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I thought this might be some useful info for owners of Canadian spec 1983 GS450TX's. I bought this bike recently and had to replace the fuel filters in the carbs and rubber plugs under the pilot jets. Some ham fist had been in those carbs before and there were screwdriver dents inside, and those parts missing, and a dubious float, but thankfully no dents in critical areas. The main problem was the missing plugs.
I got the bike running pretty good, but it was missing under load between 5000 and 6000 rpm in the upper gears, wide open throttle. If I backed off the throttle to about half, it ran okay. It also pulled hard at wide open throttle above 6000 rpm, leading me to believe the 115 main jets are correct. The boots on either side of the carbs are in good shape.
I had read that these bikes were jetted lean, so I played around with the needle position. I tried richer (clip in the bottom two notches), but the problem got worse. The stumble didn't go away until I put the clip in the top notch (leanest position). There's also a thick spacer on top of the clip (I didn't measure, but it looks to be about 0.050 to 0.080" thick).
The Hayne's manual says the US spec bikes had a size O-6 needle jet with 5CDT60 needle, but my bike has a series 414 O-9 jet with 5CDT61 needle. I'm guessing the Canadian regulations may have been more relaxed for motorcycles than the US EPA regs, resulting in richer carburetion. There are also no caps on the low speed fuel screws.
It's just lucky that the problem went away because there aren't any leaner notches on the needles. The bike works flawlessly now.
I got the bike running pretty good, but it was missing under load between 5000 and 6000 rpm in the upper gears, wide open throttle. If I backed off the throttle to about half, it ran okay. It also pulled hard at wide open throttle above 6000 rpm, leading me to believe the 115 main jets are correct. The boots on either side of the carbs are in good shape.
I had read that these bikes were jetted lean, so I played around with the needle position. I tried richer (clip in the bottom two notches), but the problem got worse. The stumble didn't go away until I put the clip in the top notch (leanest position). There's also a thick spacer on top of the clip (I didn't measure, but it looks to be about 0.050 to 0.080" thick).
The Hayne's manual says the US spec bikes had a size O-6 needle jet with 5CDT60 needle, but my bike has a series 414 O-9 jet with 5CDT61 needle. I'm guessing the Canadian regulations may have been more relaxed for motorcycles than the US EPA regs, resulting in richer carburetion. There are also no caps on the low speed fuel screws.
It's just lucky that the problem went away because there aren't any leaner notches on the needles. The bike works flawlessly now.