Building a race motor

Don't be cheap. That's rule #1. Just have a look at my "disaster" pages. That should scare you some! :-) Parts will break, just accept the fact. However, you can minimize the chance it will happen with some "must have" parts and "must do's". From top to bottom:

Cams & rockers: Unless you install a top end oiling kit, get hardwelded cams and hardwelded rocker arms. If you have .380" lift cams or less you can use the stock rocker arms. Your stock cams are good as a core to be hardwelded and machined to new specs. You can use GS/GSX performance cams if you machine a new bearing surface to them. No hardening afterwards required.

Cam sprockets: Use the sprockets that where broken-in with the cam chain, otherwise the "new" sprockets will wear out the cam chain in no time. If you have to use new sprockets, install a new cam chain too.

Cylinder head: The B12, GSXR1127 and GSXR1052 heads are 26.5 cc. The -88 -89 (73 mm bore) gsxr750 head can be used to increase the performance as the intake runners are located higher up (and have a more straight path). Stock valve seats will accomodate 30/26 valves. If you have a 85 mm or larger bore, weld up the D-shaped locating holes on each side in the head and use two cylinder block dowel pins at the two middle front studs - that'll make the copper head gasket not leak on #1 and #4. You could also drill a 6 mm hole and use a smaller locating pin.Use the stud o-rings up to 84 mm bore. Coat the copper head gasket with a very thin layer of Copper-Spray-A-Gasket (for a better heat transfer). Use black RTV (silicone) at the cam chain tunnel and around the outer studs and the two innermost front studs. For a flow job, let a reputable shop do it. I trust Mike "Lazer" Hubsher on that. Btw, put the nitrous foggers in the intake boots, there's no need for those expensive (well) billet adapters. Spend the money on a fuel pressure safety switch instead.

Cylinder head rebuilding: The valve seat press fit in an aluminum head should be 1/250 of the valve seats diameter. The valve stem to guide clearance should be around 0.03 mm on the intake and 0.04 mm on the exhaust. But most rebuilders seem to machine the GSXR valve guide holes to exatcly 5.00 mm (even the Suzuki factory does it) so the intake gets a 0.04 mm and the exhaust gets a 0.06 mm clearance. The intake valve is 4.96 mm and the exahaust valve is 4.94 mm.

Valves: The valve seal surface is most often 0.80 mm on the intake and 1.00 mm on a race motor but I think that is too hard on the valves so I set them both to 1.00 mm if it's a naturally apsirated motor. However, a Turbo race motor likes a bit more exhaust seal surface, I set those to 1.50 mm to allow some extra cooling. On a street bike I set both to surfaces to 1.50 mm which allows plenty of miles on the road before the valves goes south and have to be resurfaced or replaced again.

Valve springs: Stock valve springs are set to 40 Lbs. It's plentyful for a .370" WebCam if you keep the revs below 11000 rpm. More agressive cam grounds needs more seat pressure. A Pro Stock .430 cam will need up 60 Lbs of seat pressure. A seat pressure of more than 50 Lbs REQUIRES installation of hard welded rocker arms. A turbo motor may require a seat pressure of 50 Lbs even if you use stock camshafts - just because the intake boost pressure tries to open the valves for you. A really hot turbo motor may require up to 60 Lbs of seat pressure, but then you have to be in the +20 Lbs boost range.

Cylinder head gasket: You can use the spring steel gasket up to about 250 on nitrous and 300 with a turbo. More than that and the peak combustion pressure will exceed the pressure that your flimsy stock cylinder studs will handle and the cylinder head will lift and the gasket will melt. Get heavy duty studs AND heavy duty nuts if you plan on more than 250/300 horses. I use stuff from APE. The copper head gasket MUST have o-rings (copper or steel wire) installed in your sleeves, power rings is another word for it.

Cylinder block: Use an aftermarket Big Block if you plan on cranking out more than 300 horses. The cylinder block is a support for the crankshaft. Have the sleeves o-ringed and use a copper ring if you plan on re-using the head gasket once or twice. A steel o-ring will "bite" too much and will make it impossible to turn it up-side down and re-use it. If you're lucky you might get away by installing it the same way as the first time. If you re-use the copper head gasket - heat it up until it glows cherry red and let it slowly cool down. Do NOT cool it in water. Ask a PhD in physics why it's that way. Btw, get the APE heavy duty studs and nuts. The stock studs will flex when you crank out more than 250 hp nitrous and 300 hp turbo and that'll blow the head gasket before you know what happened.

Pistons: If you use the stock cast OEM pistons they're good for about 250 hp with nitrous and about 300 hp on a turbo application. Nitrous oxide increase the flame speed and increases the pressure in the combustion chamber much faster than a turbo do. For more than that you have to install heavy duty forged pistons with a thicker dome. 7 mm material in the dome is a must for anything more than 300 hp. Have the sleeve to piston clearance set to 0.003" in a setup less than 300 hp. 0.004" is recommended in a 300+ hp setup. Uhm, if you can... use a circlip if you plan on keeping the revs below 11000 rpm. The teflon buttons tend to compress over time and they will eventually end up useless in the oil pan and the wrist pins will destroy your sleeves. Teflon is for racing only and circlips for street riding and low revving motors   (less than 11k).  Set a nitrous motor ring gap to .004" per inch of bore.

