If it was me, first I would put the old spring back in, to check that all is well - that nothing has been omitted or replaced incorrectly - especially the linkage. Then, if all is ok then I would try another replacement spring, because it may be that the spring has not been properly tempered and so will not work correctly when installed in your bike.
Good of you to detail the mods to make the bike competitive. I think you're quite an experienced rider - how do you feel about the bike in comparison to the mainstream two strokes for trials use?
Lastly, are there any differences between the Sherco and Scorpa?
I rode new Sherco 250 and 125 two strokes for several years and before that Beta two strokes, competing in Trials - usually Novice sections every week.The first thing I always did was to explore methods for softening the power delivery - flywheel weight, low compression head, retard the ignition, smaller/larger sprockets etc.
I tried a Sherco TY125F, but in my opinion it is a Trail bike, not a dedicated Trials bike. "Sherco have no interest in developing this bike for Trials - we just sell them" - quote. Scorpa did limited developement work on a couple of these bikes in 1919, but no longer do so. To make them competitive you will have to do it yourself! (Luckily, in a former life I worked as an Engineer).
The power delivery is different on a two stroke, because as the engine revs climb, so the power increases. On this 4 stroke, the power is less, but there is no step-up in power as the revs climb - no power band, just smooth, constant power. Much softer, tractable and controllable power.
The Sherco and Scorpa TY 125F are exactly the same, just different graphics.
The suspension is fine - as good as on a comparable modern Sherco 125 or a Sherco 250 two stroke (owned both and rode regularly in Trials). The front forks on the TY125F are different from the Sherco 2 strokes, but work well. (The frame and geometry are exactly the same on all of the bikes - only the front down tube is different).
Ground clearance is a bit less on the TY125F - perhaps by 25mm. Lighter riders likely wouldn't notice it !!!
Brakes are excellent.
Fuel consumption is much less than on Sherco two strokes!
The MH200 came with a plastic tank and seat unit, like the MH349, there was no cover with a tank underneath so it sounds as though someone has made a modification. It was the ealrier UK sold bikes with fibreglass tanks that had a seperate tank and cover
The original MH tanks aren't affected by modern fuel. If the tank on yours is one of the pit bike type tanks, same as used under some TLR Honda tank covers they are fine with modern fuel
... "aren't affected by modern fuel" ... Brave comment!
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Edited by stpauls Updated and added further information.
Sherco or Scorpa TY 124 4T Classic or Adventure, 2018 onwards.
I have read much in the media about the 2018 and later Sherco and Scorpa TY 125 4T Classic and/or Adventure. Some of it is completely wrong!
If you want a small, 4T Trials bike then your choice is very limited. For use in Novice Trials sections, this bike is quite good, but only IF you do some work to it first.
The engine is made by Jianshe-Yamaha, in China. It is a clone of a Yamaha TTR / YBR. The engine parts are mostly interchangeable. The factory is part-owned by Yamaha. Any small Yamaha motorcycle purchased in Europe now has it's engine made by Jianshe - Yamaha, in China - even if it says Yamaha on the engine cases!
The carburettor is a Mikuni BS25. Used in some quads. Due to very restricted avaliable space, it is a good compromise carburettor for this bike. The standard jetting is: pilot/slow jet = 17.5. The main jet is 130. If you fit a 150cc big bore kit, you need to increase the size of the main jet to 150. Increasing the size of the slow/pilot jet also improves slow running, bottom end torque and aids starting.
If you want to use it competitively for Trials, then the minimum you will need to do is:
1. Change the tires - Michelin trials tires. Or, Michelin front, IRC on the rear.
2. One tire clamp on the front. Two tire clamps on the back.
3. Put a spring tip on the rear brake lever.
4. Replace the exhaust pipe and CAT with a pipe from S3, or, buy an even better one from: Iron Davis at Excel Engineering, in the UK: 01554 751935. Same price.
Additionally, for a much better, competitive trials bike:
5. The clutch is quite stiff and very on/off. Make the clutch actuator arm longer to make the pull lighter and to provide more control. I also removed the hydraulic clutch on mine and replaced it with an ordinary clutch lever. Much, much better clutch control.
6. Fit an in-line fuel filter. The pilot jet hole is tiny and it's hassle to get to, to clean it.
7. I found mine to be a bit quick in the Sections, so, as the engine sprocket is already very small, Talon, in Yeovil made me a one-off 63 tooth rear sprocket, to replace the standard 57 tooth. This also allows 2nd gear to be used in some sections.
8. Remove all the lights, horn etc. Install a Stop Switch.
9. I removed the heavy battery and heavy starter motor from mine and repositioned all the electrics to up near the steering head. Additionally, removed the starter motor gears from inside the engine. The kick start works fine. Remove the spring from the right hand foot peg to enable the kickstart to clear the footpeg.
10. The engine cases overhang the standard bash plate by quite a bit. You can buy a proper, flat one from Excel Engineering, in the UK: 01554 751935
11.DO NOTRemove 5mm from the carburettor overflow tube (a tiny brass tube, inside of the float bowl). (This modification was recommended by Scorpa). However, if you adjust the float level in the carb properly (and possibly increase the pilot jet 1 size up} then this modification is NOT necessary. (I cut 5mm off mine, then had to solder 5mm back on after I had sorted the carb out. It now starts first kick, every time!
12. Fit a big bore kit and bigger jets:New Sherco Trials 125 4T 150cc Big Bore Kit Straight Fit Oe Yamaha Cyl & gaskets | eBay
13. Remove the big engine sprocket guard - leaving the small one in place.
I know of 4 trials riders that have done that for a living. They all had over 100 competitions and were top riders in there class. Two men and two women. Two of them made a career out of it. Good luck!
Any new model of bike would do. You would need to add your location.
I have Wulfsport and Gaerne's. The boots offering the best protection by far are Wulfsport. Wulfsport boots are made of thicker, stiffer leather and the soles are much stiffer too. Gaerne's are soft and comfy but offer little ankle protection - I broke my ankle earlier this year wearing my Gaerne boots. It wouldn't have happened if I had my Wulfsport boots on. However, the most popular boot at trials competitions are Gaerne.
Bend the kickstart back to it's correct angle: Take the kickstart leaver off. Put it in a vice. Heat it up with a blowlamp, or preferably an oxyacetylene torch to a red colour, then bend it, perhaps using a long length of pipe. When you are happy with the angle then heat it up again to red, then quench it in a bucket of cold water to make it tough again. Simples.
Rough, poorly maintained, but cheap bikes can be a money pit. Unless the bike's a classic, then it is often better to pay a bit more for a good example.
You need a windy gun/impact driver to undo it. If you don't have one, take it to your local garage. (leave the nut exposed). It would only take them a minute to undo it.
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Posted · Edited by stpauls
If it was me, first I would put the old spring back in, to check that all is well - that nothing has been omitted or replaced incorrectly - especially the linkage. Then, if all is ok then I would try another replacement spring, because it may be that the spring has not been properly tempered and so will not work correctly when installed in your bike.