lorenzo

Hi, Ellessemo - Welcome to the Bultaco forum. Just checked a couple of mod. 85 resistors with analog multimeter. They both measure 4.7 ohms across the tags of the actual resistance; one measures 22 ohms, the other 25 between the spade terminal on the green wire and the frame mounting bracket (earth/ground) i.e. with the diode in circuit. Can't vouch for the accuracy of my meter, mind you........... HTH

atitagain - As you have a later swing arm, I wonder if you also have a later rear wheel (17mm. spindle, rather than the earlier 15mm.) ?

feetup - My 85 is a late one - well into the 6000's, and has the same details as your later one. Bultaco went to welded-on footrest mounts ser. # 2328 onwards. Not sure about the recessed s/arm pivot or steering lock fitment, although addition of a steering lock took place on contemporary? Sherpa model 91 quite early on in its production. Rearward chain tensioner and chain oiler swing arm from ser. # 2546 onwards. This information from Bultaco parts listings, not from personal experience of examining every Alpina 85 ever made, you understand..... Does it agree with your actual serial nos. ?

atitagain - Model 85 had a roughly 4-year production run and underwent many detailed changes. Your gearbox if original is more akin to Sherpa 91/92 than model 80 ; I believe all Alpina mods. 85/97/98/99 had a spline-fitting clutch centre from the outset. It follows that the mainshaft and layshaft are the same as Sherpa 91/92, as are the two 5th. gear pinions. (Mainshaft bearing at the clutch end is same as 91/92 at 17mm. i.d.) The 13mm. /14mm. change that woody mentioned took effect on the other end of the mainshaft, i.e. also affecting the sleeve gear (5th.) and its bushes. Again, if original splined shaft this won't be an issue. You could simply replace all the intermediate pinions with a (secondhand ?) set from a Sherpa 91/92, retaining your original mainshaft and layshaft and 5th. gear pinions, if desired. As far as I know, the selector forks will also interchange. All of the above - unless someone out there with practical experience of this conversion knows differently, of course........ A gearbox strip will determine what's needed, anyway.

stpauls - In my experience, doing anything to these old heaps is likely to turn out expensive. We don't know how much elbow room the o.p. has, pricewise.......

You say "I'm inclined not to think it's a 125 with a Sherpa engine". Yes, you are quite correct. What I meant to say was you have a 125 Alpina with a 250 Alpina engine - apologies. In basic nitty-gritty essentials, that's a model 80 Sherpa. I note your bike also has a later swinging arm with trailing tensioner - an improvement over the earlier type. A long time ago (pre internet & access to online info.) I also bought a 250 Alpina, believing it to be a Sherpa..........

Yes, Alpina & Sherpa share many features. Your bike is an Alpina 125 with a Sherpa Alpina 250 engine. The tank/seat unit is Alpina. Sherpa tank/seat unit is very similar, but slimmer and with shorter seat. Front mudguard bracket is a Sherpa item of approximately the same vintage. Gearbox internal ratios would differ from those of Sherpa originally. Exhaust silencer originally would have been mounted lower inside frame tube (where it wouldn't burn your calf or set fire to your boot leg) on both Sherpa and Alpina. Change the tank/seat and the gearset and virtually you have a model 80 Sherpa. Good luck with whatever you do with it.

Why not clean the existing tap ? Beneath all that green-coloured rubbish in the slotted part of the tap (shown in the lower part of your pic.) you should find a fine mesh screen. Wash it out/ blow it out with an airline, if available. Try using a carb. cleaner aerosol, maybe.

As stated earlier by bullylover - As an aside, I'd be interested to find out when water cooling and hydraulic clutch operation happened........

Fabrice - Don't worry about your bad English, it's "parfait" as far as I'm concerned. And that's a very nice looking Alpina............

Tonyd - Numbers indicate Mk. 2 Metralla frame and (later) Astro 250 engine.

feetupfun, your 198 cylinder is stamped 165, possibly ?

Ninja - + 1 on woody's comments. If the leak persists, check that the gearbox breather is clear. It's a small hole high up on the left crankcase, just forward of the fixed end of the kickstart spring. If this hole is blocked, some have found that this can cause an oil leak from the gearbox or worsen an existing one, especially when the motor gets hot. (The air inside the gearbox will expand with heat, and it has to go somewhere, I suppose..........) On this 199 engine I've pushed a piece of wire into the breather to make clear its position :- HTH

Would be easier to fit connecting link at rear sprocket.....is the chain in two (or more) pieces ? What's happened to chain on lower run beneath brake arm bracket (bottom r/h. corner of pic) ?

Hi - Yes, it's a Cotton, probably Cavalier model about '69 or '70. Should have a frame no. stamped on headstock, which will help to identify it positively. Here's a similar one I owned back in the day :

Hi - You need to find a way of locking the engine/stopping it turning, Put it in 5th./top gear and apply the rear brake hard while attempting to loosen the locknut. HTH.

The spacer in reality is narrower than it appears on the drawing. The frame bracket provides an ideal "chute" for the spacer to roll down and out (to get lost) when the bolt is withdrawn....... Without the spacer, tightening the bolt will possibly deform the frame bracket and makes the bolt likely to come loose. .......and can give trouble even when all fixings are tight.

When you fit the head steady, make sure that the spacer #138.10 - 119 (no. 39 in the illustration) is in place on the frame fixing bolt , otherwise it will not tighten correctly. This spacer is easily lost.........

Workshop ? Parts ? Owners ?

Yes. Or a replacement spacer, like this :- https://www.inmotiontrials.com/product/bultaco-sherpa-speedo-replacement-spacer-17mm/

Slowrider - Oil breaker :- https://www.inmotiontrials.com/product/betor-fork-damper-top-tin-oil-breaker-each-136-02-105/ Works as I explained in my last post. Preload spacer :- https://www.inmotiontrials.com/product/front-fork-spring-pre-load-spacers-10mm/ Works as explained by feetupfun. HTH

Slowrider - Holes in the pistons are one part of the booster ports, the other part being the slots in the cylinder liner. You need these if your engine is to perform as Bultaco intended. First o/size Mahle piston :- www.francetrialclassic.com/en/pistons-and-con-rods/4403-bultaco-350-piston-with-clips-pin-and-rings-diam-8525-mm.html The hat shaped sheet metal caps you refer to are oil baffles/deflectors (Bultaco called them "oil breakers") ; AIUI their purpose was to influence the amount of oil coming out the top of the damper tube. You appear to have non-standard dampers, and I can't see how the caps would fit, but who knows ?.

Typical mainshaft wear :- Typical wear to sleeve gear bushes (note the step) :- Hope this helps.

Mark - Based on my experience with these engines, your main area of concern is likely to be the crankshaft assembly and its bearings and seals, and piston and bore, rather than problems with the gearbox. These tend to be reasonably robust, although possible weaknesses are covered in feetupfun's post. Did you use heat when dismantling ? Difficult to see, but from your tenth picture it looks like main bearings are possibly loose on shafts........ Are you in the UK ? Don't worry about being quite young and lacking experience - we all were once !

Homerlite alloy tank/seat unit, standard on models 124/5 and 150/1, etc. supplied in UK. (see front cover of Heinous manual).