Anyone running a 1238 GS1000 on the street?

[Anonymous]

I'm in the process of assembling a 1238cc (78mm bore) GS1000 as a road bike, and wondered if anyone has any experience of this, or could give me any useful tips.

I have a one-off big block, adapted from a Z1000 item, with nice thick liners, The top of the liners is piano wired for a copper head gasket. The cases have been machined to accept the liners.
Pistons are Wisecos, I think 10.25:1.
The crank will be welded, and I will use external oilways to the head, as well as a cooler. I have a Telcool mk1 adaptor!
As the plan is to go for big midrange, not top end,I plan to start off with stock cams, degreed to 106. Carbs will be RS36 which I already have on my 1085 bike. The head will be mildly flowed and ported.
Would oversize valves be a good idea? The head I have is brand new (big port) and has no valves at present, so its no hardship to go say, 1mm oversize on the ones I buy.

Any advice or tips, or comments welcome.

[daveo]

Kudos to You!!! Sounds like Big Fun! I can't speak from experience regarding this particular combo, but 2 things stand out to me as the way to go...the larger valves will help your low-mid range grunt, and using the stock cams will help your general engine longevity, I would do likewise. Best Luck in Your Endeavors!!!! (Endeavours?) ENJOY

[Paul]

Martin,
I would be concerned about the "meat" left in the barrels, after the liners have been pushed in, or have you got hold of a "gorilla" block? Also 1238 bore needs bigger liners in the Suzuki block, and you have to machine out the crankcase mouth to accept them. If you are going with thicker liners, obviously the crankcase is opened up more, & is therefore thinner - more chance of distortion & oil leaks?
If you are running fairly low compression you may not need the piano wire, but it is good insurance!
I think that you would have thought of these points, but just in case.
How have you done the external oilway to the top end?
What are you going to use for fuel? I don't think a lot of unleaded on a standard GS, never mind a hopped-up one!!

[Anonymous]

Cheers Paul, good points.
Yes the block is a "Gorilla" block. It was made some years ago in a small batch for a fairly well known UK drag racer (don't know which) to suit the Z1000. It has loads of meat, and similarly the liners are massive, they could probably go to 1400cc or so, but the guy who adapted it for the GS1000 was building an ultra strong turbo motor, hence the piano wiring, very thick liners etc. The crankcase has been machined the minimum to fit the liners, I think it'll be OK. Time will tell.
For the oilways I'm going to run a flexi from each side, one from the gallery plug on the RHS, and one from a drilled, tapped and welded lug on the LHS, alternator cover. Then a short link pipe on the head. Thats the plan anyway, not done yet.
I want the bike to run on Super UL. I run the 1085 on Super, but it appears to run fine the odd time I've been forced to use Premium, so Super should be OK. Do you think so? I can set the CR where I want it.
I have a couple of questions:
Will I need to machine the head?
Can I use a Cometic gasket with the piano wires in?
Are phophor bronze bushed small ends good on a road bike?
I plan to use standard oil pump gears. I personally think that the GS750 gears commonly available are too much for the GS1000 as they raise pump speed close to 30%, as against 10%ish when fitted to the GSX1100. Anyone got any comments?
Thanks Paul and Daveo.

[Dink]

Phosphur bronze is fine for a street motor. Commteic make a copper gasket that would be the perfect companion for your fire-ringed block , remember though that you ned to fit orings around the oil return paths so they dont leak with the copper gasket.
The 750 oil pump gears are the way to go , remembering the oil pumps are all the same except for the gearing, so it shouldn't create a problem, IMNSHO it is cheap engine insurance and is a very good idea considering you intend running a top-end oiling kit, the extra volume would be just the thing.
Dink

[saaz]

The GS1000 is not as prone to top end oiling problems as it is a shim design, as opposed to the GSX models. The extra speed oil gears and oil lines would help get rid of all that extra heat from the larger capacity, so I would go with them and a decent sized cooler (make sure it does not leak!). I also have a 1085 motor, and the way it heats up quicker and needs a bigger cooler than a standard motor is amazing, so your project should be very nice....

