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stew79

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About stew79

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  1. this looks very good, what power did the original make ? what power do you think it will make when finished ? i no its not about the numbers it more the feel but numbers do help to compare things. i only wish i could have kept my bored out 250 and dynoed the thing, 330cc felt so much better. stew
  2. the std ignition wouldnt advance once the engine got warm (common problem, quite dear to fix) but it dosnt advance fast enough, or far enough, and its hard to alter (cant move the max adv pick up very far, and the the speed is stuck in the electronics, but the fly wheel is way too heavy anyway) i have made cdi ignitions for many bikes, timed from the cam, so that was the easiest option. lighter honda rotors can be made to fit the crank, but still use the yam coils. (the rotors can be lightened even further depending on what you want) so with totally adjustable timing, better carbs, porting, etc, you can wear out the soft yam gear box even quicker ! stew ps home made ignition on the sp370 in the suzuki section under dr
  3. great simple bike, just my kind of thing. back in the 80,s i found a good way of getting one of my hondas to handle, stop etc better. put the engine in a zy !
  4. to split and re assemble a crank is a bit specialized, needing the right equipment. as an engineer with my own business its a service i supply. you may have damaged or distorted the crank wheels. but put the crank between running centers (thasts centers that have bearings in them) on a lathe, (very little pressure) and record the run out with a good clock. (mark with a felt pen) take out and hold in one hand. it is possible to hit one half of the crank wheel with a copper mallet, to bring it into alignment. with wedges and a press its possible to true up the faces. keep returning to the lathe and re clocking up what you have done. if you are lucky you may get it right. or take it to a machine shop. stew
  5. thanks for the replies, i chose this section as it relates to the modern equivalent to what type of bike i had. thats more mx than faster xr. my bike had a smaller much lighter rotor and coils from a suzuki, so it felt very different from an xr. as for 27bhp, i fitted an old road tire on the back, rode 20 odd miles to a good tuning shop with a dyno, (BDK race engineering norfolk) and thats what it did on petrol. (actual figure from the wheel, not from the crank) then rode home and put the knobbly tire back on, and headed off road. stew ps some pictures of the bike in the xr section under old xl250
  6. hi all, my old air cooled 250 4 stroke play bike (road legal) made 27 hp. this was all very low tech, but great fun and easy to start, ride and live with. how much power do your more modern 250s make ? stew
  7. the 550 has 4 valves just like to 600,s (not 2)
  8. nothing wrong with 2 carbs (a bit heavier, more complex) but i like them to be identical carbs, and open at the same time (so throttle response is proportional)
  9. a bit disappointed with the power from the bikes in the test. all that technological and water cooling i thought it would be much higher. my old xl250 (pictures on the honda page) made 27 bhp on the dyno, but is still a good all rounder with plenty of usable bottom end pull. (geared for 90 mph it will still wheely in third on the clutch) stew
  10. bought an old xt600 cheap, with an ignition problem. made some better headers and a better ignition. (timed of the cam) tried some rd250 carbs with the correct jets etc and it went much better than a std one. (silly std carbs are not proportional enough response for high speed wheelying) engine was old and a bit rattly, so i put together an srx400 engine from the back of the shed (only new part was head gasket) ported and skimmed the head, same ignition of the cam and rd carbs. went better than the 600 ? even with a cut down balancer it was so smooth and would rev over 9000 rpm. it felt more like a twin ? (it did go on a dyno and made 33 bhp at over 120 mph on the tall 600 gearing) re built the 600 engine and made a 2 into 1 man for a 38 mikuni. why didnt yam make the dam thing more normal in the first place ?
  11. yes they all chrome except in the last year of production there was an economy model that was painted red. (with just the 2 valve head)
  12. i have ridden a good crf250 and was impressed with its top end power, but it dose have bigger valves, bigger pumper carb, etc . my old xl used std piston, valves etc and an old vm32 (with completely different jets) it was more easy to ride having a better spread of power.
  13. some pics
  14. 1981 rm125 with sp 370 engine. play bike put together fro the kids to ride. ended up getting tuned up a bit and performing so much better that expected stew
  15. found some pics of old bike