Anyone running a 1238 GS1000 on the street?

[Paul]

I don't claim to know a lot about that but I do know that the GS1000 (the 78, 79 at least) transmission is a popular choice for GS drag bikes and that these guys will bolt up larger cylinder jugs and heads onto them to accomplish what your asking without boring out the original one to dangerous levels.

More details I don't know, only that they do it so it can be done.

GS1000 transmission will NOT take the power of a seriously tuned engine. The gearbox will burst, it is the limiting factor in a GS1000 engine, unless you go to heavily modified crankcases etc.

 

[Paul]

In Pro Stock, almost all the bikes are running 1500cc with 2 valve heads. If you are running a four valve head you are limited to 1200cc displacement.

The problem with 1500cc displacement is that there are no cooling passages between the cylinders, thus over heating becomes a major problem when you ride these bikes on the street.

Hap

Are these running stroker cranks? I suppose they must be to get that capacity.

 

[Anonymous]

GS1000 transmission will NOT take the power of a seriously tuned engine. The gearbox will burst, it is the limiting factor in a GS1000 engine, unless you go to heavily modified crankcases etc.

I understand the GSX1100 gearbox will go in with little or no modification. And therefore any race box suitable for the 1100.

 

[Anonymous]

I've just remembered - :idea: :idea: - You can fit the 4-valve GS crank into a 2-valve engine, that gives you a longer stroke which takes the capacity to (I think) just above 1300cc.?

Are you certain? I thought the rod spacing was a good bit different on the 4 valver.

 

[Anonymous]

I have heard conflicting comments about the GSX cranks in GS motors, and I'm not sure if the bore centre to centre distances are the same in these motors. Anybody got spare GSX and GS blocks around and can confirm centre to centre distances???
If they aren't the same then maybe its a case of using some GSX crank parts to build up a GS crank, to give 66mm stroke instead of 64.8mm e.g. 1238cc becomes 1261cc.

Rules governing Pro-stock motors seem to vary between governing bodies(NHRA/Prostar/etc.), but apart from a few Harleys(huge motors and aftermarket cases, heads,....everything!), and a couple of modern ZX-12's and Hayabusa's, everyone uses either GSX motors or KZ/GPz 70's/80's air-cooled motors, running 1500cc, although some go up to 1640cc. Some use the original head castings, but many use aftermarket Vortex 2-valve heads.

So, can anyone measure their spare 4-v 1100 block / 2-v 1000 block for comparison?

 

[Hap Call]

In Pro Stock, almost all the bikes are running 1500cc with 2 valve heads. If you are running a four valve head you are limited to 1200cc displacement.

The problem with 1500cc displacement is that there are no cooling passages between the cylinders, thus over heating becomes a major problem when you ride these bikes on the street.

Hap

Are these running stroker cranks? I suppose they must be to get that capacity.

Yes, they are stroked and bored...

Hap

 

[Anonymous]

I thought they were bore only, stroker cranks not allowed in pro-stock...

 

[Paul]

I've just remembered - :idea: :idea: - You can fit the 4-valve GS crank into a 2-valve engine, that gives you a longer stroke which takes the capacity to (I think) just above 1300cc.?

Are you certain? I thought the rod spacing was a good bit different on the 4 valver.

No, not certain. But I was told that this was the way to go to get mine any bigger. I don't know if you know him, but it was Alan Jefferies who told me - used to be at TTS, then NCK before going on his own. I couldn't see the point of the expense for a very small gain, so I didn't go any further.

 

[Paul]

GS1000 transmission will NOT take the power of a seriously tuned engine. The gearbox will burst, it is the limiting factor in a GS1000 engine, unless you go to heavily modified crankcases etc.

I understand the GSX1100 gearbox will go in with little or no modification. And therefore any race box suitable for the 1100.

The GSX box suffers the same sort of problems as the GS.
The aftermarket 3 or 4 speed transmissions are much stronger, but I didn't think that you could fit into GS cases.
Again, I was under the impression that you could use a GSX bottom end & put on a GS top.
I have seen an aftermarket (Orient Express 3 speed) 2nd gear split on EVERY run up the quarter.

