I have posted previously about problems with the carburation on my twin. Early in the year, after the bike was running a bit erratic (posted as "twin with fast idle when hot") I went back to basics and set the carbs from scratch, successfully making the bike run as it had last year, but when used a bit it kept fouling the front plug after 50 to 80 miles.
After seeking advice from my local section, I checked the metering wire on the front cylinder inlet valve oil feed, this was fitted, but dislodged, so I replaced it but no improvement. I then started to look at the front carb again. I had already replaced the float and float needle. The new float lowered the fuel height in the float bowl by 1.4 mm and had made an improvement, but it still fouled the front plug as described above, particularly at lower speeds.
I tried running a hotter plug (NGK Bp5EVX) which again improved things but not much and the front plug fouled again. On inspection the plug was fouled with dry powdery soot that would fall off the ceramic core like dust if the plug was tapped against the bench.
Thinking this still pointed to richness, particularly at lower revs, I recalled some postings on the forum about 229/289 needles being sourced that were out of spec. So I decided to replace the needle and needle jet on the front carb. On removal and inspection the old needle has some minor differences in the taper measurements and also about 30mm from the point end there was a score about 4 mm long around the needle.
Eureka, the bike runs perfectly, cold start is ok, idle is spot on, it will sit there as long as I leave it without missing a beat and hot start is easy. It will start when hot without touching the throttle, going straight to a steady tickover on its own.
Smoother riding, better gear changes, better economy and a bigger grin when riding it! I fitted a pair of NGK BP6EV plugs after replacing the needle and needle jet and have now done 400 miles of mixed riding without missing a beat.
229/289 carbs seems to be a bit of a common problem on the forum, but keep at it and they can be sorted and possibly / hopefully the info above may help someone sort their bike out.
Chris Smart
After seeking advice from my local section, I checked the metering wire on the front cylinder inlet valve oil feed, this was fitted, but dislodged, so I replaced it but no improvement. I then started to look at the front carb again. I had already replaced the float and float needle. The new float lowered the fuel height in the float bowl by 1.4 mm and had made an improvement, but it still fouled the front plug as described above, particularly at lower speeds.
I tried running a hotter plug (NGK Bp5EVX) which again improved things but not much and the front plug fouled again. On inspection the plug was fouled with dry powdery soot that would fall off the ceramic core like dust if the plug was tapped against the bench.
Thinking this still pointed to richness, particularly at lower revs, I recalled some postings on the forum about 229/289 needles being sourced that were out of spec. So I decided to replace the needle and needle jet on the front carb. On removal and inspection the old needle has some minor differences in the taper measurements and also about 30mm from the point end there was a score about 4 mm long around the needle.
Eureka, the bike runs perfectly, cold start is ok, idle is spot on, it will sit there as long as I leave it without missing a beat and hot start is easy. It will start when hot without touching the throttle, going straight to a steady tickover on its own.
Smoother riding, better gear changes, better economy and a bigger grin when riding it! I fitted a pair of NGK BP6EV plugs after replacing the needle and needle jet and have now done 400 miles of mixed riding without missing a beat.
229/289 carbs seems to be a bit of a common problem on the forum, but keep at it and they can be sorted and possibly / hopefully the info above may help someone sort their bike out.
Chris Smart