Mwahahahah!

Yesterday was a good day.

Alex and Black Mike turned up just after 10am, and we set to dropping
the road motor out of my ZX10R. All went very well, and it was on the
floor by midday. The only interruption was Gyp turning up on his new
(to him) TDR 250.

So we walked into town to get a bite, and sat and ate pasties while
watching the totty walk by in the sun.

Then back to my garage, and we set to fitting the race-spec motor. A
modern litre bike engine is so small and light nowadays that someone
like Alex can pick one up and carry it about. Anyway, it went in
easily enough, and the three of us just worked thru until, around 4:30
pm, it was ready to test run. Ignition on, press the button, and
immediately it fired into life. And sounded fantastic with it's new
full ti exhaust system.

We then bolted on fairing etc, and I took it for a ride. Bearing in
mind it was running a road spec ECU, and therefore the fuelling would
probably not be right, I limited myself to 2/3rds max revs and only a
couple of seconds at a time at full throttle, but **** me it goes
well. The front lifts in 1st gear at 5k revs, and in 2nd at about 8k


Then Gyp and Andy B turned up, so I let Gyp have a go, while I rode
his TDR 250. Which is a lot of fun, but I suspect the power valve is
fucked, as it has nothing below 6k, and everything above it.

Then the five of us went to the pub. And Burnt joined us. And then
to a curry house. And we told lots of old, tall stories, like you do.

Next steps on the bike are:
- get it running with the race kit ECU
- get it set up on a dyno
- fit modded, longer swingarm, with underslung brembi
- fit dymags
- get it re-painted

It's going to be a beaut!

 

Two rear brakes? Surely that's overkill.

 

I thought that was exactly the sort of behaviour expected from a power
valve 2 stroke? Certainly from an electronic power valve, or is the TDR
one mechanical? On a GFR there is nothing (OK in relative terms for a
125) until about 7k when the solenoid kicks in and the valve starts to
open.

You are meant to ride them so that the valve stays open. Which can get
interesting in the wet.


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| Pete Fisher at Home: |
| Voxan Roadster Gilera Nordwest * 2 Yamaha WR250Z |
| Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
+----------------------------------------------------------------+

 

Really? My understanding was that the PV is there to fatten the power
band, thus allowing more extreme top-end tuning. Basically, it
maintains a more constant exhaust port open period, thus matching the
spannie pressure wave timing over a wider RPM range.

Doesn't alter the fact that highly-tuned strokers will always be
pretty flat alt lower revs.

 

I suppose it depends on what you mean by 'nothing' or 'flat'. A GFR is a
special case TBF. Being electronic power valve means it literally opens
with a bang once the tacho reaches a certain rpm. In fact, when my #1
suffered a broken wire on the reg/rec and the battery was going flat
there wasn't enough voltage to open the power valve even if you got the
revs up. This transformed it into something more like a Suzuki 120 until
I got it home and sorted it out.

Up to 7000 it is like riding a bantam, from there to the red line more
like a TZ125. Claimed power is 30 BHP.

I've never ridden a TDR250 or an RD250LC, so have no idea how flat they
are at lowish revs if working properly. Presumably the YPVS system is
more progressive.

Paging Lozzo.

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+----------------------------------------------------------------+
| Pete Fisher at Home: |
| Voxan Roadster Gilera Nordwest * 2 Yamaha WR250Z |
| Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
+----------------------------------------------------------------+

 

On Yamahas, it's there to vary the port height.

 

It should be, yeah. It's a rotating part which "infinitely" varies the
port height depending on revs, controlled by a servo. Up to a certain
point in the rev range it'll do nothing, then it'll gradually open,
after which it's wide open til the redline.

The TDR is still a stroker. All the valve can do is fatten the bottom
end a bit and, at least where YPVS is concerned, smooth out the jumps on
the way up.

The RGV has something more like your GFR - two valves, opening at
different points (8500 and 10000, or thereabouts), giving two fat jumps
in the power curve. It has pretty much **** all below 8500, glorified
trundling power til 10k and then goes batshit crazy. And I wouldn't have
it any other way.

