Bigger engine - buy or bore?

[Dan Ruddock]

That's interesting. From an engineering perspective, do you see the 1100s equipped with oil coolers because of the difference in fin area and therefore cooling ability between the 1000s and the 1100s?

Yes I would agree what you have said. Because the four valve has two ports side by side they block any room for air flow threw holes between the ports. Look at a removed two valve head sometime you will see the difference, lots of air passages. The four valve the air flows around the head but the two valve the air flows threw it. Also the valley between the cams is bigger and with those air scoops designed into the valve covers also helps. Don't get me wrong the four valve is much better at high rpm hp because of the high flow four valve design and its combustion chamber is better than the two valve hemi design. Each design has it's pros and cons and yes the two valve with a good oil cooler setup could be built to run more safe c.r. than the four valve which improves efficiency if that's the goal. Dan

[49er]

As far as buying vs. building out the GS1000 engine goes, building out the GS1000 engine would truly make the bike custom - you pick EVERY part that goes into that engine and assemble it yourself. And authentic - it's the original engine. I wish I could say I could that myself (hats off to those experienced and talented to do that), but I'm still new to the world of motorcycle mechanics and my chances of pharking up engine mods or blowing up the engine would be high, unless I hired someone to do it (big $$$). So, it seems transplanting a bigger 1100/1150 motor would make more sense since they're dead reliable and would provide a nice 20-35 HP boost. Question becomes though - what do you do with the perfectly good (and well running) 1000 motor?

If you want to learn more about what works and "wot dont", you should enlist the help of a mechanically minded friend and work up your 1000.
Plan your rebuild by picking brains on this forum and don't attempt anything too radical first up. Any specialty machining should be jobbed out. If you do your homework, you wont make any major blunders. The small ones you may make won't cost you much, and you will learn heaps.
As a racer, you can't beat personally knowing the specs and condition of your engines internals.
Sounds like you've done some research on the handling and stopping departments.
Go for it.

[80GS1000]

If you want to learn more about what works and "wot dont", you should enlist the help of a mechanically minded friend and work up your 1000.
Plan your rebuild by picking brains on this forum and don't attempt anything too radical first up. Any specialty machining should be jobbed out. If you do your homework, you wont make any major blunders. The small ones you may make won't cost you much, and you will learn heaps.
As a racer, you can't beat personally knowing the specs and condition of your engines internals.
Sounds like you've done some research on the handling and stopping departments.
Go for it.

Cheers for the reply and the advice.

One of the really knowledgeable guys on oldskoolsuzuki.info said a while back that you can expect to see between 122-128 HP on pump gas, and 135-140 HP on race gas out of the GS1000 motor with the engine mods below. :shock:

If I go the route of building up the GS1000 engine, this is the likely build spec. What do you think? If done properly, would these mods create a high performance, highly reliable GS1000 motor? Or would it be throwing rods through the engine cases?

*1085 cc overbore job done professionally w/ new Wiseco pistons.
* hotter cams installed
* professionally polished/ported cylinder head
* new intake/exhaust valves
* crankshaft welded so it won't twist
* transmission undercut to keep all that extra torque from slipping the transmission out of gear under load
* heavy duty clutch basket
* 33 mm smoothbore Mikuni carbs
* stage 3 Dynojet carb kit
* Dyna S/2000 electronic ignition
* quality exhaust system
* K&N pod filters
* quality oil cooler to keep engine temps in check
* manual cam chain adjuster
* high flow Pingel fuel valve

[49er]

Cheers for the reply and the advice.

One of the really knowledgeable guys on oldskoolsuzuki.info said a while back that you can expect to see between 122-128 HP on pump gas, and 135-140 HP on race gas out of the GS1000 motor with the engine mods below. :shock:

If I go the route of building up the GS1000 engine, this is the likely build spec. What do you think? If done properly, would these mods create a high performance, highly reliable GS1000 motor? Or would it be throwing rods through the engine cases?

*1085 cc overbore job done professionally w/ new Wiseco pistons.
* hotter cams installed
* professionally polished/ported cylinder head
* new intake/exhaust valves
* crankshaft welded so it won't twist
* transmission undercut to keep all that extra torque from slipping the transmission out of gear under load
* heavy duty clutch basket
* 33 mm smoothbore Mikuni carbs
* stage 3 Dynojet carb kit
* Dyna S/2000 electronic ignition
* quality exhaust system
* K&N pod filters
* quality oil cooler to keep engine temps in check
* manual cam chain adjuster
* high flow Pingel fuel valve

Man you're planning on spending some dosh here. Bear in mind lecroy's advise.

