gs1100e swingarm conversion swap to my 78 gs400x

[theironlung1976]

New here... hello suzuki freaks! Been searchin for days n cant find a definitive answer. Tryin to see whats the haps w the conversion.

Again... all concerning my 78 gs400x...

Is it a bolt on? Im readin reamers n spacers all over then hear one er 2 say its a bolt on swap.

From what i gather it longer... i read here 2" and 1 1/8". Is the additional length before or after the shock mounts? Id guess before makin the shocks lay down a little more. The next question is if its before, what length shock is everyone runnin to get it back to the same ride height?

Last question, does anyone know what axle size is of the gs1100e? Just wonderin if im lookin at wheel bearings too.

Been lookin on do the ton (great site too) n everything i was lookin for i couldnt find specificly to my gs... great to find a model specific site. Got some more motor questions that ill post in the motor section. Many thanks guys! Larry

[Chuck78]

Hey Larry, if you're keeping the original drum brake wheel, all you'll need to do there is add more spacers & have a brake stay mount tig welded to the bottom of the aluminum arm.

As for the frame, it is definitely a smaller pivot, & you need to ream out the hole to accept the 16mm gs1100 bolt (I believe a 5/8" reamer bit makes a slightly tighter hole than 16mm). Look up the build thread on DTT of the guy that built a 673cc GS550. He's on GSR also, but his thread on DTT will be much easier to find since there are only two or a few people on there with 673cc gs550 plans. Very nice completed build he has.



If you are looking to do a rear disc wheel, you will need to run an offset front sprocket or use the cush drive sprocket hub piece from the 400 twin's rear wheel. You'll need to fab up master cylinder mounts on the frame (or add modern gsxr rearsets with mc) to run discs on that frame. So drums means tig welding to the al swinger, discs means mig welding to the steel frame for mc mounts or rearset mounts.

On the 400x, you've got drum fronts which aren't all that great...a disc front wheel is easy to find for $50-100. A disc rear, very difficult. Get a disc front wheel from a twin (4cyl's are 19" front stock, 2 cyl = 18"), get non-leading axle gs850g triples upper & lower (not the L model, leading axle forks and less offset in the triples), & get some '89-2010 GS500 fork legs and brace & brake caliper. Then look up the Dan aka salty_monk "twinpot" brake conversion & source a single front rotor from a 296mm diameter Honda variety with the 6 bolt pattern in the right pitch circle diameter (74 or 78mm, I forgot), drill the holes out from 6mm to 8mm in a drill press very precisely, & bolt on! The "599" or "Hornet" rotors are a direct fit after drilling. The others require a 5mm spacer behind the rotor, as they are only 17mm offset.
There's a guy on gstwins.com that makes AWESOME CNC machined 1/2" thick gs500 fork braces for $40 shipped. Stockers are thin steel & may crack the bolt holes out on hard cornering bumps. ask big rich about the guys contact info.

[Chuck78]

My mistake on the brakes, you need the 310mm Honda cbr900rr rotors with the 21.5, 22, or 23mm offset. 2 years have that offset. Otherwise the cbr1100xx blackbird 310mm rotors will work, but I think those had the wrong bolt pattern but could be drilled using a gs rotor as a template. I believe those had the correct offset, but the cbr900rr fireblade rotors had the right bolt pattern but 5mm less offset (needed spacer). Monster single disc front to give excellent stopping power for the lightweight twin, & keeping the weight down by having one massive rotor & caliper vs 2 slightly smaller 296mm rotors.

I posted a comprehensive guide of all the Honda rotor specs several pages in on one of salty_monk's threads on the "twinpot upgrade for the skunk" or similar thread.

[Chuck78]

Oh, and welcome to the forum! No one has dropped you the BassCliff welcome package yet! It will be coming, lots of useful links.

Another thing, ditch that stock regulator rectifier & clean all your wiring connectors everywhere with deoxit & lube with silicone dielectrode grease, making sure all crimped bullet connectors etc fit tight. Upgrade your regulator rectifier setup (2 pieces if still original) to a Shindengen SH775B or SH775BA off of a late model Polaris RZR 800 Ranger ATV. Best unit you can find ($55 used on eBay) other than a $209 compufire regulator rectifier. Search here for "Shindengen SH775" to get the Polaris OEM part # that always shows up on eBay.

