motor help 1979 gs750

[andtex24m]

ok so i just bought a gs 750 1979 8v and im torn on what upgrades i could do to the motor well to start out the motor has 86k on it should i look for one with lower miles... bc what i wanna do is bigbore kit/ k&n/ nice carbs(flat slides)/ dyna kit/port and polished heads(any one know a good vender?) vance hines exhaust... what more is there to do besides turbo/nitro any ideas plz help or let me know if im wasting money to begain with or theres more to do

[psyguy]

850 pistons and cylinders bolt right in

you can use post '80 cams for a stronger bottom end power

unless the bike has been really trashed 86k should be still very ok

[andtex24m]

sweet thats a cheap way for power im game dose everything else sound ok though?

[psyguy]

sweet thats a cheap way for power im game dose everything else sound ok though?

yup, sounds just like what people do to those bikes

also, you may want to play with different size sprockets or use aftermarket cams for top end power

[andtex24m]

now in comparison how fast with it be compared to a modern r6? just for ****s and giggles? if i do all that i said i was going to do?

[psyguy]

seriously...

never rode an r6 myself but i'd say that the speed also depends on the riders ability

[chef1366]

Buy an R6. You could throw two grand at that bike and still have to play catch-up. Plus you haven't even thought about the suspension. You'd be better off buying a new bike.

[andtex24m]

but i have a new bike this is just my toy i just wanted an idea of what i was getting in to thats all

[TheCafeKid]

Ok, before you go buck wild spending money on that motor, understand that that bike and that motor are early renditions of the GS line.

I think our 8v 750s on paper were rated at about 74BHP at the crank. Im estimating that puts the horsepower to the ground at about 65HP.

Ok knowing that, and that the bike weighs 492lbs dry, you're already hampered a bit. A big bore kit, which will cost you $500 for the pistons, rings, wristpins and circlips alone, not including the cost of machining the bores we'll call it 60 bucks a hole there, so a total of another $240 bucks, you're already up to $740, and you havent even got to cams yet. We'll say those, at a streetable grind, are about 300 for the set. TO get the most out of them, you'll need degreeable sprockets, another 40 bucks each...so now, you're up to $1120, before the headwork. $600 there, you're up to $1720. A motor like that wont run for sh1t on P&C ignition, so you need a Dyna S ($120) and 3ohm coils ($120) $1960. Flatslides, as far as I know, wont mount to that head, since it uses mechanicals, so you're looking at VM29SS Smoothbores, or maybe VM33 smoothies...plan another $500 there for ones in good shape. $2460. Exhaust? $300 bucks. $2760.

Now the big bore kit for the 8v 750 from Wiseco will get you up to 844cc.
A 1979 GS850 jugs and piston set will BOLT RIGHT ON to your motor, and garner you 843cc. You can likely find a set of those ( i know someone who has a set for sale right now) for...maybe $2-300? Including the rings and wristpins and circlips probably.

You're overall HP gain out of that nearly 3000 bucks MIGHT be 50HP? Thats probably stretching it really. Lets call it 35HP at the wheel gain. So you went from 65HP at the wheel to 100HP at the wheel, on a 500lb bike. Yeah, its a bit of punch, but not alot. Lets say you weigh 150lbs. so with gas and oil in the bike (50lbs) and you, we'll call her 700lbs. Thats a 7:1 ratio. Yeah, you'll feel it, but is it worth it? Prolly not. If you want an R1, or R1 like performance, you'll be greatly disappointed. But, if you want a BAD ASS old school machine, you might think it was money well spent. Believe me, i did not nearly those kind of mods on my cafe, and im into it for 4grand including the cost of the bike. You'll find that just getting it LOOKING the way you want it will cost you quite a bit.

My advice? Buy the 79 850 jugs and pistons, a complete gasket kit, some smoothbore carbs, a nice header, and the Dyna S and coils, and call it a day. You'll still get a nice performance gain out of it, but not break the bank. The trick on a cafe is to cut weight, and gain HANDLING. Fast is great, but if it wont handle, you'll be dead real quick, or really pis$ed off, one or the other.

Do the above engine mods, install a GS1100E alu boxed swingarm, get some killer shocks, racetech or progressive fork springs, a fork brace, and some rearsets and clipons or clubman bars. Make it look the part too...you'll be deep in your pockets just doing that. And you'll be happy with the end result instead of irritated that you have a bitchin motor, but the bike wont turn.

Just my .02

TCK

EDIT: Mind you, I say all this, yet *I"M* about to spend 2 grand this winter on my 1100 putting gixxer and bandit suspension on it, and another 2 or so grand NEXT winter putting a 160ish HP motor in it! LOL. The question you really have to ask yourself is: IS IT WORTH IT TO ME? I'LL NEVER GET THE MONEY BACK OUT OF THE BIKE THAT I PUT IN, SO IF I DO THIS, ITS A KEEPER. IS IT?

[almarconi]

Are you talking about the yamaha yzf-r6? Dude..the performance wouldn't even come close. That bike weighs less than 400lbs and puts out about a little over 100hp. The gs750 is much heavier..even modded I doubt that engine would approach the r6. If you want sportbike performance by a crotch rocket and keep the gs750 for your classic ride.

[andtex24m]

thanks for the input guys my gf will be happy that ill be saving money hahahaha but honestly tons of help