Tales from the Emporium

**warewolf** · 17th May 2007, 16:41

Originally Posted by NordieBoy

The thing with carbs seems to be that what you think will happen may bear no resemblence to what actually happens.

That is because the carb is just part of the whole system of the engine.

Futzing with one small part of the system can have a complex effect on the whole system, but hopefully a positive one.

As a possible reason for your increased fuel efficiency, it seems that the net result of the carb spring change is to keep the slide lower. One of the issues with CV carbs is that they meter the fuel mixture better at small openings as there is a greater vacuum differential, and a higher speed flow through a smaller opening. One of the carb gurus calls this the "signalling strength" of the carb. So it could be that now your just-off-idle system is working better than before... more efficiently. (This is off the top of my head, so I could be arse about face on this one.)

Now on top of all that, making the slide bleed hole bigger tends to lift the slide faster, giving better throttle response at the expense of fuel economy. (I'm just about to do this with my 640.) It could be that you've had your slide lifting too fast, now with a stiffer spring it's lifting slower again... quite possibly just like a standard system!

**NordieBoy** · 17th May 2007, 16:49

I'll have to get it back on the dyno sometime and check the torque and air/fuel graphs to see what's changed there.

So...
Who's up to fuel inject their 650?

Has to be easier than carbs

**Crisis management** · 17th May 2007, 16:55

Originally Posted by warewolf

This is the bit I'm challenging: don't think this is correct at all.

Right, step outside........you can start without me if you want

Bugger, I just spent 10 minutes disagreeing with you and ended up proving you right.

I hate it when that happens.

I should have stuck to abuse and shouting loudly.

**warewolf** · 17th May 2007, 17:14

Originally Posted by Crisis management

I should have stuck to abuse and shouting loudly.

Yeah, and then we'd get sin-binned, but at least it'd be what people usually expect on this board.

**cooneyr** · 17th May 2007, 17:53

Originally Posted by warewolf

This is the bit I'm challenging: don't think this is correct at all.

If you uncoil the spring into a straight line, it forms a lever. (After all, a coil spring is simply a more compact form of a straight spring.) If you shorten the length of any given lever, you reduce it's mechanical advantage. We perceive this as "stiffer".

Try it with a ruler on the edge of your desk or bench; 10cm hanging over the edge is a lot stiffer than 20cm. The stiffness of the material doesn't change, but the effect of the leverage changes the effect at the free end quite a bit.

Told you I'm a dumb engineer. I hated structures anyway so I'll stick to counting cars.

This is the most logical explanation I've heard. Moment is the correct term for force times distance about a fulcrum.

R

**NordieBoy** · 4th June 2007, 20:21

Aired the tyres down to 25/30 and took Victor through the Maungatapu today.
I don't know if the track was better/cleaner (definitly wet) but it was the smoothest ride I've done through there.
2-up and the DR just kept on trucking.
Felt really stable and went right through and back without any co-pilot dismounting needed.

The rear E-07 is worn down to the centre ridge now but only slid a little in a couple of downhill wet clay sections.

Hmmm, some rim-locks and 18/23psi may be in order for the next solo ride through there.

Here's a co-pilots eye view of the ride (he took 80 odd photos whilst cruizing along).
Not bad for his first time on anything more than gravel.

**NordieBoy** · 15th June 2007, 22:50

Stock pipe went back on (again) today.
DJ150 main and needle 4th from top.
Through the Maungatapu again (the things I have to put up with).
Much better than as jetted for the SuperTrapp (DJ155 main) and can listen to music whilst riding as well now.
Not as much go as with the SuperTrapp (3.5s 70-100 in 4th) but acceptable.

The idea is to get some numbers so I can jet correctly for either pipe as needed.

**Crisis management** · 16th June 2007, 11:49

God its tough living down there....you have absolutely none of my sympathy!

I'm surprised the supertrapp and jetting combo doesn't seem to have worked well for you, is the airbox opened up? Everything I have read indicates they need unplugging at both inlet and exhaust to get the airflow up enough.

By the way, I cleaned up internal weld on the exhaust pipe header last night and I see what you mean by "obstruction", it took about half an hours filing to get it sorted!

**warewolf** · 16th June 2007, 12:41

Originally Posted by NordieBoy

Through the Maungatapu again (the things I have to put up with).

Bit crisp yesterday morning, was it?

**NordieBoy** · 16th June 2007, 15:21

Originally Posted by Crisis management

God its tough living down there....you have absolutely none of my sympathy!

Ha Ha!

Originally Posted by Crisis management

I'm surprised the supertrapp and jetting combo doesn't seem to have worked well for you, is the airbox opened up? Everything I have read indicates they need unplugging at both inlet and exhaust to get the airflow up enough.

Oh it works very well indeed and is jetted pretty well spot on according to the dyno.
The airbox, carb, header and pipe have all been fiddled.

But if I want the quiet pipe on (cruizing through the Maungatapu listening to Enya) I want it to be jetted correctly too.

Originally Posted by Crisis management

By the way, I cleaned up internal weld on the exhaust pipe header last night and I see what you mean by "obstruction", it took about half an hours filing to get it sorted!

Carbide burr took about 10mins

Makes a difference alright.

**NordieBoy** · 16th June 2007, 15:25

Originally Posted by warewolf

Bit crisp yesterday morning, was it?

That was 2:30pm

The Nelson side of the saddle and the water crossing before the Rock were a bit frosty but the rest was sweet.

Met an old Sabaru station wagon coming down the Nelson side.
Standard ride height and it looked to be in one piece still

**NordieBoy** · 21st June 2007, 19:35

Just started the road to enlightenment today

**NordieBoy** · 22nd June 2007, 15:42

A small pair of 55w spotties from SuperCheap and a harness for $50 and a bit of fiddling around and...

Ummm...

It's bright but doesn't seem to throw much light.
Need a night test to see though.
Should be a good wide beam to compliment the high beam.