A GR650 Overhual!... And Improvement!

[Jedz123]

Howdy Folks
So I bought a GR650 back in August for $400 from a mechanic in Orwell VT. It was corner of the shop, dead battery, dead charging system but the carbs were in good shape for they were drained and I'm about 90% sure only real gas was run through them last. I bought it, replaced the stator, battery and R&R in the driveway and drove it off with 13k miles on the clock. Put a tire on it and finished the season with it.
What she looked like when I first got it:


I decided since it was so crudded up to give it a full detail restore and replace any worn bits, check the engine over, do valve clearances, port match the boots and intakes. Exhaust is going to be a custom 2-1 (don't make a post factory GR650 exhaust). I've already put on super bike bars and am using an HID lighting kit and upgraded all the Dash lighting to LED made a huge drop in charge load off the charging system.





When she entered my shop for the winter:



Shortly after the first day of tear down:



Engine On the bench for valve adjustment and port matching


Wow look how uneven the ports are to the boots...


Even themed out with the burr tool I used for my FZ1 (freed up a noticeable amount when I did this on my FZ1), next to sand smooth


Motor back in the frame, Frame painted silver like the newer E's. Gold Chain, new sprockets.


Next step is to replace the rear shock unit with an R6 unit. I also will be looking into upgrading the front shocks so I can run a twin disc setup with stainless lines. I also will be running pods with a stage 3 jet kit. Fabbing up the 2-1 is quite a challenge but I think I will be successful. the tins and tank are going out to be professionally painted Suzuki blue with red and silver accents like the GSX650F I have. I'm debating running the chrome fenders or not... any input?

Pic of the color scheme I want.

[Chuck78]

This is awesome! I was debating my 2015 project being either a BIG bore '79 GS425 @ 475cc with stock sleeves bored to the absolute max of 71mm, or 502cc/516cc with gs1100g or gs500 sleeves & custom 73mm or 74mm pistons. The GR650 would have more power for far less money even compared to the custom high compression JE or Wiseco slugs @ 516cc on the old hemi head twin. The GR650's tdcc (twin dome combustion chamber) piston/head design is very excellent at making power efficiently. Quite a light bike (with great frame/rear shock) but the gs425 I think I could make about 40lbs lighter with kick start only & my usual mods/weight savings. Going for a very crisp handling lightweight corner burner. The GR is pretty much that in stock form, a little more weight than a small twin but far better frame and much more power.

There is a Honda adjustable cartridge fork that would be a great swap on there if your looking to deviate from the GS dual disc offerings. Two years of gsxr forks are also typically a direct triple/fork swap, just look it up on here. Someone posted measurements of fork legs fully extended, and I believe mentions of what triple/stem heights worked for the swap. Look for the build thread on here for the gs1000 with dunstall faring and all sorts of vintage parts, and a braced GS1100e alloy swingarm with parts from a CBR swingarm brace welded on. That bike is posted for sale now. He used that Honda fork. The GS twinpot front brake mod caliper brackets could be modded to work on those forks also since they are steel caliper brackets & can be welded onto & shaped as needed (see my photo albums for bracket fab shots of the ninja calipers)

[Jedz123]

I love my GR. It's light like a GS twin but has more umpgh then a GS500. A shame they only made them 1 year here in the states. Unfortunately the braking system is horrid. I never went to hot into the turns with it for the brakes got overwhelmed very easily. Going up the mountains was a blast... coming down not so much, I often relied on engine braking to help slow it down...
Motor is filled with oodles of low and mid range power and despite what others think, the gearing is perfect for me. I have hit 115mph on it(top speed) and it accelerates nicely to it. I can see where most add a larger sprocket to bring cruising RPMS down but I often bomb on the thing everywhere so Shorter the gears the better!
It's good bike on dirt too surprisingly...
As for the front end I'll investigate where I want to go with this. I would like twin disc stopping power. If I can cut the stopping distance down by 33% I'll be happy. Right now you just grab a handful of mush and she slows slowly. My old GS750L was the same damn way, upgraded to 1100E front brakes and it was perfect, so I think on this lighter bike the same remedy with stainless line will be the perfect fix. The rear drum does well and doesn't lock up easy I'm not looking to really do anything there. The 35mm forks are decent but I'd like an upgraded 750 front end and she should be good.
I like the spokes too. If I can get my paint job to look like this I will be Happy:

I plan on having a $600 paint budget for this type of getup...

The rear end will be coming from a GS450E... Need to figure out how I will lighten the front fender up...

