If you post clear photos showing the cylinder head fins on the RH side, the induction pipe (carby to cylinder), the clutch actuation arm, the undersides of the motor and the cylinder fins it would help with identification
According to my trusty Bultaco engine number identification charts that is a El Monterdero MK 2 350 engine 1971-72 which it does not look like it is. So some more photos would help us out in trying to work out what motor is actually is. The old 4 speed Bultaco engines have a look all of their own. Judging by the gear shaft on the left hand side it is a M158/9 engine or later as these were the first Sherpa`s to have the shaft all the way through the engine.
Also, a whole lot of bearings, gaskets, seals and stuff arrived today. Along with a manual.
now I'm scared.
Got the BBQ ready.
Will need to get the crank re-done. So will send that away.
Cant afford to pay someone else to rebuild the rest so away I go.
I saw that people Locktite the crank onto the bearings, any other little tips for along the way.
Do you use a Puller/splitter to open the casings or whack the crank with a soft mallet? is that OK once warm.
I'm nervouse about the kickstart and all the shafts falling out and getting messed up….. I have seen people wire it all together but does that preclude putting new roller bearings on the shaft.
Hopefully it's all ok in there but I will let you all know.
It looks like a 250 engine. Might be a M158, M182 or a M190. Just measure the bore when you have the head off. A 250 of this era will have a 71mm bore standard and the 350`s will have a 83.2 mm bore standard. The kickstart shaft stays in place when you split the cases and the only washer in the gearbox goes on top of the kickstart gear. They really are very easy engines to work on. You can find workshop manuals online for these engines and they are all mainly the same. They changed the primary gearing on the M 199 A`s and B`s which were the last ones. I`m not sure but there might be a number on the barrel on top on the thick aluminium next to the liner, 158 maybe. Don`t forget to use new rubber O`rings on the crankcase seal holders, the primary side of the crank and behind the clutch. You can get all the bearings and seals at any Bearing shop. Use two normal oil seals on each side of the crank and face them face to face, one opposite the other. The clutch spring nuts are supposed to be four turns out from up firm but not tight. Always check the clutch after you bolt it all up by holding the clutch in and kicking the engine over and checking the plates are level and not wobbling. If they are just adjust the nuts until it spins straight. The primary side is the side that comes off the crank and I just use a soft hammer. They usually split easily. Don`t forget to pull the top of the gear change drum off. Three flat countersunk screws. The 250`s I have found like to be timed at 2.6mm BTDC but some like 2.9mm. Make sure the plug has a .4mm gap which is the same as the points. They don`t like a wide plug gap. Have fun. Graham
Wife thinks I'm nuts reading a manual like its a magazine but apart from a few scary bits re layshaft and gears which I hope to avoid I'm probably going to be ok.
I note there's no chain tensioner on the primary chain which is a sign it may not be a sherpa engine.
The primary drive flywheel is single-sided and the front sprocket is for a single row chain. Sherpa Ts and some Alpinas usually have twin flywheels on the drive side. This means that the primary drive is either Alpina or Sherpa T. Some people machine off one flywheel half. The cylinder head having only one plug hole says something but I'm not sure what - my Alpina from the same vintage M138 (1975) has two plug holes and my Sherpa T M198 (1978) has a single hole. From the way the fins have been machined to give clearance for the exhaust, the cylinder head is either Alpina or Sherpa T or the last model of the Matador which also had a high pipe and was that same era The front sprocket being 13 teeth 520 chain means that whatever motor it is, it was probably used for trail/road riding rather than for trials competition The lack of a tensioner on the primary chain means nothing because they are commonly removed and not replaced when they break, and make no discernable difference to smoothness of the motor, but are a liability that can destroy things when they get chewed up by the primary drive
