GS Twins Wiki.

[Mekanix]

Hi, Hopefully I can make a collection of all the information I've come across for all twin engines and all mods.


I'm going to take up a bunch of posts and edit them as I think of things or as people suggest things. Its just to keep the first posts the most relevant for those searching in the future.

This is the format I'm thinking of:
It will probably get updated allot.

Engine
Bore: ID
Bore: OD
Stroke:
Wrist pin
Compression:
Base gasket:
Head Gasket:
Carb type:
Main jet:
Pilot:
Intake cam lift:
Exhaust cam lift:
Intake Duration:
Exhaust duration
Cam journal:
Intake valve:
Exhaust Valve:
Valve clearance:
Combustion chamber:
CFM

etc

Mods

Interchangeable parts.

[Mekanix]

Engine: GS250

I know very little about this one, Got to dig into the manual's , IF you know anything please post it and I'll update it.


Engine
Bore: ID 60mm
Bore: OD 68mm
Stroke: 44.2mm
Wrist pin: 16mm
Compression: 10.5:1
Base gasket:
Head Gasket:
Carb type: BS30SS
Main jet: 117.5
Pilot: 17.5
Intake cam lift:
Exhaust cam lift:
Intake Duration:
Exhaust duration
Cam journal:
Intake valve: 21mm
Exhaust Valve: 18mm
Valve clearance: 0.003- 0.005"

Combustion chamber:
CFM

[Mekanix]

Engine GS300



I know very little about this one, Got to dig into the manual's ,

IF you know anything please PM me it and I'll update it here.


Engine
Bore: ID 60mm
Bore: OD
Stroke: 49.6mm
Wrist pin 15mm
Compression: 10.5:1
Base gasket:
Head Gasket:
Carb type:
Main jet:
Pilot:
Intake cam lift:
Exhaust cam lift:
Intake Duration:
Exhaust duration
Cam journal:
Intake valve:
Exhaust Valve:
Valve clearance:
Combustion chamber:
CFM
Stock front sprocket: 16 tooth
Stock rear sprocket: 45 tooth

[Mekanix]

Engine GS400 (4 valve) (pre 1979)

76 to early 79 roller bearing engines with or without kickstart.
This engine is slightly longer than its successors because of the kickstarter assembly.
It cant just swap into a newer frame or vice versa. ( would have to modify the mounts.)
Very few parts interchange with newer model engines but there is lots in common with the gs750 and gs850s of the same years and a few of the newer years.

Bore: ID 65mm OD XXmm
Stroke: 60mm
Wrist pin: 16mm
compression: 9.5:1
Base gasket: 0.020 (0.5mm) gasket
Head Gasket: 0.043" (1.09mm) Fiber
Carb type: similar to BS34SS but with some differences in the bowl designes.
Main jet: XXXXXX
Pilot: XXXX
cam lift: Depends if you have an gs400 A, B or C model engine
MAXIMUM stock cam lift is XXXX when valve hits piston
Stock timing: Intake XXX Exhaust XXX degrees
Duration:
Cam journal: 22mm
Intake valve: XXmm
Exhaust Valve:XXmm
Combustion chamber cc
Valve clearance
CFM

Popular modification:

GS850 stock pistons.
Cometic head gasket to match, fiber is cheap and works just fine. No need for copper gasket.
Bore cylinders to match the pistons at 69mm
There will be 2mm left in the center of the cylinder liner.

The gs850 pistons are actualy designed so that the dome is lower and the compression ratio will stay the same as with your old pistons.
Although there are some high compression pistons for the 850, the stock ones will be good to go and have all the right clearences.
I think back then they had the 750 and designed a big bore kit that made it the 850 but kept the 750 head which is the reason for designing a piston that won't raise the compression.

Jump form 400 to 450

[Mekanix]

Engine GS400 ( 8 valve) (1980-1987 special model)

from late 79 to 88 this engine was produced with the half of the GSX750 in mind.
Flat top pistons with 4 valves per cylinder
Just about everyting from the cylinders down is interchangeable with the gs450 and 500's
Some slight differences came in after 83 but mostly just upgrades to address problems that came up.
There are two different heads, The good one came in after 83 and you can tell which is which because it has more bolts holding the valve cover on in the newer one.
Previous ones had issues cracking between the spark plug and exhaust seat.


