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Posts posted by evansm
  1. Hi, I have a TY 175 Whitehawk and when I removed the head and barrel for a rebore I noticed that the head bolts had been modified and cut down as the stud holes in the barrel were a smaller diameter than the head.

    Does anyone know if this means I have a DT175 head or did the TY175 have different variations?

  2. Hi all, I am rebuilding a TY250 Twinshock engine but I am trying to source the two Transmission roller bearings.

    Fig 6 item 12 P/N 93311-42018 has a number stamped on which is 20NQ3212.

    This bearing is available through bearing suppliers and TYtrials sell it as the Yamaha P/N.

    Fig 6 item 27 P/N 93313-31709 doesn't have a number stamped on it, it just has IKO.

    I have searched for the Yam P/N and there are a few available in the USA but obviously an expensive option.

    Does anyone know the generic P/N for this bearing which would give me the option of obtaining from a UK bearing supplier?

  3. Thanks Woody

    I will try the weight off the fly wheel next, most mods I have tried have been with replacement parts so I still have the originals to fall back on.

  4. I bought the bike in question last April from Bavins of Diss.

    It is a Majesty replica and he had done all the frame mods, the engine craddle has been moved upwards, the steering angle altered and the rear shocks angled.

    I initially found the engine very flat and I was struggling on climbs, on short climbs it was like the power was coming in at the wrong time instead of making your speed first the power was coming in when I would usally be wanting to back off and find grip.

    I looked through this site and there was alot of advice on lightening the fly wheel.

    I bought a spare fly wheel and had the weight skimmed by approx half of the original, and this did make a difference, I have never tried it without a weight.

    I also noticed that on uphill sections the front wheel was way too light.

    I measured the wheel base and it was approx 50" so I bought swing arm extensions and had these welded in.

    This made the bike much better on uphill sections.

    I contacted Craig from the Majesty site and he said that 52" is about what I should be aiming for.

    I do have TY Mono forks to try once I find a Mono front wheel and yokes.

    At a trial I let a guy with a Majesty 175 have a go on it and he said that the gearing needed changing and the damping from the rear shocks was poor.

    I changed the gearing and bought Rock Shock rear shocks and Magical front spring from Craig.

    All these things have improved the bike and it does turn and handle very well it is just that I thought that the 320 mod might be the ultimate mod for the engine

    I had a go on a TY175 and that did rev quicker than my 250 but at 6ft 2" and 15 stone I wonder whether it may be a bit small for me.

    I have also spent a fair amount on the bike so I would like to stick with it.

  5. Wow

    Thanks for the repies guys, and for going into the subject with so much detail.

    It really does give me something to think about so I may take my time and ask for a go on one first.

    I will also give Nigel Birkett a rind and ask for a price on the porting.

  6. Hi all

    I am interested in modifying my standard TY250 engine to a 320

    I would like to buy a replacement cylinder and head so that I would always have the original parts to fall back on if needed.

    Would any of the TY twin shock cylinders be ok to use for the conversion?

    There is a cylinder on ebay at the mo but the guy does'nt know what year bike it came from.

    From one of the posts it said to use a DT360 piston, I have only looked on ebay but they only look available in the USA.

    Does anyone know of a supplier in the UK?

    The Majesty site wants £150 for a piston kit but it looks like I could get a DT360 kit for approx £100 from the USA.

    On another post one guy asked if he needed to buy the DT360 liner for the barrel but the advice was he didn't need to.

    Does this mean that the person tasked with fitting a liner would be able to modify something that is readily available?

    In another post "feetupfun" said that the head would need welding and machining, would you be able to explain this in more detail?

    I beleive you also need to fit a spacer under the barrel and "Woody" said that this should be approx 2mm.

    Would this need to be played with or is 2mm a general standard?

    Does the standard 250 jetting need changing once the modifications are complete?

    Any help would be appreicated

  7. Hi all, i'm new to the Bultaco forum.

    I have a 1973 91 model 250 Sherpa.

    The bike starts fine, ticks over fine and runs very well at slow speeds.

    when I get to approx 1/4 throtle opening I get what I can only discribe as a clacking noise.

    It will rev through this with more throtle but once you back of the noise returns.

    When riding between sections I find myself short shifting so that i don't ride in this rev range.

    Any idea's?

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