 

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Champ <> saying
something like:

Nice one.

Any progress?
Surely the proddy race guys know something about this?
Ok, given that a road ECU would be required for a proddy racer, there's
bound to be someone or more than one who's fitted a race ECU to a road
loom.
Fwiw, I bet it's annoyingly dead simple.

 

Well done those merry men.

Wish I could've joined you, but after a day of humping several loads of
broken-up concrete to the tip I could barely move. I'm definitely too
old for this shit!

 

TZR and TDR250s are extremely tractable in the middle part of the rev
range, but flat as a fart just off tickover. The Powervalve doesn't
start to open until about 6K revs, but it should still be fairly
torquey below that from 2.5K upwards. You know when the valve opens as
the tacho needle buries itself in the redline.

 

Yes: by varying the port height, you vary the period the port is open.

The engine will be tuned for maximum power when the valve is fully
open; at lower revs the second reflected wave will hit when the port
is still wide open, so its effort will be wasted and fresh mixture
will have time to spill into the exhaust. However, by lowering the
port at low revs, the piston will close it off sooner, so the
reflected wave will hit it closer to the point wher the piston closes
it off. The timing of the reflected waves is more-or-less fixed by the
geometry of the expansion chamber.

 

TBH, the only power-valve bikes I've ever ridden have been 'crossers.

Oh, 250LCs don't have power-valves!

 

I thought the later one did.

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+----------------------------------------------------------------+
| Pete Fisher at Home: |
| Voxan Roadster Gilera Nordwest * 2 Yamaha WR250Z |
| Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
+----------------------------------------------------------------+

 

Some ideas on paper.

well, there isn't much actual 'proddy racing' anymore - it's been
re-invented as Superstock, and you are allowed to do a limited amount
of things. But, running a kit ECU would almost certainly be illegal,
I'm sure.

 

I thought you had a different sort of humping in mind.

 

Err, there was an (I think) RZ250 that was US-spec and had a PV engine
in a 250LC-alike, but I didn't think they were imported into the UK.

Paging Lozzo!

 

Ah. I wonder if those blighters I used to have to race against in the
Formula 50 racing club[1] on my 250 single had got hold of them.

[1] GP125s, 250 singles, 20 LCs and unlimited four stoke twins in one
race!

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+----------------------------------------------------------------+
| Pete Fisher at Home: |
| Voxan Roadster Gilera Nordwest * 2 Yamaha WR250Z |
| Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
+----------------------------------------------------------------+

 

Pip Luscher wrote:

Nope. The RZ250 you're thinking of was basically a 250 version of the
350 Powervalve we got, but made for the Japanese market. The original
4L1 250LC was also designated RZ250 for Japan.

 

It's certainly illegal in MRO Superstock 600 class. You can change
stuff like shocks, plastics and exhausts, but we even have to use stock
screens[1] and brake discs. One poor sod got excluded from the results
because he was running a wavy rear disc on his hopelessly outclassed
2000 model R6, which was right at the back of the pack anyway. It
wasn't like he'd used the damn disc to his advantage cos he was still
slow as **** with it.

[1] We play cheeky here because there was a special edition 675 that
came from the factory with a Triumph branded double bubble screen, so
we use one of those. All the other bikes out there have shitty low
screens that force you to crawl under the paintwork to make effective.

 

Reminds me of the only time raced my Morini Sport. It was a VMCC
meeting at Snetterton, but featured a production race. Good job really
as my 1929 350 Raleigh blew up in practice.

The scrutineers got very huffy about a 'production' bike with clipons
and a bum stop seat. "Came from the factory like that", was my answer.
Still second from last in the 350 class anyway - pesky RDs again.

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+----------------------------------------------------------------+
| Pete Fisher at Home: |
| Voxan Roadster Gilera Nordwest * 2 Yamaha WR250Z |
| Gilera GFR * 2 Moto Morini 2C/375 Morini 350 "Forgotten Error" |
+----------------------------------------------------------------+