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jon v8

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About jon v8

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    Advanced Member

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  • Bike
    AJS,James J9,BSA,TY

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  • Location
    Bath UK
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  1. I had a couple of early Cota 247's a few years back, yours looks like an early Mk3. They didn't have tailpipes and are quite noisy... Mk 1's look quite different and are rare, the Mk2 is very similar to yours and had much larger hubs, this is the main difference to the Mk3, the small hubs borrowed from their little road bikes.I think the works riders used to retro fit the bigger front hub where higher speed road was involved. The pic shows the Mk3 I started restoring, but sold early on...
  2. Pair of Levi's with some knee pads underneath did the job for me yesterday. Boots and helmet way more important.
  3. jon v8

    ty250 piston

    I've just fitted a 2mm O/S Wossner piston and ring kit into my old banger of a TY... It was the only size I could get, but not bothered because I have spare barrels. Pleased to report it runs very nicely, I did remove some unnecessary weight from the inside of the piston with a Dremel drill. The wrist pin is shorter than the old one and was a fair bit lighter. The assembly was just over 1.5 Oz lighter than the old one. It has certainly made the motor much more zappy, and the big bonus is the lack of rattling ! Just need to get used to riding a 2 smoke again...
  4. Use the clutch more, keep the revs up. Back in the 80's I used to be always stalling my TLR and RTL 250's, they just don't plonk at low revs. Or put a BSA C15 engine in it if you want a proper trials engine, they are luverly...
  5. I've been using WD40 for years, there is no problem with it at all.
  6. This is the kit; https://www.venhill.co.uk/universal-2-stroke-decompressor-kit-vdec.html Works very well with the lever setup on the left bar underneath the clutch, just the same as all my 4 stroke bikes. I use it to prime the engine with fuel via 2 or 3 kicks, then release it halfway down the next kick. The engine fires up straightaway then. It also makes life easier for the kickstart gears etc, maybe not important on a Yam, but it makes a big difference on a unit BSA engine.
  7. If its kicking back the timing is too advanced. They are not the easiest bike to start because the kickstart shaft is so high up. I'm only 56 but my right knee is not too good, fitting a decompressor into the cylinder head has helped me starting mine mine a great deal.
  8. The time you are spending researching and pontificating over which way to go with this situation, you could easily strip down,set up and enjoy reliable service from what you already have. Its not that hard,and decent quality service parts like points and condensors are easily available at very little cost.Even if you bought 2 or 3 of everything you would have enough parts to keep it running for another 20 years of trail or trials use...
  9. Just to add to the advice given, the standard ignition on all Yamaha TY's with points is very good quality and extremely reliable when set up properly. For the little effort it is to make it work properly I don't think the cost of electronic ignition is worth it. Yes, the 175's may benefit from the extra power available at the top end, but 250's make enough power for the bulk of riders. Personal choice and only my opinion. Only once in the last 15 years of using Ty250's have I had a problem with the ignition, my fault for using a dirty old set of points that I didn't bother to check when I built an engine out of 3 boxes of bits, using only a couple of new gaskets and circlips. The moving point was tight on the pivot and tightened up when the engine got warm. Cleaned out and greased, its not missed a beat since.
  10. I would also be suspicious of the spark itself, as already said modern plugs don't work very well when fouled. My 350 AJS when running on a Lucas racing mag,(Which was in good condition) would go through a couple of plugs a year, I could always tell when the performance was dropping off. When I changed it to a BTH electronic mag I could run the same plug all year without even cleaning it. The BTH mag clearly had a stronger spark which could cope with a dirty plug. I proved it using an inductive pick up and viewing the spark trace on a laptop based oscilloscope. The Lucas spark was less accurate and weaker. Then when the condensor started to fail I could make the spark trace disappear by applying 100psi of workshop air to the plug. If you have access to this kind of kit it would be good to compare the HT trace of your bike to a similar one that doesn't eat plugs.
  11. Money spent on the mag and carb will be the two areas I'd go for first. The Amal Premier carbs are great, a decent carb and spark then the rest is fiddling. Do you know if its got trials ratio's in the gearbox ? A set of Mick Ash gears in the box also is a huge benefit if its still on a road cluster.
  12. I can't be sure, but the frame looks very like the one I had a few years back. That one was made by the late Alan Brown from Bristol. Having a Monobloc carb on it shows it as being a good few years old too. Thats going to be a big heavy handfull... I gave up on mine and sold it,my little,(By comparison) rigid 350 AJS is much easier to ride,steers better,has softer,more controllable power. Just more difficult on big rocks or steps etc. HT5's are nice bikes, but in most cases the 500 engine is too much,and unless they are very trick they can be heavy and hard work.
  13. I think mine is on 12/53 too, but its at work so I can't check till tomorrow. The one I'm using at the moment is a D model, but the engine is more than overdue a rebore and piston. (The A model is more snappy from memory) Saying that it still goes very well and does not hesitate in picking up the front wheel in second, although third does take a bit more of a pull on the bars... I run a slow throttle too. This bike is currently only used for club trials and playing in the woods, but I never get the feeling that it needs more power. What I do like about it is its ability to run down to absolutely nothing then pick back up again without complaint. At the trial I rode on Sunday I made it do this several times where slipping the clutch would have been very risky in terms of losing traction. It just did what I asked of it and found grip on slippery mud and tree roots,not even a finger hovering over the clutch...
  14. By coincidence I have just fitted a shortened cover to my TY250, only to save the completely undamaged original. They are expensive now and hard to find, the one I have fitted was badly cracked, but JB Weld has done a brilliant repair. If you are worried about chain damage it might be worth making a case saver similar to this only which quickly popped up on a search. The one in the pic is for a later Mono engine, but you get the idea.
  15. I'm happy with a 428 chain on my current 250, but the one I'll build as a Majesty is on a 520 setup. The 428 is lighter, remember Sammy Miller went for a small chain to cut down on weight...
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