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5 Posts
Discussion Starter #1
Hello all.

My name is Johan and I'm from Sweden.

I own a -98 Gsx750 and long story short, it's not running as it should.

I have spent many hours troubleshooting and I can't find anything wrong with it though.

The bike starts easy and idles well but as soon as you open the throttle more then 1/8, the engines dies.
It cuts off just like you have turned off the ignition.
When it dies, it blows squirts of gas back out of the carbs.

A list of the work done up until now:

*Measured and tested all of the electrical components and there's no problem with them.
All is ok, I have also borrowed som components from a working bike but to no success.

*Cleaned the carbs, checked the floatheight etc, condition of the carbs is great. All is stock, jets, needles etc.
I also tried some other carbs from a working bike but no success there either.
I have tried setting the carbs rich and lean = no difference.

*I have checked the whole wire harness = it is in condition like new.

*The engine has good compression, it ranges from 173 to 176 psi.
Did a leakdown test on every cylinder and that showed 5-6% leakage.

*The cam timing is correct according to the workshop manual.

*New fresh gas

*The exhaust is not plugged or stuffed, it flows freely.

*Tried new set of spark plugs and another coilpack but that did not change a thing.

I'm completely out of ideas now, everything that I have checked turned out to be faultless, but still the engine runs like crap.

I have a video on Youtube that shows how it runs, but since I'm new on this forum, I can't post any links.

Thanks in advance and best regards from a really confused Swede 馃檪

5 Posts
Discussion Starter #3
Yes, I have tested the engine both with and without the airbox.
No difference, it acts the same.

5 Posts
Discussion Starter #4
Since i'm totally out of ideas of what the problem might be, I'm about to remove the engine out of the frame and dig deeper into it.
Such as removing the cylinder head and check for anything suspicius.

262 Posts
These bikes had a vacuum operated petcock, have you tried with an external fuel tank without a petcock and just blocking the vacuum line? I woudln't drop the engine yet, if there was a problem with the head or timing it wouldn't idle.

5 Posts
Discussion Starter #6
Yes I have tried both the stock fuel tank/petcock and also a external tank.
No difference unfortunately.

No airleaks, the carbs are synched and they do not flood.
The valve clearances are correct according to the workshop manual.

I have been a mechanic for about 25 years but I think I will bite the dust with this bike 馃檪

It is so strange, I have checked and doublecheck everything and can not find anything wrong with it.

The swapped parts (carbs, intake, coilpacks, sparkplugs, pulse generator, etc) that work great on my other 750, does not cure the problem.

5 Posts
Discussion Starter #7
Here's a picture that shows the video on Youtube where you can hear the bike and how strange it runs.
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