The pistons were the first item on our list to tackle. All of my years of experience with the US-made motorcycle pistons had not been good. I had huge success with Cosworth pistons, but they no longer made pistons for motorcycles. There were no off-the-shelf pistons that I could convert either. So, the search was on to find a good piston.
One day, while working on another project with Kelley Roberts of Racing Engine Components (REC-the former US importer for Cosworth motorcycle pistons) I voiced my frustrations with the quality of the pistons available. Kelley enlightened me to the fact that he was trying to have his own pistons made to fill that void in the industry. He offered to help us with our project.
Kelley proceeded to start designing the new pistons with all the performance concepts of a Formula-One car. Since there were no forgings available to start with, he opted to have he entire piston CNC machined from billet. Again, not trusting the usual US companies, Kelley chose to have the pistons manufactured by a source in the UK that he would not divulge.
The process to get the pistons took months; closer to a year actually. There were a few times I was wondering if I would ever see a piston. Nevertheless, they finally came, and they were amazing. The skirts were shorter than anything I had ever seen. The skirt contact area was as narrow as possible. The wrist pins were so short I was afraid to breathe for fear of inhaling one. These pistons were of a design that I had only seen in hi-dollar Factory projects.
Honda's cast-in liners weren't always on center from the factory. With the first 444cc motor we saw that was built by another engine builder, it looked as though the cast-in liners were going to be too thin for the overbore. In one liner, it looked as though there had already been a problem as the engine builder had to re-sleeve that cylinder. My biggest concerns were heat transfer and cylinder bore distortion. I imagined paper-thin liners that would break through at any moment.
So, after long discussions, we decided to contract Millennium Technologies to bore out the cast in sleeve, and create an aluminum sleeve insert that was NikaSil coated and sized for our pistons. This decision was actually made at the time the pistons were being designed, and the expansion rate for the Aluminum/NikaSil liners was taken into consideration in the design.
Aluminum liners and NikaSil expand much closer to the same rate as the piston, so tighter clearances could be run. Aluminum also has a better heat transfer rate, so we were hoping to keep the pistons cooler, which in turn also allows for tighter clearances. This was all in the Master Plan for a reliable motor.
I figured the crankshaft was going to be one of the easier pieces to modify. I have been using a gentleman named Armando Ayalla of Custom Crankshaft Repair for over a decade for crankshaft repair and stroke work. He is local to me, and his work has always been some of the highest regarded work around. The plan was simple: Grind the existing Nitriding down, weld up new material, offset grind the crankpin to the new stroke, re-heat treat, finish and go. This is what has worked for us on every other crankshaft we have had modified by him.
Once we received the cranks from CCR, we sent them off to have balanced. I have been very skeptical of who to use for balancing as I think there is some black magic in the art of balancing that I just don’t understand. Originally, we chose a local shop, but his work didn’t sit right with me, so I ventured to try a place in Oregon called Lyon’s Technical Machining. Speaking with Franc Lyons, the owner/operator, he sounded like he knew what he was doing and the work he turned out was well done at a reasonable price. The motors seemed to run smoothly, so I presume he did what was necessary. With balancing, I don’t know how else to tell.
The forces acting on the big-end of a connecting rod and crank pin can be in the range of 5,000 to 8,000 pounds when running at full force. Reducing the reciprocating weight can help reduce this force and increase reliability. So, in consideration of this, we wanted to go with a Titanium connecting rod. Unfortunately, the budgets of my customers were not really large enough, so I went off to find a financially reasonable source to make the rods.
I was referred to a guy in Northern CA (Petaluma Area) named Larry Childs of Design-It Prototype. Larry had made Ti rods for some Audi car racers with success, and sounded like he knew what he was talking about. He showed me several FEA (Finite Element Analysis) renditions that looked as though they took all the forces into consideration. So, for $1000/set, Larry was contracted to build me 3 sets of Ti rods for the VFR400 and 3 sets of rods for a GSX-R1000 project I was working on as well.
Again, the manufacturing took much longer than anticipated, and we missed several races due to delays and design problems with the rods. Finally, after about 6 months, and a few lawsuit threats, we received our rods. They were extremely light, and very trick looking. The rest was only a test of time.
I set out to test the best cylinder head configurations I could come up with. This is a laborous task on the flow-bench as you have to set-up and break-down after each little change. The set-up and break-down time takes longer than the port mods and teting itself. We were increasing the volume by 13.5cc/cylinder. By increasing the bore 2mm (3.5%) and the stroke by 2.5mm (5.5%) we were increasing the pressure drop in the cylinder, as well as the velocity in the ports. Yet, I was very surprised at what I found.
The Exhaust ports, even with a good exhaust system installed, still flowed too much air compared to the intakes. The rule of thumb is you want the Exhaust tract to flow 65%~75% of the intake for a normally aspirated engine. However, I was seeing numbers in the 90%~105% range for the exhaust. With this information, I decided not to port the exhaust at all. And I found that using a certain Serdi cutter would actually hurt the flow of the exhaust enough that, when matched with the better flow of the ported intake, gave me the percentages I was looking for.
