Gen II motor build questions

[Draco1340]

I've been away from the org for the while while the bike has been sitting lonely in the trailer all season. Time to tear her open for the first time and build her up. Since I've been away for a while, I was hoping to get a couple of questions answered.

1st - The Gen II has a smaller 18 mm wrist pin located higher up in the piston to accommodate the longer stroke. Has anyone felt this to be a design flaw at the 300 HP level. Are folks converting back to the 20 mm wrist pin and accomidating for the longer stroke with spacer under the block. If I need to change pistons and rods, should I stay with the Gen II setup or not?

2nd - I need to change Pistons, which means I need to bore the block. Several years ago, the turbo guys were complaining that the Gen II blocks were cracking. I don't recall what power level this was happening at, or if this was only at the 84 or 85 mm bore. I would be happy with 83 mm, but again plan on putting down around 300 at the tire on dope. Do I need to track down a Gen I block? What is the basic difference between the two generations of blocks?

3rd - this may cause some controversy among the vendors, but is there any known issues people are having with pistons or rod manufacturers. I just built a freind of mine's ZX14 motor this past weekend with Wossner pistons and Carillo's. Nice looking parts, although I thought the valve pockets and features on the pistons were razor sharp and needed breaking and polishing.

4th - What seems to be the limit the stock rods can take assuming no detonation. I log every pass, and make fuel adjustments as necessary, so I don't typically detonate even though I do run dope.

Thanks for your help.

 

[crawler]

1. The gen 2 design is fine in an aftermarket piston rod combo. I've seen many a 400hp turbo bike run it without issue. I know the hit on the dope is different but they'll be fine.

2. On a 3mil setup I would not run a Gen2 cylinder. Less bore may be fine, may not. But I've witnessed quite a few crack at 3 mil. Two didn't make it past the dyno tune. Some guys say they're fine. I'd never run one though in an overbore situation.

3. I run Wossner pistons in my build and know a ton of people that do. No prep work on the piston itself is needed in the Gen2 Busa piston. Carillo or Wossner rods are great bang for the buck.

4. Stock rods will run up to the 300 mark on turbo bikes. On NO2 bikes I stop trusting stock rods around 250.The torgue spike on a nitrous hit can pop a stock one like a twig. I know there are guys that will argue and say 300 is safe. But when rods are 550-1000 depending on which you do, and it'll cost 300 bucks in gaskets and bearings not to mention the risk of a blown case, ruined head, ruined pistons; Id do the rods while I was there.

 

[crawler]

I appreciate the "like" Professor.

 

[Draco1340]

Thanks Crawler. I will take your advice. Guess I need to look around for a block on ebay...

One more thing. I ran thousands of passes on my "stock" bottom end, and never missed a shift. Are the Gen II transmissions undercut on second and third gear? Do I need to get it cut, or at least remove every other dog? I HATE tearing into things and changing things that aren't broken...

 

[Jay]

The gen 2 18mm pin design is not a design flaw. We have an 18mm pin tht has made mid 6 second passes. It is way stronger than the oem 20mm pin. APE - Tool Steel Wrist Pins

You will notice we have a part number that is a direct replacement for a gen 2 busa, as well as Wiseco, JE and CP sizes.

The gen 2 block is weaker, but we do a huge amount of the big bore blocks, and have had only one, maybe two that have cracked at 84 mm.