feetupfun

Maybe a broken con-rod? Is the piston moving when you kick it? Is the crankshaft/flywheel turning when you kick it?

If you use Pursang in-line forks in Sherpa T clamps, in a standard Sherpa T frame, set to provide the same height for the front end, you will probably have interference issues with the front wheel and the front downtube when the forks are compressed. If you use long fork tubes to provide the required clearance for the wheel, you will make the front higher and the steering even slower than it is already. You may be on the right track with the geometry change though. A couple of us experimented with our KT250s last year and one experiment was very similar to what you are suggesting. We fitted TY250 (in-line) forks and wheel into the KT250 clamps. KT forks have a similar axle offset to Sherpa T forks. The front end ended up being very close to being the same height as standard. The effect was that the KT then steered like a TY250 (steering became quicker). That experiment worked OK though because there is more clearance for the front wheel on a KT than on a Sherpa T. I like to have bikes set up to feel correct for the period though so it is back to being a normal KT again now. There really is nothing "wrong" with a Sherpa T, they just require a different riding style and it is hard initially to swap between something like a TY250 or an OSSA and a Sherpa T, but if you spend time on the Bully and ride in a way that suit the bike, they do feel great to ride. I totally agree with Woody and whoever else said it on the path you should take - longer shockies or shockie extensions will make the world of difference to the steering and it is so easy to do! A bloke over here made up neat-looking flat steel brackets for the bottom shockie mounts of his M198 that fit over the bottom shock mounts and bolt to the holes just ahead of the shock mounts - no welding required and no damage to the frame. Instant quicker steering! I rode it like that and the bike that the steering reminded me most of was my 250 Godden Majesty (and they steer pretty well)

The WES muffler pipe is straight and misses the shock so unless your muffler has the entry pipe on the "wrong" side, there is something pretty strange going on.

Good to see you have put some photos up. What you need to do to know of you can buy a different needle and needle jet is to take the needle jet out and read the stampings on it and on the needle and compare them with what is available from the Mikuni agents and maybe from the manufacturer of the bike that the carby came from originally. I would imagine it came from something like a late '60s early '70s trailbike of about 175cc like a Yamaha CT3 or Suzuki TS185. The needle jet will have both size and type ID stampings like the stampings on the slide. The square-in-a-square stamping just means the part is genuine Mikuni. I also suggest you post your next questions about your OSSA in the Twinshock forum as I only noticed your latest posting by accident in the "Introductions" forum.

I only buy bikes I have the hots for and the price is usually quite irrelevant. If it is a 349 that you want, and it is only being offered to you, keep trying to get your price. What do you have to lose? If you don't know what bike you really want, buying your buddies 349 just because it is available to you is probably not the best move.

I got bombarded with popups and got out as fast as I could. Didn't get as far as seeing any content.

No both are 6 speed An easy way to tell is that 348s have frame tubes under the motor 349s have an aluminium plate 348s have a rear frame loop and 349s don't The motors look different too but it is hard to describe the differences Both have motor prefix 51M 348 - 1976, 77, 78 349 - 1979, 80, 81, 82, .....

Lizzy The jetting in the 26mm Mikuni KT250 carby on my 250 OSSA is: Main Jet 85R (be careful here because the type of main jet in this carby is different to what is in an aftermarket pattern Mikuni and probably uses a different numbering/hole size system also) - the hole size is much bigger than an 85 size jet would be in an aftermarket VM Mikuni main jet. Air jet 2.5mm Needle 5D1 with clip in mid position Needle jet O-8 Needle jet type 8 172 Slide cutaway 2.0mm Pilot jet 30 Air screw 1.5 turns Checking in my Mikuni catalog, I see that 5D1 needles and 172 pattern needle jets are not not listed as spare parts. This is common with OEM Mikuni carbies and probably means you will need to either buy the items from Kawasaki as spare parts or use the Mikuni catalogue information to choose something dimensionally close to them. I still haven't found the DT175 carby jetting specs for use on a M198 but I do remember it was very close to standard DT175 jetting.

These photos are of my son Darcy at a trials riding demonstration yesterday on his OSET 16. I'm very proud of him going over the pallets as it is much higher than obstacles has ridden before. David Lahey

Paul, I have a 250 MAR with a Mikuni carby but it is an OEM Kawasaki KT250 26mm Mikuni carby, which is quite different to an off-the-shelf 26mm VM Mikuni carby and the main jet in it uses a different sizing code to an off-the-shelf VM26 Mikuni. I've not yet looked at the sizing codes on the needle and needle jet to see if they are recognisable as being the same system as for off-the-shelf Mikunis, but will have a look today and reply again. 26mm Mikuni OEM carbies from DT175, KT250, RD350, TY250 are all quite different designs and also to what you get if you buy a new carby from Mikuni. My other comment is that a friend has his M198 (238cc) Sherpa T running wonderfully with a DT175 OEM carby and somewhere in my shed I have his jetting specs. From what I have found with swapping carbies between 250cc 2 stroke trials bikes, a carby that works well on one non-reed motor will usually work quite well on another non-reed motor so his DT175 carby specs might also work with your OSSA. It would help if you could tell us what sort of Mikuni carby you have there and what size it is. David

Thanks Alan. Thats great to hear.

