pschrauber

Looks slightly different but shoud be the same as just the center is a little bit different in geometry. The other model mounted to the Sherpa is the Femsa, (on the upper left, slighty lighter):

There where two different magneto types mounted to the Bultaco Sherpas. Some magnetos came from Femsa some from Motoplat, the later Bultacos which where build outside Bultaco at the Derbi facilities came with all kinds of magnetos as these bikes where build from the remaining spare parts. A picture would ineed be very helpful. Here a picture of the Motoplat magneto that should be mounted to the Sherpa or Alpina:

To the size of the airbox, as more room you have as less bad influence from the pulsating airflow you will have inside the airbox, if you have a tiny airbox you might use resonators to deal with them as the airbox is a resonance/volume chamber so you can even adjust an engine with the size and geometry of an airbox. In short: as less complicated ways the air has to flow towards the cylinder as easier it is for the engine to get the right amount of mixture ... (The return button doesn't work in this forum ...)

No errors I believe, but sadly I mixed up the units. Air flow is calculated in m/s or m/min and I had to transform the ccm in m³: 175cc are 0,0175 m³ or 174 x 10^-4 but m³ is difficult to imagine so I recalculated it in Liter. I see it's not wise to combine translate and math ... too much tasks at once ... The output of 23 would right here I skipped the internal calculation about the medium flow rate thought first to show up with digits behind the comma but then messed with the comma ... anyway. 23m/s is the right outcome ! I will correct it. And there is another problem my RETURN button doesn't work when I use the editor here ???

@woody: Thank you for the pictures. To the question is air flow a task and why bigger airbox can be an improvement, here some math: engine capacity: 175cc rpm: 1.250 (just above idling) rpm: 3.000 (lower mid range) (engine capacity) 17 5cc x rpm = air volume per minute 0,0175 m³ * 3000rpm = 52,5l/min with a diameter of 22mm the air has an speed of 23,0m/sec or 138,11 m/min which is a speed of around 83km/h. 0,0175m³ 1250rpm = 21,9l/min with a diameter of 22mm the air has an speed of 1,0m/sec or 57,61 m/min which is a speed of around 35km/h In this speed range any edge, ridge in the air flow and yes also the capacity of the airbox makes a difference. For comparison: Drive your car just 35km/h and hold out one hand and turn the hand surface against the airstream and you will see. I think this pictures very well the dynamics you have inside the intake carb and airbox as it is easy for you to try out how much influence a proper design intake system has. Sorry for the math I tried to make it as easy as possible I will not bore anyone here more with the physics then I did already ... correction see bold

That is one good idea. I believe it will work very good when I also take out all the restricting plastic tubes inside the air box where the intake is located. But the bike will snorkle like hell and the noise will increase a lot, that is not so nice for my and others ears. I personal like quite and good sounding bikes. With a cover / panel the airbox keeps the bike also quite, something I don't want to miss. Photos of self build airboxes would be nice ..

Doesn't look Bultacoish I guess a support/holder for cables, you need one where the rear cables go to the rear light, mine looks different, more curved ... and one near the steering stem, also to support the cables. It might be also some self build holder for the airbox, you need three: one in front and two at the rear. Patrik

Hi, I' am rebuilding my twinshock TY, this is a long time project, whenever I have time I do something for the bike .... Anyway the airbox of the TY 125 / 175 is very tiny it has more likely the size of a can of sprats then a airbox for a 175 to 200cc motor. A larger one should improve power output. Can any one tell me where I may get a larger capacity airbox for my TY, also some stories / how to ... for custom made air boxes would be very nice too. Many Thanks Patrik

They also look good with patina: You can't do anything wrong with them beside mounting plastic fenders ...

Very artistic indeed, ... another reason for me (this is my personal view) not to visit the show. There are pretty little really rolling wheels involved. Anyway thank you a lot for posting !!!

Anyway which too choose, I prefer the yellow black ones with 280cc. The color combination is nicer, .. I know not related to the way it performs but I have my own taste ... The 350cc is overpowered for my weight and skills, the 125cc has a flexy fork in my view and when I tried one out, (32mm). Some pic's of the original bike that Burgat rode in 1980 - 1981 would be nice. I believe as Burgat won the GP with the yellow black one this should be his best bike in memory ... this is a guess ... someone should ask him?

One easy improvement is to install as soft brake pads as possible and het rid of decade old brake pads. This is easy done. Second machine the brake pads (mounted to the brake plate) so they are aligned to the drum. Third use the longer steel brake arms front and rear, they don't flex and hive more torque = more braking power, (don't show up very often in craiglists but sometimes). Fourth the lining with steel inserts, standard steel quality SRJ 235 is completely OK. Or new hard chrome linings, but this is the most expensive way to do. You need a professional hardchrome coating company that is specialist for chroming machine components, Wissing-Hartchrom is the only company I can name here, €€€! I would first do 1. then 2. ... until you are satisfied with the outcome. lf you want a perfect result you have to spend a likewise effort in the project which means time and money that has to be named too ...

