suzuki gt350 jetting

[Gil Gallad]

as many will know, i built a gt350 engine [64 x 54] from an original gt250m. i had 64mm liners fitted and ts185 standard pistons. 4mm base plate under the barrels and exhaust ports were widened 1mm either side and 1mm on top. aside from this the engine is just a bigger gt250. so, i thought to myself, this is basically the same as the rd250/rd350 conversion, so i put 28mm mikunis on it and jetted it as an rd350. this worked ok with the standard gt250 exhaust on it. started easily and ran nice and crisp through the rev range. then i put spannys on it. once it was running it sounded glorious, in fact it sounded like a tz350, but it just wasn't quite right. so i did some reading on here and found most rd350's with spannys were using #32.5 pilot jets and 190 mains, so i tried them - still not right. the rd350 is of course a reed valve engine, mine is piston port, so would that make a difference? what i could do with is an r5 owner, running spannys, that's got the jetting right - forget the sea level thing, i'm about 100ft above sea level here. i'd just like to know if i go up or down on the jets? jetting carbs isn't my favourite pastime, so any way i can shorten the job is good news for me  ;D
cheers, gil.

[2 Stroke Jamoke]

Reed valve engines are generally a little richer setup. The mixture travels back and forth in a piston port engine ,picking up more fuel as it goes. Maybe you could try a little leaner jetting? What do the plugs look like?

[quocle603]

Try to get it close to stock as possible and modify for there. Obviously double check your timing, compression, and as well as for any airleaks. Once everything is kosher, then jump into jetting. Jet accordingly and note the RPMs and throttle position that the bike is struggling at.

Good luck

[Gil Gallad]

thanks for the answers  ;D plugs are very slightly sooty and i mean slightly. it seems to be midrange where it doesn't seem quite right, so the 190's could be ok. i'll have a piddle about with lifting or lowering the needles and turning the pilot airscrews in or out. it's not a million miles away, but these barrels are one offs [or two offs?] and i really don't want to risk a seizure. there are definitely no airleaks. anyway, thanks again.
cheers, gil.