stevem75

Yes it is a Montjuïc race bike. The engine is a 4 speed 350cc This engine was used in the bandito and el montadero models. As well the M29 TSS used it. The preproduction Montjuïc road bike that never came to be used this power plant in its early development stage. Note the center port exhaust exclusive to this engine type. I believe the factory called this the “pedrables” engine. Whereas the 5 speed models were called San Antonio. There were only 2-3 of this montjuic built by the factory for 24 hours racing. It was likely loosely built around the 350 TSS but didn’t carry the M29 designation. Highly regarded and exceedingly rare Steve

Bultacos are never referred to by year. They are referred to by model number. A M151 is a 326 cc Sherpa T that was produced for a very short period of time (1975). However it cannot be called a 1975 model year. If you order parts from any Bultaco parts dealer for a 1975 Sherpa t it means nothing to them. The only correct reference is the model. Bultacos were made so that many parts were interchangeable. This kept production costs down. So for example an engine case cover for a pursang would fit a Sherpa t. If you have a non matching serial number between frame and engine you’d need to order correct parts for each model number. Make sense ? It would be more helpful if you mention what parts you think will need interchanging. As mentioned most parts will be to an extent. Steve

True prototype bultacos carried the M100000 serial. Before the purists tell me M100 was the 125 pursang please know factory protos always were labelled M1xxxx. They could have been metrallas, pursang or anything bultaco wanted. Most Sherpa T factory rider models were actually numbered model units taken from the assembly line and given to respective riders. Be it M80,92,133,159. Bultaco did whatever they pleased it seems. Vesty has many times corroborated this..... see his Facebook page and pics for evidence of this. True factory Sherpas were carefully blueprinted well set up bikes for lampkin, vesty , soler, bulto etc etc The G on the headstock more than likely was used to identify what the particular tube on the frame was to be used for. Bultaco frames were not assembled and welded at the factory. They were all pre made at another factory away from the assembly line. This assembly plant likely needed identifying marks to know where to place each tube in the jig for welding. Hence the letter stamp. I have a M27 that has the same letter on the headstock. This isn’t coincidence. They probably did hundreds of frames a month if not thousands and each piece would need to be labelled to know it’s fitment. Steve

I’d say the frame is earlier than 158. I’d guess 124. The give away is the gusseting at the headstock and the tube that runs from the upper frame tube to the bottom (right where the 158-159 airbox would go). As well if this was a later model frame than 158 then the swing arm and rear motor mount would have been separate pieces. None the less still a good solid bike to be out riding on!! steve

I think your original post said when you grounded the green you had spark. Problem solved. Yes the green does terminate at the resistor ground. This is normal. It could also be grounded to the ignition coil bracket. Both ways will work I’m not sure I understand how you’re using a test light to diagnose. This would mean you have some sort of powered light that will illuminate when you have a circuit. This type of test will prove nothing with this system The black wire from the magneto goes to the ignition coil. The green wire goes to ground. The green wire grounds the magneto..... sort of. It’s function is to activate the rear brake light if so fitted. ( through the resistor) If it isn’t fitted or you’re not using the brake light then ground the green wire !! please do not jump to “it must be the coil” conclusion. I’ll say it again. It’s not the coil. ! Check simple things first. Known good plug. Known good plug cap. Clean electrical connections. Disconnect all peripheral components except the black and green wires. Check for spark. If it doesn’t spark with black to coil and green to ground. Then un ground the green wire and leave it connected to nothing. Check for spark again. If still nothing then make sure points are opening completely to enable the circuit to break. This problem Won’t be more than dirty points, bad/broken wire or connection, or bad plug. Highly highly unlikely that the low tension coil or ignition coil are the issue

Black wire from magneto goes to the ignition coil. If the condenser is frame mounted,black would go to the condenser and then from there to the ignition coil terminal. Green must go to ground in order to spark. Don’t replace the coil it’s not the problem. Wiring diagrams for that bike are plentiful on the net. Steve

We don’t know exactly what model your bike is. You haven’t told us what the numbers are. You mentioned on the motor you see M and the frame you see B. What are the numbers after the letters ? Those numbers are a reference to what model it is. A M85 is an alpina 250. An M99 is a 350. So let’s say it is an M8500123. That would mean it is a 250cc alpina and that it was the 123’rd alpina built. Roughly that bike was produced from 71-73 but there’s no way of knowing. So write down your number and check the model reference list that was mentioned a few posts back. As mentioned the number will correlate to a model, a displacement , and rough year of manufacture. But without either checking it or posting here we can’t tell you for sure what it is steve

