Bigger engine - buy or bore?

[80GS1000]

If you want more displacement from your engine, is it better to bore out your existing engine and replace the pistons, or buy another, bigger engine?

I'm considering boring out my GS1000 engine to 1085 or 1100 cc for more power. Will overboring reduce engine life?

If you could find a GS1100/1150 motor in good shape, would that be the better option?

[Dan Ruddock]

What kind of power do you want? and how big of a increase are you looking for? Careful tuning with the displacement you already have might give you what you want. Cam timing can move the power curve around more to your liking and can even increase the peak torque. I too am looking at increasing my GS1000's displacement and am some what uncomfortable with thin cyl walls. I am looking into installing the GS1100G cly block onto my engine to maintain the thicker walls. Some may say it is over kill but I like over kill which sometimes can be the difference between success and failure. Dan

[80GS1000]

The more power, the better. This bike will see a roadrace trackday at the local track or three once completed. Basically trying to build a hotrod street/track bike.

If hopping up the GS1000 motor is the way to go, I'd like to get as much HP/torque as possible out of this engine while keeping it streetable and without breaking the bank or throwing parts at me at high revs.

The stock 1980 GS1000E motor makes 90 HP. I'd guess with the V&H 4 into 1, and the stock airbox with a K&N filter and the rejet the PO did, I'm making maybe 95-100 HP. It has an AMAZINGLY fun and broad powerband, pretty much linear from about 4k to 8500 RPM. You better hold on tight when you're gunning it. Great for street riding. But, it peters out over about 90-100 MPH because of the lack of HP.

Compare this with the GS1100/1150, which make anywhere from 110-125 HP stock. Plus all the other parts in those bigger displacement motors are designed to withstand the loads imposed on them by the increased torque/HP.

It seems like from a pure performance, ease of installation, and bang for the buck perspective (engine mods are big $$$), transplanting a later, bigger motor into the GS1000 frame would be the better option. From a purist's perspective, this may be a bit disrespectful to the original design of the GS1000.

What do you think?

[49er]

If you rework your own 1000, you will know the condition of the internals and the likelyhood of it holding together when/if you decide to hammer it.

[Dan Ruddock]

If your in love with the way the older bike looks (myself included) do an engine swap. If not get the whole bike and sell the GS1000. Dan

[80GS1000]

If your in love with the way the older bike looks (myself included) do an engine swap. If not get the whole bike and sell the GS1000. Dan

I do love the way the GS1000 looks, and the riding position is just perfect IMO. Newer sportbikes make more power, but I don't like their Tupperware looks or the forced riding position with the clipons.

So for your bike, are you leaning toward an engine swap or hopping up the existing motor?

[lecroy]

The more power, the better. ...

If hopping up the GS1000 motor is the way to go, I'd like to get as much HP/torque as possible out of this engine while keeping it streetable and without breaking the bank or throwing parts at me at high revs.
...
What do you think?

"As much power/torque as possible", "keeping it streetable" and "without breaking the bank" just don't belong in the same sentance. That's what I think.

If you want a lot more power I would just buy a new bike. This has to be the cheapest way to go in the long run plus the bike will handle much better.

[80GS1000]

If you rework your own 1000, you will know the condition of the internals and the likelyhood of it holding together when/if you decide to hammer it.

True. Kind of like buying a premade Dell computer versus buying the parts and putting it together yourself.

[49er]

Are we talking Dell 1000 or 1150 here?

[80GS1000]

Are we talking Dell 1000 or 1150 here?

Dual core Pentium D @ 3.2 GHz, 800 MHz FSB, 4 GB DDR2-1066 RAM, 1 TB storage capacity....

hold up, we're talking about hopping up bikes, not boxes.

Amazing how Pops Yoshimura got 133 HP out of the GS1000 engine by tuning. Wonder how long those engines lasted...?

From the looks, sound, and sledgehammer torque perspective, it's hard to beat an aircooled GS engine. \\/

[49er]

Yeah. Pops did well at 133hp. You need to keep things in perspective though. Every possible bit of weight was saved within the racing rules of the class and era. The specs show him running 11.5:1 on premium gas. I read a few weeks back, from another Yoshi data sheet that he was running the total standard advance of 36 deg. These specs show him using a CDI. No mention of mechanical advance figures though, or cam specs. The earlier specs mentioned him drilling holes through the cooling fins. Not sure whether this was purely to save weight, enhance cooling or both.
These engines were probably rebuilt 2 to 3 times per race season.
Yoshi road kits used to be available, from memory Stages 1-3 depending on how radical you wished to go, and how much money you were prepared to throw at your project.
So, do you work yours up or fit a bigger engine?

[Dan Ruddock]

So for your bike, are you leaning toward an engine swap or hopping up the existing motor?

My goals are different than yours. Lots of torque and drive ability are important plus the 2 valve head has better fin area for cooling which will allow more c.r. and better efficiency. I would not want something too fast that would scare me. So I will stick with the two valve engine. Dan

[80GS1000]

My goals are different than yours. Lots of torque and drive ability are important plus the 2 valve head has better fin area for cooling which will allow more c.r. and better efficiency. I would not want something too fast that would scare me. So I will stick with the two valve engine. Dan

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?

[80GS1000]

Yeah. Pops did well at 133hp. You need to keep things in perspective though. Every possible bit of weight was saved within the racing rules of the class and era. The specs show him running 11.5:1 on premium gas. I read a few weeks back, from another Yoshi data sheet that he was running the total standard advance of 36 deg. These specs show him using a CDI. No mention of mechanical advance figures though, or cam specs. The earlier specs mentioned him drilling holes through the cooling fins. Not sure whether this was purely to save weight, enhance cooling or both.
These engines were probably rebuilt 2 to 3 times per race season.
Yoshi road kits used to be available, from memory Stages 1-3 depending on how radical you wished to go, and how much money you were prepared to throw at your project.
So, do you work yours up or fit a bigger engine?

Great info there, cheers for that.

Not sure about the engine. Gathering motor thoughts, ideas and info for phase 2 (engine mods) of the GS trackbike/streetfighter project.

I want to go to roadrace trackdays and show the GSXR and and Yamaha R(x) riders what the tail light of a proper AMA style GS superbike looks like.

Gotta finish up phase 1 first though which is the suspension mods. I've got the Gixxer 1000 front end on, which should vastly improve braking and improve handling.

Next is the rear monoshock conversion - which will allow a radial 180 in the back for more cornering stability at speed, a much stiffer, braced swingarm and a modern rear brake.

It's gotta have an aircooled GS engine. I've seen pics of GSXR 1000 motors stuffed into GS1000 frames, and it just doesn't look or sound right.
A black GS1150 motor slotted into the GS1000 frame might look trick though - not to mention the dragrace winning power of the 1150 engine and the better handling of the 1000. \\/

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?

What would you do?

[tkent02]

I can help you with this problem...

Question becomes though - what do you do with the perfectly good (and well running) 1000 motor?

What would you do?

Not a problem.