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When stripped for competition a standard TLR200 is pretty much the same weight as the other popular full-size twinshock trials bikes from the early 1980s. Many people make their TLR200s lighter using different exhaust systems and fuel tank/seat arrangements. As good as the TLR200 is, they are not the lightest-feeling bike of the twinshock era. The small Montesas, the TY175 and some TL125 specials I have ridden all feel lighter than even a lightened TLR200 They are a full-sized bike and are very similar in height and length to the other full-sized trials bikes of the early 1980s.

If you are using the standard ignition then 0.4mm to 0.5mm plug gap

There is no oil level in a two-stroke crankcase The gearbox and the primary drive cases have separate oil systems, and there are no dipsticks, tell-tale screw holes or level glasses in either. To make sure there is the right amount of oil, drain them, and then refill with the recommended quantities. If the motor is working properly, the oils should stay where you put them. If not, oil can transfer from one to the other, or get sucked into the crankcase, or leak out or do any combination of these things. Measuring what comes out when you change the oils is a valuable technique for monitoring what is happening inside.

look up the catalogues/reference material of current piston manufacturers and see if you can find a piston that has the same dimensions or can be modified to suit your cylinder. You will need to know nominal diameter, height from centre of pin to crown, centre of pin to base of rear skirt, gudgeon pin diameter and piston ring locating pin locations. There are very few of those bikes in use so you may well be the first person wanting a piston for many years, so you might have to do some legwork If you post up those dimensions, someone might be able to help you with the search. If it is just the L ring you want, then you can measure yours up and search for one of them. I know there are still lots of new L rings out there for old Yamahas and Bultacos, and probably others had L rings too If you are desperate you could have a new groove machined to allow fitting of an available ring, or have the old groove machined to suit an available ring, of the right diameter

Nice model Alpina. They have a great look "round barrel" 250 Bultaco motors like yours are prone to getting quite hot if ridden slowly in hot conditions, mainly due to the close fin spacing. 260 degrees F near the sparkplug is nothing unusual, and also quite meaningless unless it is measured while the bike is being ridden. For what you are trying to achieve (checking the jetting), observation of the behaviour of the motor (how it runs at different RPM and throttle position) is the more usual way to check the jetting. If you are going to ride it through long sand washes or at sustained high speed, then I would suggest also doing plug chops using s "safe" heat-range plug (NGK BP7ES or BP8ES). A more sophisticated method for setting the jetting for road riding is to use a cylinder head thermocouple that fits between the head and the body of the sparkplug. I see that the carby looks like the original AMAL concentric. They are prone to rapid wear of the needle jet, needle and slide, so generally run too rich everywhere except full throttle and idle unless they have just been rebuilt. Why do you want to fit a tacho to an Alpina? Does the fork brace hit the front guard on full compression of the forks? It would hit if it was on my Alpina

Yes it must have had plugs in the balancing holes at some stage Something odd: I've not seen crank balancing holes on the opposite side of the crank wheels to the big end pin on a trials bike before. I'm thinking aloud about what might be the reason: We know this motor is currently 250cc. Maybe when the crank was made, it only had balancing holes in the pin side of the crank wheels, and it was balanced to suit a bigger diameter(heavier) piston than what is in it now. Then for some reason the motor was then converted to a smaller piston (the 250cc it is now), and to get the crank balance right, balancing holes had to be put in the non-pin side of the crank wheels

yes you have to take the clutch cover off to get the drive gear off the inner end of the pump shaft

RAD Hard Chroming in Sherwood, Brisbane, Australia are highly regarded for rechroming fork tubes. Last set I had done there were AU$150 per tube plus freight

Michael I looked at your blog, but was not able to comment on there about the rebore on the TY175. Pistons are made smaller at the top (at room temperature) because the top of the piston expands more in diameter than the bottom of the piston when the motor is running. It is usual to use the diameter of the piston at skirt height for setting the clearance and yes it is very unusual for a cylinder rebore specialist to suggest that the customer should achieve the desired clearance by shaping the piston. The machinist should either bore to the right size, or bore undersize and then hone to size

As you found with the motor when you pulled it apart, they usually have only one metal shield on that bearing and it is located on the outside of the bearing. That bearing has a shield to better manage where the oil goes inside the gearbox and primary drive case while you are riding and falling off. The reason the shield goes on the outside is that there is a better oil supply to the bearing via the gearbox side, compared with the primary drive side. It is common for bearings to be supplied with two shields, or two seals, to reduce inventory in the supply chain. Yamaha have been rationalising many parts in their supply chain for many years, so nowadays you might buy a genuine Yamaha magneto case breather for example, or a genuine nut or bolt for a TY175, and find it is a different colour or finish than the original item, but it still fits and works as intended. The unwanted shield can be easily removed

You are pretty lucky to not have a leak at the head joint, with that bolt missing/broken. Yes fixing it is likely to be do-able. What is needed to fix it will not be known until you know what the female thread in the barrel is like