You might be lucky and find a set of those chinese footpegs that fit the twinshock TY with a bit of grinding, drilling or filing. A friend of mine did just that to get pegs for his KT250. There was only minor mods needed to make them fit. Where I live there are shops that sell those cheap chinese pretend MX bikes and you can measure the cheap accessory footpegs there to find something that can be made to fit, if you are so inclined. I would have expected that sort of shop would exist in most countries. The weld-on extensions for TY pegs work pretty well and would be a known quantity as far as durability goes.

Sounds like a crankcase air leak has developed - possible locations: rubber connector between carby and reed cage cylinder base gasket crankshaft seal

Symptoms indicate: Slipping clutch - maybe needs freeplay adjustment or has sticky clutch cable Possible sticking throttle slide/throttle cable

I've got a little story about a Bultaco M49 I bought from a distance having only seen photos. The bike was advertised as a "1976 Bultaco" and it was in the classified section of a magazine with no photos but even if there had been photos I doubt I would have recognised it as a M49. I phoned with the thought that it could possibly be a Sherpa T of some sort and when the photos turned up showing engine number M49-00100 I had to have a very hard look to recognise it. Someone had "converted" it to a dual seat trail bike. A 7kg (approx 16 lb) home-made steel-based double seat had been fitted, including bending the rear frame loop down flat to get the seat to fit better. Front and rear footpeg sets were supported by 32mm x 6mm flat steel strips running along the bike and attached to the original bolt-on footpeg locations. The shockies were gas konis with springs suitable for MX with a heavy rider and the leaking fibreglass tank had been coated with about 5mm of green spray putty and covered with a blue paint scheme reminiscent of a late 1970s Pursang. The frame and swingarm were horribly twisted and yes someone had respoked the rear wheel with the rim way off where it should be. Things that surprised me were that the front wheel still had an early 1970s Firestone Vee pattern trials tyre and the original aluminium mudguard and stays were there and relatively undamaged, with original riveted brake shoes, wheel bearings and spokes. Unusual spares that turned up with it included a cylinder head (not sure why they needed a spare head) and go-kart sprockets! Lots of hours went into the fibreglass and the frame. Its not meant to be a show bike, just to be recognisable as a M49 and able to be confidently ridden in competition.

Its the TY250 monos that need the piston skirt trimmed depending on what piston is used. The twinshock TY250 can use the DT250 piston of the same era without modification. Yamaha and Wiseco DT/MX250 (and probably other brands too but I haven't tried them) pistons work fine in TY250 twinshocks.

You next step is to work out why you can't turn the crankshaft. As Andy.T said, drain the gearbox oil and take off the primary drive/clutch cover so you can take the gear off the end of the crankshaft and see if the problem is with the crankshaft bearings or with something else.

So you don't have to carry a socket set in your backpack to get the cover off if you need to while out riding

The white is either mould or aluminium corrosion product and both are quite normal for a bike that has been stored damp. The white stuff is the least of your problems. Can you clarify what you mean by "I can turn it though, not a bit"?

I couldn't find an open-face helmet small enough for my kid (boy on right) so we got an MX type. Competition insurance requirements here mean the helmet has to be either road legal or approved for use in motorcycle trials to an international standard. That MX helmet is road legal. The other kid (girl on left) has a Shiro trials helmet on but they only go down to a certain size and my kid's head is still too small for them.

Theres no crankcase drain on a TY175. Turn the whole bike over and catch it in a pan. If youve taken the handlebars off it might be easier to remove the primary gear and the spacer behind and tip the bike on its right hand side. Don't take the motor out of the frame till you have loosened all the shaft nuts and engine inner casing screws as it is a good way to hold the motor still.

Exhaust shops sell perforated steel plate in sheets too so you can roll your own to whatever diameter you want.

Breaking a ring is relatively common in YZ and IT Yamahas but that's the first I have heard in a TY250A. I am interested in the failure mechanism in your bike. Here are some things to check that might help work out what happened: Was there much gum in the ring grooves? Which ring land failed? What side of the ring groove broke away? What port did it catch in? Was it the original piston and rings? Is there evidence on the rings of uneven ring wear? (uneven radial thickness) Does the port that broke the ring have chamfers around the edges? Is there evidence of ring blowby on the bore (uneven ring sealing?) How rattly is the piston in the bore without any rings? Is there a lip near the top of the bore? (if the little end develops play, the rings can hit a previously generated lip)

Here in the most nannified country in the world, competition rules require not just self-returning- folding footpegs, but they must use a spring to return them not just gravity. Here is what I did on my TY175 with Miller pegs. There is a spring loaded pin that will lock the peg in the up position, and it releases by just bumping the peg after the motor starts.

No Yes If the main bearings or big end bearing has suffered any corrosion at all, they will self-destruct soon after you start the motor the first time, sending metal particles everywhere, meaning that you will need to rebore the barrel yet again. It is the bearing surfaces that usually rust - the balls and rollers etc, it doesn't creep in from elsewhere. By the look of the piston pin, I would say that there has probably been corrosion happening within the crankcase. When you work out why the crank will not turn, you will be in a better position to know what needs fixing. The bottom end may not be siezed via corrosion in the bearings. It could have something jammed in the meshing region of the primary gears. I have seen that in a TY175 motor with a loose piece of clutch casing floating around until it jammed up the primary gears, bending the gearbox shaft and wrecking the primary gears in the process. Until you can see what is really happening, it is all just conjecture.