I have vacation coming up and I will be doing allot of work

[Chuck78]

I think some of the larger bikes have a wider spacing on the triples, so be careful there. Almost all the early GS750's used the 35mm forks, and I believe into the early 80's as well. Of the ones I browsed for a Tarozzi fork brace for my 750's GS650 forks, there were only 2 models of 750 listed at 37mm forks. The GS850's had 37mm forks, but a whole lot of those were "L" cruiser trim models with the leading axle forks and lazy geometry in the triple clamps. The GS650 forks were slightly shorter than the GS750's by 3/8", so keep the height in mind when shopping for swaps.

Rear end from a GS450E? You mean tail light/fender/seat/etc?

I think if you are lightening the bike a slight bit with a 2-1 and center stand delete etc, and you just put in some fresh brake fluid and stainless line with new pads, you would notice a big difference in braking. My 844cc GS750 was quite fast when I got it, and about 512lbs wet weight, and at that point, riding in the hills in a spirited manner, the 295mm single disc was barely enough to keep things in control. mountain downhills would surely fade the pads more as they heat up.

I think there is a good possibility that a single Kawasaki Ninha Tokico twinpot caliper with a special bracket or modified stock bracket to work with a CBR1100XX Blackbird 310mm rotor, with stainless lines, rebuilt master, and good pads, would be adequate stopping for that bike. Look up Suzuki_Don (not sure on exact spelling/spacing/characters) on here, he did the same thing. I have the rotor and a few of those spare Ninja/GS500 Tokico calipers here. I mocked it up on a single disc fork for the 295mm stock rotors, and the 310mm rotor required almost the exact same adapter bracket angle to realign the lower caliper mounting hole (as compared to Salty_Monk's caliper conversion brackets that he sells on here to use the 275mm dual disc forks to run the Honda CBR/etc 296mm rotors with those calipers. A set of cartridge emulators to take over the fork dampening valve duties would make things handle better up front. the Tarozzi Fork brace helps add a slight bit more rigidity to the 35mm forks, and keeps the lowers tracking evenly to avoid any unwanted suspension side load binding.

[Chuck78]

Good forks to swap in the photo below, running the same exact rotors I used for my 296mm Honda CBR rotor wtih Ninja caliper swap. With these Honda VTR1000F adjustable cartridge forks, you could run those even fancier calipers off that donor bike and they would be in the right spot for the rotor diameter that we commonly upgrade GS's to, and then just play with rotor spacer thicknesses to get the rotor centered in the caliper on those forks, and make axle adapter spacers (i.e. see your favorite machinist or friend with a lathe) and potentially get different bearings with the Honda axle ID and the Suzuki hub OD (have to bore out the Suzuki speedometer drive if the Honda axle is larger).


Info from the build thread of that bike:
Originally Posted by John Kat

Looking good
What's the length of the front fork?
I mean fully extended from the center of the wheel spindle to the top of the triple tree?
Here are some forks, I measured personally:
Katana 1100 SD/SZ : 800 mm
GS 1000 E/S : 775 mm
GSX R 1100 G/H (RSU 41 mm) : 767 mm
Yamaha YZF R6 98-03 (RSU 43 mm) : 760 mm
Kawasaki ZZR 1100 90-92 (RSU 43 mm) : 760 mm
GSX R 1100 K (RSU 43 mm) : 745 mm
GSF 1200 Bandit 96/02 (RSU 43 mm) : 775 mm

The VTR1000f fork length is 775mm from the center of the wheel spindle to the top of the fork tube, where the fork cap seats.

Measuring to the top of the triple tree on this fork setup is not an accurate measurement, due to the fact that the stock clip-ons mount above the triple clamp. Therefore.....you have about 2 more inches of usable fork, which I took advantage of for exhaust headers clearance. I mounted my clip-ons below the triple clamp.
The front end/brakes are off of a 1998 Honda VTR1000F, with a 1994 Honda CBR900RR front wheel/rotors

[Jedz123]

I think I want to keep the forks in the GS realm. I want the bike to be a fun but I'd like to keep it in a decent budget for I am in saving mode for my New bike (Gen 2 Haybusa or B-king). The rear end of the 450 is just the rear peice, seat, plastics and lights. The GR was dressed with the L model chrome fenders which are very heavy. I plan on replacing those with plastic bits or just running them without fenders...

Dropping the exhaust and going 2-1 and running a Yoshi RS-3 muffler is saving huge on weight, I'm figuring out how to fab up the exhaust now.... Dropping the huge air box and going pods helps too. I'm considering running a lithium Ion battery to further weight savings... I don't want to take away the practicality of the machine and will likely keep the center stand on it. I'm not going for a full blown stripped and lightened machine but one that will perform well, look nice and be practical in all circumstances. I still want to be able to ride 2 up with it and cruise around on 200+ mile travels without killing my back or going def from a horrid cut straight pipe.


