Project Fuel Injected Turbo FZR250, half

Right , Hampton Downs. This is a big circuit with interesting corners and elevation changes. The track took a bit of getting used to and will need more time to get it sorted properly. The bike really didn't help. The boost was really slow to build, which I sort of expected due to the setup. It was really fussy about which gear was used in a corner. One gear too high and it was a complete dog exiting the corner. I had also geared it a bit high which meant I was only getting to the top of 5th gear. It also meant that I was between gears in a few places where ideally I would have been exiting corners at revs with full throttle. The corner leading to the uphill to the front straight was a classic example, down one gear to get it to launch away from the corner and it banged the rev limiter very early. A gear higher and it was just plain slow to get going.

I already have a new setup which should sort out getting boost much earlier and also softened up the rev limiter. It was setup to 100% cut the fuel if it got to the rev limit. Looking at the logs it shows that the inlet temp is exceeding 100°C so now I'm looking for an intercooler. Given location restraints and the size of the smallest core I think it will become my new front number board. I'll probably get one custon made rather than mess around trying to get something else to fit. The high inlet temp would have resulted in the timing being backed off a few degrees as a safety which would knock the power off.

As expected, it wasn't actually making the power that the dyno reported. Being a bike it was only spinning the front rollers and not the rear rollers. The missing inertia made the motor look a lot better than it was. It's not bad for a 125cc and at the end of the start/finish straight it was pulling in the slower 300cc class bikes. It was also making pretty impressive "bangs" when changing gears. The rev limiter was cutting fuel. The new setup cuts the ignition so it will probably be blowing flames when the limiter is reached. Very cool, or not.

The fuel pressure regulator was also changing all the time which I almost expected. Each time I came in I checked the pressure and before I went back out I checked it again. I often found a reasonable change. I've ordered a new Turbosmart rising rate pressure regulator. It has a range of 35-80psi where my default pressure is 35psi. Hopefully this regulator will have the 1:1 rising rate that will make tuning the bike simpler. The logs showed it running very rich at times which may have been due to the regulator, partly at least.

Anyway, it was good to have a shakedown run and confirm that the basics seem OK. It's now time to sort it out

 

I dropped the kart starter back to Kev's place this morning. He gave me another one to use as long as I want. I just need to get a battery for it. In conversation I mentioned that I've been playing with brakes and was about to look at another caliper for the rear. After a bit of fossicking around he comes back with the caliper in the photo and says I can have it. It's one of the cutest calipers I've seen. The good thing is that it is solid mount due to having pistons each side which will make fabrication of the mounting a lot easier. The caliper I was going to use slides on pins. I will refurbish that one but will put it back on the RS.

This caliper can be mounted up either way on either side by switching the hydraulic fittings around. Nice and simple. I'll replace the manky bolt with a nice stainless pin with split pins each side. You have to wonder what they were thinking after making such a nice caliper.

 

The bolt is standard and has a hole in the end for an R clip. Karting requires the clip over the bolt so extra holes have to be drilled.

 

I have ended up fitting the new caliper to the FZR chassis which has an MB100 engine in it. I also bought and modified a new rear sprocket to suit the MB engine better. Photos show the mounting bracket and stay arm that I made and on the other side the sprocket. It all came out looking pretty good I reckon. If I was to do it again I would mount the caliper on the bottom and the bracket would have a thin tube that fits into the chain adjuster in the swingarm like on a RS125 for instance. This allows the axle to be removed and the wheel lifted out leaving the caliper in place.

 

I've spent a bit of time on the dyno and made quite good progress with the tune. It was building boost so slowly it really hindered riding. I wrapped the exhaust to contain the heat in the exhaust and added a spring to the wastegate to hold it closed until more boost was created. with a small change to the boost control it now builds boost a lot quicker. It's still a bit slow but it's now useable. Changing up at 17,500 and 190kPa(90kPa boost) it drops to 14,000 and 140kPa and immediately builds boost again. Sadly boost is limited by the fuel injector duty cycle. Anything over 200kPa at very high revs sees the duty cycle at or over 100%. I'm running it real rich and my tuner guy is not keen on leaning it out for safety reasons. That's piston and valve safety. Apart from that, the only problem left is an annoying trigger error that happens when I back off over 16,000+. It recovers nearly instantly but I don't like it as the ignition timing and injection goes all over the place. Anyway, it's making a reasonably happy 30(ish)hp with more to go if we lean on it. We know it likes a bit more timing and we could lean it out a bit more, and the times I h so they have allowed it to make more boost it made more power with no obvious problems.