Also, make sure you clean all of your ground connections & add more even. Engine to battery - & frame to battery -. Lastly, with an SH775, you definitely can unhook the 3rd stator leg bypass that sends the ac voltage from the stator to the headlight switch so as to leave that leg disconnected from the reg-rect if the lights are off. Run all 3 outputs from the r-r to the 3 terminals on the sh775. Also, you should test your stator quickly (resistance while off, & running ac volts with ignition running on battery alone, stator unhooked, testing ac volts on all three legs to ground at idle & then 4000 rpm & then 5500 etc. Read the stator papers on here to find what voltage readings you should get, as well as ohm readings.

Dyna makes a great ignition for gs twins, & MAC makes a 2-1. Japan.webike.net has some KILLER exhausts for the gs 400/425/450 as well, with orders over a certain amount getting free sshippingacross the ocean even!

Lastly again, Japan.webike.net also sells very nice & beautiful Takasago aluminum H-section rims in 2.15x 18 & 2.50x18, as well as spokes for the gs400, so you can jump up 2 sizes on each rim & run a 100/90-18 front Shinko 230 or Pirelli Sport Demon, and a 120/90-18 rear. Those are the 2 best gripping tires for our bikes on a decent budget. Avon AM26's if you do several very long road trips a year. The demons are the best grip overall but last half the miles of the Avon. Shinko is almost there with the demons, and at 60% of the cost, but less available sizes.

Best of luck. Drop me a line anytime. Where ya from? Info isn't on your profile.

[theironlung1976]

Hey Chuck... many thanks for the reply. I stopped at a local motorcycle salvage yard n looked at an 81 swingarm. I found out alot just by havin one in front of me.

From what i can tell, w a tape measure in inches (im sure its dimensions were made w metric), its 2 1/4" longer before the shocks. The other dimension i was curious about... the most important one i guess... was the pivot width. Just putting a tape between the rails of my frame, havent taken my swingarm off yet, my swingarm at the front width looks like its 8" wide. The 1100e swingarm was 8.75. I heard one er 2 guys say they spreading the frame to get the swingarm in but 3/4 of an inch seems like a lot to squeeze in. I think all the dudes i saw do the upgrade had 4 cylinders. Could the width of the front of the steel swingarm b the same as the width of the 1100e swingarm n thats why im hearin its a bolt in (other than their pivot bolt diameter)? I dont think ive seen anyone do the swap on a twin yet... ive read so many i cant remember now.

About the pivot bolt diameter. Im unsure why its being reamed. I understand why it needs to b enlarged, bigger bolt thru a smaller hole. But why a reamer? That would make an angular hole, larger from whatever side u start the cutting. Couldnt u just measure the size of the 1100e pivot bolt n use a thru hole to enlarge it?

Will check out the things u recommended. Im in South Georgia. Ill have to go into my profile n update all that stuff. Appreciate the responses. Larry

[theironlung1976]

Hey man... didnt see the other posts u left... just the initial response. Thanks for those as well. Ill b lookin into the wiring soon. Guess im just tryin to get the upgrades bought n put on the bike. Then all the little stuff to get it runnin. I wanna do a top end soon (head gasket looks like its seeping a little oil) so i wanna look into the 69mm pistons from wiseco. I own a small cylinderhead shop n wanna do the head on it... a little bowl work, 3 angle valve job, backcut the valves, tickle the runners. My clutches r stuck together so im hopin i can bump em apart. I wanna look into the gs500 carb upgrade. Definitly lookin for an exhaust upgrade too. Appreciate the suppliers u recommended. Mac was the only one i knew of.

I moved to Georgia about 2 years ago n literally, THE DAY before i left my home state of Pennsylvania i started into the wiring. The move was quick n hurried. The bikes been put on the back burner n finally about to get back to it. I tore a bunch of stuff apart on the harness n labeled everything but wiring to me is one of those thing i need to start n finish in the same day. If i walk away from it, its a nightmare to come back to. I love doin wiring but man its tuff walkin away n comin back. Just bought an original 78 suzuki manual w a good diagram. I wanna buy the clymer too... from what i hear it has an upgrade section about cams... guess the "C" cam is the ****. Would like to flip thru that section in that book. But the upgrades u mentioned, as well as things to do to avoid the pitfalls, will b used n r much appreciated. Ive read a few things about solid state from later bikes but kinda just put it in the back of my head n figured i can come back to it after the expensive stuff is bought. Guess im tryin to get the big dollar stuff bought n can sit down n do the smaller, easier work after. Wiring, make brackets, adjustments here n there, assembly. Got the msg saved. Will definitly refer back to it when its time to conquer the spaghetti. Thanks again Chuck, Larry

