GS1000G mods- big bore and fuel injection

[GS1000G Shopper]

Today I cleaned the base gasket surface on the block, then installed the new pistons, oval o-rings and base gasket. I'm not going to try the hose clamp cylinder install, and instead ordered two of the adjustable ring compressors made for the job.

As soon as the cylinder is on, I'll try and wrestle the engine back into place.

[Dogma]

Would you mind linking the ring compressors you picked out? I have a top-end rebuild coming soon, and I'd like to see if there's something easier to use than the hose clamps that can still be removed from among all the studs, connecting rod, etc.

[GS1000G Shopper]

Ebay links don't last, so instead just search for "Motorcycle ATV Piston Ring Compressor 52mm to 85mm" and you'll see them. They are right at $28.95 each with free shipping.

This was the tool they used on the GSXR1100 video I watched. It's several minutes in.

[Dogma]

Ebay links don't last, so instead just search for "Motorcycle ATV Piston Ring Compressor 52mm to 85mm" and you'll see them. They are right at $28.95 each with free shipping.

This was the tool they used on the GSXR1100 video I watched. It's several minutes in.

OK, thanks. Nice little tool. If they came in pairs for that price, I'd be a lot more tempted. I just don't think hose clamps just aren't that difficult to use. If I expected to do the job more than once every few years, I'd have a set, though.

[GS1000G Shopper]

The aggravating job of installing the cylinder is over! The tool has three loops. The largest one looks too large when fully tight with your fingers, but the clamp actually places a little more on it. I tried the medium one at first w/o any success. I did try a hose clamp, but found it was not wide enough to work properly. I could have eventually done it that way, but the tool made this difficult job that much easier. I also used some 1" square aluminum tubing to hold the #2 and 3 pistons square when I was lowering the cylinder. This helped a lot.

The next big job is re-installing the engine into the frame. I'm on the tail end of the flu that has been going around, and we're hitting another cold snap tonight, so it will have to wait. Here are some pics from today:

EDIT
I ran into an oil leak at the front of the engine by the 6mm bolt that goes into the head using the head gasket supplied with the eBay kit. Apparently there is a difference int he cam tunnel area between the 1000G and 1100G motors. I am going to use a gasket for an 1100G and will update here with results.

[GS1000G Shopper]

I used a small 3cc syringe and a piece of clear acrylic and I cc'd both heads. The 1981 GS1000G head came in at 39cc. The 1983 D-port GS1100 head was 36cc. These numbers should be fairly close, as I had a good seal on the acrylic using grease to hold it to the head.

I went here : http://www.csgnetwork.com/compcalc.html and plugged in my numbers, some of which were a best guess.

Using:
Bore: 73mm (big bore)
Stroke: 64.8 mm (GS1000 crank)
Head gasket bore: 75.12 mm (measured)
Compressed thickness: 1.3 mm (best guess)
Chamber volume: 39 cc (GS1000)
Piston dome volume: 12 cc (best guess)
Piston deck clearance: 1 mm (best guess after installing the cylinder, this is BELOW deck, negatives here mean ABOVE deck, see above photo)

CR is 8.34:1

Changing this to a 36cc chamber, it goes up to 8.99.

I found baseline GS1000 specs, and saw the CR was 9.2:1. I adjusted some of the guesses with the baseline GS1000 bore & stroke and smaller head gasket (72.1 mm). By changing the piston volume to 12 from 18, I got 9.26:1.

Using these numbers with the 73mm pistons & large head gasket, I get 9.76:1 with the GS1000 head, and 10.7:1 with the GS1100 head.

I'll likely need to run a better grade of fuel if this is the case. I'll try and measure the cylinder later today and see how far off my 1 mm deck clearance guess was. Some of that will go away as the thicker GS1100 OEM base gasket is compressed.

Everything I've found for the 1100G is that the CR is lower, 8.8:1. Seems odd since the chamber is smaller. It may have used a smaller dome in the piston to do this.

[mrl1000l]

1100g piston dome looks much in comparison, I think I post a link to comparison photos earlier in your thread. That's why I've been hesitant to use the stock 1100 pistons and cylinders on my upcoming build, seems like a decrease in power overall if you just do a straight swap.

