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Gsxr750 hybrid engine info required


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55 minutes ago, GSXR4814 said:

Hmmm.....my 73mm barrels and pistons turmed up today.

They were listed as 1992 GSX750F.

My current 70mm barrels are approx 75mm high...new 73mm ones are 69.5., these dimensions are approx as the battery is flat in my vernier so using a tape measure.

Little ends are bigger and centre of little end to top of piston is greater by about 3mm???

Does this sound right?

I didn't think 1992 GSX750F was short stroke which these parts seem to be?

how do you think they made the 750f  748cc with 3mm larger bore than long stroke 749cc motors...

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I think what i started with was a bandit 600 bottom end, cases, crank and rods  with a complete gsxr or maybe gsxf 749 top end, barrels pistons and head, head is rocker and screw type.

the plate i cant made cheaply and easily enough, the rods however are not going to be so easy.

Anybody know what diametre the little ends are on an RF900 as i see they also have 73mm pistons.....i would assume they would also be bigger but you never know!!!

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RF 900 rods little and big ends are the same as the short stroke rods 19 and 36mm

The spacer plate should theoretically be half the increase in stroke (@5.8mm from memory) assemble the motor without base gaskets and check piston to deck height this will be the size of the spacer plate/s/gaskets needed.

My mechanic did a top job milling a spacer plate out of 6mm 6061 Al and was set up  with zero deck height and no base gaskets.

Cometic (I've heard) and Orient express (I asked them they make them to order) also do spacer plates can check by contacting them

WP_20180907_17_28_13_Pro.jpg

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6 hours ago, Lachie04 said:

RF 900 rods little and big ends are the same as the short stroke rods 19 and 36mm

The spacer plate should theoretically be half the increase in stroke (@5.8mm from memory) assemble the motor without base gaskets and check piston to deck height this will be the size of the spacer plate/s/gaskets needed.

My mechanic did a top job milling a spacer plate out of 6mm 6061 Al and was set up  with zero deck height and no base gaskets.

Cometic (I've heard) and Orient express (I asked them they make them to order) also do spacer plates can check by contacting them

WP_20180907_17_28_13_Pro.jpg

Do you think he fancies making another one?

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13 hours ago, GSXR4814 said:

Do you think he fancies making another one?

Yeah nah I don't think that would happen. I don't even know if he's back at work after spending 2-3 months in Hospital after being rear ended on the track.

Your much better off sourcing this locally and or checking with orient express racing they came back to me quickly when I inquired about their spacer plates just takes them about a week to have them made up.

Or APE on the link before

Otherwise there maybe someone else on here who has done a stroker engine could give you some suggestions

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  • 2 months later...
On 6/17/2019 at 10:01 PM, dupersunc said:

you'll need either  a short stroke 748 ,  or any of the big block 1100 heads to go with the 748  block.

A long stroke 749 or b6 head won't work as the cam chain tunnels don t  match up.

Any idea if they could be modified to fit? I only ask as the 750 one on has been nicely ported etc.

Getting ready to start attempting to put mine back together shortly.

 

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On 6/19/2019 at 7:06 AM, Lachie04 said:

Yeah nah I don't think that would happen. I don't even know if he's back at work after spending 2-3 months in Hospital after being rear ended on the track.

Your much better off sourcing this locally and or checking with orient express racing they came back to me quickly when I inquired about their spacer plates just takes them about a week to have them made up.

Or APE on the link before

Otherwise there maybe someone else on here who has done a stroker engine could give you some suggestions

What did you use camchain wise mate? Think i've got all the other pieces of the jigsaw lol

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On 9/19/2019 at 7:55 AM, GSXR4814 said:

Any idea if they could be modified to fit? I only ask as the 750 one on has been nicely ported etc.

Sort of related - I built a GSXR head onto GSX barrels and gasket around the chain tunnel  was marginal so we welded in some 6mm ali before it got decked to provide the extra real estate for copper gasket. Oh and due to the stroke difference we had to add two extra links to the cam chain - normal roller not Hyvo though!

Edited by Gixer1460
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  • 3 weeks later...

I assume those that have done this exhausted all lines of enquiery re correct length rods before sticking with the 600 bandit items?

I've ruled a few out, but if anyone can add any to the 'doesnt' fit' list that would be handy to save me covering stuff thats already been tried. Ta

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  • 1 month later...
On 6/18/2019 at 10:36 AM, Lachie04 said:

RF 900 rods little and big ends are the same as the short stroke rods 19 and 36mm

The spacer plate should theoretically be half the increase in stroke (@5.8mm from memory) assemble the motor without base gaskets and check piston to deck height this will be the size of the spacer plate/s/gaskets needed.

My mechanic did a top job milling a spacer plate out of 6mm 6061 Al and was set up  with zero deck height and no base gaskets.

Cometic (I've heard) and Orient express (I asked them they make them to order) also do spacer plates can check by contacting them

WP_20180907_17_28_13_Pro.jpg

What cams are you using?

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17 hours ago, GSXR4814 said:

What cams are you using?

 

On 9/19/2019 at 9:03 PM, Lachie04 said:

Used the Hyvo chain as the only option to match the crank Hyvo sprockets slotted and fitted to the 89 Cams. Pretty sure B6 use Hyvo

Check tension on the chain as we ended up taking a link out not sure why that happened as I hadn't heard of it before (just one of those things). 

Dot head and 89 spec GSXR dot cams with Hyvo sprockets 

From the notes the initial setup resulted in 105 deg exh  and 108deg  inlet the inlet sprocket was slotted back to 104

But that could vary project to project  as before check check & check everything

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13 hours ago, Lachie04 said:

 

Dot head and 89 spec GSXR dot cams with Hyvo sprockets 

From the notes the initial setup resulted in 105 deg exh  and 108deg  inlet the inlet sprocket was slotted back to 104

But that could vary project to project  as before check check & check everything

Thanks boss

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