I'll look for GS650 Forks for they support twin disc and I can just slide the tubes into my triples and not mess the geometry of the bike up too much... You can usually find a complete set for cheap on fleabay. I will be ordering my R6 shock this Friday. I also have to buy Christmas gifts too so Budget for the GR is tight for this month.

I send the tins out early January and should get them back after a couple of weeks. January I will get the battery and install the jet kit and hopefully start to dial in for idle.

Goal is to be ready for Americade and take it there and have one sweet looking machine!

[Chuck78]

This whole thread will show you what upgraded Honda/Kawasaki brake setups to look for if you want a single 310mm floating rotor and 2 piston caliper or a dual 296mm floating rotor setup with Tokico calipers from a Ninja. Ninja 250's and Suzuki GS500's use the same caliper but only come in a single disc, I believe both left side. Some years CBR900RR used 296mm rotors, some used 310mm. The CBR1100XX Blackbird used 310mm with the proper offset already to bolt on with only enlarging the bolt holes from 6mm to 8mm. Two years only for that one, at the end of the list I posted there. The next page of the thread has some useful photos from the maker of the adapter brackets and rotor spacers, Dan aka Salty_Monk. The page after that has a useful parts breakdown of the calipers.

http://www.thegsresources.com/_forum/showthread.php?140253-Twinpot-Brake-upgrade-on-78-Skunk/page7&highlight=twinpot+skunk

What Regulator-rectifier did you upgrade to? If you installed LED's and upgraded headlights to lower your charging system load, it doesn't do much good unless you used the popular Shindengen SH-775 series style regulator rectifier or the fancy aftermarket Compufire unit. basically all others that can swap to our bikes are shunt style, and basically ALWAYS run the stator at full load, and just shunt off the excess unused voltage to ground. I assume maybe you already picked up on that tip from here, but just wanted to check. Best of luck

[Chuck78]

I read on another thread a reply from Big Rich that said that the spacing width on the GR triples was different, and to run the GR wheel in GS 35mm forks with the GR triples, the axle spacers were all wrong. He said you need the GS triples and fork legs both to use your GR front wheel. He also said something about the GR rear wheel being spaced different with the sprocket etc at a different spot, said a GT750 hub was very similar as to lining up with the engine's output sprocket, but not a GS hub. If you lace in an 18" rim instead, try and buy one from Buchanan's or Woody's Wheel Works and send them the hub so that they can drill the rim for the proper spoke angle and measure the correct length spokes to get made for you (very hard to find custom length spokes for sale). Unlike bicycle wheels, the spoke hole angle in the rim is very critical on motorcycle wire spoked wheels. Not just any rim will do.

With a light 400lb twin, I wouldn't write off 35mm forks, as with a Tarozzi fork brace, they will be a bit stiffer already. 37mm adds weight but also makes them even stiffer. I have a pair of GS750 forks on the shelf now that I could measure the total extended height of if you were interested. The GS650 forks were 3/8" shorter than the 750's. I got 1/4" taller rear shocks and 3/8" shorter forks to quicken the steering a bit on mine.


Dan aka salty_monk sells the brackets and spacers to run dual disc 2 piston Tokico calipers and the Honda rotors, but if you want to explore the single 310mm twinpot setup, it is best to fab up a bracket as I did on both of my 296's. Running the larger offset 310mm CBR1100XX blackbird rotor (2 years only listed with the 22mm-ish offset needed) eliminates the need for a hub spacer on the GS's (and probably yours as well, looks to be same 17.5mm offset rotor as the GS's). Here's mine:



Big question - what diameter is your front rotor currently? I suspect it's smaller than the stock 295mm that a lot of the 4 cylinder bikes got (both of our 77 GS550's and 750's). And those all steel snowflake style GS rotors you have on your front were prone to warping under heavy extended braking. They flex a lot. Not as stout as the older massive aluminum center GS rotors. If you are at 295 now, I'd just try swapping to the 310mm CBR1100XX Blackbird rotor and necessary caliper bracket mods or adapter bracket to run teh Ninja/GS500 Tokico caliper. See if the braking is to your liking then with a stainless line and new pads. If not, then you are in luck, as I'm sure that setup would be easily sell-able here on the classifieds to many GSR members. I am planning to do GS550 35mm forks and the 310mm single disc twinpot setup on the GS425 that I plan to build next year. Maybe it will be a GR650X if I can find one locally. Best of luck

[Jedz123]

With a light 400lb twin, I wouldn't write off 35mm forks, as with a Tarozzi fork brace, they will be a bit stiffer already. 37mm adds weight but also makes them even stiffer. I have a pair of GS750 forks on the shelf now that I could measure the total extended height of if you were interested. The GS650 forks were 3/8" shorter than the 750's. I got 1/4" taller rear shocks and 3/8" shorter forks to quicken the steering a bit on mine.