[Paul]

I have a couple of questions:
Will I need to machine the head?

Not for the bigger bore

Can I use a Cometic gasket with the piano wires in?

As long as the copper rings are on the piano wires. The idea of the piano wire is to dig in to the copper to form air-tight seal - essential on very high compression motors. Thats why so many drag racers use them. Remember what Dink says about the O-rings!

Are phophor bronze bushed small ends good on a road bike?

Why use it? It won't do any harm though

I plan to use standard oil pump gears. I personally think that the GS750 gears commonly available are too much for the GS1000 as they raise pump speed close to 30%, as against 10%ish when fitted to the GSX1100. Anyone got any comments?

I would play safe and use the 750 gears. The very fact that they push pump speed up by 30% makes it a good enough reason for me! Anyway for a road bike you are not going to be up on the redline very often are you! And with all that extra torque that you should gain you will probably be revving it less!

Are there any casting marks in the side of the barrels?

[Anonymous]

Are phophor bronze bushed small ends good on a road bike?

Why use it? It won't do any harm though

I plan to use standard oil pump gears. I personally think that the GS750 gears commonly available are too much for the GS1000 as they raise pump speed close to 30%, as against 10%ish when fitted to the GSX1100. Anyone got any comments?

I would play safe and use the 750 gears. The very fact that they push pump speed up by 30% makes it a good enough reason for me! Anyway for a road bike you are not going to be up on the redline very often are you! And with all that extra torque that you should gain you will probably be revving it less!

Are there any casting marks in the side of the barrels?

I'm planning to use the phossy bronze bushed rods 'cos I got given a set, thats all! May as well use them, as long as they're not going to be worse.

There are no casting marks on the side of the block. It was made by a small concern as part of a very small special order batch.

My concern with those oil pump gears is that the pump may turn too fast at the top end of the rev range, leading to possible cavitation. How fast can these pumps turn before they go outside their efficient range? Does anyone know?

Thanks for the input everyone.

[Anonymous]

Have you got an old copy of Streetfighters, Jan '98 ? There's an incredible-looking GS 1240 in there, a proper mega-bucks job.

Spec. listing is fairly comprehensive; 11.8:1 compression, 40/33 mm valves, Web .425 cams, 8-plug head, etc.

Bike built by some outfit called RB Racing, in Holland. No idea if they're still around, but their address / phone no. is there. Perhaps they'd give you a few pointers ??

Let me know if you want their number.

[Anonymous]

Yes, I've got that issue. Extremely nice bike that.
Bit "full house " for what I want! Lots of ideas though.

[Anonymous]

How is this project progressing?....Any updates?

[Anonymous]

Stalled due to lack of funds! Progress on this one will be sloooww...

[simon lambert]

Big bore kit

I ran this engine combination for quite a few years on the street with no real problems. The problems that did occur were poor battery performance.. ended up fitting a larger battery, poor starter clutch life..
(the starter clutch actually engaged once while riding.. over sped the sarter moter and it disintergrated) and poor transmission clutch life.

Apart from these short comings it was brilliant.. what helped the cause was this engine was fitted to a GS650 frame..

Regards Simon

[Anonymous]

Thanks for that Simon. Nice to know that someone out there has done this too. I have a stock of starter clutches!

Mine will be in a 750 frame, currently has a 1085 in.

Cheers,

[Anonymous]

What is the physical limit to the 2-valve GS1000 bore size? Is it 78mm to give 1238cc(which seems to be the generally accepted limit) or can it be taken further? Z1000's can be taken out to 85mm to give 1500cc, and 4-valve GSX1100's can be taken out to 85mm and beyond - I wonder if the arrival of the 4-valve motor in 1980 ended serious development of the 2-valve motor prematurely, and if an 80mm+ bore is possible (with a huge selection of Z/GPz pistons to choose from?!?).

At the moment I'm not too concerned about the cooling issues, as I'm thinking 'drag only', just whether its physically possible. I vaguely remember reading about a UK Pro-stock rider, possibly in the late 80's, building/planning a GS1330...