woody

No, unfortunately there is nothhing at the moment to replace the Ossa ignition unless you can explore the Sherco or Sherpa options mentioned previously. However, there is someone here in the UK who makes ignitions for the TY250 (not the same one that has been available for a couple of years, this is a different system) and he is looking at making one for the Ossa as he has a couple himself (very rare TR303 Rojas no less.....) Nothing definite and no timescale but hopefully it will happen and it would suit all trials Ossas which have the electronic motoplat fitted. Not sure about the points models.

Ossa Motoplats weren't prone to regular failures, but they definitely weren't failure free. I've had a few go over the years. It wasn't unknown for them to fail when they were new although not to the extent that the Beta ignitions seem to do these days. Buying one off ebay is a real gamble as there is no way of knowing its condition - most are pushing 30+ years old now after all. Even if it came off a running bike it doesn't mean it is working 100% correctly. Two of mine gave a weak spark at low revs, typically after rolling down a descent with the throttle closed with the engine close to stall speed. Opening the the throttle at the bottom resulted in a flat spot or the engine dying completely, just like a weak mixture from the carb. It was also a sod to start sometimes. Swapping the stator for a good one cured the problem. Would it be right of me to sell that stator on ebay as working ok as it came off a running bike. A buyer would have spent ages trying to cure the hesitation in pick-up by messing with carburation, which obviously would never sort it. Personally I wouldn't buy a used one unless it came very cheap, as then it would still be cost effective to send it off to MotoplatUK (now in Spain as mentioned before) to have it repaired if it was faulty. I had a couple done a few years ago and they worked fine afterwards.

Not sure about where you are but replacement motoplat coils for the Ossa electronic ignition are (or were) available from Bultaco UK.

I know of someone who once fitted a 250 Sherpa ignition including the flywheel to an Ossa (they are on opposite sides but doesn't matter) I've no details on this but I'm assuming the Sherpa flywheel must have fitted the Ossa taper on the crank ok. If the Sherpa ignition does fit an Ossa ok - you'd need to establish this - then another possibility is the Sherpa electronic ignition that is now available, you'd need to get a Sherpa flywheel too - 325 is a heavier flywheel than the 250 but both probably lighter than the MAR flywheel so engine response whould be quicker because of that too. DabDab - did the Sherco iignition go straight on your Sherpa without the need for any mods. Does it fit in the Sherpa flywheel ok. Which model Sherco does it come off (I know nothing about Shercos) - basically what does fitting it to the Sherpa involve?

Rossi fans go very quiet when he isn't doing so well

That would make it an earlier Godden framed bike which should have the rear mudguard loop. 81 in the number means 1981

Assuming you still can't loosen the nut to move the wheel forward, put the split link back in the chain with the chain OFF the sprocket. Then pull the top of the chain backwards until it is taught and place it onto the top teeth on the rear sprocket and then as far round the sprocket teeth as you can stretch it. When you've got as far as you can go wheel the bike backwards which will run rest of the chain onto the rest of the sprocket. The chain hasn't changed length so it will go back on without moving the wheel as the force of the bike moving backwards will stretch the chain enough to pull it onto the sprocket. The new tensioner pad won't affect this.

The DT/YZ400 piston which is 82mm gives 340cc, so the 82mm oversize pistons go out to almost 360 I've run mine as 320 and 340 and can't tell any difference between the two