There is also a GSX400 as well just to confuse things even more. It is a 4 cylinder that looks just like a mini 750 :P

For now this is the information for the twin cylinder model only.
Bore: ID 67mm
Bore: OD 75mm
Stroke: 56.6mm
Wrist pin
compression:10.5:1
Base gasket: 0.020 (0.5mm) gasket
Head Gasket: 0.043" (1.09mm) Fiber (rounded square combustion chamber shape gasket)
Carb type: BS34SS
Main jet: 117.5
Pilot: 42.5
cam lift: 0.270"
MAXIMUM stock cam lift is 0.378 when valve hits piston
Stock timing: Intake 104' Exhaust 106 degrees
Intake cam lift: 0.270
Exhaust cam lift: 0.270
Intake Duration: 262 degrees (Center @ 104 ATDC )
Exhaust Duration: 262 degrees (Center @ 106 BTDC )
Timing: 20 pins between 2 and 3
Cam journal: 22mm
Intake valve: 23mm
Exhaust Valve:20mm
Valve clearance: 0.03-0.06 between valve stem and screw.
CFM Stock is 64 (Per RapidRay) Maximum nearing 90 cfm with larger valves and porting (per RapidRay)


Lots of GS750 16 valve parts for the top end are interchangeable and are the same part numbers:
Valves
Pistons
Springs
Rockers
cam chain tensioner

Some 1100 parts can be used as well. Some even as upgrades, like valves, timing chain tensioner (APE ST1100).

Some GS500 parts can be swapped over for upgrades.
Such as:
Cylinder Blocks.
Oil pump gears (must swap both!!!) I'd recommend this for everyone though for more volume.
Entire Clutch basket and center. ( lighter, stronger, faster :P and more options for springs.
clutch two piece Pushrod (prevents wear)
clutch engagement cam, (it has a bearing drive instead of metal/plastic version which makes it feel smoother.)


MAC makes a 2 into 1 exhaust that will fit this. It also fits the 450's!

[Mekanix]

Engine GS 450 (1980+)


Was the end of the line for the small twins until the 500 came out in 88.
Not much changed from 81 to 88, except upgrades.
Seemed to be the biggest displacement they would go with those sleeves.
I find they like to leave the cylinder sleeves about 4mm thick in the center.


Bore: ID 71mm
Bore:OD 79mm
Stroke: 56.6mm
18mm Wrist pin
compression: 9.0:1
Base gasket: 0.020 (0.5mm) Gasket
Head Gasket: 0.043" (1.09mm) Fiber
Carb type: BS34SS
Main jet: 115
Pilot: 45
Intake cam lift: 0.330
Exhaust cam lift: 0.322
Intake Duration:
Exhaust duration:
Timing: 18 pins between 2 and 3 Remember that the GS400 with the 8 valves has 20 pins between the cam marks !! but the manual is confusing sometimes and gives both in different places. Actually its harder to find the GS400's timing.
Cam journal: 22mm
Intake valve: 36mm
Exhaust Valve: 30mm
Valve clearance: 0.003-0008"
CFM: Unknown.
Stock front sprocket: 16 tooth
Stock rear sprocket: 45 tooth



MODS: Parts needed:

• Gs500:
  cylinders
  Pistons
  head and base gaskets
  camshafts
  tensioner
  Slot cam sprocket (because they will be 2-3 degrees retarded from the whole head being 0.010 shorter than it was)
  K&N filter
  Mac 2 into 1 pipe
  Gs450 head with larger gs500 or even gr650 valves if your adventurous.
  Port the 450 head and instal Gs500 valves is the safer option.
  You would have to deal with clearances and use the proper gaskets to get the right deck height and squish band. You could use a combination of gaskets from the 500 and 450 or get custom ones made.Then get the cams dialed in again because they will be off by up to 8 degrees depending on the gaskets used.

So far the following people have successfully created a gs450-500 swap

wera90ex
bwanna

Easyest way to go is: GS500 pistons, cylinder block, chain tensioner, head gasket, gs450 base gasket, gs450 head.

