lemur

Are you aware they generally put an adjustable potentiometer on the control board so you can curb the performance ?

Link for the event entry is posted here : https://www.ataont.ca/category/events/upcoming-events/

From here it sounds like a very poor fitting piston and rings and I would be concerned with the bottom end seals because of the bikes age and that sound. Compression testing would be a good start followed by inspection of the top end and if you don't find stuck piston rings or serious damage there you might be looking at a major overhaul that requires splitting the cases.

If it is a non-original carb, how did you set the float level? If the valve clearances are set perfect, I’d be visiting the float level to possibly address the off idle stumble. Carburetors need to be isolated from heat that can boil the fuel and from vibrations that can turn the fuel in the float bowl into froth. Plug read should tell if carb settings are rich or lean, post up a photo of your carb setup and sparkplug after running for a while might help us to assist.

Does the bike currently have a lighting coil installed?

No tail light leaves you required to hand signal stops. 1975 Bultaco Sherpa 250 pretty sure did come with lights unless they were removed at the dealership to race prep. Brochures from the period show them with scooter sized lights and a rubber plate mount on the rear fender, speedo and a horn.

Here's the catch as quoted from the SY250F owner manual: "As the time goes along, the play of the valves changes and it may alter the ratio of air to fuel of the inlet air-fuel mixture. The solution is so to make it adjust by your dealer, as often as written in ‘List of the regular maintenance and lubrications’. It is a really complicated operation, which requires a professional expertise." Twin cam with 5 valves all adjusted by bucket and shims on cams that do not ride on roller bearings is a bad design for trials bikes that might regularly encounter low oil pressure because of slow engine speed operation, low oil pressure is the reason the 4RT engine cam rides on roller bearings and uses roller rockers.

One of my friends that has always ridden Scorpa had one of those for a very short time, after a spill I seen him trying to start it and that was the last time I seen him riding that bike. Twin cam engine maintenance reads as an issue even in the manual and carburetor is likely the root of the starting and performance issues which could be solved if it had Honda fuel injection technology.

😎 Almost completed setup and loop marking for the July 20th & 21st. 8 sections per day and three or four loops to be determined by the weather, pre-registration is greatly appreciated. I'll post the official flyer here soon I hope.

My venue has the reputation of being very hard but that is because we have the roughest natural terrain around and I think hard is what the more serious riders want. Very difficult to set out novice sections here because the loop I ride all year round including winter is apparently too much for anything short of a competent and slightly brave rider. Pro rider class only exists when you have enough extremely talented riders to support it and that is another area I am lucky with, it's difficult terrain that attracts the top riders on a regular basis. We were recently been compelled to somewhat standardize gate colours but the recommendations are not very conducive to the materials and terrain available here, plus they don't even match the number plate colours which is only sensible. We set out 5 lines of difficulty per section here so there is always a significant number of options and I build sections to have optional lines at some of the really hard stuff. After it's all setup and ready the whole thing is at the mercy of the weather gods to make the event easy or crazy hard. Success is when everybody has fun and nobody gets seriously damaged. One serious problem we are seeing here is too many classes, eventually you can't attract the required 3 riders per class to call it an official class competition and the results are discarded, which is significant when you travel great distance at considerable cost only to discover too few riders entered to make it count.

You can also determine max torque values by knowing only the material used in the nut & bolt and the size of the threads, there are charts based only on that information. Maximum torque will typically be something prior to elongating the bolt or spoke unless the bolt is designed for single use like in some cylinder head bolts, this is not the case for spokes and barring physical impact damage we hope they last the life of the machine. There is a lot more flex and movement in a spoked rim then most might think, watching a pro riders rear rim impact a rock face during a big splat will reveal just how much deformation can occur and how far a rim can spring back to being round again is fairly amazing to watch.

Wet or dry? ... hit one of the old spokes with penetrating oil first, might make a huge difference in the readings.

Ouch looks like she swallowed some sand pit, new parts are in order. Service manuals will show you how to test measure the crank short of taking it apart.