I really didn't want to. The bike handles great with it's stock suspension... For an 80's bike that is. As long as the GS750 forks would support twin stoppers I would be very interested. Just shoot me a PM. I'll look into a fork brace as well... Where would one source that?

I just did some reading and overseas allot of guys just swap to stainless lines and the stock brake is more then adequate afterward... I'll look into the twin pot upgrade as well for pricing....

Thanks Chuck!

[Chuck78]

salty's bracket for the 296mm dual rotors on GS forks intended for GS 275mm dual discs puts the Tokico twin piston caliper almost right where it needs to be on forks intended for the 295mm single disc, when running the 310mm honda rotors, so maybe this would be a good thing to buy one of just to test things out before you go too far into fabbing a properly aligned bracket. The angle was a degree or two off as I recall from my mockup of my blackbird rotor on my GS hub and GS650 dual disc forks, but would allow things to work, but pad alignment was not perfect. The top bolt on the 295->310mm setup and the top caliper mounting bolt on the dual 275->dual 296mm setup both remain in the stock hole on both the fork and caliper, but the caliper needs to pivot out from there as you see in my photos in order to have a full pad sweep area on the rotor without overhanging the edges.

FastFromThePast.com sells Tarozzi fork braces. Most of those brace part numbers fit more years/models than they list. Some seem to be identical to other Tarozzi braces in specs, but then you will notice some have the center piece clearanced for taller wheels or shorter forks, as opposed to the other which is the same thickness all the way across the center section. They bolt on where your fork seal dust boots go, and you relocate the dust boots to an identical flange on the fork brace once the brace is bolted on. They run $99-ish. Sometimes you see old Telefix braces and other brands on ebay, but Tarozzi is the only one still being made for nearly all GS's. There was another site in Australia that distributes Tarozzi, and they had far more specs listed than FFTP. I don't recall the actual Tarozzi site being very helpful for researching these, but I' sure email to them would get you the knowledge you need.

MikesXS cartridge emulators work great in our 35mm forks as well, and give you proper individual dampening for compression vs rebound as well as low speed travel damening AND high speed travel dampening, as opposed to the stock damper rods which just use two orifices for high and low speed compression and rebound. one orifice does all, pretty primitive but cheap to manufacture, hence damper rod forks were so widely manufactured for far beyond the usefulness of their technology in contrast to modern tech. Straight rate springs from Sonic Suspension or RaceTech in a stiffer/more proper rate for your rider+bike weight will really improve things further with emulators.
If going with 37mm forks, you have to spend double on the emulators and go with the RaceTech gold valve cartridge emulators, as the MikesXS ones only work on 35mm GS and 36mm KZ forks in addition to the Yamaha XS forks they were intended for.

[Chuck78]

From what I posted on salty's thread, these two rotor variants would be the easiest swap as they already in the acceptable offset range AND have the proper bolt pattern. Unfortunately they are less common used, but you can easily find new aftermarket rotors if you want to pay $180-230 a pair.
SINGLE 310mm DISC:

CBR900RRW/X 98/99
310mm (needs different adapter bracket from the 296's, can use a single 310 on a single disc left fork leg also)
62mm inside diameter
78mm bolt circle diameter (PCD)
6 straight 6.5mm diameter holes
4.5mm thickness
21.0mm offset
CBR900 RR-W,X Fireblade Front 98-99 Model: ZC 923
Disc Outer Diameter: 310 mm
Disc Inside Diameter: 62 mm
Disc Thickness: 5 mm
Number of Holes: 6
Bolt hole Diameter: 6.4 mm
Boltpattern Diameter: 78 mm
Offset: 21.5 mm

DUAL 296MM ROTORS:

CB1 400 1989-1990
CB400 FOUR 1997-2000
CB400 SUPER BOL D'OR 2005
CB400 SUPER FOUR 2005
CB400SF 2002-2004 (92-97?)
CB600F "599" HORNET 1998-1999
Outer Diameter: 296mm
Inside Diameter: 62mm
Bolt Circle Diameter: 78mm
Bolt Hole Diameter: 6.4mm
Bolts:6
Disc Thickness: 5mm
Total Thickness (width/offset): 23mm

The CBR1100XX rotor is a perfect 23mm offset but the bolt pattern would need completely redrilled a half hole off from the original slightly smaller bolt circle (use GS/GR rotor as template). I forgot about that since I last visited the rotor options in depth a few years ago.