Wrist pins: Huh? Can they be that important? YES! Stock wrist pins WILL break in a 250 hp nitrous motor and in a 300 hp turbo motor - eventually. You can have the heavy duty wrist pins for FREE from JE with a new set of JE piston. Otherwise, get the APE tool steel pins. When a wrist pin breaks it will crack the piston, push it up towards the valves and they will crack the valve guides - break the rocker arm and of course bend the valves. Then it will destroy your connecting rod and the connecting rod will poke holes in your cylinder block AND motor cases. Nothing else will cause more damage than a broken wrist pin to a motor. Using new piston, a new wrist pin should have a "floating" fit into the piston, if not - make it so. After some usage the C-clip will create a small "lip" or ridge inside the hole for the pistons wrist pins. Just heat the piston to 50 - 80 degrees Celcuis and the wrist pin will fit smoothly again. Be careful with the piston rings if you're using a blow torch.

Connecting rods: For anything above 250 hp, get a set of Falicon or Carrillo rods. Disregarding what bolts you're using, don't torque them to anything more than what instructions tells you, use a moly-based lubricant on the threads. The bolts will otherwise stretch too much and WILL snap when you hit the high rev limiter the next time. 32 ft-lbs seem to be the standard torque number, at least with ARP bolts for the GSXR. Plasti-gauge the big end clearance to 0.003". Your local dealer can order the Master Bearing Suitcase from Suzuki and if you're really nice they might let you borrow it over the weekend and you get to choose the bearings in your own workshop.

Crank: Have it magnafluxed, balanced and polished. The 1127 crank is prone to crack (it might even be cracked from factory!). The 1052 crank is stronger. Some guys replace the B12 HyVo crank but I haven't had any problems with it. Plasti-gauge the crank bearing clearance to 0.003" to 0.004". Better loose than sorry. Use a good 20W50 oil instead of tight clearances.

Cases: Get the APE heavy duty case studs, they wont flex and will keep the crank in one piece.

Gear box: If you want to spend the money, have it done by R&D in Florida. That'll make it shift even during a wheel spin. The stock gear box is already under cut so you only have to freshen up the 2nd/5th gearsr once in a while. Cost, about $100 at Orient Express (you can do it once or twice before you have to get a new pair).

Oil pan: Make sure the oil pickup isn't restricted. It seems that Suzuki might have a design flaw here. Put a dent in the rear of the pickup (small oil channel) so it isn't starved from oil.

Oil: Use an oil with a high viscosity (crank bearings) and a high flame point (clutch). Change the oil every 30 pass if you're on nitrous or turbo. I'm stuck with Castrol GTX 20W-50. I've tried several other high performance high dollar oils but can't get the clutch to work, not even GTX 10W-40 works for me.

Ignition: If you plan using a rev limiter, shift light, nitrous etc - get the Schnitz Pro Series II box. That box contains everything you'll ever need on a dragbike. Retard the ignition about 1 degree for every 10 hp of extra power you add to it using nitrous oxide or turbo. A naturally aspirated 4-valve 15:1 motor should have about 34 of ignition advance. With a 100 hp nitrous shot it should be about 24 degrees. The Schnitz box has got a "starting  retard" function that allows you to crank a 17:1 motor with the on-board starter.


Motor rebuild notes (11/22/98 - 2/6/99)

The shift detent lever is a cheap design, when you have the motor completly disassembled you should shim the detent lever in such way it will ride in the middle of the shift drum cam. Let there be a 0.02 clearance. If not modified (shimmed) it may cause the gears to pop out and/or give you false neutrals. Check out my picture of the shimmed detent arm.

Be VERY careful at reassembly, don't overuse the RTV goo. Make sure that it DO NOT come near the oil galleys for the gear box and crankshaft. The 6 mm bolts and nuts should NOT be torque to more than 7 ft-lbs, it states otherwise in the service manual. Make yourself and your bike happier, 7 ft-lbs on 6 mm. Make sure you use a lot of moly paste on the crankshaft bearings, rod big ends. Everything else should be soaked in fresh motor oil. Replace the Philips screws for the shift mechanism with Allen type.

Don't disassemble the oil pump unless you suspect there's some debri in it (the pump gears HAS to be in their ORIGINAL position).

Torque the cam chain tensioner bolt (19 mm wrench) to 14 ft-lbs, it's easy to strip its threads.

HeliCoil the 7 mm cam bearing caps for the valve cover bolts, you'll be thankful after the 3rd valve adjustment.

Before you fire up the motor, check out "Dr Brock's" break-in procedure, it's a fast and reliable procedure to get your street or race bike in top shape after a rebuild. Prepare yourself with 2 gallons of Castrol GTX 20W-50 and two new oil filters.