* Check the CR of the wiseco pistons, I think that they are 10.25:1. I won't run anything over 10.5:1 for road use.
* Hot cams are biased to straight out racing. You'll loose some of your bottom end.
* Don't get the ports polished. Reshaping for greater flow/less turbulance is best.
* Larger valves, less bottom end flow.
* Yes - weld the crank.
* Yes - transmission undercut of gears.
* Yes - heavy duty clutch.
* No - 33 smoothbores unless it's for racing only. Why are they so rare ? The early 1000's (78-79) were fitted with VM28's. By going up 5mm in bore, you are increasing the cross section area by 39%.
* Yes - Carb kit and Dyna S 2000 elecronic ignition.
* 4-1 exhaust designed specifically for road or race and matching top end mods.
* Oil cooler highly recommended, also higher volume oil pump gears (GS750)?
* Manual tensioner, optional.
* High flow fuel valve, it won't harm the cause.
This is just my opinion, you know what you expect from your ride.
Good luck.

[Mike_H]

I haven't seen this mentioned yet, so I'll throw my 0.02 in. You need to consider your usage. It sounds like your looking for a quick revving engine, mid range grunt, and durability. Yet you keep mentioning the 1150 because of its drag prowess. Road racing, and drag racing are completely different animals, and as such entail completely different builds.

Personally, I would keep the engine stock. I don't know how your trackday event work, but when I used to autocross cages, they seperated cars out based on modifications. I think you'll have a better chance with a torquey, dependible engine in a stockish class (you've already bumped yourself with suspension mods) rather than a full-blown heavily modified class, where you'll be racing with GSX-R 1000's and the like that have been heavily modified. You'll get whoomped.

[80GS1000]

I haven't seen this mentioned yet, so I'll throw my 0.02 in. You need to consider your usage. It sounds like your looking for a quick revving engine, mid range grunt, and durability. Yet you keep mentioning the 1150 because of its drag prowess. Road racing, and drag racing are completely different animals, and as such entail completely different builds.

Personally, I would keep the engine stock. I don't know how your trackday event work, but when I used to autocross cages, they seperated cars out based on modifications. I think you'll have a better chance with a torquey, dependible engine in a stockish class (you've already bumped yourself with suspension mods) rather than a full-blown heavily modified class, where you'll be racing with GSX-R 1000's and the like that have been heavily modified. You'll get whoomped.

All very good points.

By roadrace trackdays I mean just for fun - not serious competition. Get out there and learn how to drag a knee on the GS1000 Wes Cooley style.

For serious competition you need serious artillery, which these days are bikes like the GSXR 1000 (175 HP stock :shock and Yamaha R1s. I'd get lapped if I tried to take the GS1000 against that kind of hardware.

I love riding the twisties and I think going to the roadrace track is the next logical step to learn how to really ride well and know what the bike can do - no cops, no speed limit, no opposing traffic, good instructors, and smooth, debris-free pavement.

The bike will probably spend 10-15% of its time on the track, the rest on the street.

I mentioned the GS1150 motor because it makes so much horsepower - the most out of the GS series. How would you describe the motor in terms of revving speed, torque, top end speed etc? Never ridden one, but the fact they won so many drag races before the 'Busa came out says a lot about the engine.

You're right on the money that I couldn't race this bike in its class by the suspension mods that have been done, but that's OK by me. I think the better brakes, tires and handling will be worth it.

So yeah, I'd love to have a quick revving, reliable engine with lots of middle and top end grunt, from about 4000 RPM to redline in all gears. I really like the way the 1000 dishes out the power now, with a very broad, very linear torque curve. If I could just get some more top end speed and torque, and a taller rev range (the Yoshi GS1000 redlined at 10500 RPM vs. the stock 8500 RPM) I'd be a happy camper. The local track has a 7/10th mile main straight, and I don't want to get left in the dust for lack of top end speed.

Which, if any, mods should be done to get there?

[Big T]

All very good points.

So yeah, I'd love to have a quick revving, reliable engine with lots of middle and top end grunt, from about 4000 RPM to redline in all gears. I really like the way the 1000 dishes out the power now, with a very broad, very linear torque curve. If I could just get some more top end speed and torque, and a taller rev range (the Yoshi GS1000 redlined at 10500 RPM vs. the stock 8500 RPM) I'd be a happy camper. Which, if any, mods should be done to get there?

A couple of points:

1. based upon your mod list, and your mechanical ability, you're probably looking at $3,000 for the package
2. your bike would be less fun on the street
3. The Yosh race engines get rebuilt every other race, contain parts you'll never find and require constant service
4. I think you'd be better off getting something 5-8 years old for track days (maybe the SV 1000 with the bars on the top of the triple clamp) 2003? for just a bit more money

The 1100/1150 motor gets its power increase from its 4 valves and other changes more than just the displacement.

