carl ekblom

As far as I know gearbox oil has a significant smell when burned and should easily be detected. Totty79 seems to have a good theory.

I suggest partly blocked idle system or an air leak. Idle air/Idle mixture screw and idle stop screw must be correctly adjusted. Also check throttle cable and throttle. They must be well lubricated and move freely. A good reseller should be able to give you information about correct jetting. Make notes about your jetting and changes you do. I know, if everything is correct, advancing the ignition a few degrees sometimes can help a little to reset the idle quicker. About going downhill, I think full clutch, apply foot and hand brake to slow or retard Carl

Fork seals might be 35x47x10. Old bikes often use 2 seals/leg which really isn´t needed. Use one seal, for the 2nd make a plastic spacer. Avoid "All Balls" seals. They are of a high friction type. Green SKF (Kit 35M) are among the best

A more and more common problem? These people seem stock some https://www.francetrialclassic.com/en/engine-spares/68-bultaco-sherpa-250-350-primary-transmission-chain.html Perhaps Spanish?

Unusual dimesion? Found it: https://joresa.com/en-gb/about Pitch should be 9.52 (3/8) Roller dia should be 5.08mm

Measurements taken at one original 199B chain Roller dia: 5.0 (4.98mm) Pitch: 9.5 (9.46mm) Inside width: 7.5 (7.52mm) No of rollers: 52 Clutch chainwheel width is 6.95mm

Yes, but remember to have the spark plug earthened and away from the spark plug hole. I guess 30-40 quick kicks is needed.

If you have the Mikuni carb it may have flood and you ought to clean your crankcase With Mikuni carb: 1 Always close the petrol tap when parked. 2. Never park the bike pointing downhill. 3 Check the float valve and float level l

Check that the key is there and the flywheel is correctly seated. The key can fell out during assembly (I know?). Normally you don´t need a capacitor with electronic ignition. The instructions should tell. /Carl

I think 199B can be made of different things. My 199B top nuts have allen key at top. Rule of a thumb: Inside female diameter is outside male diameter-pitch. Measured inside the stainchons M30x1,5 should be 30-1.5mm or close to 28.5mm. M31x1.5 should be 31-1.5mm or close to 29.5mm. Those may fit https://www.feked.com/ossa-bultaco-fork-stanchion-top-nuts-with-ball-valves-35mm-betor-forks.html

My nut measures 30.8mm so it ought to be M31x1,5. Quite unusual.

As far as I can remember ?some oil may drain but nothing more will happen. Do not compress the fork. More oil may drain. You can try 1-2 aluminium sealing washers. They are made of soft aluminium and may seal better. I also think it is good practice to replace the fork oil once a year or so. /Carl

At Ebay. Problem can be to find correct dimensions. If your stanchions are as thin as 30mm there will be problem as SKF start at 35mm. Kit 35M (35x47x10) fit many classic bikes. SKF also make for DH-bicycles. Perhaps you can find something there. http://www.jwtimports.com.au/downloads/SKF-Fork-Seal-Measuring-Guide.pdf.

To me that sounds pretty normal Normal starting from cold would be on any two stoke trials bike I know Full choke - start engine- after a few seconds - close choke - until engine is warm enough - run carefully Air screw has no function at mid throttle. Use it for idle mixture (throttle closed)

I tried those Allballs fork seals and found them to make high striction. I think green SKF seals are among the best. Use fork oil of correct grade. Or hydraulic oil. VG32 often OK. VG15 is thinner and VG46 is thicker However, old forks will always have more striction then modern with teflon bushings and DLS coating As mentioned, make sure there is no tension between fork legs. They must run as parallel as possible. /Carl

I would try normal Nitrile O-rings. If problem I would use Viton O-rings. https://www.nes-ips.com/viton-vs-nitrile-o-rings/ Carl

Perhaps https://www.electrexworld.co.uk/acatalog/STK-009.html#SID=826 ?

2,5 years on ElectrexWorld for Sherpa. No problem at all. Runs well. I think they have something for lighting also.

WM3 (2.15) is what moden trials bikes use at the rear. In the 1970s WM2 (1.85) were not uncommon. WM1 (1.6) is for the front.

Hi I know you have a lot of area and mountains around Sofia (Vitosha, Old Mountain etc). Hope also some good places for motorbike trials. Happy riding Carl

Anyone having alcohol problems can use alkylate petrol. Like Aspen which is a quality product. I use it but mix it with ~1% E85 https://aspenfuel.co.uk/ Several other brands are available.

Interesting. Montesa used a petroleum-safe-forever glassfibre..... At least safe for 40 years or so

I had to look at a Bing 84 from a Sherpa -Lever down (axle up)- Choke on -Lever up (axle down)- Choke off

OK at 199A. Should be OK also at 199B. My filters are later production from Inmotiontrials. Little bending is required to make them fit inside airbox. As you say, a good narrow clamp is needed at the carb intake, I remember that a wide clap caused some problem https://www.inmotiontrials.com/product/bultaco-sherpa-199b-air-filter-on-hose/

You need the Correct intake rubber Carb, Throttle cable Mikuni/Amal to Domino (assuming you have the Domino throttle) Air filter for 199B. Also good for 199A. Others I don´t know Inmotiontrials should be able to supply the parts needed