Rings are available I believe but the problem is identifying the rings you need to match the piston. As it is now on oversize it could be difficult to identify exactly what piston it is as 81.3 seems an odd size. Standard bore for the 320 is 80mm and Yam pistons go up in 0.5mm oversizes as far as I know. Piston for the 320 came from either a DT360 (windows cut into the rear skirt) or a YZ360 (no windows as a big arch was cut out of rear skirt) There are a couple of Yamaha dealers in the back of TMX who specialise in old YZ Yams - Motoward and Yamaha Spares UK I think. We've tried them for rings but they need the part number of the piston to be able to match the rings properly as there are different types of piston/ring combinations apparently. May be worth giving either a call. There is also Keith Lynas in the US who specialises in Ossa but also has a good knowledge of Yams too and he advertises Yam DT/YZ NOS pistons and rings on his website, so maybe he could help also. He's very helpful with enquries. Keith Lynas Alternatively, if you know Shirty, try him but if you don't I wouldn't waste your time - I don't, I did and I did - in that order.... Or try a mate of mine who knows a fair bit about Yams and has some pistons, but no rings I don't think TY Offroad For a sidestand and exhaust shield try the breakers Ellastone Offroad or A&B Autos, both advertise in TMX under spares. Both have broken a good few TY250 Yams.

OK, no problem, if you can get them it would be interesting to see them. If you can't don't worry about it but thanks for trying

Be interesting to see how the new owners take the business forward. There is no doubting Sammy's enthusiasm for motorcycles in general and he has made available a lot of products over the years to enable similar minded enthusiasts to keep their old bikes running - but let not's forget that this isn't out of the goodness of his heart and to give the stuff away for free - it is a business and he does it to make money where there is a lucrative market - and there is nothing wrong with that. What I disagree with is his telephone manner to customers, such as myself, when phoning to ask a question or to make a purchase. I don't know him personally and he doesn't know me, so there is no 'history' but his manner on the other other end of the telephone is brash and utterly unfriendly to say the least and has been rude for no reason on more than one occassion. I was taught good manners when I was young and I expect the same, unless occassion arises that dictates otherwise. I've used Millers for years and when Jeff Bungay was there always received a polite and friendly welcome and he was someone who would take the time to listen if you had questions. All that changed when he left. I've actually had Miller throw the phone down on the desk when he's had to go and find something out rather than place it down gently in the usual manner. And I've even been told to hurry up in no uncertain manner when giving credit card details in payment when I dropped my card whilst reading the number and had to take a few moments fishing it out from under my desk. If I hadn't needed the parts so badly I'd have told him where to get off and shove his order. I didn't really intend jump on a character assasination as I've always avoided that before but I get fed up reading how marvellous and faultless his service is. Yes, goods are normally received next day and that is a good standard but should also be the norm these days for a mail order service. Some of the parts produced are of a good standard, others are not. Some fit well, others have to be 'coaxed'. So what I mean is it's not all roses but it's not all bad either. Different experiences for different cusotmers. If you know him personally you may get a better reception but that is not how it should be. No doubt he has to deal with complete idiots and worse on a daily basis (I used to take phone calls in our local dealers when he was dealing with shop customers, so I know) but that is no excuse for rudeness. And that is the one lasting impression that myself and many of my bike riding friends have of him - his brashness on the telephone. And please, no-one say that 'that is the man as he's no sufferer of fools' as that is just an excuse for someone who is ignorant and intolerant. And who is one person to decide who is a fool or not....

Thanks for the responses, gives me something to go on. The Armstrong trail bike is the one I was thinking of, just never seen one, as there is more chance of finding one of those at a breakers than Kramits, Puch etc as I'd guess very few arrived in the UK. Love the picture of the Kramit with the blue engine though if you google Kramer Motocross as suggested by Bo Drinker. Tried Peter Knight but doubts they are available new anymore. Armstrong did do a 350 Jumbo trials (badged as a Canam stateside) there is one being ridden in the ACU Classic but he's had a few problems to sort with it so hasn't been at all the rounds. Nice to see one being ridden though.

The reed induction 350 engine fitted to the SWM Jumbo and Armstrong 350 trials bikes was also used in some trail bikes I believe and possibly some motocross bikes as well. Does anyone know which other bikes used these engines? I think they were fitted in some Armstrong/CCM trail bikes but not sure which. I'm hoping to find a spare clutch cover but it doesn't have to have come from an SWM Jumbo engine, it can come from anything as long as it fits, I don't care if it doesn't say SWM on it. If I knew what other bikes these 350 engines were fitted to I could ring around some of the bike breakers and ask, but at the moment I don't know which bikes to ask about. Anyone got any ideas?

