pschrauber

Indeed very well ridden The Video is taken in France by P. Frei in Switzerland, he has a lot of nice ride reports with pictures and videos on his website.

Fur the clutch and primary drive: There can be used SAE 10 - 5 (older recommandations) from the mid seventies or SAE 30 (newer recommandations) from the beginning 80's, in pesonal experience ATF works too very good. (As thinner the oil as easier the clutch will slip). For the gear box where the transmission is situated SAE 75 - 95 works fine, Castrol EPX does the Job really well you can use either SAE 80 - 90 or even SAE 85 - 140

Just forgot the frame of the 125 cc and the 175 cc model are pretty much the same.

Not necessary the dimension of the cylinder is normally easy to detect as the cubic cc is printed on the cylinder from the outer side! You find in near the intake on the left side (in driving direction), if it is a 125 cc model there should be printed 123 cc If it is a 175 cc model there should be printed 171 cc It is not possible to rebore the 123cc cylinder to a 171cc piston! See here:

600cc for the gearbox, 300cc for the clutch and between 150 to 180cc for each fork leg. To the quality: good gearbox oil SAE around 75 - 95 works fine, for the clutch SAE 30 or SAE 5 - 10, here ATF work's very good Elf HTX even better. Forks should be SAE 10, I personal use SAE 7,5 being a light rider.

Yep condensator might be the problem. To check the condensator turn the rotor until the points are open, then connect the condenser to a multi meter, adjust measuring resistance (20M Ohm), when the multi meter is connected the resistance should rise up. If the resistance goes down or a short circuit is shown the condensator is faulty / broken.

No disadvantage in my very personal opinion

Very sweet, I' am too in the process of electrical wiring, where are the switches? BTW.: In Germany you have to have silly flashes for road registering if the bike is younger then being build in 1962! I don't like flashes they are very weird on a trials bike. Using the Hercules K125 flashes that are mounted to the bar ends as these are made out of polished aluminium, at least contemporary and they are really solid and do work also as bar ends ... (will of course take them of once the bike is registered ...)

Yes the left foot brake assembly works much better as it doesn't have to deal with the cable bow and can be actuated with a steel rod. But you have to get used to the flipped operating elements. Here I have my (personal) problem I can't switch with ease as my other bikes have the brake paddle on the right side. Therefore I am still using the brake set up on the right side. To avoid as much flex as possible got these cables which are NOS / 100% clones and work very good, (the upper one with the brake light switch integrated works even better then the lower one where the brake light switch is detached). While rebuilding the bike I tried out different Bultaco levers for the foot brake, the black painted earlier ones are much fragiler as the later polished ones: But you need different spacers for the shaft to mount them proper. (Sorry for the bad capture). I manage to bent the black one with ease where the polished one is really solid and very resistant. To the foot pegs: I am still using the original foot peg position on my Bultaco and even on the SWM (The SWM also with the tiny original rests, I would otherwise have the problem of a not well placed front footbrake position on the SWM).

You can get these cables still on the continent, even with integrated brake light switch (or without). With the very strong inner cable around 2,5 - 3mm inner diameter, oiler and the solid bend where it is attached to the swing arm. Not too expensive: around 35 Euros when I remember right.

Somewhat exaggerated. The left foot brake is really better then the right one, but for the gear lever it's up what you are mostly used too.

<p><p>Femsa model 92.20-010 with 3,4 kg will fit definitely, this model is installed to my 199b from the factory, (my Bul was produced for the Italian market in August 1981).

The lighter flywheel sounds too, truly will eliminate the little break you have when picking up rev. but too will reduce the "rubber band" effect the engine have which I now after 1'5 years of riding with the bike like more and more. My be I'am getting old style ???

Yes very nice, there is one thing that does look somehow too modern in my personal view (or not matching too well). This are the rubber tune protectors for the stanchions. The standard dust covers look so much better ( in my personal view). Beside this very personal thing perfect, looking forward for an update !!!

Sort of cool to store the bike in the in the bedroom . my better half would chance my life dramatically (to the worse) ... if I would do or only attempt to do so.

The Femsa unit (rotor) is The lighter then the Motoplat unit. At least the models I know: Motoplat (210.20-001): 3,7 kg, Femss (92.20-010): 3,4 kg. As I have heard so gar from other riders there are no benefits from using the elevtronical system in comparison to the magneto system beside that the electronic system is maintaince free. If your original system is still working proper I would save the money for other useful stuff. To the Electrex ignition, here I have too heard about issues about their reliability, especial for older MX and Enduro bikes. Just my 0,02 € opinion.