If motorcycle salvage yards where you live are anything like here you get 2 completely different results if you phone contact a wrecker, or go there in person and have trusted access. Telephone contacts for a specific part to a wreckers will often be ignored, it's the difference between you locating and identifying the part or the guys wife on the phone giving you the stock answer to locating some weird part request. You also get 2 different prices and the deals are on the in-person purchases. You only have to put yourself in the wreckers position for an instant to realize why it is this way.

Riding trials bikes renders all other forms of physical exercise boring.

Small aluminum shovel can be cut and converted into a cheap but very effective bash plate 🤓

I have an awesome riding area if you travel to Central Frontenac Ontario hit me up 😎 I regularly host competition events and riding is all I do when I'm not fixing broken things.

Do you have nice wide grippy foot pegs mounted now? they make a big difference, do that first before altering peg positions is generally best. Biggest problem I had with any twin-shock bike was all the bruises on the insides of my legs. Best riders don't use the bash plate so on that item ymmv depending how good you ride. Crashing is going to happen if you try hard enough stuff and at 69 I don't mind the crashes if I can ride the harder stuff, crashing is motivation to ride better 👍 I stud the tires and winter ride too which is a blast and extends the riding season significantly for our latitude. On gearing you need at minimum one off road gear range that takes you from 0 to as fast as the engine can hall you by only just controlling the clutch friction zone, biggest hills you need to climb or biggest splats you will ever ride are usually the best gauge. Some of your questions require seeing you ride, knowing body weight and dimensions, level and terrain you typically ride etc. Reflex is almost as good as twin-shock bikes come next to SWM but brakes and suspension would be inadequate for where I ride and I know I would crash badly. Ride lots and prosper 🖖

Maybe I will rip an old one apart and see, otherwise I have fallen prey to the same advertising misinformation bait & switch for the past 25 years.

" Brand MICHELIN Tire Profile: TRIAL Tire Classification Racing / Trial / Tyre Size Front Tire: 2.75/-21, 80/100 R21 Rear Tire: 120/100 R18, 4.00/ R18 Carcass Type: Tubeless / TubeType / Diagonal / Radial / "

I guess some riders don't remember how much of an improvement radial tire technology made to trials bikes. Radial is now the first and most important spec I look for when buying a competition motorcycle tire, be it for street or dirt the radial tires blow away bias tire performance by a huge margin. If it does not say radial on the sidewall or have an R represented in the tire size code, it's probably an inferior product and I won't be buying it.

Darned if I can find the answer to the most important questions; is the TL01 front even a radial ply tire? and are TL01 stamped 'Not for road use in North America' on the sidewalls?

The dellorto tuning manual available free online states: "prolonged use of a vehicle at an altitude higher than 1500 metres" in reference to jetting change requirements, that's almost 5000' so I would read that as you being able to adjust the carb for the elevations you are riding using stock jetting. Have you already adjusted the needle valve cir-clip position? You won't be able to tune it until you have the air intake in place.

Other than the copper wires looking over gauge, the white glue looking very heavy and the green colour finish on top of the normally bare steel magnet cores. I think you are looking at a non-oem refurbished part. "… holding the throttle wide open, engine surging but not reviving. Had to walk back and get the truck. Started later. " sure sounds more like a carburetor float needle and seat problem from here.

I agree with you that brake model is a pos. Had one just like it seize up on only the outside pistons and it was braking only on one pad. Worked again after I used the hydraulics to break the stuck pistons free (with a bang) so assumed it was corroding on the inside and lost faith in it, bought a Beta brake to replace it and then ran into some issues with the size of the hydraulic fittings. I've never experienced this problem with the brake models fitted with a bolt or a spring pin to hold the pads in place. Speculating it was related to covid era production shortages just like the 'pink' rims and anodized parts that came on my 2021 TRS 300 e-start that were suppose to be 'red' but material shortages caused production problems with the anodizing process and were allowed to pass quality control due to covid times, that's my take on it.