It's not so much a lack of horsepower, but wind resistance, that slows you over 100 mph. A good, large fairing would be helpful

[NoBars]

go balls out and swap in a oil cooled GSXR 1100

[NoBars]

If you go to a 4 valve GS, stick with an 1100 motor, they are considerably cheaper and easier to find than 1150s and have the same potential for performance when being modified.

[80GS1000]

Thanks for all the tips and advice guys - much appreciated.

Let's go down the engine swap road for a minute.

I have a line on a 1980 GS1100E parts bike for cheap ($150). It's complete, minus the headlight, carbs, and airbox. The guy says it makes 120 psi dry, 140 wet on a compression test. The motor appears to be leaking some oil, but so does my GS1000 motor. It's unknown how long it's been since it ran. What kind of questions should I be asking from the seller?

Who knows, maybe the 1100 will turn into a restoration project.

The GS1000 is my first project bike and first effort at motorcycle mechanics - it's been a lot of fun and very educational so far but I've barely scratched the surface. You guys are the gurus. :-D

Here's some pics of the parts bike and engine:

[Mike_H]

So yeah, I'd love to have a quick revving, reliable engine with lots of middle and top end grunt, from about 4000 RPM to redline in all gears. I really like the way the 1000 dishes out the power now, with a very broad, very linear torque curve. If I could just get some more top end speed and torque, and a taller rev range (the Yoshi GS1000 redlined at 10500 RPM vs. the stock 8500 RPM) I'd be a happy camper. The local track has a 7/10th mile main straight, and I don't want to get left in the dust for lack of top end speed.

Which, if any, mods should be done to get there?

Boy, You wanna be able to rev higher too!! Basically, how quick the engine will "spool up" is a function of recipricating mass. How heavy is the stuff that moves in an engine (crank, flywheel, etc). The lighter it is, the greater the rotational acceleration of the crank can be. Stroke is also a big part of the equation. Ever notice how quick a modern bikes (esp 600 class) will spool? They have very short stroke lengths, which keeps maximum piston accel down. Lower acceleration values means the pistons can change direction more quickly, and with less strain on the conn rods, and crank. All of this in turn keeps the engine from becoming a grenade. Maximum RPM is basically a function of how fast the valvetrain can rotate, and not have the valves "float" off the camshaft. Heavier (more spring pressure) valvesprings and lighter valves help out here.

All of this means that your basically constrained to what the engine designers gave you, within say 10 percent increase. It can be done, and I know a lot of people on the boards have installed big bore kits (pretty much the easiest way to add power, after a free flowing exhaust and high perf air filter), but there will be tradeoffs. If you insist on more power (and who doesn't ?) I would say try to find an 1150, and shoehorn that in. If you still want more, go buy a 'busa, chip it, and put a wet NOS system in it. That oughta blow your hair back! Keep the GS for everyday riding and nostalgia.

Oh one other thing, You mentioned an 8500 RPM redline. Is that the published figure, or just what you indicate at top speed? If its just what is indicated at terminal velocity, you could try dropping a tooth on the wheel sprocket. That will make the bike easier to "push" through the wind, and should allow the engine to spin a tad faster. Wind resistance increases exponentially as speed increases, so at 100 mph, your aerodynamic drag is holding you back more that engine power. Put a 1/4 fairing on, I bet you pick up 5-10 mph in top speed. I was reading Cycle World, and they had a side bar about a guy who took an old WW2 bomb housing, and designed a motorcycle around it. The bike made about 70HP, and his top speed was over 200 MPH. Food for thought.

[80GS1000]

Wonder if it would fit in the frame...? Looks like they peak out at about 145 HP (at least the air/oil cooled versions), which would make the bike a wee bit on the fast side.

But it's not a GS engine - would look funny with that huge radiator on the front, and not period correct either.

But it would make it easier to find parts, especially exhausts....

go balls out and swap in a oil cooled GSXR 1100

[terbang]

I shoe-horned a 16 valve 1100 engine into a 750 frame a few years back. The 750 engine was blown beyond recognition and it was an easy job to fit the 1100 engine. It went real well for an old 750.

[80GS1000]

I shoe-horned a 16 valve 1100 engine into a 750 frame a few years back. The 750 engine was blown beyond recognition and it was an easy job to fit the 1100 engine. It went real well for an old 750.

Got any pics of that GS 7/11? Sounds great.

[terbang]

Sorry it was a while back so no pickkies.
I had to fab up a couple of bottom mounting brackets and fit the 1100 airbox outlets into the 750 airbox. Changed the front sprocket and all the rest was the same. Only those that knew GSes could tell the difference.
Ping, a 100HP Sevenfiddy..!