GS400/500 Gr650 Hybrid engine

[WolfTechnics]

Wow, very interesting and awesome news for those wanting to build a maxed out big bore 400/425! This also could mean the potential of running GS1000/1100G pistons in a big bore GS400...

I'd be very interested in the GR650 pistons and head, but am concerned about the modifications needed to the crankcase to move the inner cylinder studs to match the GS450/500/GR650 stud pattern...
The GS650 4-cylinder and the GR650 2-cylinderby far are the best head and piston design on any 2-valve per cylinder GS ever built... As they use the bathtub/kidney bean shaped combustion chamber to induce the modern swirl concept into the air/fuel mixture that the TSCC 4-valve per cylinder 16v GS big fours really pioneered - a drastically better combustion design.

The stud spacing has already been modified on the crankcase Chuck!, maybe one day I'll restore all the photo's in this topic but for now take my word for it. It involves machining aluminium plugs that are screwed into the stud holes using the strongest epoxy glue one can find and then re-drilling the holes. It will all be shown once I start building a mock-up engine.

I don't claim my solution regarding the studs is any good mind you...if the cylinder block is lifted during WOT I'll know it isn't.

[WolfTechnics]

Small update.

I received the parts I ordered.

I got SKF IR 28x32x20 bearing races, they will have to be modified.
Two oil feed holes will need to be drilled, as shown in the drawing below.
It's hard to measure accurately but they should be spaced 88 degrees apart from each other.
Diameter of the holes is about 2.6mm, with a small chamfer.




I did some math using a calculator and the press fit is a bit on the loose side, 0.008mm interference.
According to the calculator it should take about 26Nm to rotate the sleeve around the big-end journal, I think it will be fine.
The conrod doesn't really produce a torque around the journal, only a radial force aimed at the center-line of the journal.



Got myself some appropriate KT323920-C3-IKO bearings as well.


The next step now is to find a company that can drill into the bearing races, and figure out how I will press them onto the journals.
I need to think about how to put the sleeve o the journal lined up with the oil holes and centered between the counterweights.
And, then what to do about the brass washers that control the conrod sideplay?
Probably I will utilize small brass spacers with an 32mm OD in between the bearing sleeve and the crankshaft counterweights.
I will use the GS1000 32mm ID washers to control conrod sideplay.

[grcamna2]

Following along on your work.
I have an 81' GS450E which I plan to install a GS500E cylinder block w/ custom pistons.

[WolfTechnics]

Following along on your work.
I have an 81' GS450E which I plan to install a GS500E cylinder block w/ custom pistons.

Welcome!

The stock GS500e pistons should fit that motor, or do you plan to increase C/R ratio as well with custom pistons?
It's a real PITA that the exhaust exit angle is different on the GS500 heads, otherwise you could have used those.

If you are going to source custom pistons, might as well try to find a GR650 cylinder head...

[GregT]

If you are going to source custom pistons, might as well try to find a GR650 cylinder head...

Don't. You'll drop a huge amount of compression with a 650 head on a small motor.

There's nothing wrong with the 450 head. A mild port job and a recut of the valve seats is all that's needed.

[WolfTechnics]

Don't. You'll drop a huge amount of compression with a 650 head on a small motor.

There's nothing wrong with the 450 head. A mild port job and a recut of the valve seats is all that's needed.

True, but that issue is mitigated with custom pistons. Hence, why I said "if you are going to source custom pistons".
I take it, "custom pistons" means having them made by CP Carillo or equivalent.

[grcamna2]

True, but that issue is mitigated with custom pistons. Hence, why I said "if you are going to source custom pistons".
I take it, "custom pistons" means having them made by CP Carillo or equivalent.

Yes,I plan to have a pr. of custom pistons made;I want to have the piston maker form the dome to be exactly the same shape as the OEM Suzuki dome(considering the low quality of pump gasoline out here in Ca.)and going from 71mm up to 74.25mm using the 450 head and the same dome shape(and stock 450E exhaust)may give me almost 10:1 CR?,which is enough for this street bike.
I was quoted a price by Terry Stewart(CP Carillo)of around $1600 for 4 pistons,but I just need two.. I'm considering calling JE Pistons also.

[WolfTechnics]

Yes,I plan to have a pr. of custom pistons made;I want to have the piston maker form the dome to be exactly the same shape as the OEM Suzuki dome(considering the low quality of pump gasoline out here in Ca.)and going from 71mm up to 74.25mm using the 450 head and the same dome shape(and stock 450E exhaust)may give me almost 10:1 CR?,which is enough for this street bike.
I was quoted a price by Terry Stewart(CP Carillo)of around $1600 for 4 pistons,but I just need two.. I'm considering calling JE Pistons also.

Thats a good plan, Can I follow your progress somewhere?

[grcamna2]

Thats a good plan, Can I follow your progress somewhere?

I haven't started a thread.
I see now that I should;during the process of getting the $ to have the machinist do the cylinders(pistons first) & head,get the pistons made,and the $ to get a pair of mild Mega-cycle camshafts($600+),the ones that are good for stock pistons and valve springs.
My goal is to have a good running '500' in a GS450E(450 bottom-end)frame that will hold together for many years w/o needing constant tweaking;I have a set of carbs. from an 83' GS450E,or I might get a set of GS500E carbs?
I'm thinking that I can use an OEM Suzuki GS500E head gasket on my GS450-head/GS500E cyl. engine?