 

[Hap Call]

I thought they were bore only, stroker cranks not allowed in pro-stock...

Must be of a type specifically designed and manufactured for a production motorcycle. Engine manufacturer will determine make of bike. Harley-Davidson V-Twin unlimited bore and stroke; Kawasaki 2-valve roller bearing crank, unlimited bore and stroke; Suzuki 2-valve and 4-valve roller bearing crank, unlimited bore and stock stroke. 2-valve and 4-valve 1994 or newer plain bearing imports unlimited bore and stroke. Suzuki 2-valve 66.4 or smaller stroke allowed. Modification to main engine cases only permitted for repair purposes. CLUTCH: Slider clutch permitted. CYLINDER HEADS: After market cylinder heads permitted with prior approval and consent of the NMRA Technical Department (see General Regulations 1:4). Modifications to the cylinder head may not affect its appearance. All engines must be self-starting. Plug-in electric starters permitted. Push or roller starts prohibited. Snap back throttle return mandatory. TRANSMISSION: Any transmission with a maximum of 6 forward speeds, minimum 4 forward speeds permitted. It must be contained within the stock case, and shifted from gear to gear manually or by air shifter. RPM or computer-shifted gearboxes prohibited. Engine recommended to be equipped with a lower-engine-ballistic/restraint device; (unit must be NMRA accepted) or chassis should be equipped with a sealed fairing or belly pan with a minimum 1 inch raise on all edges and cutouts to cover the bottom of the engine.


Kinda confusing...

Hap

 

[Anonymous]

Hap, I have to agree....These are part of the revised European Pro-stock rules taken from http://www.dragbikes.com/.



Date: 11th December 2003
Headline: UEM Rule changes


Gossip:
The 2004 UEM rulebook has now been published. Important changes to the rules include Pro Stock Bike weight breaks, the relinquishing of the requirement for an annual medical examination until a rider reaches the age of 55, an increase in the prize fund and a standardisation of the ticket allocation to entrants.

The full rule book will be posted on our UEM Championship tomorrow:-

RR09 .1.1 Weight Limits

Minimum weights of bike and rider equipped with:

2-valve DOHC 265 kg max. 1510 cc

4 or 5 valve 265 kg max. 1300 cc

2-valve DOHC 270 kg max. 1600 cc

4 or 5 valve 280 kg max. 1600 cc

2, 4 or 5 valve 285 kg max. 1650 cc

2 cylinder / pushrod 250 kg max. 3000 cc

2 cylinder 220 kg max. 2000 cc

2-stroke 220 kg/n?o allowed max. 1000 cc

For combinations running fuel injection, an additional 10kg must be added to the weight. Use of UEM approve after market cylinder head, add 10kg to the weight.

To get somewhere nearer to the original topic, its been suggested that Rick Gero ran 80mm pistons in a stock block(with big liners) in his GS1000 pro-stocker way back in the late '70's/early '80's. I guess the only way to find out is to try it, although 76mm(1176cc) or 78mm(1238cc) used to be much more common. Anyone forsee any problems in using Wiseco or MTC Kawa Z/GPz pistons?

Paul,
didn't Alan Jefferies race a Kawasaki(?) Funny Bike back in the '80's. What's he doing these days?

Finally, anybody have any experience of 8-plug heads???....

 

[Paul]

To get somewhere nearer to the original topic, its been suggested that Rick Gero ran 80mm pistons in a stock block(with big liners) in his GS1000 pro-stocker way back in the late '70's/early '80's. I guess the only way to find out is to try it, although 76mm(1176cc) or 78mm(1238cc) used to be much more common. Anyone forsee any problems in using Wiseco or MTC Kawa Z/GPz pistons?

Paul,
didn't Alan Jefferies race a Kawasaki(?) Funny Bike back in the '80's. What's he doing these days?

Finally, anybody have any experience of 8-plug heads???....

One reason that a lot of people used 78mm(1238cc) pistons was that they were the largest that Wiseco made for the GS1000! I've just sold a GS1000 block that was fitted with 78mm GPZ pistons, so that is a good substitute for Suzuki pistons. Running bigger pistons could (would?) cause overheating problems, but if you have a large enough budget to go racing it isn't so much of a problem!

