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TOPIC: 84 GPZ 750 A series

84 GPZ 750 A series 12 Jan 2020 23:42 #817010

  • The_Fixer
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Hi guys.

Was given a what I think is an A3 model a couple of years back, had been sitting under a tarp against a building for 5-6 years.

Have rebuilt the forks and unistrut setup, blasted and painted the frame.

Decided to pop the head off and have a look inside. The oil I drained was quite clean and the motor is very clean inside. Cleaned out the starter and found some new brushes and bearings. Brushes were kind of awkward to get, they only seem to sell the 4 brush setup and mine is a 2 brush one. Had to really shop around, using the vernier measurements and specs - got them from a Suzuki parts list.

Anyway, I measured the piston to wall gap, pecs says 0.06 mm, mine are 0.6mm. Looks like a rebore needed.

Parts guys seem to only want to sell the 810 bore kit, but I and a bit cautious of that, in case it leaves me with nowhere to go in case of a future next rebuild.

A mate of mine has an 80 Z1000 MK II. He's had it tricked up a bit and was advised by his mechanic not to go for the full blown oversized kit. Reckons the bike don't seem to get their best from it and going up just a little bit makes the engine even better and you'll still have a rebuild left in it.

Anyone have any knowledge to share over a rebuild? I'm more interested in a good machine over max speed/power think (getting a bit past that stage now).

I had new bushes and grommets machined up to replace the crapped out ones in the unistrut suspension. Only cost me about $220 to completely rebuild that including bearings and seals.

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84 GPZ 750 A series 13 Jan 2020 04:41 #817016

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OEM oversized pistons are discontinued. You may be able to find a set from ebay but the path of least resistance is an 810 kit. Cruzinimage has a kit for a crazy low price that's actually pretty decent. I wouldn't worry about the over bore since old used cylinders are plentiful on ebay. And speaking of that, if you get lucky you may even be able to find a good used cylinder. You never know.

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Last edit: by Nessism.

84 GPZ 750 A series 13 Jan 2020 21:40 #817064

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Damn! Does not ship to Australia! That's a blow...

Thanks Nessism.
The big spend on the project is officially on hold for a spell whilst I take care of other things.
Otherwise the elbow grease side will progress slowly.

In the meantime, I'm just researching things and getting options together so a decision can be made later.

Do I need to re jet the carbies? still in the process of restoring them as well.

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84 GPZ 750 A series 14 Jan 2020 16:51 #817083

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I wish us 900 guys could go to a similar CC increase for that cheap
1976 KZ 900 A4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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84 GPZ 750 A series 14 Jan 2020 22:59 #817098

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So far, I've found a few kits available here (even from the states) for around $1100. Mostly Wiseco stuff.

Pretty steep. I'll keep looking around and see what turns up...

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84 GPZ 750 A series 16 Jan 2020 09:22 #817208

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Nessism wrote: OEM oversized pistons are discontinued. You may be able to find a set from ebay but the path of least resistance is an 810 kit. Cruzinimage has a kit for a crazy low price that's actually pretty decent. I wouldn't worry about the over bore since old used cylinders are plentiful on ebay. And speaking of that, if you get lucky you may even be able to find a good used cylinder. You never know.


How munch longer will a Wiseco piston set keep going? Or can it be the same? Only increase in compression only differens?
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine
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84 GPZ 750 A series 16 Jan 2020 10:43 #817209

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>>> "Anyway, I measured the piston to wall gap, pecs says 0.06 mm, mine are 0.6mm. Looks like a rebore needed.
Parts guys seem to only want to sell the 810 bore kit, but I and a bit cautious of that, in case it leaves me with nowhere to go in case of a future next rebuild."

Kawasaki supplied two over size pistons for most models, usually 1mm (.039"), check with Kawasaki dealer.
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84 GPZ 750 A series 16 Jan 2020 10:48 #817210

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gordone wrote:
How much longer will a Wiseco piston set keep going? Or can it be the same? Only increase in compression only differens?

There is no comparison between the Wiseco and Cruzin image pistons.
You get what you pay for.
Wiseco are high performance forged pistons and the Cruzin image which are made in Taiwan are cast copies of the stock originals.
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Last edit: by zed1015.

84 GPZ 750 A series 16 Jan 2020 16:40 #817222

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If you google Cruzinimage pistons there is quite a bit of positive information. I don't think they measure up to Wisco but if you are not racing and money is a factor they will likely serve just fine for a good long while.

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84 GPZ 750 A series 16 Jan 2020 16:41 #817223

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73z1 wrote: >>> "Anyway, I measured the piston to wall gap, pecs says 0.06 mm, mine are 0.6mm. Looks like a rebore needed.
Parts guys seem to only want to sell the 810 bore kit, but I and a bit cautious of that, in case it leaves me with nowhere to go in case of a future next rebuild."

Kawasaki supplied two over size pistons for most models, usually 1mm (.039"), check with Kawasaki dealer.


OS pistons are long out of production. I think they would be a great option if available, but that's a huge if.
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84 GPZ 750 A series 17 Jan 2020 02:56 #817243

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The winesco 810 I installed had higher compression then orginal.

Is it a cheap way of increase performance or is it cheaper ways to increase the same in performance?

Just ask so we compare on the same «basement».
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine

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84 GPZ 750 A series 17 Jan 2020 11:01 #817273

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Higher compression alone wont make a big difference in performance, however higher compression will let you run hotter cams effectively, and with port work/carbs it will make a big difference. Any one of those changes will not make a big difference alone but together they will.
-Vic
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'78 kz1000 LTD long term project

'80 kz750G project
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84 GPZ 750 A series 17 Jan 2020 13:11 #817293

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DoctoRot wrote: Higher compression alone wont make a big difference in performance, however higher compression will let you run hotter cams effectively, and with port work/carbs it will make a big difference. Any one of those changes will not make a big difference alone but together they will.


I understand, so install hotter cam will have a large increase in combination with higher compression.

So by a exstra block for spare is a good dection then, so you backup if you borr up to 810 and need a new borr in the future.
1981 KZ650-D4, with 1981 z750L engine (Wiensco 810 big bore).

Project:
www.kzrider.com/forum/11-projects/607213...sr-1981-z750l-engine
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84 GPZ 750 A series 17 Jan 2020 13:32 #817300

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You will need a good port Job first to get more power on your 810 ccm Setup. Ports are the bottle neck that has to be open first.
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84 GPZ 750 A series 17 Jan 2020 14:12 #817304

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The holy trinity of increasing power is increase compression/hot cam/ increased flow. Flow is carbs/porting/exhaust. advancing ignition can help as well if retarded to begin with
-Vic
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'78 kz1000 LTD long term project

'80 kz750G project

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84 GPZ 750 A series 17 Jan 2020 17:04 #817313

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A member here is selling a 67mm MTC piston kit for the 650. I "think" they would fit in a 750 but not positive. Does anyone know? The stock bore is 66mm so 67mm is a nice clean up bore and the liners will still have lots of meat left over.

www.kzrider.com/forum/23-for-sale/612121...d-sprockets-and-jugs

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