Mmmm.... that's interesting, and a timely subject for me, as I am currently trying to sort a piston/barrel for my mod. 85 Alpina.
The liner of the original cylinder has effectively been ruined by some PO idiot with a grinder. The best cylinder I have (from a mod. 124) is on STD. bore and Mahle piston, but this has the shortest rear skirt of any 250 piston that I have ....
(I have a few new Sherpa pistons on the shelf (Mahle and Dinamin) and I've also kept some of the old pistons I've replaced in the past, for the purposes of reference and comparison etc. in the future.)
All the 350 (83.2mm. & oversizes) pistons have front and rear skirts of equal length.
All the 250 (72.0mm. & oversizes) pistons have a rear skirt shorter than the front ; this also applies to the later 240 (71.0mm. & oversizes) pistons.
I think this explains the reason for Saddleback's question raised in his o.p.
I know that mod. 212 is a 250, but unfortunately I do not know what piston would have been fitted originally, although it seems likely it would have had a shortened rear skirt.
I think Sherpa325 meant to say RIGHT side case.........
Just one word - BRILLIANT !!
Let us know how it works.
(You've got me wondering about the switch for my mod. 85 Alpina now.............)
You meet the nicest people on TC.........
Dinamin became GPM, and both are now no longer available, as far as I know.
I have no personal experience of Wiseco , but read lots of bad reports from users Stateside.
The original Mahle pistons always were and probably still are, the ones to go for, but are now almost totally unobtainium.
Most, if not all currently available new pistons are Italkit , I believe (but I also have no personal,etc.....)
yamanx - the first question any supplier will want answered is "what size ?" ( "Bultaco Sherpa 250T" could be 71mm. - 73.5mm. depending on year and
Other opinions are available........
But that's almost unimaginable luxury...............
Feeling bored when we had a few days of snow recently, I thought some time in the shed was in order.....until I actually tried it !
Highest temp. in my shed on 4 consecutive days was -2deg. C. (I don't have heating for fear of the fire risk)
Hoovering, etc. looked positively inviting !!
As I understand it, if your hub is 2-piece with a removable spoke flange, as in the pics. from feetupfun , then it's the old style "heavyweight" item. This would have an iron brake drum which was actually cast-in as an integral part of the hub, and brake shoe linings 40mm. wide..
Hardchrome lining is a feature of the later one-piece "lightweight" hubs with brake linings 25mm. in width.
Remember, blueflag - a picture speaks a thousand words.........?
Hi, Groover, and welcome.
A couple of nice looking machines you have there......the one out back is a model 80 ?
Don't think I've seen a Homelite tank painted in those colours before...
This type of alloy mounting was not one of Bultaco's more successful designs........
Makes good sense to replace it with a steel fabricated item, as fitted to the later bikes. (like the white one in this pic.)
Also, when you refit the engine to the frame, pay particular attention to the condition and fit of the head steady .
Welcome to TC.
Bully looks nicer than any of mine were when purchased.
Good luck with the rebuild - lots of help available from knowledgeable folks on here, should you need it.
OK, but that's YOUR electronic ignition, fitted to YOUR bike - not netley's..........
Personally, I'd want to check out the timing, as suggested by oldjohn.
(and check dynamically, if electronic advance is involved)
Agree wholewheartedly with your comments.......and I think I recognise the reference to a very famous Sherpa rider and his recommendation
of a more advanced ign. timing - I did wonder about the need (or indeed the wisdom) of this at the time. But hey, what do I know ?
I urge you to inspect the bore and piston, before you do any further possible damage.
Tried to PM you, but am told you cannot accept messages ?
As I understand it, Sherpa 5-spd.internal ratios were changed to provide a wider spread of ratios, by lowering the intermediate ratios.
(Compared to the previous set-up)
As top gear remained unchanged and is direct (1:1), higher top speed in 5th. would result only from changing the secondary ratio.
Glad you've got the rear wheel sorted.
Re the front wheel : do stay with the X-3 spoking pattern - both sides.
The nearest thing I have to an original, unmolested front wheel is this one :
It's not a wheel that I've rebuilt, and as near as I can tell has not been rebuilt by a p.o. (So "original" that I had
to replace the tyre a couple of weeks ago, as the old one had completely rotted away !)
OK, it's a Pursang - flanged rim, etc. but it uses the same spokes as a Sherpa, and consequently the same
spoking pattern. (It's also the same pattern as used in the three mod. 199 wheels I referred to in my last
Hopes this helps.
I've been waiting for someone/anyone to chime in with all the answers, but it hasn't happened, so here goes.........
In response to your original query, it appears from the pics. that these are the correct standard Sherpa hubs and original Akront alloy rims.