[Chuck78]

Here is a 1977 GS400X frame with a GS1100E swing arm, GS450 engine, GS(550?) dual disc forks (with Kawasaki rotors redrilled?) and some nice DID gold ano alloy rims. The owner of the Rice Paddy (Vintage Japanese MC parts and salvage business) was building this once upon a time as a future race bike, but never finished (he usually runs Kawasaki's exclusively). I will have to ask him if he machined the sides of the swingarm down to fit in the GS400X frame. I can't imagine anyone spreading the frame apart to fit the swingarm in... that is an absurd idea. I can run out to the garage next time I am over at our rehab/future house and measure the frames myself. EDIT - I just measured the GS750 frame that I have in my living room next to our 14+ bicycles (ha...I am a total GS nutcase!), the GS750/1000/1100 swingarm width is just a hair over 8-15/16".







Milling ~3/8" off the sides of the arm is do-able but would require removing the needle bearings and possibly boring the inside of the arm if it isn't possible to press the needle bearings in further after milling. And then the dust caps won't fit as well.

[Chuck78]

GS400's are a serious cult classic and very abundant motorcycle in Japan, and this website is an AWESOME source for parts most people on this continent have never seen! plus, shipping on orders over $400 USD or so is FREE, and that's coming FROM JAPAN!

http://japan.webike.net/SUZUKI/GS400/613/mtop/

Mad*Star GS400 Aluminum Swingarm eye to eye shocks and drum brakes (or GSXR underslung rear disc caliper with modified spacing on a GS rear disc wheel) $527


BRC (Takasago?) H-section aluminum rims 2.50x18 rear 2.15x18 front $406 drilled for GS400/CB400/CB250 hub diameter spoke angles, lets you properly run wider 120/90-18& 110/90-18 tires (or lower profile 120/80-18 and 110/80-18's) in an Avon AM26 RoadRider, Pirelli Sport Demon, or Shinko 230 TourMaster - the best 3 tires for the money for our bikes for the ultimate in grip, (Avon is double the mileage, shinko and pirelli are the stickiest grip ever):


PMC GS400 butted chrome spokes $131:


Mad*Star Shimura Aluminum 2:1 exhaust weighs only 6 lbs! $478:


Mad*Star O-Ving Aluminum 2:1 exhaust weighs only 6 lbs! $478:


MadMax Shortpipe 2:1 Exhaust for GS400 $181:


MadMax Monaka Tube Exhaust for GS400 $313 (photo appears to be a generic photo, shows a 4:1 pipe, description says it's for a GS400):


KSY Racing project full race pipe 2:1 system $320 (very nice!):


MadMax 2:1 system for GS400 $243

[Chuck78]

Hang onto your rear drum wheel and you can run that Mad*Star aluminum swing arm if you can drop that kind of money (fair price for a new piece) for it. Then you can find a very prevalent front disc wheel off of a GS twin or a 1st gen GS550/750 (easier and cheaper to find than GS1000 spoked wheels that have alloy rims), and lace those BRC H-section rims in. They look VERY VERY classy and allow you a decent width tire front and rear, as the stock rim/tire sizes are anemic even for a small light vintage twin. All the front disc wheels, single or dual disc, share the same dual disc ready hub shell (a single 310mm with the 2 piston sliding Tokico caliper is all the brakes a light bike like this needs though). Probably the same front axle diameter as well on all GS front hubs. Snag any GS wire spoked wheel or hub and lace up those rims. Or contact Woody's Wheel Works and get a 2.50 front and 3.50 rear, and a 520 chain conversion and probably an offset front sprocket. Woody's will run you $750 probably, cheaper than the alternative from Buchanan's. Best two spoke wheel sources in the US. The 2.50/2.15 H-sections are by far the best price I have seen for a wider rim conversion. Adequate size for the twins most definitely.

[Chuck78]

I wanna buy the clymer too... from what i hear it has an upgrade section about cams... guess the "C" cam is the ****. Would like to flip thru that section in that book.