[Chuck78]

Google tells me you only have a measely 260mm single disc... wow. Upgrade to GS forks and triples in either single 295mm version for the 310mm rotor or else dual 275mm version (I believe that is correct, please confirm before buying forks, but most gs dual discs are the right size for the 296 dual rotor swap).

www.ebay.com/itm/131239393120 that has some wear on it but that's what you'd be looking for in the 310mm single

[Jedz123]

Chuck
I'm still working and till about 3AM so I'll measure the disc tomorrow and report. It would make since why the front brake is total junk if its really that small... It rubs when I use it allot so it over heats like a mother... Use to commute over a mountain every day... Killed a set of pads fast. I'd be interested in going down the single stopper route with it. Would I need to get GS forks regardless? I'll do some measurements and report, just tell me what I need to measure. Single stopper would help keep the weight down. Front end is the final bit I will be tackling in this project... That and new tires. Any input on that? I'd likely get Shinkos
Thanks!

[Chuck78]

Shinko 230 TourMaster, very grippy & great profile! If you need a wider size not offered, look at the Shinko SR741 rear, same compound but wider lower profile options. Try to stick with optimal sizes based on the inside width of your rim (should be stamped into wheel/rim somewhere). If you must go bigger, don't go more than 1 size over recommended for that rim width from the tire manufacturer, as this starts squeezing the tread into an oval shape & you actually lose flat contact patch area & the tread radius gets ovalised to make the steering kinda floppy. I'd leave a 3.00x17 or 3.50x17 rear rim in there and run a 130/70-17 130/80-17, or if 3.50, a 140/70-17 tire up. You probably have a 120/90-16 or 130/90-16 now.

Avon AM26 RoadRiders are the other popular alternative.they run double the cost of the Shinko, but last 7000-12000 miles vs the Shinko at 5000 miles (front tire lasts double that). The Shinko grip is phenomenal for the price, but get very soft if riding on a 100 degree sunny day. The Avon's grip very well but aren't quite as soft, and I suspect t aren't as confident in mild temperatures (like in high altitudes or autumn mornings).

I might try an Avon AM26 rear & Shinko 230 front be t time to keep the super grip up front & give myself more miles on the rear before the tread has a flatter profile from city/highway riding. The SR741 rear when freshly broken in is a DREAM for cornering, but when at 3900 miles it is less round when you go to lean it over into a turn.

If using your stock rims, I'd just go for the Shinko 230's front & rear for now. Then consider lacing in an alloy 3.50x17 in the future with help from Woody's Wheel Works or Buchanan's.

[Chuck78]

Those rotors you have are crap for sure. In a dual disc setup they don't get as hot so they are "acceptable" for stock, but in your tiny single, that is your entire problem. Look at GS650G (NOT "L" or "GL" leading axle) forks & triples (mostly dual disc) or '77 GS750 forks as they are surely tall enough & are single disc. The '77 GS550 forks are the same but the uppers are shorter. Not sure what height your gr 650's are. If I have time I can measure a spare set of 750's. If I can get a hand, I can lift the gs550 front end up & measure axle center to fork top fully extended. You definitely could find a set of single disc forks from someone that upgraded to dual disc forks on their heavier 4 cylinder, but make sure it was the 295mm single disc. Read salty's thread in full (12 pages) "twinpots for the 78 skunk" or something like that.
You may be able to find '78 GS1000 forks in 37mm & single disc as well if you really think your light twin could benefit from the stiffer forks if you ride it really hard, or possibly 1980 GS1000G. I'm not sure exactly what models after 1977-78 thay were commonly found with single disc front forks.
Then get the AllBalls needle bearing steering bearing kit for the forks/stem. As far as 35mm vs 37mm, you might want to ask around on here for opinions, but I think with the lighter 2 cylinder, 35 would be adequate. Not sure if 37 would be worth the weight gains if you are not pushing it to the extreme. If you are looking to buy a Hayabusa... Maybe you will be pushing this GR to the limits... In that case be happy that you saved weight by going with a lighter & much larger single disc rotor vs the added unsprung weight of a 2nd front disc & caliper.

Suzuki_Don't fully endorses the 310mm Honda rotor & 2 piston Tokico caliper for his GS550 673cc conversion which is faster & heavier than yours. Message him about his setup. I think he said he can stop so hard that he felt like he could rip the spokes out of thefront rim...