Loss of power...90's cb750

[Johny85]

Hi guys!

My cb has lost a fair bit of power recently. Its still running smooth and starts fine. I thought I'd just got used to the power even though I'd noticed it was slower accelerating. As I was riding earlier I played with the choke whilst in 2nd gear , then all of a sudden that missing power came back & blew me away turned the choke back off & power had gone again.. can anyone steer me in the right direction on what's going on & solving this issue? Feels like someone swapped my engine for a 400cc. There's no spitting & farting,just a decrease in power!

Thanks for reading!

[fastbob]

Sounds like a blocked jet , best cure is to strip and clean the carbs but before you do try and determine which one is the most likely culprit. This won't be easy but you could try the old spit on the finger method to see which downpipe is coldest or you could spray them liberally with WD40 and see which one starts smoking last upon start up. Having said all this, you might just try an air filter and plug change to see if there is an improvement.

[iangaryprice]

Since the power increases when the choke is on. it is almost ceetainly carb releated.

Check the intake rubbers - any cracks or splits will allow air to enter weakening the mixture, reducing power.

Try draining the carbs one at time into a clear jam jar. Check how much petol come soutof each.

If any carbs have less then the needle valve could be sticking.

If there is any water or dirt inthe fule then the carbs will need claening.

Sometimes a dose of redex will work, it does not do any harm if it does not work so worth a try,