1980 GS1000 restomod

[80GS1000]

Nice!
Background scenery is okay too i guess.

Is the thermostat inboard enough you don't foul it with your right knee?

No clearance issues with my right foot or knee.

[dorkburger]

Love it. Looking sweet.

[80GS1000]

Test & Tune ride #2 results:

THE GOOD:

• Engine starts up and holds a smooth idle around 1000-1100 RPM. No unusual noises.
• Ergos feel good with the cut down seat, superbike bars, and rearsets. Kind of halfway between a sportbike and the stock GS1000 ergos. Reminds me of the Speed Triple I tried a while back.
• Handles really well. Wet weight (all fluids topped off, ready to ride) is in the 435-440 pound range using the bathroom scale method so between the revised steering geometry and the weight loss it feels much more nimble and lighter than stock.
• Stops really well. GSXR 1000 brakes with steel braided lines are no slouches.
• Cosmetically I'm really happy with the way the new blue / paint turned out
• New Hindle 4-2-1 exhaust system sounds great. No ground clearance issues noted
• Charging system is pumping out the correct voltage

THE BAD:

• Carb jetting feels too lean in the mid to upper rev range after installing the Hindle 4-2-1 exhaust system. Feels sluggish and runs hot in the mid to upper rev range. Probably will richen the needles by a notch and go up a size or two on the main jets and reevaluate. At the end of the ride the engine started pinging even on 91 octane ethanol free fuel. Oil temp was 260 in 90 degree weather so it's running too hot.
• The KOSO gauge loses its programming for the speedometer (wheel circumference) and time of day when you turn the key off. Need to contact KOSO for ideas on how to fix that...

THE UGLY:

• Oil cooler adapter on the block is leaking, somewhat badly. Enough to get oil on my left boot. Going to take the oil cooler adapter off the block and reinstall it with some high temp Permatex gasket maker (Motoseal) since the supplied gasket that came with the adapter isn't effective.

[80GS1000]

Test & Tune ride #3

I spent some time in the garage today and dropped the needles one notch and bumped up to 127.5 mains from 125 mains and holy sh!t this thing moves now. Pulls super hard to redline and wants to lift the front wheel from 6-8K RPM in the lower gears. No pinging anymore either. A side benefit over enriching the AFR is that the overheating seen yesterday is now gone too. Cruising oil temps were around 235 range, going over 245 when stopped at a light but dropping once moving again. Calculated fuel economy is 37 MPG, not bad.

I kinda want to put a wideband on it now and really dial in the carbs to about a steady 13 - 13.1 AFR (this AFR feels amazing on my GSXR, lots of power and smooth). Does anyone have experience using a wideband on a GS, and what AFR did you target?

The oil cooler adapter leak now appears to be fixed, but it appears that the stator cover gasket has sprung a leak. Luckily I have one in my parts stash so next up is to replace that gasket.

Finally, I retorqued the steering damper bolt which made a marked improvement in the corners. The bike feels much more planted now when leaned over.

[Grimly]

I kinda want to put a wideband on it now and really dial in the carbs to about a steady 13 - 13.1 AFR (this AFR feels amazing on my GSXR, lots of power and smooth). Does anyone have experience using a wideband on a GS, and what AFR did you target?

Still in progress, and I'm not using the factory carbs, but a single S.U. so results from mine only broadly compare to yours.

The previous damper spring was stronger but it went like a scalded rat when the AFR was sitting around 13:1 as you say.
Replacing that with the standard spring results in a slightly less greedy rate of fuel consumption, verging more towards 14:1 at most steady throttle settings and still dipping nicely into 13:1 territory on hard acceleration as needed.
Best single improvement recently was cleaning up the intake throat to the carb and allowing a free flow through a bigger filter.
Still testing towards nudging the maximum top end upwards.

[80GS1000]

Still in progress, and I'm not using the factory carbs, but a single S.U. so results from mine only broadly compare to yours.

What carbs are you using? I have Mikuni RS34s on mine.

[Nessism]

Super cool project. Congrats! Shedding that much weight while adding performance sounds like a match made in heaven. And speaking of heaven, your riding area looks like that. Wow!

[Grimly]

What carbs are you using? I have Mikuni RS34s on mine.

HIF38 SU single carb. Once I get this one dialled in properly I'll re-fit the HIF 44 I had on it for years but could never get it to idle properly, because of low air speed through the venturi.
The addition of an AFR gauge to the toolbox really kicks things along.

[80GS1000]

HIF38 SU single carb. Once I get this one dialled in properly I'll re-fit the HIF 44 I had on it for years but could never get it to idle properly, because of low air speed through the venturi.
The addition of an AFR gauge to the toolbox really kicks things along.

What's the advantage of using a single carb vs. the normal motorcycle configuration of one carb per cylinder?

[80GS1000]

Airflow & oil leaks

Airflow:

I relocated the oil cooler higher onto the frame and flipped it over so that the ports now face down. The cooler is now much better exposed to free air versus the airflow being partially blocked by the front fender. A side benefit with raising the oil cooler is that airflow to the cooling fins on the cylinder head and block is no longer blocked by the oil cooler.

This has caused oil temps to drop by 20-30 degrees! Before peak oil temps were up to 250 degrees; now they max at about 220 degrees.