Ah yes right you are. M85 would be correct

Bultacos were given model numbers instead of years. You look to have an M99 I’m guessing. The 99 is the model. Using the link to the reference list in another post you’ll note that a M99 is an alpina. These were produced over several years which is why bultacos cant accurately be referred to by year. That model was made for several years and it would be impossible to know exactly when it was made Now to the running issue. It takes three things to make and engine run. Spark, fuel , and compression. Start simple and remove the spark plug. Connect it to the coil wire and lay it against the cylinder head. Crank over the engine with the kickstart and watch to see the plug spark. If it doesn’t then get a new spark plug. Bultacos use the most common spark plugs in existence. Any Napa or auto parts store will have them. NGK is the most common brand and B8ES is the type of plug you need. They’re cheap. Buy a few to have around. With new plug in hand check for spark again. If still no spark then there is likely a wiring issue somewhere in the system. Or the points need cleaning because of sitting Fuel is next..... if the bike has been sitting you need to make sure the carb is clean. It may need to be disassembled and thoroughly cleaned to get old residual funky fuel out of. Same goes for the fuel tank. Make sure you’re using fresh fuel and mix it properly with a good quality 2 cycle oil. We could argue about who uses what oil at what ratio but just buy a name brand two cycle oil and mix at anywhere from 30-50:1 and you’re good. Compression is next. Any two cycle engine requires primary and secondary compression. Primary compression means that the crank cases are sealed properly. This is done on the bultaco (or any other 2 cycle engine for that matter) with crank seals and a Center case gasket. These seals help to hold the atomized fuel inside the crankcase and not allow it to leak out. As the piston travels down the bore it pressurizes this mixture and forces it through the cylinder transfer ports and up above the piston where it will then be compressed in the combustion chamber. Combustion chamber compression can be considered “secondary compression “. So basically you need to have no ability for the fuel to leak out or around the crank seals, Center gasket , base gasket and piston rings. And not to mention no way for air to leak in through gaskets and seals. Using starting fluid you should at least be able to get the bike to fire. If only for a moment. You may have leaky seals or gaskets Not surprising on a bike that’s 40+ years old They’re easy to replace and readily available Spark fuel compression. Yor bike is not running because of one of those three things. Or a combination of those things. Steve PS : in North America there are two very good bultaco dealers. Hughs bultaco in upstate New York and Mobley’s in minden Nevada. The UK also has an array of dealers. In motion trials, Sammy miller. All the above noted dealers have anything you’d ever need for that bike

I’d use (and have used) the reputable dealers as mentioned above..... but when possible always purchase an original mahle piston if available through these dealers. They may cost more but are worth every penny. Without opening a huge debate; simply stated the wiseco brand pistons are very finicky to use. Because they are a forged piston they expand very quickly causing cold seize issues. When the cylinder is bored to fit the cold clearance needs to be in the neighbourhood of .004”. You can drive a truck through that !!! A stock mahle piston when new is .0015-.002 when cold. Much tighter clearance. Wiseco has a reputation of “making more power “ or being high quality. In 25 years of working as professional motorcycle mechanic I’ve never seen a wiseco 2 stroke piston that hasn’t seized. No matter the set up they will always scrape a little bit. But due to their lightness they probably would make more power (less reciprocating mass) If you’ve been lucky enough to use one of these pistons without issue then you are the exception and not the rule. As the NOS pistons become more and more scarce we are all looking for decent alternatives. And the use of wiseco pistons in the bultaco is becoming more and more prevalent as they are the only source we have for new parts. Just be very very careful with initial set up. And always warm the engine fully before riding to prevent cold seizures. Import duty and tax would play a role for me. If you have to spend more to buy local then do that. steve

