feetupfun

Looks like a Cota 248 with a Yamaha fuel tank

A change in the front sprocket of one tooth makes a noticeable difference. Two teeth on the front makes a large difference

Guy, Mikuni agents normally also have the pilot jets that fit TY yamahas. This is the web page for the Aussie Mikuni importer to show you the range they sell http://www.mikunioz.com/product-category/jets/pilot-jets/

Number 1 not certain but probably where the fuel goes in (looks too small but that might be from taking the photo so close) Number 2 is where the engine oil is injected Number 3 is the float bowl overflow Number 4 not certain but looks like float bowl vent

another thought for your weak spark is to check the strength of the flywheel magnets

not sure of this applies to your source coil, but I have fixed a couple of TY175 source coils by unwinding the last few turns, to remove a corroded section of the winding. There are other ways for the coil to fail though apart from corrosion at the outer end. The winding might have a break/crack or have corrosion that can't be seen. As for the electronic option, I have had a good run with ignitions from John Cane with TY175 and TY250 motors. Both ignitions are many years old now and had no issues. I do live in a dry climate though which might make a difference to reliability

Last one I had done was about $AU100 (by a local auto electrician)

for weak spark after changing the stator coil and points, check that: The coil laminations are not touching the magnets The coil laminations are well earthed The wire up to the HT coil has no broken or hard sections The HT coil has a good earth

while you are trying different points settings, set the clamping screw just tight enough to hold it in place. This makes it easier to make changes through the slot in the flywheel. When it is set right, you can then tighten the clamp screw fully

They are a quirky bike all right. If I had known you only had a ride with no trials usage involved I would have said the same as bisby In case you are doing it some other way, I recommend you drain the gearbox with the bike vertical

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.