Jump to content


Site Supporter
  • Content Count

  • Joined


About lorenzo

  • Rank
    Advanced Member

Previous Fields

  • Bike
    (6X) Bultacos 73-81

Profile Information

  • Location
    East Anglia UK
  • Gender

Recent Profile Visitors

4,382 profile views
  1. 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 left 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 ?
  2. Yes, late model Sherpa. You may find a date on the underside, at the rear. Here's a NOS one in my collection :
  3. Engine : model 68 Pursang 250 Mk. 4 Frame : model 90 Astro 250
  4. 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.
  5. lorenzo

    front sproket seals

    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.
  6. 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.
  7. 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 ?
  8. 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 !
  9. 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 ?
  10. lorenzo

    Crank centering

    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........
  11. lorenzo

    Crank centering

    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.
  12. lorenzo

    Crank centering

    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" ?
  13. 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 ?
  14. 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.
  • Create New...