In most of the motors I have stroked and bored in the past, I have found that the intake ports were too large to begin with. Therefore, once the performance was increased, the ports were now better suited for the application. This definitely held true for older generation Honda 600cc motors, and the VFR seemed to hold fast with this as well. Another indicator that this was the case was the NC-35 (next generation of NC) came out with smaller ports. That motor produced 5hp more than the NC-30, but it also had several other changes that obviously contributed to this as well.
On several of the Superbike projects I had worked on, I had seen great improvements with larger valves. However, I had also seen this go the other way as well. Because this was just the beginning of our development with this engine, we decided to leave the stock valves alone for the time being. We hoped to test larger valves once we established a good baseline.
In addition to the reasons listed above for valves, there has been a lot of controversy behind a good cam design. I took a performance class taught by a reputable cam manufacturer, Dema Elgin of Elgin Cams. In his class, Dema was able to enlighten me to the do’s and don’ts of cam manufacturing. With this, I discovered that most of the cam manufacturers of motorcycle cams don’t take the time to really test what they are making.
So, with no proven cams out on the market for this bike, I decided I would put this project on the back-burner until I could spend the time necessary, with the right people, to come up with a cam and valve spring combination that would allow this motor truly make more power and still live.
8. Exhaust System:
There are a few systems on the market for these bikes. However, only a few are truly race tested. We had the opportunity to test 5 or 6 systems back-to-back on the dyno. Our conclusion isn’t all that conclusive though. The only thing I can truly say is, these motors don’t like to be choked. They prefer a 1.75"~2.00” core, and anything smaller creates holes and flat-spots in the power than cannot be tuned out.
We chose to run the RLR “Side-by-Side” system that they ran on their Isle of Mann winning NC-35. This system runs the front and the rear banks of cylinders completely separate from one another (virtually two 2-to-1 exhausts systems). We weren’t too disappointed with this set-up.
After initial break-in and tuning (and a little problem chasing/solving) we saw approximately 85hp at the rear wheel. Our goal was anything over 80hp, with the hopes of 85+. We met our expectations. However, we did have our share of problems along the way, and afterwards.
The excitement came the first time we were able to run that bike on the track. Mike Lohmeyer won the race, and I believe he set a new lap record doing it. 2nd place was nowhere to be seen. This was the beginning of a great run with this bike. Lohmeyer set several lap records, won many races, and even won in Formula-IV.
During testing on the dyno, we discovered we were having some issues with ring seal. The power would drop off radically, and inconsistently, after about 11,000 rpm. We hooked a water manometer to the crankcase to see what would happen, and right at the moment the power would drop off, the water would blow right our the top of the manometer. We tore the motor down many times in the hopes of finding the answers.
We suspected that the pistons were expanding too much at the top (above the top ring) pinching off gas flow. We also suspected that the cylinder walls were possibly distorting allowing extra blow-by. We even suspected that the rings were fluttering due to, well all kinds of theories. This issue sent us in circles, and will be highlighted in our Part Evolution: Piston Section later.
Unfortunately, during all of our testing, we discovered another inherent design flaw in the motor: the rods. During dyno testing, one of the Design-It Ti rods failed dramatically, destroying the motor in a split second. I will never forget that sound of shrapnel flying against the dyno room walls, and the rod hitting the starter motor. We can only be thankful it didn’t happen on the track, but that didn't prevent that overwhelming sick feeling in our stomachs, like we'd lost a child.
After long debate and investigation, we found that Larry Childs of Design-It had overlooked a very simple design aspect of rod manufacturing, and left a sharp stress-riser edge in the design of the rods. Unfortunately, we did not catch this error in time to save one of the GSX-R1000s as it also had a rod let go for the same reason.
You can see here the fracture in the rod started where the relief notch for the rod bolt left a sharp edge after machining. That edge caused a crack propagation and the rest is history. Here's another view showing the sharp edge. The lesson learned here is to radius everything.
Due to time and money, I was forced to pull all remaining motors with these rods and have the rods replaced with Carrillo steel rods immediately (at my expense). Lesson learned here; “You get what you pay for”. Don’t ever "cheap-out" on some of the most critical components in an engine. Let the experienced, reputable companies do what they are good at. This mistake was one of the the primary reasons G-Force is no longer in business. The financial hit of replacing all of the engines and components to our company was too big to eventually overcome.
For the first real season with these bikes, Mike Lohmeyer was able to finish the season 2nd place overall in 450cc Superbike. This was his best-ever finishing rank for the season. Mike Norman, David Crone and Bob Gardner were able to clinch the AFM 450cc Class 4hr endurance win away from Lohmeyer and his team for the first time aboard David Crone's NC-30.
Bore x Stroke: 57.0mm x 44.5mm
Pistons: REC/G-Force Design
Rings: Yamaha FZR400 (3-Rings)
Bores: Millennium Aluminum/NikaSil sleeves
Rods: Design-it Prototype Titanium
Crank: CCR Weld-up stock crank. 1st Generation
Max rpm: 14,500rpm
Carbs: VFR 32mm CV with HRC F-III kit set-up (no airbox)
Race Fuel: VP Ultimate 4 (oxygenated)
DEMISE: Failed Design-It Prototype Ti Rod