Not b*****ks at all - what we used to do we can't do anymore. There were plenty of places local to me where we could practise and no-one bothered us. Now they do so we can't. What we used to do is irrelevant, its today we are talking about and people's attitudes and the law are different from days gone by - unfortunately. If you're caught on MOD land on your own two feet I'd guess you'd be in trouble for trespassing, never mind on a bike. As far as advice is concerned about the court appearance, I doubt there is anyone qualified on this forum to give you an answer. I'd suggest you ask a solicitor for an opnion.

Before you go mad with an air gun on the flywheel nut, they aren't all left hand thread. The MK1 has a smaller crank assembly and is a different thread from the MK2 onwards but off the top of my head I can't remember whether it's the MK1 or the later models that are left hand - later I think. Just make sure you know which you've got before letting rip with an air socket. It is possible to twist and break off the end (threaded part) of the crank if too much force is applied - yes, I've done it, although on the clutch side and manually, not with an air socket. A flywheel holder is pretty simple to make, long peice of 1" wide steel bar that will reach to the footrest with two lugs welded on it to fit in the holes in the flywheel, one about 12mm to fit in one of the the larger holes, one about 6mm to fit in the smaller hole that is a couple of inches away from one of the larger holes. Or make a V shape so you can use both of the larger holes either side of the nut. Either way, then just jam the other end of the bar above or below the footrest and it will hold the flywheel. You don't actually have to weld lugs on. I use a piece of bar with two holes drilled in it to take a 12mm and 6mm bolt and hold them in situ with gaffer tape. This holds them in place well enough to hold the flywheel - obviously better welded in place though. There is a tool to remove the cush drive sleeve and you can get one from Keith Lynas in the US - link to his site is on Mats Nyberg Ossa site. Don't know of anywhere to get one here. Or you can make one. I used a round piece of metal about 4mm thick and about 3" diameter. Drilled a hole in the centre wide enough to be a snug fit over the sleeve but it must be able to slide freely on the sleeve without being loose. Then machine a recess in the disc around the outside of the hole, 2mm deep and about the same in diameter. You then need two C shaped collets that will fit into the groove in the end of the sleeve but they must protrude from the sleeve rather than sit flush. I made these by finding a very thick washer that just happened to be the right outside diameter, thickness and inside diameter and cutting it in half. The idea is that you slide the disc onto the sleeve, fit the collets into the groove on the sleeve and then pull the disc towards the end of the sleeve so that the disc comes up against the collets, the collets fit snugly into the machined recess which stops the disc being removed from the sleeve, holds the disc in place and stops the collets dropping out. Then, using a conventional three legged puller around the back of the disc (which is why it needs to be about 3" in diameter, you can pull the sleeve off. These sleeves are a tapered fit and can be a real bitch to remove as they can be incredibly tight. If it is stubborn you can heat it and whilst it is under tension from the puller tap the end of the puller to try and shock it free. When they let go though, they can fly a good few feet. If the engines never been apart expect it to be really tight. Don't be tempted to try and get behind it and lever it off as you'll only damage the casing and and possibly break a piece off the sleeve - you won't lever it off, trust me. When you split the cases tap the shafts gently from the clutch side as you need all the gears to remain in the timing side casing when it splits rather than rolling all over the bench. If you can seperate it gently enough all the shims should stay on the shafts although they may also stick to the bearings in the clutch side casing so check that too. If you can keep them from falling out you can just reassemble it replacing the shims in their original positions - you are supposed to re-shim it but you should get away with doing that. There are shims on the crankshaft too, maybe both sides.

