woody

Manual specifies SAE 80, or any modern light gear oil will work. 1 litre, but 900cc for an oil change as not all of the oil drains out 50:1 is ok with modern synthetic or semi-synthetic such as Castrol Power 1

Does the plug get wet? If not, as it has been left for 20 years, a blocked pilot circuit in the carb is a possibility, if a pilot jet or aiway is blocked it can be vitually impossible to start a bike. Put fuel down the plug hole or spray easy start into the carb, if the bike runs but quickly dies, chances are it's a blocked pilot circuit, try having the carb ultrasonic cleaned You mentioned the ignition timing, check that the woodruff key hasn't sheared when you've been kicking it and the flywheel moved out of position

The only similarity is the bore size, the porting is completely different in either cylinder

The 350 MAR was produced from late 1975 so it has the later type shafts for kickstart and gear lever. It will be the same spline as the enduro engine, assuming no-one has changed parts on it at any time. Just count the number of splines and compare to double check

Same for all models, they changed the gear and kickstart shaft sizes around late 1973

Yes, you'll need another kickstart and gear lever with the correct number of splines, the earlier engine shafts have more splines than post 1973 engines The exhaust won't be a straight fit, yours has a flange held in the cylinder by the threaded screw in collar. The exhaust on the enduro engine is a push fit held with springs. To get yours to fit you have to cut off the flange so it pushes into the cylinder and weld two hoops on it to locate the springs - as long as it is the right diameter to fit. But how the enduro motor will run with the trials exhaust I wouldn't know You also need a carburettor, yours won't fit as it is bolt on and probably also too small for the porting, whereas the enduro cylinder is a stub fitting

The stator can be checked, you'll need the workshop manual which will give the expected readings, I've no idea, electrics are a mystery to me. In the UK we can get them repaired. The motoplat coil for the Ossa is a combined coil / cdi so you need the two connector type. New replacements are available (at least here in the UK they are) When I saw the picture of your replacement engine I assumed it was the same year as yours but someone had changed the cylinder head for a later one. It seems the chassis number list I have incorrectly lists the engine as a 1972 but it's actually a 1976 enduro version, so, the kickstart and gear shafts have a different number of splines from your explorer engine. I think that the exhaust fitting on the later enduro motor is push fit with springs, not threaded collar, so your exhaust header isn't a straightforward fit To be honest you're probably better off fixing your explorer engine, all parts are available.

The centre cases are all the same casting so are interchangeable. The reason the ignition cover might look different is because the rear most part sometimes gets cut off or modified, either to stop a build up of mud or they simply get broken by derailed chains The replacement engine is an enduro engine, the Explorer is a trials engine. The enduro motor will have a different state of tune/porting and different gear ratios. They also use an expansion chamber motocross type exhaust although your Exporer exhaust should still fit into the cylinder. They use a 32mm carb as they're basically a race engine It's not an uncommon problem to find a different engine won't slide into the rear frame mounts. You might find that the mounting brackets have been squashed inwards slightly with repeated tightening over the years. You can try puting a piece of solid bar against the inside face of one and putting a solid bar through the hole in the other and tapping outwards, then repeat on the other side to try and open them out a bit. Or just take a bit off the engine to enable it to slide in

In the US you have Hogans, Alex Snoop, Keith Lynas, Vintco

The retaining nut is almost as big as a 10 tooth sprocket which means the chain rides up over the points of the nut when it is flush against the sprocket. To use a 10 tooth there is a nut with a shoulder on the inside to give clearance to the chain, you need to use this nut Depends where you live, in the UK, In Motion have all you need I run a dished rear sprocket on my MAR which only comes in 44 tooth size, this works well with the 10 tooth front

It's a 1972/73 Sherpa, the model number is 92. The frame/engine numbers are close because the UK importer used to sell them as 'kits' to avoid purchase tax, so when the bikes arrived from Spain with engine and frame numbers that matched, the importer removed engines and then sold a bike and engine to the customer as a 'kit'. It's a Bultaco frame, series 2 type 92, no idea why the top half looks chrome, the rear shock top mounts have been lowered to make them more angled. The tank is a UK made item as using the original Bultaco fibreglass tank on the road was illegal at the time as fibreglass tanks were outlawed, so UK bikes could have these fitted

An Ossa TR77 can't be started with the clutch pulled in as it doesn't have primary kickstarting

Sorry I'm useless with electrics so no help with testing electrical components. The 5 speed manual is available to download which should have readings in it. Or you can send the stator and coil to Bradford ignitions as he can test and repair Motoplat stators and sometimes coils If your wires still come out from the bottom of the ignition casing and run under the engine, there's a chance that they may have got chamfered or broken as they have to bend a sharp 90 degrees, once old and brittle the sheath can crack causing shorts or they can just break. Also, with a bike that's used hard the bash plate gets smashed up towards the engine and can help break the wires. A mod to stop this is to drill a hole through the top front of the casing by the engine mount and run the wires behind the stator, through the hole and up the front frame tube. This involves grinding away some of the ribbing behind the stator to accommodate the wires. If your bash plate has go bent upwards, also worth checking that the head of the sump plug bolt isn't exposed as that can end in tears if it catches a rock. Tapered headless allen bolts solve that problem

The end float on the gear shaft won't affect the plunger as that acts on the selector drum, but too much end float on the gear shaft means the selector fork is not in contact with the selector drum when the shaft moves too far to the left. Inside the clutch case there are two washers on the gear shaft, normal and wave washer, located by a circlip. These restrict the shaft end float, if they aren't there the shaft will continue to work its way outwards, disengaging with the drum, nothing that a kick with your heel won't solve to push it back in though

If the engine is in the bike, put it in 1st and try just tapping the gear lever into neutral with your heel whilst rocking the bike. If the shimming is making the gear selection a bit stiff it could cause the selector to go straight past neutral to 2nd and vice-versa. Tapping it with your heel should move it just enough for neutral. It's how I get neutral on my 250 as the gear selection is a bit stiff, my 350 gets neutral a lot easier