Hi folks I'm new to the site and currently restoring a Bultaco 350 t (159). I took the lhs engine casing off and the nut on the magneto looks wrong to me as it is not sitting all the way down though it is tight. Does this picture look right ? Any advice appreciated many thanks !

Paxo

The standard nut does stick out past the flywheel, but yours appears to be sticking out a bit more than normal. It might be sometning as simple as there being too many washers behind it, or the nut may be longer than the original, or it may be standard and your photo makes it hard to judge exactly how far it is sticking out.

It has to stick out somewhat, or you wouldn't be able to get a standard-walled socket on the hex.

The flywheel appears to be much better-looking than the usual Bultaco flywheels I see which has me wondering if it is a non-original flywheel

That isn`t a standard Femsa flywheel. The standard ones hat Femsa stamped on them as well as the points gap was stamped between the holes as well. It had .35-.45mm stamped on it. The standard ones were also aluminium alloy on the 250`s and on the 350`s I think. The size of that one looks like it could be a 250 one. The 350 ones were heavier.

maybe that one has been turned down - it might explain why it is so clean too

I agree its not the right flywheel but it looks like a Femsa one that was fitted to early Bultaco's , riveted centre instead of later one piece flwheel, it should have a stamp around the circumference

The 159 and most 325's from m92 on should be stamped Femsa VAR 41-52 and would weigh about 2.8 kg, the VAR 41-51 on some 250's weighs about 1.7 kg but it also does not have the rivets.

The nut in the photo does look like its protruding more than normal it should be about 8 mm so maybe it does have a extra washer or the key may not be sitting right

As above, looks like a normal 250 flywheel from an early bike - pretty sure it's like the one on my M49 but that's tucked away and I can't get at it.

Fitting the 250 flywheel is a way of making the engine pick up quicker due to the lighter weight, so not too unusual to see a 250 flywheel on a 325 motor.

The nut does look to be sticking out too far but I can't remember whether it's the same nut on the 250 and 325 engines. The 325 flywheel is deeper, so maybe the 325 nut, if different, sticks out more with the 250 flywheel. Or as someone else mentioned, there could be pack washers behind it or the flywheel isn't fully home on the shaft.

Thanks very much for the replies :-)

I've taken the magneto off and all looks ok, woodruff key etc locating fine and rotor seats hard down on tapered shaft ok. There are 2 washers, a normal plain circular washer(quite thick) and a very thick spring washer. I think that the very thick spring washer may be the culprit so I'm going to fit a thinner spring washer.........hmmm or thinking about it now should I just fit the plain circular washer and use thread lock solution ?

Many thanks

Paxo

Edited February 19, 201313 yr by paxo

Unless the nut rubs on the cover you don't need to do anything as there is no problem