748cc to 1004cc with 749cc crank?

[gsx-f__k]

Hi,

I'm planning to build 955cc engine out of 748cc by swapping crank from 749cc and overbore from 73mm to 79mm.

Can 748cc be bored to 79mm? I know older 749cc can't, just 91-92 has enough material.

I have sleeves from B12 I could use if they are shortened.

I know I can get 79mm pistons from JE, but they are bit pricy, looking for cheaper alternative method.

I have B12 79mm pistons, but they have 20mm wrist pin.

Does anyone know wich pistons would work?

 

EDIT:

This project seems to have another issues too..

See below.

Edited February 2, 2016 by gsx-f__k_UH13

[Gixer1460]

You may have to siamese the liners as the overbore will probably break through between 1-2 and 3-4? Then if they get bored to 81mm ! ! ! you could use Gen 2 Busa pistons which have 18mm pins? That'll be well oversquare.

[gsx-f__k]

B12 sleeves OD is around 85mm and there is 15mm gap between 1-2 and 3-4 and 40mm between 2-3.

 

Edit:

I talked with my machinist guy and it seems we decided to go with B12 sleeves, K8 Hayabusa pistons and long stroke crank.

Result would be 1004cc.

IIRC, K8 Hayabusa pistons would be around 2mm lower than gen1, right?

Edited January 24, 2016 by gsx-f__k_UH13

[Gammaboy]

I think ZX9 pistons are 79mm with an 18mm pin? I've got a set at home somewhere...

 

[cregnybaa]

Don't think zx9 are 79mm not from the c model on anyway but bmw s1000 might be worth having a look at they are 80mm.

[tabby59]

Don't forget about probably needing the cases to be bored also.

 

[canamant]

How are you going to put a long stroke 749 crank in 748 cases ?  The mains are different if my memory serves me right.

 

[slingy1157]

Mains are the same i thought,  but big ends are different though so you cant put the short stroke rods onto the longstroke crank. And maybe the teeth number on the crank so may need the clutch basket to match the crank. I looked into all this when i had my 750 turbo.

[cregnybaa]

Ant is right mains are 33mm  from memory.

[gsx-f__k]

On 29.1.2016 at 0:01 AM, tabby59 said:

Don't forget about probably needing the cases to be bored also.

 

Yes, I'm aware of this, few millimeters must be bored from top case.

On 30.1.2016 at 0:38 AM, slingy1157 said:

Mains are the same i thought,  but big ends are different though so you cant put the short stroke rods onto the longstroke crank. And maybe the teeth number on the crank so may need the clutch basket to match the crank. I looked into all this when i had my 750 turbo.

I'm going to use long stroke rods and I was aware of clutch issue too, teeth number should be different IIRC.

I thought I'd look for possibility to use K4 GSX750R or GSX1000R clutch mod, with B12 engine it is possible.

On 27.1.2016 at 3:01 AM, cregnybaa said:

Don't think zx9 are 79mm not from the c model on anyway but bmw s1000 might be worth having a look at they are 80mm.

Thanks for tip, I'll look into this.

[gsxr884]

Look on the Wiseco website plenty of info on there re piston size and pin dia  http://www.wiseco.com/

 

[FJD]

interesting topic there, so you are sure you can swap the crank from 748 + 749 cc ?

[cregnybaa]

25 minutes ago, FJD said:

interesting topic there, so you are sure you can swap the crank from 748 + 749 cc ?

Long stroke mains are 33mm, short stroke mains are 34mm if I remember correctly, 1100 crank will go into short stroke cases I have done it.

[gsx-f__k]

5 hours ago, cregnybaa said:

Long stroke mains are 33mm, short stroke mains are 34mm if I remember correctly, 1100 crank will go into short stroke cases I have done it.

http://oldskoolsuzuki.info/archives/404

3. A 750R-88/89 top end on a 750R 90/91 bottom end (or 86-87 bottom).
This is a bit more difficult, since it needs some more work and imagination then the plain
assembling of a B6/750.
The 750R-88/89 have a bigger bore, so the idea of this combo is to increase the capacity of the
engine.

(You could also take this combo the ‘other way around’, and fit a 90/91 crankshaft + clutch in a 88/89 engine.)
 

Since the dimensions of the heads are not the same, it is not possible to only put the 88/89 pistons+cylinders on the 90/91; the head of the 90/91 would not fit the cylinder block.

So the complete 88/89 top has to be installed on the 90/91. The wrist pins on the 90/91 are 18mm, on the 88/89 20mm,
so the small end of the 90/91 rods have to be bored to 20mm.

Now the whole thing could mechanically be assembled, but since the stroke of the 88/89 is smaller, the height of the cylinder block is smaller.
This has to be compensated by putting a spacer under the cylinderblock. (This spacer would very roughly have to be 1/2 x the difference in stroke, but the only right way is to measure/calculate the
compression.