Bultaco engines where designed to use 1% or 1:100 with synthetic two stroke oil back in the days. With standard mineral oil a ratio of 4% where recommended. If the engine is "fresh rebuild and runned in" (and you use gasoline with less the 5% ethanol in combination with a synthetic oil that can be used up to 1% by the manufacturer), then - also today - 1% is possible. I only used 1:100 / 1% when the two stroke oil made for Bultaco still was availalbe, (which was btw. completly synthetic): Now as ethanol free gasoline is difficult to get and many other indegrents are enclosed in the gasoline I personal use IPONE synthesis at 1:75 mix ratio for trials in every bike SWM, Bultaco, Yamaha, (which is 1,3%). For trails riding with longer routes on lanes up and downhill I use a ratio of 1:67 = 1,5%. Here the front page of the Bultaco quick guide I still have: I personal would use as less oil as possible as puttering around the trees in low rpm will clogg your motor interna and the exhaust very quick. When the engine have already some wear the piston have got some carbon build up, here a good example, old used Bultaco piston on the left, new one on the right side: Many of the full synthetic oils including cleaning agents for the combustion chamber of the motor. When the engine has been used a lot with standard oil I would stay with the oil which was used previous. Otherwise the cleaning agents of the new and different two stroke oil might remove the deposits which then can lead to piston seize.

I only have one photo from me and my Bultaco Sherpa back in the days left: The photo was taken in a trials event in 1981 the conditions where extremly wet and muddy, the front wheel of the bike blocked two times due to the muddy conditions. Oh and I weard my green Italjet rain coat. Guess what bike I rode after the Bul.

welding or brazing the leak area is the best solution. As a workaround depending where the leak area is you might put glas fiber cloth underneath the area and wrap wire around. (this "solution" will not last long ...)

The color stays on the handle bar very long in my experience, here at least a 20 year old yellow painted handle bar ... : Some scratches will occur but what do you expect it's a dirt bike. Patrik

Original the handle bar was black: Anyway some riders painted their handle bar white or mounted alloy bars mostly coated (anodised) in silver or gold back then when I remember right.

Boost bottle !!!, E P I C, very interesting and contemporary indeed. How did you measure / calculate the bottle, do you have used the Information given from Trialsport in the beginning 80's: or do you have used any other ressource? Have you any practical advice to tell ! Looking forward for any news on that.

I had to add the describtion how to get through the www site as it's obviously programmed with active x components ... now it should work ...

There are decompressors for Rotax (SWM) engines still available, very priceworthy, around 21,60 €, (without the cable and the extra lever attached to the bar which you will certainly need too). Rotax part nr. : 291600

You will find a maintain and repair manual with part lists and the recommended oil quantitys form Marzocchi forks of the beginning 80's here: http://www.heskethownersclub.org.uk/ Look at the left menu, click on: Spares & Technical A new page will appear. Then browse down the page until the section: HESKETH TECHNICAL INFORMATION there will a appear a box with different repair manuals choose, click on: Service Manual for Marzocchi Forks)

Depending your needs, I was recently in the situation to get the engine completly rebuild. It took some time and one part had to be exchanged as it first come not in the right dimension,. (exchange was no problem but took again a couple of days) But it worked out quite well so far. Reinhard Hallat in northern Germany still offers parts and repairs Rotax engines, even special orders / custom parts. Here his adress: http://www.rotax-deutschland.de/

It was an honour to me, been fascinated by these bike builds.

OK, I hope I will not forget, stiction sounds so unfamiliar in combination with friction and reminds me in word melody more to a stick, stitch, ... might sound stupid for you but english is not my mothertongue. As said I will do my best in future. Patrik

That's a custom build twinshock bike from Pavesi Pericle in Mailand. The name of the bike is PCL 26.4 Trial It's a Suzuki engine and the rest build "scrath" around to the demands of Pericle and Pavoni Franco You find the story of this bike here: http://www.pavesires...i.com/Trisu.htm There are some really nice other rebuilds from him: - Bianchi 203: http://www.pavesires...i.com/Biatr.htm - Bianchi Tonale 260, (a 4 stroke!): http://www.pavesirestauri.com/ton.htm - Parillia Trial 280: http://www.pavesires...i.com/patri.htm In my personal view one if not the best trials bike builder, not even to transform them technical, (none of the mentioned bikes are designed in first hand as a trials bike), but also in view of design in appereance.