750 Sport, fuel pump or ignition problems ?

[Winder]

Hello you nice motor cycle doctors,

I´m having a problem with my 1988 Sport. When I start the bike it runs very well for about 15 minutes then it starts to blurr and shake and losses power. I have to drive slow for about 5 minutes then it wakes up again. Full throttle and it sings again...... for 5 minutes.. back to shaking mode, lack of power. My first thought was fuel pump problem but now i am into ignition problems. Over heating of coils ? Please, could you give me some ideas how to solve the problem ?

Kind regards
Bo from Sweden

[Mc tool]

Sounds like it's dropping one cylinder. What sort of carbs does it have ? 2 barrel Weber or 2 single carbs ?. Could be a fuel flow issue to one csrb if single carbs are fitted ( check float valves ). Are you able to get your hand on the coils to check the temp ( reaching under fairing )? And ,probly pay to give the wiring a good check over too.

[lodola235]

Hi,
I also have an 750 sport(bj90)
I had already mounted an mikuni from an 900 SS (hope to put 2 dellorto's later) wich solved bad starting, and an smoother run
now, my voltage regulator blew up, and I'v mounted an ignitech CDI(plug and play) and an camro voltage regulator (2 wire connection instead of 3 , just isolate 1 wire instead of connecting two together like the manual says) , everthing seems an improvementant I've mounted an yamaha TRX vacuum fuel pump instead of the electric one wich had too much fuel pressure (was an bit more work to bore out the fuel tap where the old fuel line was brazed on), have done already little distance but not an long ride ; but it seems to work ok

[Tamburinifan]

Vacuum fuel pump can be semiworking, due to bad diaphragms. There are replacement avaliable.