Running problem in '89 Yamaha FZR 1000 EXUP

My father has an '89 Yamaha FZR 1000 EXUP. He's experiencing a problem
with it. When he's riding it, it tends to struggle when he opens the
throttle between 3000 and 4500 rpm (or attempts to pass through this
range). If he tries to accelerate in this range, the engine stutters,
loses power and often dies. If he winds the thottle on *very* slowly,
it's OK.

As long as the bike is kept out of this range, it runs flawlessly.

If the bike is *stationary*, it has no running problems whatsoever - you
can take the engine throughout the entire rev range without a single
stutter.

Any idea what the problem might be - and why it would only occur when
the bike is moving?

 

The behavior is not linked to the bike being stationary or moving,
it is whether the engine is under load or not. I really have no
idea what the root cause of the problem is, though, sorry.

 

I would say it is fuel starvation or vacuum leak. A lot of the time these
problems tend to only appear under load with throttle open so diagnosing in
the garage is hard. Check for cracks, loose calmps etc. A mechanic with a
dyno will sort out the problem quickly though. I've gone mad trying to find
vacuum leaks in the past.

 

That'd be my first guess. Second would be a dying computer module.
My 1100 Virago had similar symptoms.

Debbie could verify that it's 'under load' instead of just 'when
moving' by putting the bike in neutral while moving and see if it
rev's as it should.
--
gburnore at DataBasix dot Com
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Can you be more specific about just what the problem is?

 

I certainly hope that the OP has solved the problem with his/her
Yamaha, as the original message is more than a year old...

 

Bizarre. I didn't even look at the date on the message. lol