[GS1000G Shopper]

I think you meant to say looks much smaller. My pistons are not 1100G pistons, the company claims they are replica GS1000 pistons just of a larger bore. The lower 1100G dome would explain the lower 8.8:1 CR and the need for a smaller chamber. This will accordingly raise the CR using the aftermarket pistons. If these are of similar quality to the OEM ones, they are a great value seeing as how they were like $168 shipped with pins, clips, and rings.

[mrl1000l]

Sorry for the garbled english, I shouldn't post before coffee. You are correct in assuming what I meant. I was just about to jump on board with getting a set of these pistons off ebay, but I just found out that a set of 74mm 10.5:1 can be had for VERY cheap! Even in you are getting 10.7:1, I think it would fine with pump gas.

[GS1000G Shopper]

If more than one set is available and you'd care to share a link I'm sure others would be interested.

My wife's 2009 vehicle has a sky-high 11.x:1 CR but runs fine on regular gas with computer control and direct injection, so it should be possible.

I just need to find the energy to wrestle the heavy engine back into place.

[mrl1000l]

After payday, I'm going to buy a set then post the info, don't want to ruin it for myself. Although if anyone were to PM me, I'd have no problem telling them.

I thought I'd also make a note about your numbers. Sorry this is so lengthy, but it might payoff for you. Hopefully I can explain this correctly.

On your new pistons are written "8920" and "8919" and whatnot, this refers to the machinist measurement of the pistons exact diameter which is 2.8920", giving you a bore of 73.45mm

The gs1100g had a longer stroke and a thicker base gasket. If the cylinders were made specific to that stroke, then the stock gs1100 cylinders MIGHT be a bit longer from base gasket to deck along with having a thicker base gasket. In other words, your assumption that a stock gs1000 piston sat "about 1mm" below deck because that is what it currently looks like might be wrong. If I were to just change the base gasket to the stock thickness of .5mm from the 1100 gasket of 1mm, the stock piston with stock cylinders might have sat .5mm below. Let's say the compressed gasket and OEM gasket bore diameter are correct at 1.3 and 72.1 (this would be easy to measure from your old gasket), & OEM bore of 70mm and stock gs1000 39cc combustion chamber volume. Using these numbers to achieve a CR of 9.2:1, I would get a dome volume of 15.8cc.

I hope you are following me here. So lets carry those numbers over to the corrected numbers for your new set up.

Bore: 73.5 (73.45 was the piston size)
Stroke: 64.8 mm (GS1000 crank)
Head gasket bore: 75.12 mm (measured)
Compressed thickness: 1.3 mm (best guess)
Chamber volume: 36 cc (GS1100G)
Piston dome volume: 15.8 cc (from above)
Piston deck clearance: 1 mm (due to thicker base gasket)

You end up with 10.1:1

If you were to remove .5mm off the top of your cylinders, you'd get 10.8:1

I hope this is helpful to you.

[GS1000G Shopper]

Thanks for the info, but the pistons are a nominal 73 mm not 73.45. As evidenced by the picture on page 12 (copied below), my digital caliper had them at 72.88 mm. I would take the "8920" as 72.8920. I did measure one of the cylinders and got 73.38 mm, so the bore is probably close to what you said. A 10.1:1 CR would be fine with me.



Some more progress today. Using the info here on the forum, I placed the engine w/o head on a piece of plywood & used my Harbor Freight motorcycle lift to hoist it up next to the frame. Within 10 minutes I had it in place. Then I remembered I forgot to order a new boot for the shaft drive. Hopefully there is enough wiggle room there to replace it.

I drilled a 5/8" hole in the right exhaust pipe so as to mount the 18mm bung for the O2 sensor.

My new fork springs arrived, so that is on the list to be done.

[Mekanix]

Why are you measuring the diameter at the top and not at 1/2" from the bottom of the skirt?

[GS1000G Shopper]

Because I didn't know that was where to measure them.

I can't measure the new ones, but the old one on my desk is 69.83 at 1/2" above the skirt and 69.32 at the top, .5 mm or so difference. This would make the 72.88 ones about 73.38 +/- above the skirt.

Learn something new every day.

[Mekanix]

Wohoo looks like the numbers work better now.

Yeah all piston measurements I've seen have been from there.

The head will expand allot but that area won't.