YZF750 problem: STILL...
Angel Palacios 2410 6035
Well,
After installing a MICRON pipe, jetting the carbs (from 122.5 to 126 main),
KN air filter, now I have an increase of 7-8 HPs, a louder motorcycle,
BUT, (I WAS AFRAID OF THIS) my bike STILL have the same problem:
big hesitation between 7-8K rpm, and "pulses" @ high rpm, 4th gear
(you can REALLY feel the bike pulsing/jumping)
"pulses" BAD in 5th gear
I HAVE NO 6th gear!! there is no performance what-so-ever...
I can't even cruise 60-70mph in 6th gear
Now, check this out:
First ride in the morning (engine is just warming up), I can get good
performance out of the bike most of the times, but only for that first
"take me up to 140 mph".
I remember, the first time I felt the hesitation, the OIL light went on
at the same time the engine was quitting on me. I thought It was the
electronic engine cut off; wrong. Added a bit more oil (which I wasn't running
low), and it stopped doing it for a while (I think it did stop, but I'm not
sure about when I started having the problem after this, since I only ride
the bike over the weekends when there's no rain).
Did some brainstorming and trials using a Dyno:
- the engine with a jumper in the radiator' fans: no difference
- completely disconnected the alarm system: no difference
- cooled down the engine: a bit better, still pulsing
What else can I do here??
I'm already calling MICRON, Yamaha, and some other folks... waiting on them.
I'm taking the "brain box" to the Yamaha dealer the get it checked, but,
so far, I'm NOT A HAPPY COSTUMER since the seem not to care.
I will try for two more weeks to get this resolve.... After that, there will
be a '94 YAMAHA YZF750FR for sale real cheap....
Any ideas?? Thanks for the input...
A.L. Palacios
(I want a fast toy, not a headache)
KimDN
When you say you jetted the carbs by installing a bigger main jet, did you
install an aftermarket jet kit as well? That would include different
needles, maybe pilot jets, etc. Also did you adjust the mixture screws?
If you didn't do these things than they will surely help.
A friend just bought a new YZF750 a couple of days ago, and had a bad
hesitation problem. One of the spark plugs turned out to be defective.
Changing the plugs helped a lot, but he still needs to do some
re-jetting.....
Another possiblility would be that your cam timing is way off. This is
unusual to happen straight from the factory, but is does happen sometimes.
Your best bet would be to find out the best cam timing specs from someone
like Vance and Hines or anyone else who races the YZFs competitively, and
have your cams dialed in. Even if that isn't the problem it will improve
your performance. Good luck--
Aloha,
Kim Nakashima "That's only a 250?"
THRRA #9
1992 Yamaha TZ250
Jim Brewer
> Your best bet would be to find out the best cam timing specs from someone
>like Vance and Hines or anyone else who races the YZFs competitively, and
>have your cams dialed in.
That's good advice. A.L., if you email me (j...@hpesjjb.fc.hp.com), I'll
send you the settings for my YZF. It makes 110 HP with a Yosh pipe and
has a good, linear power band.
-Jim
Patrick Ludwig
>After installing a MICRON pipe, jetting the carbs (from 122.5 to 126 main),
>KN air filter, now I have an increase of 7-8 HPs, a louder motorcycle,
>BUT, (I WAS AFRAID OF THIS) my bike STILL have the same problem:
Now that you've invalidated any means to deal w/this problem
thru the dealer network you should probably put a for-sale sign
on it now. Of course who's gonna buy it running like that?
BTW, don't remove the EXUP motor. It's a closed loop system
& removing it will cause many problems. You'll find it on
Tom Kipp's (SS)race bike as well as mine. I'd recommend you put the
OEM exhaust & jetting back on & use your head when dealing with
Yamaha. I had the same problem, my dealer also had the same problem
on his personal yzf750. We resolved ours thru normal channels. Call
up the Yamaha service chain. The resolution may be all new '96 carbs.
p
yzf750
ccs #26/wera #16
Patrick Ludwig
>I remember, the first time I felt the hesitation, the OIL light went on
>at the same time the engine was quitting on me. I thought It was the
>electronic engine cut off; wrong. Added a bit more oil (which I wasn't running
>low), and it stopped doing it for a while (I think it did stop, but I'm not
>sure about when I started having the problem after this, since I only ride
>the bike over the weekends when there's no rain).
BTW, my oil level sensor failed mid-season last year. It has failed on both
of my Supersport motors & has NO feedback to the cpu. I'm curious what your machine
made HP wise post breaking the warranty?
p
KimDN
That should help a whole bunch.