Suggest on engine head modification work of 81' GSX1100EX

[Anonymous]

chrille:
Did your friend get the 135HP out of stock pistons?

Thanks, Steve

[Anonymous]

If I?m not mistaken, a friend of mine had to modify his engingeblock from the transfer 1074 to 1197cc, so sure as anything you need to do this. Then there is another issue too To get good endurance in the enging you will need to weld and balance your crankshaft, since your?s is not if it hasn?t been already. When I asked Moto-Speed when you need to weld and even go for straight cut gears on the crank/clutch they say "as soon as possible". However, a -81 I know of, that is equippet witha 1168cc, 28mm intakes and stock 23mm outlets but witha a very heavy portet head with even heavier cams and RS36 carbs did the quarter mile at best ET: 9,90sec 20 years ago. That engine still runs today, and the crank has been welded but have the stock sprockets. It all depends on how eager you are at the stoplights..... :P But I strongly recommend the welding though. Wouldn?t want to hear about some engine seizure somewhere in the HONG-KONG area, now would we?

[Anonymous]

SRIVETT

No, he runs Wiseco Aftermarket pistons. I think the stock has 9,7:1 compression and Wiseco should be around 10,25-10,4:1 Not that much a difference. However, if you want to increase anything such as middle-band power raised comp. is one sure way to go. In general a higher comp. increases the load on the piston-rods. But I say. Who cares? A welded crank with stock rods is with you up to around 170 rear-wheel HP. That is not an issue for me anyway. I have a -83 with stock engineblock and factorywelded crank(never been touched) that was news on the -83 GS engine. Above that is a 1168cc JE-piston kit wich is more expensive than the Wiseco. They couldn?t offer me anything else at that time so...
But if you look at the JE they are small masterpieces. Nothing bad about Wiseco but they are different in manufacture. My head is at the shop now for replace of valveguides and 28,5mm intakes and a portingjob of the larger scale(not pure race though) With that I run MIKUNI RS36 carbs wich are sooooo nice. And A 4-1 system to make it complete. Moto-Speed says that the engine should provide somewhere round 140-145 hp at the wheel with stock cams. I?ll let you know when I run the bike in the Dyno.