feetupfun

it either leaked out while you were riding or you processed it through the motor (as lineaway said)

Some of them are stamped with model number of the first model that used that design of barrel. An example of that are my M49 barrels that are stamped 27. M27 is the first model 5 speed Sherpa T and M49 is the second model

partially or fully blocked pilot jet or pilot mixture passage

Cutting the axle avoids the risk of bending the frame by using force If your only problem is the axle being frozen in the inner bush, it is relatively easy to release the axle from the inner bush once it is out of the swingarm If the inner bush and outer bushes can be reused, all you need to buy is a new axle. If the inner and outer bushes need replacing, you needed a kit anyway There are two kits and one is much more expensive than the other

http://www.motoguapa.com/BULTACO/BULTACO%20ARCHIVOS/Alpina/Bultaco%20Alpina%20Mod%2085%20-%2099%20r.jpg This shows what the original tyres on an M85 look like

clutch drag possible causes: incorrect adjustment (too much freeplay) insufficient travel (wrong handlebar lever ratio or lengthened arm on camshaft) plates not flat spring pressure not set evenly sticky surfaces on plates grooves worn into basket fingers It is fairly normal to have more clutch drag when the motor is stopped due to the difference between static friction and dynamic friction between the plates

Check for a sheared flywheel key. With this you will get spark but it won't run because the spark is not at the right time

It was fashionable at the time. There is no downside for unpainted cases if you clean the mud off after riding.

I wondered that too after looking at the photo again so I had to go up to the shed and look at it properly. I've been using that screwdriver for about 10 years and had not noticed that ball on the end. It is pretty weird

The kickstart return spring sits beside the kickstart lever and should make no difference to any slippage. Before you go to all the trouble of pulling the motor apart, are you sure the clutch release cam and spider are working correctly? (especially after fitting new plates) Another thing to check for diagnosing clutch slippage is does the clutch slip under hard acceleration in 6th gear? If it slips when you do that, then it will probably slip when you kick it over cold

It's a pretty close fit all right and is the same problem as on 348s. Mine is set with the exhaust very close to the seat tank unit, to maximise the gap to the airbox. I think the inside of the seat tank surface may have originally come with piece of reflective insulation. I have seen Cota 348s and 349s fitted with Cota 247 airboxes (a completely different design)

I overhauled another set of them last weekend. Lovely shocks

Not at all. I though it was bit funny though because I looked at the newspaper page in one of the photos and thought "that looks familiar", then I saw my vice and realised it was me!

I've just rebuilt some mid-1970s Betor shocks for an Alpina, but I would think that they are not the same as what would have been on a 123 Cota. Can you post a photo showing these shocks? Most old trials shocks that are intended to be rebuilt, you take the spring off and unscrew the seal retainer

I usually check how much slack there is in the primary chain every time I take the cover off, and if you are even more risk-averse, they are pretty cheap to replace. Beware of the primary chain tensioner falling apart and getting munched up. My M49 had a tensioner slipper that was a block of brass instead of the later type hard rubber wheel. I didn't like the look of it and just left the tensioner off and the bike has been fine. I think the mounting for the tensioner in the early 5 speed motors is different to later 5 speed motors too. M27 clutch may be the early 5 speed type with segmented blocks of friction material on the friction plates. later 5 speed clutches were steel/steel and the basket is different. I suspect that it might be hard to get new plates to suit the old basket and hub if you need to. Can't remember if you need to replace the gearbox shaft to fit a later clutch. I'm thinking the old type clutch hubs drove on a key and the later ones have a spline If it has done a lot of miles, the gearbox output shaft which is hollow and runs on the gearbox shaft using a sintered brass bush which might need attention.

That's my hands and my workshop in those photos

even if the epoxy did bond, and I'm pretty sure it would not bond, the epoxy would crack if the tank got a thump, being much stiffer than the HDPE

The frame appears to be modified with the front end of a Yamaha trailbike frame. The motor looks like Yamaha single cylinder air cooled off-road bike from the 1970s, I'm thinking early IT175 except for the cylinder head which looks like it is from a Yamaha road bike The front end is from a late 1980s early 1990s trials bike (Aprilia Climber era) The Aprilia swingarm appears to have been fitted upside down so that the chain is on the side that suits the Yamaha motor

We have to run folding pegs here. These work OK

I don't think the drive side crank seal is gone, but if you really want to get that drive gear off, you will benefit from a very strong puller that doesn't damage the gear teeth, and cycle it hot and cold while it is loaded up. If you search in the forums you will find many discussions on the subject of 1970s Montesa Cota drive pinion removal. Black oil dribbling out the exhaust is definitely not a leaking crank seal. It is just part-burned two-stroke oil. If you do more than just tiddling around on it you will burn more of the premix oil and lessen the goo production rate and might even clean some of the goo out. Also make sure you don't have too much oil in the premix or a too-rich fuel air mixture Gearbox oil leaking into the crankcase forms a dense white/light grey cloud of exhaust smoke which stinks and the oil level goes down Normal exhaust smoke is clear pale blue and smells like normal two-stroke exhaust

Please let us know how you go. I plan on having an M198 rebored soon

The (very high) standard gearing on the TY125 may have been chosen to help meet noise level standards rather than be ideal for road performance. It was common practice in the 1970s

12/53 is what I use. 13/53 is OK too if you don't mind using the clutch here and there

For all the years that Scorpa trials bikes had Yamaha motors, Yamaha badged them as Yamahas in Japan, so it is nothing new

They can run backwards, just like many other two strokes can. The tendency to run backwards can be almost eliminated if you set the spark timing correctly and get used to using the unusual kickstart. Yes it is a common occurrence for the 348 Cota to shift poorly when the motor is stopped. Mine won't shift down gears at all unless the motor is running (ie rocking the bike to move the gearbox output shaft does not help). They also have a tendency to drop out of second gear if it is not properly engaged