It's impoosible to diagnose really, there is nothing specific about an Ossa gearbox that I can recall that could cause this. The fact that 1st and 2nd can be selected suggests the selector mechanism and the selector fork that engages the drum are okay as it engages up and down. Sometimes the tips can break or wear off the end of the fork that engages with the pis on the drum but that usually reults in a moving gear lever but no selection, rather than a jamming lever. If it is jamming when trying to select 3rd then it could be a bent selector fork (ie; one of the forks that slides the gears not the selector drum fork) or maybe something has broken in the gearbox, like a tooth, and there could be a bit of metal jammed in the slot in the selector drum that the 3rd gear fork uses. It could be anything really, even incorrect shimming as the Ossa relies heavily on shims to get the gearbox to work smoothly - they are on most shafts and on either end too. When engines are stripped they sometimes get thrown back together without any shims and it is pot luck whether they work well or not. Some will, some won't. Was it working ok before and has this just happened or is this the first time you have run the engine and found there is a problem. If the engine has been apart, incorrect shimming could be a possibility. It isn't possible to get anything out of alignment on the selector mechanism with the selector drum, it will only go on one way. If the spring on the selector shaft was not located properly it is unlikely you would get both up and down selection, usually just one or the other - not impossible though so that is also a possiblility, although remote. Unfortunately, all of the mechanism is in the gearbox so you have to strip it to see if anything is wrong, no other way really

Later TYZ was fitted with these too, supposed to boost bottom end torque I think. I remember cutting mine off to soften the power delivery as it was a sharp motor on that particular bike.

The 175 and 250 engines are completely different as budgie said, the 250 is much bigger and won't fit a 175 frame (well, not without the grinder, hacksaw and welder) Maybe you're thinking of the 250 and 320. The 320 is a bored out 250 so they are the same engine.

Yep, should run no problem, one of our lot has that combination on his 320 Majesty and it runs fine. I had some lugs welded onto my WES middle box to bolt the heat shield on. You can hold it on with a couple of good strong cable ties though. I've also done this without problem, they don't melt.

No, that's a one off pipe made by someone for Ian

depends on the piston used, there are various options and I think it's correct that not all need a spacer as some have the same pin to crown height on the piston as the 175.

Sorry, no idea what the number 18 signifies. Perhaps Nigel Birkett may know if some were stamped for any reason, he's your man for anything Yamaha. Piston kits are generally a reasonable price, but if the barrell needs replating then that costs a bit. Head gasket is pricey. The TYZ shouldn't rattle so something is worn but obviously impossible to say what, could be piston, small end, big end or all three. It's an amazing motor the TYZ, they really will take some abuse. My Birkett framed TYZ suffered a heat seizure on the road in the SSDT after a blown head gasket let all the coolant out. It was locked solid and very, very hot. After it cooled down I filled it back up with water, managed to free it off and kicked it up. It had no compression so I guessed the rings were stuck but it started and got me back to Fort William. Fitted a new head gasket and managaed to get another couple of days in before I retired as it was still losing coolant and I didn't want to damage it too much or get stuck miles from anywhere. I didn't want to get spat off it on the road either if it locked up again as one near miss was enough... When we took it apart after getting home we couldn't believe what a mess it was inside. The mains were gone, so was the small end and big end and the piston was worn. Parts of the plating on the bore of the barrell had picked up and embedded themselves in the piston in several places and the rings were also welded into their grooves in a few places, the bottom one probably 90% stuck, both of these due to the heat seizure when the head gasket went. Despite all this the bike was still running fine, wasn't rattling, just a bit of a grumble from the mains and it was still pulling like a train with no apparent loss of power. It was still pulling 4th and 5th up the sides of the mountains on the moor crossings no problem and showing a decent turn of speed on the road. Looking forward to seeing what it goes like when the rebuild is complete

Yes indeedy, got the regs and definitely be riding, hopefully bring one or two more as well

who else is doing front pipes for TY250 twinshock apart from Miller?

Yes, as Pitley says, Godden framed 175/200. It has the bend at the bottom of the front down tubes. Mini Majesty tubes are straight. Only way to tell if it is a 200 is by the bore as they use a 70mm piston.