[Mekanix]

Engine GS500 1989+

Bore: ID 74mm
Bore: OD 82mm
Stroke: 56.6mm
18mm Wrist pin
Compression: 9:1
Base gasket: 0.010 (0.250mm) Steel
Head Gasket: 0.010" (0.250mm) Steel with 4 O-rings for oil passages.
Carb type: slingshot......
Main jet: 122.5
Pilot: 42.5
Intake cam lift: 0.345"
Exhaust cam lift: 0.326"
Intake Duration: 243 degrees (Center @ 104 ATDC )
Exhaust Duration: 246 degrees (Center @ 103 BTDC )
Timing: 18 pins between 2 and 3
Cam journal: 22mm
Intake valve: 39mm
Exhaust Valve: 32mm
Valve clearance:
Combustion chamber: 25cc with stock pistons
CFM
Stock front sprocket: 16 tooth
Stock rear sprocket: 39 tooth


Popular mods:

Vance and Hines complete exhaust. (if you can find them)
K&N "lunch box" or part number RC1822
Dynojet kit. (you need the needles only, the rest works but not necessary)
And mikuni 142-147 main jets.
Bridgestone battleaxe's are the best tires I've use on it and recommend them.
Rev limiter ! (I find this thing wants to over-rev easily and that is the first thing that will take out the crank bearings or connecting rod bearings.)
LED signals and REQUIRED LED flasher or nothing works :P
SV 650 clutch


You cannot disassemble the top end of the engine in the frame unless you remove all but the lower rear bolt holding the engine.
After it rocks forward, You can get everything out through the top but Its tight !!

Wera90ex and ben2go are also very familiar with this bike.

[Mekanix]

Engine GR650


Bore: ID 77mm
Bore: OD 84mm
Stroke: 70mm
compression: 8.7:1
Carb type: BS36SS
Main jet: XXX
Pilot: XX
Intake cam lift: 0.364"
Exhaust cam lift: 0.364"
Intake Duration: 2XXdegrees (Center @ 98' ATDC )
Exhaust Duration: 2XX degrees (Center @ 99' BTDC )
That explains the low torque curve.
Cam journal: 22mm
Intake valve: 40mm
Exhaust Valve: 32mm
Valve clearance: 0.03-0.08mm
Combustion chamber CC:
CFM

[Mekanix]

Reserved, For things I forget


Mods maybe, Or just a scratch pad for random bits of information.

• Acetone works great for dissolving old gas varnish.
• Vinegar is great for cleaning rust and tanks. Just neutralize it with baking soda and water after your done.

• Cams are interchangeable between the following:
• GS400. 450. 500, 650. 4 valve only.
• MAC 2 into 1 DOES fit the gs400 gs450 from 1981 on up.

• GS400, 450, 500 cylinder blocks are interchangeable. Max the case can take is 83mm before you need to bore it. You can fit GR 650 sleeves in there but it requires boring the case bigger than 84mm.

• I've noticed the OD of a cylinder sleeve has been the stock ID + 8mm for the 400, 500 and 650.

• GS400, 450. 500 Engine bases are the same except certain parts like the shift drum's and disengage mechanism.

• There are 2 shift drums for them. One gives you 1 down and 5 up (normal) and then other has 1 up and 5 down. Depending on if you want the shift lever facing forward or backwards.

• Two oil pump gear sets are available for any of the bases. The GS500 has a higher ratio than the gs400 and 450. You need both gears! Same principal as the gs750 gears the guys put in the 1100's for more flow/pressure)

• You can use almost any clutch drive or driven plates from the gs400 to 500 up to 2007, Ive found that the the superseded part numbers are the same on this site: http://www.cmsnl.com/suzuki-gs500-19...?model_q=gs500

• This is where I go for parts and part number correlation. http://www.cmsnl.com/suzuki-motorcycle_model13053/
  
  
• A good combination of stock and after market springs is half and half.

• Timing chain tensioner can be replaced on the 400-450 with the APE ST1100. Its for an 1100 but works on the 1100, 750, 450, 400. The part number for the original stock tensioner is the same for each model.
• Late 1979 is when they changed the base from a roller bearing engine to plain bearing.

• Changing the head and/OR base gasket on the GS400x and GS450 with one or two from the GS500 will reduce the deck height and gain a little compression ratio. You still have to do the math to figure out valve clearances and compression ratio but you could reduce the overall deck height from ( base 0.020 + head 0.043) =(0.063) down to ( base 0.010 + head 0.010)=(0.020) which is 0.043 or 1mm. So effectively your loosing almost the head gasket entirely worth of clearance. I have not messed with it but I just noticed this while comparing gaskets.