My 199 parts book lists :-
Fr. wheel spokes 18x left hand side 241mm. long
9x right hand side 225mm. long (inners)
9x 227mm. long (outers)
36x nipples (alum. alloy, barrel 6.8mm. dia.)
R. wheel spokes 18x right hand side 196mm. long
18x left hand side 176mm. long
I've checked some of the genuine Bultaco spokes I have for mod. 159 and mod. 199 wheels and they all conform to these measurements.
From the pics. it looks also that the nipples used on your wheels may be undersize - maybe you can confirm the barrel dia. of these ?
If you are having a problem with (apparently) short spokes, have you considered that the spokes may be correct, but laced to an incorrect
pattern ? How are you measuring your spokes ?
Using the above lengths of spokes I don't recall having the problem that you are experiencing but (from memory) none of my wheels are laced like yours; I'm unable to get to any of them at the moment to verify.
"Right" and "left" hand above refer to sides of the machine as seen from the rider's view, by the way.
Rear rim offset : I've always measured this from the spocket flange on the hub to the outermost edge of the (standard Akront) wheel rim and notes I made for the last three mod. 199 rear wheels I stripped indicate 1 9/16", 1 17/32", and 1 5/8" - take your pick!
Front rim offset I can't find at the moment, but would probably be academic, anyway. I usually just centre the rim to the steering axis, as close as poss.
Caveat : I'm NOT a wheelbuilder or any sort of expert - someone who is may care to rubbish any or all of the above.
I also spotted the Pursang - but didn't notice the Ossa.
Do I qualify for the hoodie (blinkered view) award ?
The pulverised swarf in the bottom of the mag. housing says it all !.........
Your bike is a model 92, which is a Sherpa T 325. This is essentially a "big-bore" version of the Sherpa 250 (model 91) available at the same time. To avoid confusion (in the UK, anyway) Sherpa 350 usually refers to later models/versions.
Assuming that your bike was originally supplied through the UK concessionaires, engine and frame serial nos. are
probably original, even though they don't match; to avoid purchase tax at the time, bikes were supplied as a "kit" for assembly by the purchaser.
Although the bike would have left the factory with matching nos. It would seem that the UK importers were not very particular about serial number matching when it came to selling in this country. My own model 92 has a frame no. quite
close to yours, and a non-matching engine no. very close; this bike was supplied new and road-registered in April 73. I have owned it since Jul.75.
The tank/seat unit is a Sammy Miller aftermarket replacement for the "Slimline/Kit Campeon" unit supplied as original
equipment by the factory. A number of other parts are not original - hardly suprising on a machine this old, but not really
a concern where usability is concerned. (With the glaring exception of that open bellmouth on the carb. - you need good air filtration on an off-road bike)
Here's an idea of what it looked like 40-odd years ago.......
Good luck with the wiring, etc.
That's gonna be one pretty bike when it's back together !
Where DID you get that tank/seat unit ?
Guessing there's a "lady-of-the-house", I hope that's the spare bedroom...........
If you need a wiring diagram for any old bike, a good place to start looking is in the maufacturer's OWN literature (if this available), rather than aftermarket manuals which in the interests of sales appeal try to cover a whole range of different models/years/markets, etc. - a task at which they are inevitably doomed to fail..
I've made a scan of the wiring diagram in the original OE instruction manual supplied with UK-market Alpina 85 bikes. There you go :-
Incidentally, an identical diagram also appears in Sherpa 91/92 instruction book; it may be of use to UK owners of those models.
Larry - Too much time on your hands ? Doesn't seem ever to be the case for me...............
Some of the engine rebuilds "pending" :-
Have a nice day
Bondy - ref. the pic. in post #55 - is that a new cylinder liner ?
.......Copper head gaskets no longer made, eh ?
I'm glad I bought some when they were still available (and possibly less expensive).
I think the last time I saw any for sale they were about £20+ each, although Bultaco UK offers an aluminium version at £15.99.
Done no actual work to the bikes beyond sorting out what needs to be done, and in what order - organising parts, etc.
You know, all the boring stuff.......
The spacer is #39 in this parts book illustration - the trouble is, if you don't know it's there you remove the top bolt and before you realise it, the spacer rolls away down its custom-made chute (the frame bracket) - never to be seen again.......
The part no. is 138.10-119 and it's described as a bush.
scot and bondy -
Show me yours and I'll.........well anyway, here's mine -
as fitted to my 199B when purchased.
Apparently this was the "fix" adopted by Comerfords (the UK importers) on their own team bikes and approved by them for other users.
Make sure the distance piece is in place in the 'U' of the frame bracket when refitting the top bolt - it won't tighten properly without it.