the performance of the motor relies on the harmonics inside the main chamber and this can be affected by the holes in the mesh getting blocked. There will be deposits inside the header which might not stop you pushing a tube through but it means that it is no longer the ideal diameter and surface drag for ideal engine performance.

No way. It is very likely just the single lip seal causing it. If the seal diameters are 25 mm ID and 40 mm OD like I suspect they are on your 247, you can use a Yamaha TY175 magneto side crank seal. I discovered that the Cota 348 seals are the same size seal as the left TY175 seal when I changed the crank seals in my Cota 348. The seal would also be available from a Montesa twinshock-era parts supplier. The reason you need a double lipped seal is that it has to seal with the high pressure side alternating from crankcase to drive casing every time the motor turns. So if you want to use single lipped seals and can fit two thin ones in the holder, make sure you fit them in opposing directions.