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Mr stinkwheels Group: Members Posts: 206 Joined: May 2006 Posted: July 26 2006,16:56 Does anyone know the answer to these questions? If I removed the air boxes from my 3XV-1 with standard 28mm carbs, and replaced the internal components of the upper carb with the internal components of a spare lower carb, and up jetting sufficiently, would this improve the performance?, taking into account I would then have identical carburation for both cylinders. I could also replace the internals of the lower carb with the internals of a spare upper carb, would that be better or worse? I am still not sure why Yamaha chose to have different settings for the carbs on the R model. Are the SP and SPR carbs the same and what about the TZ? Any help would be appreciated. Back to top

gbowie Two stroke spirit Group: Members Posts: 264 Joined: May 2006 Posted: July 26 2006,20:21 Best power I ever got out of 28mm carbs was with no airboxes, drill both jets out with a 1.5mm drill bit, fit an advancer key.. around 8 deg, around .5mm off the heads to give a squish of around .7 to .8mm. This suited Bosson pipes so you could be way out with yours. Have spent many hours on the TZ site as we race one ( unsuccessfully so far ) and my guess is that about 50% of riders run the same jets in each cyl, only the real top guys suggest staggered jetting when going for the last ounce. There is no dust in England ! why not run open carbs on the road ? ( bike sounds good too. ) Dead cheap to try this setup ( other than the heads ). Oops!! Just realised, all this was done with leaded 98 octane. Standard pump petrol here until a couple of months ago. (Greenies caught up with us as well). Maybe try to find some avgas and give it a go. -------------- You'll live a lot longer if you give up the things that make life worth living ! Back to top

jools Group: Members Posts: 1221 Joined: Oct. 2005 Posted: July 27 2006,02:00 I found with my standard motor that it was running rich on standard jetting. On the dyno it made 37hp at the rear wheel. removing the airboxes and not touching the jetting it put out 43hp and was running much cleaner. Dropped the needles a notch though. This was with Swarbrick silencers on STD pipes and a sugo CDI & harness which didn't really suit the std pipes & porting as it wouldn't really produce anything above 9500. This is on std BP Ultimate 98 pump unleaded and the autolube. WHip off the airboxes and give it a run. One other point - there is a pronounced lip on the inside of the intake bell of the 28 carbs. Smoothing this off will help air flow -------------- "The only thing worse than being talked about is not being talked about...." oscar Wilde Back to top

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