Here is the #4 bike on my project bike list... the first two are dirt bikes, one doesn't need that much work , actually removing the museum-quality pieces off of it and fixing up some beat up body work for it... then a full restoration and modification of a 1977 PE250B Pure Enduro Suzuki. Then a new top-end on my gs750. Then this! Should be early summer...
Poor pic, but the bike in the background is my 79 GS425E that I picked up for dirt cheap, my gs750 is in front of it, I was comparing the tanks when I first put an E tank on my 750. I did not like the blue striping, so that was the first thing to go.
The 425 had been laid down in the city on both sides, shifter pedal, brake pedal, all of the lights, they are all cracked or bent. Photo makes it look much nicer! It is fairly clean other than the damage from low speed drops
Even though I like the styling of the wire spoke models better, particularly the GS400X with its speedometer and tachometer with the indicator lights built into the tach face, I had to have a 425 cylinder and head at least, for my project, as the 425 cylinder will accept slightly bigger sleeves... You see where I'm going with this?! Also the 79 models got the extra bolt at the front of the cam chain tunnel on cylinder head and cylinder to stop the early 77/78 model oil seepage (all 77-78 GS's had that issue, ans Z1, KZ1000, etc; 79+ GS's this was remedied. So a 425 cylinder and cylinder head were an absolute must on the list.
Due to a mishap on my 920cc GS750 engine, a slightly bent valve cause the mixture to be off and caused some serious detonation, ruining one piston and the head on number 4 cylinder as well. So I ended up with three good spare 72 mm Pistons. The compression height and pin size, as well as valve placements, are identical spec to the 400 / 425, 750, and 850. This was a no-brainer... I envisioned some custom pistons to go 502, or maybe 516cc, with GS450 sleeves installed in the 425 cylinders (blocks are slightly different stud spacing and deck height so they are not interchangeable between 1st & 2nd Gen GS4xx twins). Anyhow, I decided for now that I will run the 72mm 489cc setup since I have it right here... the pistons are very old school, early 1980s, a bit on the heavy side, but should do the job...
Once I get my 750 ported head back from Rapid Ray, I will be dismantling a spare 425 engine to send him the head and cylinder for resleeving and head porting. I have a hollow core set of GR650X camshafts, they are a decent performance upgrade to a GS 400 / 425 / 450. I may however have webcams re-grind them into a bigger profile, and I think Ray has me talked into going shim under bucket on this engine especially.
While I am going for it, if I weigh the pistons versus stock 425 pistons, and determined the big old MTC Pistons are too heavy for this balance shaft twin, then I may go ahead and have a set of JE Pistons or or Carrillo Pistons custom made... 502cc at minimum (73mm)
I was interested in going CR 31 Round slide smoothbore carbs on it, but my buddy had a set of RS 34 is with a broken slide, and slides are not available, despite most other parts on the carb being available. So like the pistons, I have three, might as well forget using it on a 4-cylinder, re-rack these with some custom shaft spacing & fuel Tee adapters, to fit the 120mm spacing on the gs425! This will not be AHRMA legal however. It will be a canyon carver and track day by primarily, but I sincerely hope to start doing some WERA Formula 500 racing with it at some point, where the RS 34 carbs would probably be allowed to slude on the rules, unless I start beating enough people and someone protests them! I'm a long way off from the podium spot on the racetrack, however. I need to attend some riding clinics and get more track time in
Here are all the parts I've amassed for this much anticipated project:
*GS450S/E tank (the sought after classic...!!!)
*Giuliari GS400/425 Italian aftermarket seat
*GS750/1000 disc brake wheels with D.I.D. MT3.50X18 & MT2.50X18 alloy rims
*GS500 fork and front brakes, CB1 (?) 310mm rotor, braided stainless lines
*GS1100E alloy triples (82-82 non-leading axle)
*Custom billet GS500 fork brace
*Fox Factory Shox emulsion versions (very rare, awesome valving, nitro charged)
*MAC/Kerker 2-1 exhaust hybrid (have a different gs twin 2-1 I may also use)
*Hayabusa rearsets (I have some billet Old School speed rearsets I may also use)
*Dresda style swingarm custom made ( similar to stock wheelbase, I might end up having to use a GS1100E aluminum arm that I have as this thing will not want to keep the front end on the ground, I need the extra length)
*early slabside GSXR underling rear caliper and hanger (not pictured, will need to turn down the diameter of this rotor a fair bit to use the GSXR caliper hanger which looks very trick)
If I do race, I have a set of Akront TC rims to use (3.00x18 rear), as the 3.50 rear is too wide to legally run in WERA Formula 500. It would be a good excuse to have a second set of wheels with dedicated race rubber on them anyhow. Because I can definitely see myself riding this bike deep in Appalachian Southeast Ohio with all of the amazing twisty roads that I have mapped out for our rides...
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