I took this from service manual:

GSX750R

Crankshaft and bearings

Main bearing oil clearance
Standard 0.020 to 0.044 mm (0.0008 to 0.0017 inch)
Maximum 0.080 mm (0.0031 inch)

Main bearing journal diameter 31.976 to 32.000 mm (1.2589 to 1.2598 inch)

Crankshaft thrust clearance
1985 through 1987
Standard 0.04 to 0.18 mm (0.002 to 0.007 inch)
Maximum 0.25 mm (0.010 inch)
1988 and 1989 0.05 to 0.13 mm (0.002 to 0.005 inch)
1990 on 0.055 to 0.110 mm (0.0022 to 0.0043 inch)

Right thrust bearing thickness
1986 and 1987, 1990 on 2.425 to 2.450 mm (0.0954 to 0.0964 inch)
1988 and 1989 2.42 to 2.44 mm (0.095 to 0.096 inch)

Connecting rod side clearance
Standard 0.010 to 0.020 mm (0.004 to 0.008 inch)
Maximum 0.030 mm (0.012 inch)

Connecting rod big end thickness 20.95 to 21.00 mm (0.825 to 0.827 inch)
Crankpin width 21.10 to 21.15 mm (0.831 to 0.833 inch)

Connecting rod bearing oil clearance
Standard 0.032 to 0.056 mm (0.0013 to 0.0022 inch)
Maximum 0.080 mm (0.0031 inch)

Connecting rod journal (crankpin) diameter 33.976 to 34.000 mm (1.3376 to 1.3386 inch)
Oil pressure (60 degrees C/140 degrees F) 2.97 to 5.86 bars (43 to 85 psi)
Crankshaft runout 0.05 mm (0.002 inch)

 

GSXF 750

Crankshaft and bearings

Main bearing oil clearance
Standard 0.020 to 0.044 mm (0.0008 to 0.0017 inch)
Maximum 0.080 mm (0.0031 inch)

Main bearing journal diameter 35.976 to 36.000 mm (1.4163 to 1.4173 inch) <-- THIS CAN'T BE RIGHT, SHOULD BE SAME AS GSX750R 88-89?
Crankshaft thrust clearance 0.05 to 0.13 mm (0.002 to 0.005 inch)
Right thrust bearing thickness 2.42 to 2.44 mm (0.095 to 0.096 inch)

Connecting rod side clearance
Standard 0.010 to 0.020 mm (0.004 to 0.008 inch)
Maximum 0.030 mm (0.012 inch)

Connecting rod big end thickness 20.95 to 21.00 mm (0.825 to 0.827 inch)
Crankpin width 21.10 to 21.15 mm (0.831 to 0.833 inch)

Connecting rod bearing oil clearance
Standard 0.032 to 0.056 mm (0.0013 to 0.0022 inch)
Maximum 0.080 mm (0.0031 inch)

Connecting rod journal (crankpin) diameter 35.976 to 36.000 mm (1.4163 to 1.4173 inch) <-- THIS CAN'T BE RIGHT, SHOULD BE SAME AS GSX750R 88-89?
Oil pressure (60 degrees C/140 degrees F) 2.97 to 5.86 bars (43 to 85 psi)
Crankshaft runout 0.05 mm (0.002 inch)

 

There must be error at service manual because:

http://www.partzilla.com/parts/detail/suzuki/SP-12229-06B10-0A0.html

1988 GSX-R750L CRANKSHAFT (MODEL J-K)

1989 GSX-R750L CRANKSHAFT (MODEL J-K)

1992 GSX750FT CRANKSHAFT

I'll have to check these measurements as soon as my new crank and rods arrive.

[Oilyspanner]

Pretty certain that the short stroke engines - GSXR750J/K and up to '99 GSX750Fs had the same size mains as the 1100s - 36mm. The long stroke 750s had smaller sized mains, the small end is smaller too as you've noticed. You can put an 1100 crank in the short stroke 750 cases (don't know how the primary drive/clutch works out, change to suit I guess), but you can't drop the long stroke 750 crank assembly into the short stroke cases obviously.
My Haynes manual has all 750Rs lumped together for mains sizes, this isn't right - especially as it's got the GSX750F listed as 36mmmains, like the 1100s, this is correct. The short stroke engine was designed to rev hard, so Suzuki upped the big/small end sizes to cope.

 

[gsx-f__k]

3 hours ago, Oilyspannerlyspanner said:

Pretty certain that the short stroke engines - GSXR750J/K and up to '99 GSX750Fs had the same size mains as the 1100s - 36mm. The long stroke 750s had smaller sized mains, the small end is smaller too as you've noticed. You can put an 1100 crank in the short stroke 750 cases (don't know how the primary drive/clutch works out, change to suit I guess), but you can't drop the long stroke 750 crank assembly into the short stroke cases obviously.
My Haynes manual has all 750Rs lumped together for mains sizes, this isn't right - especially as it's got the GSX750F listed as 36mmmains, like the 1100s, this is correct. The short stroke engine was designed to rev hard, so Suzuki upped the big/small end sizes to cope.

So, after all it seems i have at least one more problem..

Feels silly to even ask, but could this be sorted out just with playing with bearings?

Edited February 2, 2016 by gsx-f__k_UH13

[Gixer1460]

No!

[gsx-f__k]

Hi guys,

after some setbacks, this is coming to sort out.

Atleast when UPS finds my pistons from Germany.

[Oilyspanner]

Are you going with liners and big pistons - 884/907 ? - they're good motors when done well.

[gsx-f__k]

11 hours ago, Oilyspanner said:

Are you going with liners and big pistons - 884/907 ? - they're good motors when done well.

I got a 91 long stroke bottom and short stroke top is being bored to accept B12 sleeves and will be bored 81mm to accept gen2 busa pistons.

I have a question:

Actual dimensions of crankshaft and rod bearings ID/OD and bearing type?

Green :

Black :

Brown :

Yellow: 

Why I'm asking is, I'd get new ones directly from bearing supplier to save some money, for example clutch axle bearing: Suzuki part 49€ vs. supplier 6.82€.

[Gixer1460]

Never known a bearing supplier have white metal shell bearings - such a specialist item so good luck.

[beam]

gsxr750m 1991

 

[gsx-f__k]

I just heard same from another forum, well it doesn't cost anything to ask when I get clutch bearing.

Thank you beam!!

[bluedog59]

+1 on that. If anybody has the serial numbers for any of the bearing that we pay for the nose for, please post them up

Maybe they should be listed in a "sticky".