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Z750e dropping to 2? Above 5k 02 Jul 2020 07:22 #829590

  • zed810
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Hello, I'm trying to put my old z750 back on the road but I'm having running issues, it starts and runs great hot or cold but when riding above 5k revs it miss and pops almost like it's running out of fuel, the specs are:
750 with 810 kit
Web cams
Bs34s 140 mains and 40 pilots
Dyna s ignition
Green dyna coils and Taylor leads
Ramair offset foam filters.

So far I have:
Cleaned and set carbs 3 times (spotless)
Checked advance mechanism
Checked voltage at coils (11v)
Lifted needles to see if any improvement/degradation
It's really starting to piss me off! It ran faultlessly prior to putting off road and the only change was removing the cheap pod filters for another bike and replacing with the ramair one's.
1981 z750e1 gpz 750a1 tank and side panels 810 bore kit web cams mikuni bs34 vance and hines pipe

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Z750e dropping to 2? Above 5k 02 Jul 2020 07:53 #829595

  • loudhvx
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Look at the filters on the inside where they attach to the carbs. See if the rubber may possibly be blocking the vent for the CV system on the carbs. This is a common problem with some pods. It's just a matter of finding the right combination of pod design with the carbs in question (if this is nfact what's limiting your revs). It may be possible to not install the pods all the way and leave room for air to access the CV vent. That might also explain why it's only affect two carbs, if that's what you suspect.

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Last edit: by loudhvx.

Z750e dropping to 2? Above 5k 02 Jul 2020 08:40 #829604

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Sorry I meant to say that I'd checked this and clearance them.
1981 z750e1 gpz 750a1 tank and side panels 810 bore kit web cams mikuni bs34 vance and hines pipe

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Z750e dropping to 2? Above 5k 02 Jul 2020 09:17 #829609

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I have just checked the coils and seem to be OK and checked the dyna s unit and it also appears to be working.
In fact the only parts I haven't checked/replaced are the plugs.
1981 z750e1 gpz 750a1 tank and side panels 810 bore kit web cams mikuni bs34 vance and hines pipe

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Last edit: by zed810.

Z750e dropping to 2? Above 5k 02 Jul 2020 12:21 #829617

  • F64
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Are 2 cylinders cutting out at exactly the same time?
81-KZ440-D2.
Louis Dudzik's GM HEI ignitor conversion installed 2015 s3.amazonaws.com/gpzweb/Ignition/GPZgmHEImod.html
Motogadget m-unit blue installed 2017.
LIC, NY

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Z750e dropping to 2? Above 5k 02 Jul 2020 12:25 #829618

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Hards to say exactly what is happening, I'm not pulling ht leads off while riding, I've pulled the choke on and off and no difference which leads me to electrical.
1981 z750e1 gpz 750a1 tank and side panels 810 bore kit web cams mikuni bs34 vance and hines pipe

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Z750e dropping to 2? Above 5k 02 Jul 2020 13:37 #829624

  • F64
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it would be nice to have four tiny timing lights with inductive pickups.
hmmmm
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Louis Dudzik's GM HEI ignitor conversion installed 2015 s3.amazonaws.com/gpzweb/Ignition/GPZgmHEImod.html
Motogadget m-unit blue installed 2017.
LIC, NY

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Z750e dropping to 2? Above 5k 02 Jul 2020 18:05 #829647

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Not an easy one without datalogging.
I'll research it more tonight.
Can you get it to miss bringing it up to 5K in neutral or is it only under load?
You may be able to get new plugs and do a plug chop at 5K under misfire.
or just hookup a timing light to one plug wire and drive around and see if the light cuts out. Stop..move to another wire and drive around.
81-KZ440-D2.
Louis Dudzik's GM HEI ignitor conversion installed 2015 s3.amazonaws.com/gpzweb/Ignition/GPZgmHEImod.html
Motogadget m-unit blue installed 2017.
LIC, NY

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Last edit: by F64.

Z750e dropping to 2? Above 5k 03 Jul 2020 11:03 #829692

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It appears to rev crisply in neutral.
1981 z750e1 gpz 750a1 tank and side panels 810 bore kit web cams mikuni bs34 vance and hines pipe

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Z750e dropping to 2? Above 5k 03 Jul 2020 12:33 #829698

  • Nessism
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Maybe try actuating the choke while riding to see if that helps. Another thing to try is to remove the pods all together.

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Z750e dropping to 2? Above 5k 03 Jul 2020 12:33 #829699

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ok...so you have to test this bike while riding.
Have you changed the plugs yet?
81-KZ440-D2.
Louis Dudzik's GM HEI ignitor conversion installed 2015 s3.amazonaws.com/gpzweb/Ignition/GPZgmHEImod.html
Motogadget m-unit blue installed 2017.
LIC, NY

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