• GS 500 piston deck height is actually in the hole by 0.030" IIRC. Have to check again when I reassemble but Its definitely in the hole.

• You can retrofit the points setup (must include coils) from the earlier 400/425's (4 valve) onto the 80 - 82 450's. (Dunno why you'd do this but you can).
• The Dynatek DS3-3C kit is designed for the 400/425's (4 valve) but can be used easily on the 450's by retaining the mechanical advance, using a spacer that Dynatek can provide, and by running a separate wire for the oil pressure sensor. The kit comes with coils.
• From 1983 on the mechanical advance was ditched for a solid state advance and a fixed rotor.
• The whole 500 ignition setup can directly swap on to any twin 400-500 and the only difference is when the full advance is reached. It is about 1000RPM later in the 500 VS 400, 450.
• The parts you will need are: Ignitor, Coils, Rotor, pickups. Although I don't know if the coils are that important or not. The Coils for the 500 might be useful for the older bikes and the older coils might work with the newer ignition...

• Lots of GS500 parts are available cheap and they are recently manufactured. That means there are more options than NOS parts.

Such as:

Engine parts
Control's
Gauges
Cables
The 500 has a 520 chain an sprockets. Most have 530's.

• To remove sleeves from a cylinder block: place in oven at 240-280 for 20 minutes, Watch cylinders rise out of block. when they do, remove block and tap sleeves out with something soft. Wood or rubber mallet will do. The sleeves should slide out easily but if they don't, simply reheat and repeat.
• Installation is the same, heat up the block and drop the sleeves in. Pound them in lightly until seated and reheat until you're finished.
• Anytime you heat a block without any force pushing down on the sleeves, you will notice the sleeves wanting to pop up. In that case just heat them up and push them back down.
• DO NOT cool the sleeves or block rapidly. Allow them to cool naturally.

• Gs450 modifications.
  Parts needed:
  Gs500:
  cylinders
  Pistons
  gaskets
  camshafts
  tensioner
  Slot cam sprocket
• Dynojet kit
• K&N filter
• Mac 2 into 1 pipe
  Gs450 head or gr 650 head
  Or port a 450 head and jnstall Gs500 valves.
  You would have to deal with clearances and use the proper gaskets to get the right deck height and squish band. You could use a combination of gaskets or get custom ones made.Then get the cams dialed in again because they will be off by up to 8 degrees

Other things:


If you ever hear this knocking coming from the top end and its only at idle and sounds like its rythmic and sounds like cam walk...



You'll find that its actually the cam bucket that is the problem. It is walking side to side just enough to push the cam sideways and gice you that knock :P

My 500 does it, have to get in there sometime and replace it on next shim change.

[Mekanix]

Links:

• http://www.totalseal.com/TechPage.as...plessPistRings
• http://cometic.com/
• http://www.cmsnl.com/suzuki-motorcycle_model13053/
• http://members.dslextreme.com/users/bikecliff/

Images:

Pete's: 450 + Dynatek Ds3-3c

• http://s594.photobucket.com/user/sta...y/GS450?page=1
• http://s594.photobucket.com/user/sta...Dynatek?page=1
• http://www.thegsresources.com/_forum...d.php?t=158670

Mekanix:

• http://www.flickr.com/photos/61692938@N08/
• http://s1285.photobucket.com/user/me...ibrary/?page=1
• http://www.thegsresources.com/_forum...d.php?t=172422
• http://www.thegsresources.com/_forum...d.php?t=204001

[JEEPRUSTY]

You could share this with the world via wikipedia
Go ahead do it.

[Mekanix]

You could share this with the world via wikipedia
Go ahead do it.

Ive never done that before. Not sure how yet.
I'd like to get something a little more complete on here before doing that but It would be a great idea.

[eil]

Wikipedia discourages content that isn't general-purpose in nature. I see articles on motorcycles that have the bike's specs in them, for example, but I'm guessing that maintenance or engine-rebuilding info would get deleted as not relevant.

Best bet might be to maintain the info here in the forum. Maybe once you feel it's somewhat complete, you could ship it off to BassCliff.

A month or two ago I offered to host a wiki for the forum on my web server (editable by the GS community, of course), but the offer was (politely) declined.

[Big Rich]

My hat is off to you sir.

I'll look around for any GR650 info I can find to add to your list.

[wally]

That would make up a very useful wealth of knowledge!

Cool and thanx!