750 sport problem

[jpitz31]

Hello All,

Been a while since I have been to the forum. Been having lots of problems with the 750 sport.

Carbs have been switched to Mikunis from a 900 ss. Bike ran good for a while.

Then bike developed an engine miss, almost a cut out at around 4500 RPM. During troubling shooting (switching coil, spark plugs) the ignition went completely dead.

I had the marelli digiplex ignition with the single pickup. I switched over completely to the kokusan system with two pickups, same flywheel.

Bike ran stronger but engine now cuts out around 5500 RPM. (rough miss)

Changed all fuel filters and installed a new fuel pump, after market electric fuel pump listed on ebay for $55.00 Now I can hear the fuel pump when switch is turned on.

Now engine runs very strong, but engine starts to cut out at around 6500 RPM.

Anyone have any ideas on what the problem could be with the engine cutting out (missing) now at 6500 RPM.

Looks like a pattern. It is getting better, but still have not found the item.

Not sure if this could be a carb float issue. Plugs have been changed several times. I have not adjusted the valves yet. Next on the list.

By the way. I did the 17" conversion. I went with the 900ss rims. Used the stock rear swing arm, 900ss calipers and bracket. Stock front forks, raised fender and made new caliper brackets for 900ss calipers.

Any suggestions would be appreciated.

Thanks

Joe

[ducinthebay]

It sounds like a bit of dirt in your carb(s), or a vacuum leak. The SS carbs are Constant velocity, which have diaphrams that pull up the slides. If those don't have enough oomph, they don't pull all the way. Make sure all the hoses and gaskets are good.

Sounds like you have done quite a bit of work on the bike. I would say its time to take the carbs apart, but I'm just guessing from here.

Where are you located? Maybe one of us is close enough to come by and lend a hand, or ear, or set of eyes, or whatever it takes.

Cheers,

[jpitz31]

Thanks ducinthebay

I will pull the carbs and check for leaks and do a good cleaning.

I am located in Escondido, CA not far from San Diego.

Thanks

Joe

[jcslocum]

Make sure to check the Jet sizes and pay close attention to the float level. It may just be running out of fuel at high RPM's. For Jets, look to the sizes used in the 750 Monster or SS.

[jpitz31]

Thanks Jon,

When I have the carbs apart I will check the floats and the jets.

Joe

[Mustang505]

Hey Joe
please keep us posted as to what you find.
Also, as you have done a fair bit to your bike, can you take some pictures? I'd really like to see how you have done the mods, carbs, brakes etc.
Cheers
Clive