Hur går det för alla TSS500GP byggare?
Kan ju alltid slänga in en ny (nån vecka gammal) uppdatering från Twostrokeshop.
Nu verkar dom ju vara lite överoptimistiska i sina timelines...
men man får väl se det som rolig läsning och det ser ju ut som om projektet fortskrider.
An update is way overdue. We do apologise for being quiet - we have been very busy though in sorting out 11th hour issues.
Firstly, the 90 degree cranks have officially been cancelled due to recurring fuelling glitches, caused by the particular frequency and amplitude of vibes the 90 degree layout causes during (light throttle) running between 5000 to 7000prm, which froths fuel in the carb bowls. This was exacerbated when running the small 100mm flywheel on a race high-compression engine; as the inertia of the lighter flywheel made for choppy running.
Of course, this fuelling glitch should have been picked up early in the piece, and it's ridiculous that it was not. The truth is that most of the testing was done by hardened racers, on track and road, and consequently the throttle tended to be either wide open or snapped shut - as befits the press-on riding style of the race rider. This meant there was not enough running long distances at constant revs and light throttle openings - which are the very conditions that precipitate the fuelling issue.
I (Steve Rothwell) discovered the problems when road riding extensively around New Zealand, and because of this we switched to the 180 degree crankshaft - and the fuelling glitches from 5 to 7k went away. However, under increased constant-running scrutiny it emerged that there were still some burbles being caused by oscillations setting up in the inlet tract - which although it is the correct tuned length for this engine; nevetheless it is twice the length of many 250 single-cylinder MX intake tracts - and this presents with its own challenges. Please let me explain.
Note in the pic below how the distance from cylinder centreline to the end of the intake trumpets is 280mm. This longer than usual intake tract is more sensitive to engine vibrations than shorter intake tracts and because of this, there is more movement exhibited at the far end of the tract and in effect, a pendulum motion sets in at certain resonant frequencies that can unsettle the fuel in the carb bowls, again resulting in fluffy fuelling in certain conditions.
We have learned the hard way that this requires three remedies. Firstly, it requires softer, more pliable intake manifolds than we currently have (as seen in the pic above) - and which we were literally 'stiffed' with. Unfortunately the manifold manufacturer did a number on us, by sending us sample manifolds that had the right material properties (material hardness of 55 Shore) and that worked fine - but when the production manifolds arrived they were all 80 Shore - way too hard. Like I say, we were stiffed. And we put over a year of R&D into these manifolds - it was a huge kick in the guts.
Undeterred; we hired a manifold manufacturer in the UK who has a much stronger record of customer satisfaction(!) and you can see a pic of one of his manifolds below. Again we require the 55 Shore material, which is something we can consistently get from the new manufacturer.
The second part of the carb frothing remedy requires that the rear of the air filters be fastened down to the cross-bar that the seat bolts to. This arrangement, along with the pliable intake manifolds, allows the carbs to be well and truly isolated from engine oscillations. Not that the engines vibrate intrusively you understand; it's just the way the longer intake effectively 'amplifies' vibe inputs - thus the whole intake tract is more sensitive to engine movements.
The third part of the carb frothing remedy mandates that we run a heavier flywheel to smooth out the compression and power pulses. Thus we have purchased the necessary 250W, 18-pole stators and matching rotors - pics below - and also stator plates and trigger sensors. This doesn't mean to say we will be going back to a Wasted-Spark system, because we have figured out a way to run a two-channel, two-CDI ignition by using the twin-trigger-lobe flywheel in conjunction with a single trigger sensor.
As you can see on this page, we make a slot in the centre of the trigger lobe for cylinder#2, which then allows us to programme the signal this double-lobe makes into the software. This allows the dual-CDI ECU to differentiate between cylinders 1 and 2, and thereby we can retain the one-CDI-per-cylinder ignition system. This has been tested with a 1.2mm spark plug gap at 10,500rpm with no loss of engine power.
What this means is that with the kits we will be shipping the new intake manifolds, and stator and rotor and stator plate and trigger sensor setup, and a 180 degree, 58mm stroke balanced crank. (It doesn't matter if you already have one of our 90 degree cranks; we will sort that out later and of course it won't cost you a bean for the replacement crank, nor shipping any parts to us. We will sort it all out.)
It is extremely regrettable that these issues have caused delays on top of the already lengthy production delays. All of these engines and kits should have been shipped out in September. However, it was a good thing that I discovered these issues by riding at *ahem* legal road speeds and over long distances. The lesson learned here is a valuable one: "Don't let racers, no matter how good they are, do testing on bikes destined for the road." The racers were genuinely surprised by my findings, and indeed I had to send them out again on test-rides as many as three times before they were able to reproduce the symptoms I described. I was far from impressed. Lesson learned. From now on, only I will give the last word on how the bikes behave on the road.
What does this mean in terms of an ETA for engine kits/full engines? It means that now we have solved these issues, we have time to package up kits and assemble engines ASAP. The new production manifolds we will send out as soon as they are completed (mid-January) as well as the new 180 degree cranks and new rotors/stators/triggers/stator plates.
I will readily agree this has been an uncomfortably long process, and with indefensible delays such as the above making life even harder. There's a lot that just should not have happened. The test riders were evidently not able to detach themselves from the imperative of going at race pace; and did not fully enter into the spirit of what 'road riding' really constitutes. I had to come along and check for myself, and see things as they really are.
To say I am disappointed at the test riders' lack of finesse doesn't even begin to describe my feelings. But please be assured that now I am on the case, there will be no further issues. I will report again first thing in the New Yewar about shipping dates for all the components/engines.
In the meantime I wish you a great Silly Season! Please don't hesitate to get in touch for anything, anything at all.
My very best regards,
Stephen Rothwell