GT550 runs on two when under load

Having just purchased a 74 GT550 i have found that it runs well around town or on the flat but if it is opened up going up a steep hill or once it gets up to about 50-60 mph after a while it starts to run on two cylinders only; the two outer one. Once it has been eased off it splutters for a while and starts running back on all three. I have tried new plugs (the old ones once out seemed to be ok and showing no signs of oiling up or burning) but with no effect.

Any suggestions as to the next step? New points and/or condensers perhaps? Any help much appreciated.

Hi Mate.....sounds like a classic case of fuel starvation, check the float heights, middle pot might not be filling up enough, fine for normal riding, just, but put her under pressure and you get a problem....

best of luck...Derek

haddocksrock wrote:Having just purchased a 74 GT550 i have found that it runs well around town or on the flat but if it is opened up going up a steep hill or once it gets up to about 50-60 mph after a while it starts to run on two cylinders only; the two outer one. Once it has been eased off it splutters for a while and starts running back on all three. I have tried new plugs (the old ones once out seemed to be ok and showing no signs of oiling up or burning) but with no effect.

Any suggestions as to the next step? New points and/or condensers perhaps? Any help much appreciated.

Glad to see you made it here my friend - hang around a while - we're a friendly bunch too!

Sounds like you already have, but check the points gaps. I was riding mine around just fine for about 8 months without checking them and when I finally did they were all closed. I have also heard that the center cylinder was one of the common problems on these 550s. good luck.

Thanks chaps for the suggestions.
Tried new points and condensers but now the problem seems worse as in it seems to be slowly strangling it's self!!!!!!!!!
Pretty sure that as its been standing for about 10 years not flushing out the tank was a hasty short cut!!? Next step is cleaning out the carbs and checking the timing.