Yes, that's the same Alan Jefferies - last I heard he was working on his own building engines for road guys, that was a couple of years back.

8 plug heads - talk to Craig Smith in New Zealand.

You must be in UK, Yoshiman, whereabouts are you?

 

[Anonymous]

Paul,

Yes I'm in the UK, Yorkshire to be more precise. Currently in the process of making a few changes to my recently acquired GS1238 Superstreet bike. I'll be running at the Northern events (Straightliners) in 2004, and maybe at the Pod if a.)budget allows, and b.)I can run some decent times. I'm working to a fairly tight budget and don't want to get into that downward spiral of throwing big amounts of cash away in the quest for losing an extra tenth on the quarter.....
I'd like to build a spare motor over the winter, so if you've got any more 1238 blocks/pistons,etc. let me know!?!

 

[Paul]

Paul,

I'm working to a fairly tight budget and don't want to get into that downward spiral of throwing big amounts of cash away in the quest for losing an extra tenth on the quarter.....

I thought that was what drag-racing was all about - and when you've got no money left you retire because you've lost interest :roll: :roll: :roll:
What sort of times is this Superstreet running?
What history has it got?

I'd like to build a spare motor over the winter, so if you've got any more 1238 blocks/pistons,etc. let me know!?!

Sorry, I sold my spare to a guy in Dorset. I do have quite a lot of spare drag race only stuff.

 

[Anonymous]

Yoshiman I have sent you a PM.

 

[Anonymous]

brit7.11 and Paul: You've got email/pm :wink:

 

[massakins]

A few years ago in the stateside Pro Stock classes the rules were changed to handicap the dominant 4 valve Suzuki racers, thus leveling the playing field for the 2 valve Kawasaki racers. The handicap was primarily the displacement limits previously listed. This resulted in many of the Suzuki racers retrofitting the '80 and later 2v Suzuki heads to their 4v engines (requires relocating 2 (?) cylinder studs and external oiling). This allowed the racers to keep their existing clutches, transmissions and development investment intact. Note that the GPz1100 motors of '82 and later used 18mm wrist pins, like the Suzukis, so pistons were plentiful; for reference the KZ900-1000 motors were 17mm, GS750 2v motors were 16mm and GS1150 motors were 20mm. Later the Pro Stock rules were again changed to allow aftermarket cylinder heads which reduced the usage of the OEM Suzuki version. If memory serves, Russ Olmstead from Texas was the last one to run a complete GS1000 2v based motor on the national Pro Stock tour.

 

[Anonymous]

Interesting info. on the development of the Pro Stock rules. Thanks Massakins.
The Vortex heads that the Pro Stock guys use now are works of art, and should flow serious amounts of air through their 47/36 valves!

I guess anything can be made to fit anything given enough time, skill and money, but as a GS1000 head can with work be fitted on a 4V bottom end, and a GSXR head can also be fitted on a 4V bottom end, then I'm wondering if a GSXR head will fit on a GS1000 bottom(sounds like it'd need some welding and some new stud holes...!?!) That would really confuse people :lol:

 

[Hap Call]

I guess anything can be made to fit anything given enough time, skill and money, but as a GS1000 head can with work be fitted on a 4V bottom end, and a GSXR head can also be fitted on a 4V bottom end, then I'm wondering if a GSXR head will fit on a GS1000 bottom(sounds like it'd need some welding and some new stud holes...!?!) That would really confuse people :lol:

You mean like this?

More info at:

http://www.bertaut.com/gssuzuki.html

Hap

 

[massakins]

One impediment to putting the high horsepower potential top ends onto the GS1000 2v lower ends is the availability (i.e. lack of) strong transmission components. Cranks and clutches can be strengthened but transmissions are rare. Plus the GS1100 4v motors will almost fall into a GS1000 2v chassis and bolt in place. Kind of suspect thats the way to go if you need more than 250hp or so. My 2 cents. Hap, how you doing these days? Hope all is well.