I have a 199B frame and matching engine. Complete bike. But ... the previous owner disassembled the engine and used parts from the six speed cluster to make another bike work. So I’m missing the kickstart gear and 2 shift forks for it. But the cases are fully intact as is everything else for the engine. I bought a 199A set of cases complete with transmission and kickstart gear. So I can build a five speed no problem. But in the quest to make the bike matching numbers I was maybe thinking of trying the five speed in the six speed cases. I’m well aware of what the differences are between the A and B models. The main one being the bearings for the transmission shafts. I haven’t taken the two apart side by side yet to see if the conversion is possible. Was curious if anyone has. I’ve checked with inmotion and they could get parts for my six speed but 4 shift forks was quoted around 1000 dollars. Too much for my liking and the 199A gearset is close to the 199B at least the first two gears are. So I’ll be able to retain 11/39 or perhaps 11/42 gearing. I won’t know until I’ve tried it to see what I like. It’s a shame that my six speed cluster won’t work as I do prefer it over the five. Steve

Has anyone installed an M199A five speed gear set into a set of 199B cases ? I know the six speed won’t go into a five speed case. Just want to know if it’s been done Steve

Yes a thyristor will be used to trigger the voltage collapse of the capacitor. This is why this type of ignition is often referred to as capacitive discharge or CDI. There has to be a storage device of some sort in order for the system to work. Trust me it uses a capacitor that right now isn’t storing energy. Steve

I’ve seen this with motoplat before. The resistance values seem about right but I’m not 100% sure. But the real issue isn’t with the resistance of the windings within the sealed coil block. It’s the capacitor that stores the electrical charge. As the flywheel spins it induces ac electrical voltage within the winding. That voltage generated is to be stored in the capacitor until another trigger type coil fires and tells the capacitor to shunt it’s current to ground (or in this case an ignition coil) I’d bet if you are able to actually spin the engine up fast enough you’d probably generate spark because you are able to create enough stored energy in the capacitor to make the system work. Problem is it won’t last. The capacitor is worn out. The coating around it is allowing current to leak out. This is why it won’t work. There are several places worldwide that can repair motoplats. A google search can turn them up. This is a common problem with older electronic equipment. And usually is easily and permanently fixed. Ironically the best best preventive maintenance for this problem is to ride more !!! That’s right the more use the electronics get the longer they will last. Steve

They need to be inside the air box. You have them inside out. Steve

I'd start simple and replace the spark plug. If all of a sudden it stopped. Try a new plug. Steve

Oldjohn is right. The seal holders should be in place while installing the crankshaft. It does help to locate the crank in the right spot. However it is still likely that the crank will sit to one side and will need a quick smack to center it. Steve

The crank is likely sitting proud on one side of the case. Bultaco had a special tool to help center the crank. To fix this first look down at the crank from above and see which side the crank is sitting closest to. Likely the magneto side case. Give the crankshaft a good quick wrap with a hammer (deadblow hammer ) and this will "center it " in the cases. Immediately it should turn freely. Don't hit the crank too much as it can throw the alignment. You just need to swat it hard enough to push slightly. All cranks will do this. Modern bikes included need centering too steve

35 ft/lbs is the spec for these. Don't guess or do it by "feel". Use a torque wrench. Steve

All cases have the 112 number. Not sure the reason for that. It isn't a part number. Could have been a reference number that the foundry used when casting the parts. Cemoto sublet all their parts to other companies. Many parts were produced off site and then assembled at the bultaco factory. What you're thinking are mismatched cases are not. Again this looks to be something that was done during the casting process. All cases have these. Especially 199's. All three of mine do. On the older engines that drained the gearbox oil out the bottom of the case instead of the side like the 199's they had a protrusion on the bottom of the case. This protrusion was simply removed on the 199 cases and what you see is the remnant of it. Remember bultacos used a large number of same or similar parts. The 199 on the case simply denotes that they were likely lined bored and set up for 199 parts only. This was important because the 199 uses a different gear cluster set than say a 191 model before it. Later model 199's also had the stroke stamped on top of the case too. Steve

