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trialsrfun

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  1. Everything TY is here, YAMAHA TY MAJESTY
  2. trialsrfun

    Sprite 250 Mk 2

    The points side 36A magneto outer case with the round cover is perfectly okay for a trials engine. Is the flywheel fitted the all brass one or has it got the additional weight ring fitted to the outer face? Your bike appears to be a late model similar to the one shown here Sprite Motorcycles (historywebsite.co.uk) these had a longer exhaust on the right hand side, this was a big improvement over the earlier short type fitted on the left hand side making the engine run much better.
  3. Make a saddle possibly by cutting a length of steel tubing in half longitudinally then weld a bolt vertically to the outside of the tube thread pointing upwards the correct length to secure the tank as on the above post, secure the saddle to the frame top tube using two Jubilee clips.
  4. Gearbox oil should be GL4 spec as it is suitable for yellow metal bushes and not GL5 which 90s is. GL5 oil should not be used with yellow metal bush bearings. This applies to not just the Montesa but any gearbox used for any application which has yellow metal bushes.
  5. There has been some discussion recently about SM Bultaco Hi-Boy frames, the attached link clearly shows the detail. Bultaco Sammy Miller highboy frame | eBay
  6. trialsrfun

    Bultaco yokes

    This type of Montesa yoke, 247 and 348 are very similar https://www.google.com/search?q=montesa+cota+247+fork+yokes&client=tablet-android-samsung&prmd=simvn&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiMwfmkhpTuAhVaQkEAHYqUD9MQ_AUoAnoECBEQAg&biw=1280&bih=800#imgrc=9nbHRrJsOC-6cM
  7. trialsrfun

    Bultaco yokes

    A friend of mine built a Sherpa using fork yokes from a Montesa Cota 247, these seem to have possibly a 1.5° offset or run out similar to Sherpa yokes but place the handlebar mountings over the steering stem instead of behind it which gives more room on the bike. This for me being a taller rider gives much better steering and control. Steering bearing diameter is the same as the Sherpa, unsure if the lock stops or wheel spacers would need altering as the fork legs are slightly wider apart with the Montesa yokes.
  8. http://www.yorksclassictrials.co.uk/classified-ads/4543674651 Paul Jackson (number on the website) is definitely the place to go for wheel restoration and possibly for the frame rear loop repair as well. Steve Sell makes a same diameter but much stronger rear wheel spindle which in my opinion is a must have on a bike that is ridden. If the original one is not already bent it likely soon will be, Steve is the go to person for all things OSSA. The rear brake cable on the MAR is much heavier made than a motorcycle clutch cable but Steve should have the correct one.
  9. 11 - 42 is what I run I find it spot on.
  10. Paul Jackson look on the Yorkshire Classic website for his contact details. Wheel Building, Replica frames, cub PVL mounting and sprocket covers, general machining. Paul Jackson 01422 378 100
  11. First thing is to replace the O rings in the carburettor float bowl, you will see them when you remove the float bowl.
  12. Stand at side of front wheel, I then place my fingers over the twist grip while hooking my thumb over the front brake lever and squeezing the brake on, hold the brake on then with your right hand hold the wheel spokes at the three oclock position by the rim and pick the wheel off the ground and into rack like a one handed wheelbarrow. That's one end secured in the rack then lift the back wheel in however works best for you.
  13. This topic has been both interesting and thought provoking with some great information. With regard to carb venturi shape and size some I have seen have a sort of keyhole or upside down pear shape for presumably faster airflow at minimal slide openings, might this design offer any advantage for trials use?
  14. Going slightly off topic the exhaust system is a Mayfield expansion chamber. Back to the forks which are actually leading link not Earles type, if you are considering getting some leading link forks made then best to contact a frame builder, maybe look in Old Bike Mart
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