#6

[speedpro]

Finally got a solid afternoon's work done on the dyno. Still plenty to do. I left it all together in Kevin's workshop, hopefully it won't be too much in the way. It makes a good table at least. Next job will be a pedestal to mount the brake lever on and somewhere to put the laptop.

[F5 Dave]

Looks fairly sturdy.

[speedpro]

Talking of sturdy, check out the new twin plug head

[husaberg]

Talking of sturdy, check out the new twin plug head

It appears you have gone with the rarely used at the bottom of the cylinder option as well.

[speedpro]

Been preparing to do a bit of work on the motor Dave is using. Measured the squish before taking it apart and the head was a bit off forward and to one side as the squish was slightly uneven. Took the head off and it's all looking pretty good. This is after a lot of racing and as can be seen there is the slightest "crescent moon" shaped shadow of carbon on the squish at the front which isn't surprising considering the measured clearance. Otherwise the squish clearance seems to be on the money with no carbon but also no sign of contact in the squish area. Going to put the watercooled head on for the 2-hour. Done a test and it looks like the little lead acid battery shouldn't have any problem powering the pump through the race. Dave said the aircooled motor lost a lot of power once it warmed up and we know from the good motor that this head keeps the power throughout any race.

[speedpro]

Test fitted the watercooled head and found the squish is tight and also the wrong angle for the pistons I'm now using. The tightest part of the squish band is about 4-5mm in from the edge of the bore. There is also a large radius from the squish into the bowl. Looking over it with Kevin and he drags out a tool he has with the curvature of the piston ground into the end so it's just a matter of clocking up the aircooled head and checking the depth from the gasket face to the squish and then duplicating that in the watercooled head, but this time with a curve to match the top of the piston. It'll be real easy with the tool, you just mount it straight in the holder, bump it against the gasket surface and "0" the digital readout, move it over to the correct distance from the centre for the size bore, and then plunge cut to the depth measured on the aircooled head. End result will be a bit more modern cut to the squish/bowl boundary and hopefully an exactly right squish clearance.

I've been thinking about the Ryger and a few things Frits has said and I'm keen to make a new bathtub style chamber cylinder head but with 2 plugs. I think it will be possible to reduce the squish area as with 2 ignition sources within the cylinder the flame front should consume the fuel/air sooner and reduce the risk of detonation, without the need for the squish induced swirl to promote flame travel so much. Should also be able to back the timing off a notch as well. Still got a few other things to sort first, like the 2 hour bikes and the dyno.

I forked out for 4m of flexible brake hose last weekend and have more or less finished the master cylinder and brake lever box. Just need a rose joint and a pushrod and she'll be ready to assemble and bleed.

[F5 Dave]

Twin sparks are (were) often used in 500cc desert racers to stave off deto at tall gearing and sand exacerbated. Not sure they will do much good in a 54mm bore.

See what I did there?

[TZ350]

Twin sparks ... Not sure they will do much good in a 54mm bore. See what I did there?

Good idea, fit an NSR cylinder to the de stroked MB 100.

[speedpro]

I have a NSR cylinder on my bench

[TZ350]

I have a NSR cylinder on my bench

NSR/MB100 conversion .... Excellent.

[F5 Dave]

I have an NSR cylinder under my bench. For the last 20 years. Its an ornament only.

[jasonu]

I have an NSR cylinder under my bench. For the last 20 years. Its an ornament only.

You could glue those titanium surgical implants to it...

[speedpro]

Couple of videos from the 40 lap race last weekend

https://youtu.be/yFdCjRNfQRc

https://youtu.be/o8CBw78mck4

The gear pedal bolt fell out so I removed the whole link. The bike did part 2 stuck in third.

[speedpro]

Back to 4T twins. I've had it running OK without the turbo but have now fitted the turbo and now the 2.5 bar MAP sensor. Thought I'd set the EFI system up properly instead of a few hacks I've tried. It got harder to start and with the WB Lambda sensor system installed it was showing lean generally and wouldn't go over 10,000rpm without falling flat due to leanness. I spent quite a bit of time messing with the tables and had tipped in quite a bit more fuel without effect, I was thinking maybe I was running up against a limit of the fuel supply system. In the end I checked how much the fuel line expanded when the fuel pump was run and thought it wasn't as much as when it was new. We fired it up and I found by squeezing the return line closed I could increase the fuel to the engine. Turns out the fuel regulator is no good now. I could freely blow through it in both directions. When I dismantled it I found an O-ring that seems to have been caught on the edge of an internal fuel gallery. Rob is going to lend me one tomorrow and I'll be back into it. Currently it's on John Connor's dyno where it will stay until the starting is all sorted and we can run it up, after which I will transfer it to the brake dyno I've made. We don't have any power measuring system yet but the brake is all fitted and works good and will allow set loads and rpm to be held and adjustments made to fuel/lambda.

[speedpro]

Now I'm seriously wondering how long there has been a fuel supply problem. Over time I have gone from 80g to 128g injectors and the VE table had some oddly large numbers in it to make it run. I now suspect that for over a year I may have had sagging fuel supply pressure. Rob helped me out with a spare pump and we dismantled my regulator and put in a new O-ring. Turned out his spare regulator had a similar problem in that you could simply blow through it. He also lent me a "Y" piece and I have now plumbed in a pressure gauge. The bike starts and runs easy now but the fuel pressure is only 25psi when it should be about double that. Rob lent a me a new regulator and I will try that first. Even with 25psi, at low load the mixture is rich with the injector on minimum so it looks like I may need to go back to the 80g injectors.
And . . . something happened to the ECU. After trying to load a new VE table it failed and the fuel pump only blips when you power it up instead of running for a few seconds. I tried flashing it with a fresh copy of software but it failed the first time then worked the 2nd time. I then tried to load the last configuration which failed again, and then it was back to the pump just blipping when the system was powered up. I'm going to connect a car battery and try again just to make sure the supply is good later today.