14653 is documented as the last number but it's my understanding that there are several 199B's in Spain that are in the 14690 range. I have 14644 here in western Canada. As well I know 13456 is also in western Canada. To this topic and sorry to those who have read this before....... during franco era Spain all bikes that were produced by cemoto were carefully documented. All bikes left the factory with matching numbers. There could have been exceptions to this for factory bikes or internal usage bikes but anything exported was matching numbers and documented. The government of the time kept extremely strict control of imports and exports and always made sure that duties were collected. Now nearer the end of bultaco the economy in Spain was changing and probably becoming more liberal. Adding the strife at the factory between 79-83 it is likely some sequential numbering was lost. So late 199B models were produced at a few different factories and it wouldn't surprise me if some numbers were incorrect. But ... any model pre 1979 if it says for example M1994321 then you can be sure there were 4320 produced before that and so on. Not to spark the matching numbers debate but it was commonplace for importers to swap out engines and thus even from brand new at the dealer level you may not have had a matching machine. But I can tell you with great certainty that it did leave the factory matching. So you have a 199B Sherpa T that was likely built in early 1983. My bike was assembled in march 83 and yours likely very close to the same time. Maybe even the same week Steve ps : Dave renham worked at comerfords perhaps he could shed some light on the non matching numbers bikes

I had a 159 and used it for several years in regular competition. I had a mikuni round slide 28 on it and the bike had really really sharp power delivery. Lots of snort. Its was almost too sharp and would get me into trouble sometimes in the sections. I then got a 199B and also used it in regular competition. It was a much better bike I thought. The chassis seemed better, not sure if thats the box swing arm being stiffer than the 159. The frame geometry was likely the same. But it just rode better all around. Much smoother power delivery and easier to handle. I used a flat slide mikuni 28 on that one. I too regularly broke the "fork type" head steady. I eventually had a piece of cold rolled steel welded to it and that cured the problem. The triangular brace is obviously the superior set up. I've not tried a 199A but would suspect it has a more "developed" feel than the earlier bikes. I did have a M80 for several years as well. It had a great engine but chassis wise I didn't care for it. I've also had a 92, same thing but better motor. I had for a very short time a 151 and quite liked everything on it . I think this is due to the frame being updated and the use of chromoly tubing and having the better exhaust on it. Steve

The alpina 250 and 350 used different exhausts. They physically look identical but the 350 uses a wider header pipe. The same holds true for the Sherpa T's. All Sherpas starting at the 150-151 up to 190 - 191 models used the same exhausts. That is the 250 was one size and the 350 was another but essentially looking the same. The Alpina starting with the 165 -166 models did the same exact thing. 250's one size 350's another. Do you have the exhaust manifold still ? If so great. Call Tim at Bultaco motorcycles in New York. He more than likely will have a good used exhaust available. And he knows the difference between the 165-166. Sounds to me like bob doesn't have the right one that's all. You can buy a new one from Spain. Just know to buy the 250cc exhaust. Sherpa or alpina Both will fit. They are the same. Steve.

I think this topic is being a little " over thought". Engines take three things to run. Timed spark, fuel and compression. The bike starts and runs, so for now don't worry about spark. You have fresh fuel. Clean petcock. It starts and runs on choke which indicates its getting enough fuel. No choke the engine starves. There are a few possibilities. Check first to make sure that the float bowl is filling with enough fuel. Is the float level correct?. Can't remember on that carb if its adjustable but if it is be sure that it is set correctly. You indicate you have new jets etc etc. Be sure they are the correct sizes. Be sure they are clean and clear!!! Yes new jets can be plugged. I've seen it many times. You also mention that the bike runs best with the air screw turned in. Again this is an indicator that the engine is starving and needs more fuel. The passageways in the carb need to be clear. Especially between the pilot jet and the air screw. If you are certain that the carb is in good working order move onto compression. Bultacos have tons of it. You don't need a fancy gauge to let you know what the compression is. If there is quite a bit of resistance felt when kicking through then the top end compression ( that is the piston and cylinder) can be considered ok. Where Bultacos suffer is with primary compression. This is the ability for the crankcases to hold pressure. The crank seals which you've replaced help seal the bottom end. As does the center case gasket. The other place to look for compression leakage is cylinder base and intake manifold gasket. If these gaskets or seals leak the bike will start and run but won't idle down and will tend to "run on" when the throttle is opened and then shut. You don't mention this so I'll go back to fuel. I firmly believe you have a fuel delivery issue. The carb isn't getting enough fuel or the wrong size jets are used or the carb body is plugged or all of the above. I'd go back and check it thoroughly. You're on the right track. Lots of good knowledge on this forum Steve

You'd think the tire being pushed into the ground would hook up. But the reality is the suspension is unweighted and that's where the loss of grip comes from. Steve