Oil leaks:

Engine sounds/runs great/shifts well. Now if this engine would just stop leaking oil...maybe because the engine sat for a long time the gaskets/seals dried out? IDK.

I've had to replace the seal for the oil cooler adapter, the stator cover gasket, and fix a leak where the crankcase halves meet behind the front sprocket cover.

Then this happened...the valve cover gasket blew which cause a pretty significant oil leak. I have an OEM valve cover gasket and half moons on order now. Any tips on installation of these items to prevent further valve cover gasket leaks? Should I apply a thin layer of RTV on both sides of the new gasket before installation to make sure it seals?

[GSX1100 dreamn]

For my gaskets I use Threebond 1211, I have found it to be the most forgiving sealant.
As for sealing the valve cover (or any engine cover) make sure it is flat at first.
Using some 240-400 wet and dry paper and a known flat surface wet the paper in kerosene a great abrasive when it comes to lapping and working in figure 8 remove any high/low spots.
When it comes to applying the Threebond put it on the D rubbers and the head side of the valve cover gasket only and tighten evenly from the center out, working from either side of the cam chain hump out.
I have found doing this also enables me to remove the valve cover later (tappet adjusments,etc) and the cover comes off from the gasket the D rubbers and gasket stay on the head to be used again.
I have reused with no leaks 3 times so far. I also make sure the gasket is a thick one such as Cometic.
Hope it helps, Cheers Andrew.
p.s. I have always have some slight weepage of oil from somewhere on all my GSX motors invariably.

[80GS1000]

For my gaskets I use Threebond 1211, I have found it to be the most forgiving sealant.
As for sealing the valve cover (or any engine cover) make sure it is flat at first.
Using some 240-400 wet and dry paper and a known flat surface wet the paper in kerosene a great abrasive when it comes to lapping and working in figure 8 remove any high/low spots.
When it comes to applying the Threebond put it on the D rubbers and the head side of the valve cover gasket only and tighten evenly from the center out, working from either side of the cam chain hump out.
I have found doing this also enables me to remove the valve cover later (tappet adjusments,etc) and the cover comes off from the gasket the D rubbers and gasket stay on the head to be used again.
I have reused with no leaks 3 times so far. I also make sure the gasket is a thick one such as Cometic.
Hope it helps, Cheers Andrew.
p.s. I have always have some slight weepage of oil from somewhere on all my GSX motors invariably.

Appreciate the advice. Thank you!

I've been advised that the big bore kit (1100 cc high compression Wiseco pistons) may be causing the gaskets on this engine to not seal correctly due to higher than stock crankcase pressures. The stock breather may be inadequate for this application.

So, one of these clutch cover mounted crankcase breathers is now on its way. Now need to source and mount an oil catch can....

[Grimly]

What's the advantage of using a single carb vs. the normal motorcycle configuration of one carb per cylinder?

Cost.
Having two high-mileage bikes on the go at the same time I was faced with the cost of replacing two banks of carbs, plus rubbers front and rear.
Given that the bikes spent nearly all their time at steady speeds on the motorways, plus diving in and out of London, I opted for a choice which was there - using something I knew quite well, having been brought up with SU carbs since I was knee-high.
It worked out quite well, but only in recent years have I decided to get it going the best it can. It was always ok, not very wrong, but not quite right, either.

[GSX1100 dreamn]

Interesting about big bore and excess crankcase pressure, could be a contributing factor.
My 1260 Kat runs the standard crankcase breather for the last 3 years daily to work with no gasket issues.
The weepage I mentioned is from the o ring thats on the head nut.
Cheers Andrew.

[80GS1000]

So where we last left off this engine was having trouble staying oil-tight and needed some carburetor tuning.

Oil Leaks:

Reliable sources indicated that excess crankcase pressure from the big bore kit may have contributing to the oil leakage and secondary breather would be helpful in keeping the gaskets and seals from leaking.

Turns out they were right. I replaced all of the external gaskets on the bike that were leaking just to be sure and installed the secondary crankcase breather on the clutch cover oil filler hole. My friend James was nice enough to TIG together a baffled & filtered aluminum catch can to condense any oil vapor and return it back into the crankcase. I'll probably paint the catch can black when I get around to it.





One oil leak in particular eluded being fixed for a while. The engine was leaking quite a bit oil from the left side when hot, from the "mystery hole" by the starter motor, but no obvious source was found. After searching around the GSR archives for a while, someone in an old post suggested replacing the starter motor O-ring with a new one. I tried that and voila! the leak was fixed! The old o-ring was hard and square. With that leak fixed, the engine is now oil tight.



Carb tuning:

Is it too lean? Too rich? Just right? Lean at idle, rich on top? Is that stumble at 4K RPM because it's too fat or too skinny? Previous tuning techniques like plug chops had left me wanting, so I decided to use a bit of modern tech to tune the carbs.

Enter the AFM wideband AFR gauge using a Bosch wideband sensor in the exhaust. Makes carb tuning so much easier when you have a real-time readout of the AFR at a given throttle position and RPM. The payoff is a much smoother running engine that makes maximum power and fuel economy.






With the oil leaks fixed and the AFR gauge installed, I went on a long ride (about 350 miles) to properly shake the bike down. Nice fall foliage in the Utah mountains here: