copemech Posted September 30, 2009 Report Share Posted September 30, 2009 The early ones were a lot more docile than the later models, great for clubmen etc, from trying a new one out just after it had been assembled I think they're aimed more at the top guys now as the power is quite aggressive I tend to agree with that statement, although I have never been sure if what seems to be a major change in performance was due to the carbs or different cams or what. The newer gen 4T does seem to be more aggressive. As the taming of the 2.9 has been my beef all along, I admit that although I have not had the luxury of p***ing off money on quirky thoughts, the Oko has been on the radar, and now that these seem to be popping up at a decent price, I can take one and totally ruin it if i want! This thing laying on the bench has been looked at, cleaned up, and screwtinized! All kinds of mod thoughts going through the mind, should I bore it to 25? Could go 26 easily! Na, I think I will just run it as is and see what happens! Quote Link to comment Share on other sites More sharing options...
marlintec Posted October 2, 2009 Report Share Posted October 2, 2009 Hi, Great information in this thread! I'm not a great fan of four-strokes, but if it could be the way to mellow the beast 3.2 to a more docile creature, maybe I could try one on the future. The way I reduced Keihin PWK 28 to 26 are two sleeves of aluminium pressed into the bore. You only have to check that the front one has the hole for the starter circuit and the pinhole for idle circuit. The back one is just beveled to follow the trumpet. Of course, none must interfer with the slide... But... if you start from a new carb, maybe it's easy to bore out a 24 mm. If you remember the first GasGas (Halley, 1986) they fitted tiny Dell'Orto of 25 mm, bored out to 26. They were 327 cc engines... Cheers, JM. Quote Link to comment Share on other sites More sharing options...
copemech Posted October 3, 2009 Report Share Posted October 3, 2009 Hi, Great information in this thread! I'm not a great fan of four-strokes, but if it could be the way to mellow the beast 3.2 to a more docile creature, maybe I could try one on the future. The way I reduced Keihin PWK 28 to 26 are two sleeves of aluminium pressed into the bore. You only have to check that the front one has the hole for the starter circuit and the pinhole for idle circuit. The back one is just beveled to follow the trumpet. Of course, none must interfer with the slide... But... if you start from a new carb, maybe it's easy to bore out a 24 mm. If you remember the first GasGas (Halley, 1986) they fitted tiny Dell'Orto of 25 mm, bored out to 26. They were 327 cc engines... Cheers, JM. Good to hear from Marlintec again on this one. I like the test you did on the 250 Gasser, but I wish you had done it on a 280! This gives a better relation to the 2.9 Sherco or the 270 Beta, both of which can be a handfull to your clubmen riders. The late model 250 GasGas seemed to me to be very manageable to begin with, probably "butter smooth" with the Oko, sweet for many! The larger bikes can still be a bit much at times it seems, and even though my 2.9 is very good off the bottom, there is still a respectable mid range HIT that is rather non linear with the Dellorto, Boyesens and timing changes. Obviously porting and such comes into play with the tuning of the motor, and the CAMMING will come into play on the 4T bikes! The SPS system on the Sherco seems to me just a "spitback" mitigation system in the case that one Does open the throttle too quick at low revs and get a lean misfire. All good, but rider technique comes into play a bit here, the combination of a sleved down SPS could be rather good it seems! The CV carbs seem to have a certain advantage in that they will basically disallow a too quick opening due to their vacume operation on a 4T! Quote Link to comment Share on other sites More sharing options...
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