New gizmos I want are a quick shifter and a back-torque limiting clutch. I'm going to use short gearing, currently 14:60 with the option of 13:60, and there will be lots of gear changing. If anyone knows where I can get a clutch let me know

 

I spotted those clutches when I was looking around. They are a bit(???) more than I'd like to spend. The only reason I want one is that on downshifts I need to give it a huge handful of throttle to get the engine to "blip" so the downshift doesn't result in wheel hop.
I have ridden the bike around the Tokoroa kart track. I was pretty happy with how the engine ran. I was upshifting at 17,500-18,000 and using full throttle and the trigger noise was much less evident. The engine pulled nicely through the gears and reeled in a couple of others that were nearby a couple of times.
I had a couple of issues with riding it. I had to be cautious as the brakes simply weren't up to it and needed a far too heavy pull on the lever to get it to slow down. I'm not sure of the cause. I think I have used this master cylinder and caliper combo in the past and it was great, but it feels like the master cylinder is too big. I can try a standard front caliper which has bigger diameter pistons. The other issue was folding myself onto the bike and then being able to look around the corners where I was going. I've checked whether my leathers are restricting movement but it seems it is simply that my neck isn't happy being bent the required amount. Nearly guaranteed to be a result of the last big crash. I've put the handlebars back on top of the triple clamps. The triple clamps are dropped a distance down the forks so the handlebars are about 5mm below the top of the fork tubes, so only 20mm or so above the normal position.
I have ordered larger injectors. Hopefully I'll be able to juggle a few things to get them to work good enough down low and on boost I'll be able to supply the required fuel.

 

I've already swapped calipers. I have refitted a standard caliper that I have used previously which worked. I used to get great neck and shoulder massages after racing at Ohakea. They were so good I couldn't get up off the floor afterwards.

 

I have other FZR250 chassis project bikes. I'm looking at possible plans and want to know what others have done to improve the handling. I already have emulators in my turbo twin forks but have received "feedback" about the front end. That bike has a stock rear shock which to me seems reasonable but I'm not a good judge. The chassis with the MB100 engine has a standard looking rear shock but it does have an adjuster on the base of the shock. I have not played with it so don't know the effect it has. My son seems to like how the bike handles. The front forks have a few washers each side on top of the springs. Apart from that I don't know what's been done. The turbo feels quite firm, the MB/FZR feels softer front and back, and Gregs twin is softer again. Greg's bike has a shock with a reservoir and adjustment. At a guess I think it might be off a 600 maybe but with a different spring. I'm considering emulators for the front of the MB/FZR from Sports Valve. A friend has fitted them and is singing their praises. If someone knows of a good replacement shock I'll check them out.

 

OK, that's pretty definite. I've fitted the shock from another bike to the MB/FZR. Turns out it is an early GSXR600/750 shock and about 25mm longer. This is messing up the rocker geometry making it soft at the start of the suspension movement but ramping up quickly as the rocker geometry approaches ideal. The bike is also high at the rear. It does have a stock FZR250 spring fitted. You could probably get away with it as it sags into the region where the rocker geometry is correct. The problem will be under brakes where it'll top out and be promoting stoppies. All good if your name is Toprak.

I'm now looking for a suitable YZF-R6 shock. It seems that '06-'07 is the go but the '08 and later might be OK as well

 

I "eye-balled" the stock shock at 300mm. I'm not 100% sure that it is actually a stock shock as it has a damping adjuster on the bottom which I haven't seen on a couple of others I've looked at. In every other way it looks like a FZR250 shock.
The front forks in my turbo twin were constructed with bits from 3 different fork pairs. Short springs plus spacer tubes were used to get the static and rider sag correct and I fitted emulators as well. Initially the back kept coming up under brakes. One turn on the emulator adjuster screw saw the front dive under control which left the rear planted. Most impressive for someone not familiar with adjustable suspension. Other, better, riders have complained about the front end though. Both are way better than I'll ever be. Both are the type to pitch into corners hard on the brakes with the front tucked time after time.

I plan to remove the stock(?) shock from Greg's bike so I can refit it to the MB/FZR with minimal messing about. Today I've been busy making a strut to replace the shock just to hold it up. Just got a couple of holes to drill then I can jig it up, clamp it then weld it together. It won't fit of course without filing at least a couple of holes to make it fit.

I could make adjustable dog bones but I would be nervous about them staying together. One concern would be having them both adjusted to "EXACTLY" the same length to share the load equally. One way would be to have slightly differently spaced holes in upper and lower halves such that their length could be adjusted in say 1mm increments by relocating a shoulder bolt into different hole pairs.

 

Bullet bitten. Two R6 shocks are on their way from the USA, one for the chassis with the MB100 engine and the 2nd one for my turbo twin. The new injectors have arrived and I've borrowed a test jig to measure what's currently in the bike and the new ones. If a new injector is 50% larger than the current injector I'll do a bulk fuel map adjustment decreasing values by 33% which should put it in the ballpark. The plan is to also drop the fuel pressure back to 3BAR which will also require a fuel map adjustment.