lorenzo

Raoul - More info. needed :- Which coil have you replaced ? H.T. or L.T. ? Where and how are you measuring 3V ? What setting do you have at c/b. points, ? "Newly purchased mod 199" - did it have a spark when you bought it ? Why have you replaced ignition parts ?

A slight amendment to the info. I posted earlier :- "R" prefix actually denotes 238cc. capacity of model 198, a late version still identified as Sherpa "T250" (Earlier 250's that were actually 247cc had a "P" prefix). Hope this doesn't confuse the issue too much......

Gary - Frame # will be RB R = 250 B = "Bastidor" (frame) Engine # will be RM M = "Motor" Check frame again. HTH

+ 1 on that. These were my thoughts too - but expressed so much more eloquently than I could manage........

The left side spacer you need is this one (part # 67.04 - 009). www.inmotiontrials.com/product/bultaco-front-wheel-bush-left-side/ As Woody says, this is used in conjunction with a split spacer in the spindle clamp at the bottom of the fork slider. The right side "top hat" spacer behind the brake plate (part # 20.04 - 009) is this one :- www.inmotiontrials.com/product/bultaco-top-hat-front-wheel-bush-2/ As an aside, is that a crack in the spoke flange in the picture ?

Yes, late model Sherpa. You may find a date on the underside, at the rear. Here's a NOS one in my collection :

Engine : model 68 Pursang 250 Mk. 4 Frame : model 90 Astro 250

These bearings are so specialised (replacing ball thrust bearings, equally specialised) that even with a number, if indeed you could ever find one, there is no chance that you will find them at your local bearing shop. (This is of course a chance for someone to reveal which local bearing shop has them in stock - and prove me wrong ...........!!) Good luck with your quest, anyway.

There are two of these bushes in the sleeve gear - your pic. shows just the outer one. As woody says, you have to dismantle the engine to replace. You may well find corresponding wear on the gearbox mainshaft............. When you re-assemble fit a felt seal (part #414-052) as mentioned by on it. Good luck with the repair.

You can junk the cast bracket and replace with a fabricated steel one, as Bultaco themselves did on later bikes. Bracket should be obtainable new from Inmotion, or possibly secondhand on fleabay, etc. Also check carefully the (cyl.)head steady and fixings.

More information needed, methinks...... Is this a bike you have owned for some while (and had running), or a disparate collection of parts you are trying to assemble ? When did the problem first arise ? What parts have you replaced ?

cyril - Don't want to be too hard on you.........I'm sure we all made stupid mistakes as raw novices - I know I did...... However, "culprit of the nasty noise in the engine" is unlikely to be just a nut that's come undone - that's more likely to be merely a symptom of other damage. As vintagenut has suggested, the woodruff key is probably also sheared, with attendant damage to the tapers of flywheel and shaft. Also, depending on the revs. reached (and for how long) when the bike started w.f.o. you may have damaged the conrod bearings. As misscrabstick and pschrauber have said, engine now needs a total strip and rebuild. Best thing you can do is follow your own admission, and entrust the work to someone who actually knows what he's doing. Be prepared for a sizeable bill...sorry !

Jonboy - Probably nothing more than "barrel" distortion (camera lens). Did notice that the conrod. looks to have been replaced already.........and why two cyl. base gaskets, I wonder ?

DickyM - Whatever you decide with your engine, I urge you not to make any non-reversible changes - reducing the interference fit of main bearings "to make assembly" easier would be one such change............you could regret this when your main bearing inner races start to spin on the crankshaft........ Never assume that Bultaco didn't know what they were doing ..... Your con rod assembly looks like :- As far as I can tell replacements ARE available - this is one bought in January and now fitted to one of my cranks:_ (I was quite surprised to find this crank in a mod. 124 engine, which I believe would have had an 18mm. crankpin originally..! ) Also have o/size Mahle 71mm. pistons, although many have said these are "unobtainium". "Seek and ye shall find" ? The availability (or otherwise) of parts is influenced by how soon they are needed, and the depth of your pockets. I have several engines undergoing "the treatment " at the moment and I've not found one that's worked out cheaply so far........

DickyM - The small hole pictured is the gearbox breather, the only breather in standard form. It needs to be kept clear - if it becomes blocked it can lead to oil leaks and/or g/box sprocket seal failure. Attempts to provide alternative breathing through the filler plug have had mixed results, according to previous posts on the subject. Over the years Bultaco appear to have experimented with either two or three main bearings / crankpin (and crankwhee)l diameters / conrod location by big-end washers and small-end spacers / location by small-end spacers only. Your conrod/big end bearing with narrow thrust washers is the original type of set up for your engine.

But wasn't that was the very reason the circlip was introduced on later engines..? Well............ there you have it...... What are you hoping to achieve by "centre-ing" ?

Daveys - Crankcase gasket must stand proud of cylinder base joint face at assembly, to be trimmed after cases are together and all fixings tightened. This should ensure that there are no leaks at cylinder base. You seem to have taken considerable care to centralise crank within cases ; what happens when driveside nut (for oil seal sleeve and sprocket/weight) is fully tightened ?

Yes............. Crankshaft needs positive location relative to drive side crankcase half to retain primary chain alignment. Using roller bearing on mag. side of crank also makes crank width and axial location of main bearing less critical.

markg - As the inner and outer races of the roller bearing are separate parts, once fitted to crankshaft and crankcase respectively it's then possible to assemble/disassemble the engine without heat.. See above from the o.p.

Daveys - The roler bearing you have has axial location in one direction ( a shoulder on the inner race) - have I got that right ? Why not heat the inner race and fit that to the crank (shoulder to the wheel), heat the crankcase and fit the outer race ("open" side to crank). Inner and outer parts of the bearing are then located independently and you can simply slide the bearing parts together when you assemble crankcase halves. This of course ignores manufacturer's markings........( and I don't know which way they face on SKF bearing, anyway)....... having NJ series bearing also sets up requirement for the crankshaft width between bearing seats to be controlled to avoid negative axial clearance. Or maybe I'm completely off beam here.........

Model 158 original frame colour was silver.

Front wheel has had a steel/cast iron? (ferrous, anyway..) liner inserted. This is the usual means of salvaging hubs which have suffered deterioration of the chrome plating. Hard chrome originally applied direct to alloy casting. If your chrome is as intact as it looks, keep it unti it fails. Rear spokes stainless butted, or steel galvanised ?

Ian - I'm guessing here......... Front spoke part no. 86.004-003-5 appears to be one of three different spokes - with a conical hub on a Mk. V Pursang. Model 49 with parallel hub - all 36 spokes are identical.

Gentlemen, thanks very much for your response - I'm almost overwhelmed. How did we ever manage, "pre-internet" ? Vintagenut : no tabs on the air filter, and no sign they were ever there. Same thing with my mod. 92 (also '73). gooey : Alloy tank unit.........do you have a pic. ? feetupfun : Thanks again for your detailed shots - exactly what I was looking for (and was unable to find elsewhere). So it seems that the tabs were to support the front of the seat section of the fibreglass tank unit, and assuming the original "long" seat is used, support at the rear is provided by the seat resting on the frame loop ? Perhaps someone can confirm........... Additionally, could they be to maintain a clear "breathing" space above the filter intake ? This leads me to ask if anyone knows what type of seat was fitted to the UK bikes with Homerlite alloy tank unit.......my bike has a short trials type seat which may not be original, and anyway doesn't extend rearwards as far as the frame loop, meaning any weight placed on the rear of the seat would provoke bending/cracking of the alloy, assuming the tabs were still in place.