The GS500 cams (early model that has cable drive for tach) are an upgrade also, or GR650 tempter cams. The GS400C uses the same cam as the GS425N/GS425E I believe. Higher lift. You get a lot better manners and a little more power all around with a modern profile in an aftermarket cam or GS500 cam. More lift, less duration. the old GS cams from the 70's especially have crazy long duration figures, which lead to good high rpm power output, but with a stock 8.7/8.8/9:1 compression ratio, they bleed off so much potential compression power at lower rpm's, which leads to long warmup periods and lack of low rpm power. Check these guys out (call them up, their tech support girl really knows her stuff!), they'll require a GS twin cam for a core charge as they regrind the cams, but they have awesome offerings:

http://www.megacyclecams.com/

http://www.megacyclecams.com/catalog/catalog.pdf

If doing Wiseco pistons, don't mess around, just go for the cam regrind profiles they offer that state that high compression aftermarket pistons are required, and go for the one with the lesser lift, a grind around .380" lift. they have typically 3 stages of cams, an upgraded street cam for stock pistons, and two hot street cam grinds for aftermarket piston compression ratios. The .417" lift cam isn't as good of a profile, and won't be as good for high rpm use, and they recommend a much better oil and more frequent changes to combat lobe wear due to the high lift. .420" and over requires shim under bucket conversions and stiffer springs yet, and shim under bucket is a real pain in the rear to do frequent regular valve adjustments to. the .380" or so lift cam is the best. Stay away from the race profiles if ya know what's good for you. You'd then need the stiffer valve spring kits they sell with them also. About $480-$500 total. This and an aftermarket exhaust and jetted GS500 carbs will make the GS400 quite a contender with the smaller 4 cylinder bikes which I deem plenty fast enough. AND the twins are substantially lighter, big bonus for making excellent time pulling lots of G-forces through turns faster than the bigger bikes can!

Not sure if Web Cams makes anything for the GS twins, but they do make great performance and race cams for the big GS fours.

[theironlung1976]

CHCUK RULES! Thanks for the info man... takin it all in.

[theironlung1976]

I remeasured my swingarm on the 400 again. Its definitly 8", seal to seal. The 1100e swingarm is gonna b too wide. If u can think of the thread, or dude that did that upgrade, PLEASE lemme kno! I need to speak to that guy. Theres a thread i found where a pic was uploaded of a bottle jack between the frame rails. Believe me, that wasnt my intention... especially for 3/4 of an inch! Gimme a hollar if ya can think of anything... ill search till i hear somethin from ya. Thanks again chuck.

[Chuck78]

Well there you have it, the photos show it can be done! I just don't know the details of the machining that was required to make it fit.
I almost bought that project bike in the photos for $550 four+ years ago (really kicking myself, $150 swingarm & $450+ wheels... Titled frame dual disc forks, & engine & tank!!!), so I am 100% certain it was a GS400X frame, & obviously the photos show a GS1100E swingarm.

The photo you are referring to with the bottle jack between the frame rails was not moving the swingarm pivot area, that would be impossible to bend out more than 3/16" & would cause alignment issues. The bottle jack or pry bar technique is used on frames to move the passenger footpeg/exhaust mount frame hoops outward since the 1100E swingarm is wider at that point (arm gives more tire clearance for big skins).

I was told I might have a chance to buy that bike again after it was traded with another bike for a GS1000S project at AMA Vintage Motorcycle Days years ago, but was spotted still collecting dust at the owner's barn. This was late fall. I think I may try for it this summer & sell my spare GS/DID wheels or those wheels to another bud who is building a GS750C...

[Chuck78]

Here is a GS1100E swingarm at the pivot. Clearly you could machine about 7/16" off each side. I can't recall if the inside is the same I.D. the whole way through, or if it is bored out more where the bearing races press in. It certainly seems that Tom likely did this for the GS400X frame retrofit in the pictures. Seeing that bike, I always assumed it was a direct fit!

The other issue is that the shocks will be leaning in one inch more on the top. This would make it best to run shocks like YSS (or run the $30 upgrade bearings for old Ohlins & Fox Factory Shox). This would cause a bit of sideways force on the swingarm shock mounts. Widening the frame's shock mounts would seem to be the most structurally sound option as to place the force more vertically where the arm was designed to withstand it more. I will measure my spare frame again later compared to a swingarm to see if the shocks sit nearly vertical or if they lay inwards more.

[Chuck78]

looks like some machining or very careful dremel work would be needed on the insides as well to push the bearings inboard 7/16".