May be a bit stretchy what about timing. The timing of the ignition could have been changed and was not perfect adjusted when you got the engine? With a bigger gap between the points due to wear you might now have the right timing? This would be an explanation for the better power delivery. BTW.: I have ridden once the 240cc bike and in this short experience with the ride I recognized that the 240cc engine is a little bit more lively then the 280 in low to mid revs, (it was a short ride).

Mmmh 1:30 that is really quite rich, even with 1:50 the engine is spitting left over aka unburned oil out from the exhaust. Back in the day's I used the Bultavo oil, (at least produced for them). This was the only oil which was recommend by Bultaco for use with 1:100 as a mix ratio. Now I use 1:75 as premix no problems so far ... And you really use SAE 30 as premix, here I am very curious... Isn't the Sherpa spitting oil like hell or might I have misunderstood something ?

A fresh repacked exhaust will improve the flush of a two stroke engine. The SWM doesn't have a diffusor like. My 2-stroke KTM from 1989 run much better which a repacked mid and end section. The effect might not be very much but its quite remarkable. A sticky piston ring that have come loose might also have been the case, I have heard about but never heard from anybody that have found them beside in old barn finds, but why not, sounds like a good exploration. It could as a guess also have been a tiny piece or fibers of a cleaning rag which stuck somewhere in the carburetor and is now flushed away. when something suddenly runs better then before there was mostly a fail that got fixed by itself ...

As the Bul has an seperated containment for the gearbox I use SAE 90 (EPX) with API GL5 specification, which is also been used for differential gearboxes. advantage: can manage real high pressure loading downside: works really smooth first when warmed up by the engine in winter, not for use with clutch! ATF for primary is perfect

Yes I had the tab washer mounted , this prevented the nut from getting really loose, it was the old one, very dented and rough cut on the edges. I took the old one because the other one I got (NOS new old stock!), was bigger in diameter then the 11 teeth sprocket and the chain sat on it. Now I will take the new one but will have to reduce the diameter first to get this plate proper mounted. Some sort of weird that there is no tab washer that fits right on for the 11 teeth sprocket, this is the standard sprocket for the 199b ??? And probably I was to fearful when I read that the nut has to be tightened with 100Nm! in my repair manual (from Switzerland) and 90 pound-feet is even more around 122 Nm. I will also take 50 pound-feet like Scot Taco did which is around 65 Nm and will bend the tab washer on two sides. This will hopefully help in future. Maybe off topic but Bultaco related, another problem I had - also some kind of weird-. I mounted X-Lite tires and also a new chain to the bike and when mounting the chain I counted the roller of the old one to cut the new one in the right length, I counted 97 roller (with the mandatory half link), mounted the chain (with the half link) and discovered that the tire rubs a lot to the swing arm. (I now think that the X-Lite which is an 120/100R-18TT/TL is bigger than the old competition or the Pirelli which had 4.00R-18 TL) I had to replaced the half link (three rollers) against a standard link (4 rollers) no everything is OK again, (total length 98 rollers) ... and thought may be the chain will lengthen a bit. So far the chain did not lengthen a mm, at least for the Bul I can recommend DID 520 ERV3 very much, as light as the standard ones and very durable so far. To the name: Patrik or Paul not a problem as both names starts with P

Are there any recommendations for the torque of the front sprocket nut? Its a M24 but only 6.5mm thick. Mine was a little bit loose a bit but the security plate hold it in place. Now I would like to here some practical recommendations. Spec's in Nm if possible. Thank's in advance. Patrik

engine size: bore x stroke: 46,5mm x 44mm capacity: 74,7 ccm compression: 12,5 : 1 primary gear: 14/63 plug: Champion N 84 G

I would suggest to look up Italian craiglist for parts there are most used and new parts available. The engine is bone stock minarelli and actually a Minarelli engine where parts should not be a big problem. The 100 shares a lot with 50cc bike, even the engine. Gearboxwise is for example just the primary drive and 6. gear different. There some 80cc bikes with Minarelli engines in Germany around as there was a special bike class for the youth installed back then and the T100 fitted very well in this class with 74,7 ccm. Many other bike brands in this class shared this displacement. Anyway I wish good luck finding the parts you need.

Cool and there is a mud flap too, well I couldn't see the flap on the other pictures which is now visible. Depending where you ride the flap will be OK, where I live with much mud and sand I would have very fast a pile of debris between the wheel and the engine.