We use 50:1 in our 2010 GasGas Boy 50 and it runs fine (no smoke) but does drool a lot of black gunge from the exhaust pipe drains

white smoke can also be from gearbox oil getting sucked into the crankcase. It will disappear from that tiny gearbox pretty fast if you are seeing lots of smoke

My memory of the reason for the bearing seals in Sherco motors is that when that motor design went into public use in the late 1990s, they had open (seal-less) main bearings, and also suffered premature main bearing failures. It was found that running sealed bearings extended the life of the bearings, so now they come new with sealed main bearings and recommend that sealed main bearings be used when the main bearings are replaced. I don't want to go into the theory for why the seals help with bearing life because it is a subject like "how much oil should I use in my premix" or "what brand premix oil is best"

correct, it will make it run lean (even hotter) before stopping. That's why I said it doesn't always stop the motor in time to prevent it seizing - but if you do nothing it will definitely seize

if you can manage it, turning the bike upside down stops the motor instantly. I have saved two motors this way Also I suggest you try out the exhaust blocking technique with a runaway engine, rather that testing it out by seeing if your motor can start from cold with a bung in. It actually works very well in real life. I have also saved motors this way and you don't actually need a glove or a rag. If you can seal off the exhaust fully with your bare hand it is not unbearably hot to perform, unless the bike has been ridden at high speed just prior to the incident. If nothing else is possible/safe, turn the fuel off (this is not very quick acting, but it may stop before seizing) Something that did not work for me in one incident was using the use the rear brake (it just overheated the brake disc) I've had so many of those episodes (stopping peoples runaway trials engines), that I have become an advocate for using lanyard switches

the offset can be measured from anywhere you like - whatever will be easiest for you to measure when you are respoking. To get the rim in the right place, I usually fit the wheel to the bike and measure from the rim edge to the forks/swingarm. From memory, MAR wheels have no offset, ie the centre line of the rim is in the centre of the spoke flanges on both hubs

For info, this is also a M49 brake pedal, but from an earlier M49 than the ones with the pivot located inside the frame

It is important to protect the gearbox bearing and the chain from overload by making sure that when the sprocket centre, swingarm pivot centre and the axle centre are all aligned, that there is still a bit of free play in the chain. The other end of the scale (too loose) on your bike would be if the tensioner is going high enough to touch the swingarm when the suspension is fully extended. If you set yours between these two extremes, you will have a happy chain The ideal measurement you are asking about (the distance between the tensioner and the swingarm) will vary with different size sprockets and where in the stroke of the suspension you are taking the measurement, so there is no single correct dimension for a given bike unless you specify those variables.

as far as modern trials bikes go, I have not known of any two stroke piston needing to be replaced due to normal wear (a few due to seizing though), and of the bikes that get owned by the one person for long enough to be able to measure such a thing, the rings seem to last 6 - 8 seasons. If modern trials bikes were used on the road (they are not used on the road here) piston life may become important, as it was in the 1970s when it was common to ride a trials bike on the road. My original TY175 was road ridden for many years and after about 20 years had finally had enough rebores that it needed a new sleeve (at the time the biggest OS piston was +1.0mm). Another of my old trials bikes (a 1973 TY250) is still going on it's original piston and rings and runs like a dream. I bought it in 1994 and the speedo showed 3000km, and it has had lots of trail and trials riding since 1994, but has never had the cylinder head off.

front wheel, forks and triple clamps look standard. The front guard looks odd because they are usually mounted to the fork sliders, and it is a guard off something else. It would probably feel better to ride with higher bars and trials shocks. The shocks look like TS185ER The end muffler is off something else It will weigh about 95kg The year model makes no difference

They can be set up to turn tightly. 360mm rear shocks and setting the forks up properly does wonders. The motor is a beaut to use and does not stall easily. No mechanical weaknesses at all - they are very sturdy and well made. The only design criticism I can think of is that they are a bit heavier all over than their competitors. As far as ease of trials riding goes they are almost as easy to ride as a TY250, and better to ride than a standard TL250 and standard Suzuki RL250. Late model twinshocks like Fantics and Honda TLRs are noticeably easier to ride while spanish bikes of the same design era as the KT (early to mid 1970s) are a bit easier to ride than the KT. While they are fabulously reliable, you could look for rust inside the fuel tank and all the other things to look at on an air cooled drum braked bike ie worn drums, pitted fork tubes, rusty exhaust, noisy motor, parts missing, clutch action, gear shifting action They were made in 1975 and 1976 No idea what KTs are worth in NZ or what a Cota 311 is worth

the effect you describe can be caused by poor piston ring sealing

There are people who have modified 1970s MX bikes for trials, and it is a lot of work, but the designs of MX and trials bikes diverged after that era to the point that by the 1990s, MX bike design became so far removed from trials bike design that it would be extremely difficult and expensive to make some sort of trials bike from a 1990s MX bike that worked well.

the TY175 JC/JE muffler also works well on the TY250, but needs the inlet tube shortened to fit the TY250