The first nitrous blowup occurred because my dumbass self did something real stupid. I “FORGOT” to tighten one clamp on Carb # 1. The end result was a LEANOUT on that cylinder. I don’t think it would have happened under normal riding, but with 75 HP of nitrous flowing it was “JUST ENOUGH”. The engine was accelerating hard when POOF, sudden loss of power and I pulled in the clutch and the engine just died. I pulled over unsure what had happened at first. When I tried to restart, I could tell the engine was trying to run on 3 cylinders which it was but also belching a lot of smoke out the pipe. I managed to ride 20 miles home on 3 cylinders. When I got home I discovered the exhaust canister full of oil. I dropped the motor, removed the head and discovered the # 1 piston had melted a hole the size of a 1/2 dollar. It melted over near the exhaust valves, also scaring the cylinder walls. These pistons were Wiseco Forged 1mm over bore. So, I replaced the liner in that bore by heating the block in the stove, bored the liner 1mm over, installed a new piston, and was running the next day. The biggest mess was disassembly of the canister which the packing was soaked in oil, which came up thru the hole in the piston. The bike never tried to lock up or nothing. I later discovered the clamp on carb # 1 was actually stripped and didn’t tighten up, probably the result of being taken on and off a lot……., more to follow shortly on two other blow ups.
Continuing, the second blowup occurred while running on my dyno. I had come across a 91 ZX7 j1 motor. This was the “weak” motor with the so called Euro weanine cams. This was in 1994. One Saturday, I decided to see how much Nitrous HP I could get out of the stock motor. The engine stock made 85 HP. I keep increasing to larger and larger Nitrous/Fuel jets until the engine “LET GO” on the dyno rather unspectacularly. The engine was doing 217 HP when it let go. In this case, a head popped of a valve stem and you could hear it make sounds like a rock in the cylinder. End result was one ruined head from the valve bouncing around in the cylinder, and the cylinder/piston. I did not rebuild this motor as I was trying to see just how far I could push the envelope. I found it. At that point I had made 45 dyno runs on that motor, that same day. I figured I could reliably get 190 HP all day no problem.
The third blowup was a result of to much Back to back use. I had on many occasions discovered after checking my plugs that the ground strap was almost melted off. Almost disaster again. One day while riding, the engine let go under hard acceleration, just lost power again with little fanfare. Pulled in the clutch, and slowly pulled over. Again the engine had let go because I had ran the engine hard on nitrous, slowed down, accelerated hard up to speed and slowed down, and repeated this about 5 times. The end result was the spark plugs overheated (was already using 1 heat range colder), and the engine detonated on 2 cylinders. This time no riding home. Fortunately, the wife came and picked me up. End result? #1 and #3 pistons looked hammered on top, but not melted clean thru. Looked like someone smashed them with hammers. 4 partially melted exhaust valves, but the real pisser was a crack in the cylinder head, between two exhaust valve seats. I sent it to Star Racing in Americus Ga, but they decided it was unrepairable. So one brand new head later, I decided to build a new version of my nitrous motor. This time, I went with some defense measures. I replaced my plugs C9E with some Suzuki CR9k?, hell I cant remember at the moment, I will check later and post. These plugs work great in 7s. They have dual ground electrodes that are much shorter in length than the C9es, therefore they conduct the heat to the shell better. I never had another ground strap melt off. I then decided I would limit Back to back use of the NOS to two blasts, with a few miles in between to allow the plugs to cool back down. I also went to a Dyna 2000 ignition box that auto retards ignition timing when the nitrous comes on. This also is the biggest defense against detonation and spark plug ground electrode melting. Heres the problem…..part 3 coming up.
CR10EK is the plugs that I run wich are 1 heat range colder. I highly recommend the CR9EK plugs for all 7s, they now in fact come in the new 9 motors standard.
On my 93 ZX7R motor, it made best power with a +4 Vance and Hines ignition advancer. This was before the more adjustable advancers had come out. I like to retard the timing 4 degrees for each 50 HP increase in power, so when the Sims and Rhom adjustable advancers came out. I adjusted the timing as much to ideal for non nitrous settings first, then turned it back retarded with the nitrous until the power started to fall off. Unfortunately the best power with the Nitrous came with the timing 8 degrees retarded from that which gave best power without the NOS. This was a terrible compromise as the engine lost 20 HP like this under normal conditions. When the Dyna 2000 ignition became available, I was able to set my timing at +38 degrees lead which was perfect under normal power. Then when the Nitrous activates, the Dyna auto retards the timing a preset amount, only when the nitrous is flowing. I set mine to -12 degrees. THIS WORKED PERFECTLY! A wire from the Dyna wiring harness attaches to the nitrous solenoids, so it knows when to activate. I also placed a low pressure warning switch that if there was insufficient pressure, the nitrous would not cut on. At this time I felt comfortable enough to put in my very special Daytona motor, which had been making a 140+ hp alone. I put in a 50 hp shot of NOS. This combo has been making the last 2 years over 190+ no problem. I made 20 runs at the monster mile without a single hiccup. Fastest speed was 197 MPH, on this long concrete runway, that is in terrible condition, and that’s an understatement. I estimate between 200 and 250 full speed blasts between the dyno, on the road and at Maxton. The bike is stronger than ever until the nitrous runs out.
I’ve been running it in this condition the past two years. Leak down and HP rates has dropped ZERO. Nitrous really keeps the inside of the motor clean. Part 4 coming up, I have a few comments on connecting rods………,
Connecting rods,……..I’ve never had a rod break in a 7. I don’t think rods break from massive increase in power. There are two types of loads on rods. Compressive loads, and Tensile loads. Compressive loads are the result of the power pushing down on the piston. This has never been a problem. Tensile loads are the results of the rods stretching, in other words, the rods compress when pushing down and then on the exhaust stroke going up the stretch the opposite direction. This alternating stretching and compressing of the rods is what causes rods to break, not heavy loads pushing down. So compressive loads are not a problem. It’s tensile loads. Now you ask what causes great increases in tensile loads. WHY OVER REVVING YOUR MOTOR. I don’t care how much power your making, as long as you don’t OVER REV, rods want break. The tensile loads go up as revs go up. I balance all my rods to .1 gram. I weigh all 4, then lighten 3 to match the lightest. I grind off the bottom side of the cap, plenty of spare metal here. I also polish the sides of the beams, they look like chrome when done. This helps stop cracks from forming. This work can be done by Falicon for about 35 dollars a rod and is well worth it. I rev my current motor to 14,000 no problem, but I also have 14,000rpm valve springs.
To sum this all up, Motor Explosions are hardly exciting at all, I’ve never had it lock up or try to throw me off.
Now all of you see why I say, you have nothing to worry about.
Kawasakis Flat rule, its something about superior metals, and hardening techniques in the cranks and in the cases, ect. They just are hard to brake. Ridden hard. It takes lunacy like I’ve posted about to brake them. And the 7s are the best. Kawasaki way overengineered these bikes. I doubt R1s, GSXRs, CBRS, would take this type of abuse. I also have the REAL solution to the rod/crank problems in the ZX11.
All, I put a lot of effort into these posts, I hope you enjoyed and found them informative, please let me know what you think.
I have a turbo motor in development. I hope to have it running in about a month. I will keep you updated.