ESE's works engine tuner

[Bert]

Just been thinking about trying to make a new manifold for a reedblock, so that's simple enough, a mikuni type spigot bolted to a block of ally that bolts to the reedblock.

But I'm trying to think of a clever way to make a few different stuffers to try out. I'm using a TZR250 1KT 6 petal block & trying to get a block of acetal to fit tight in there & then bore & port it sounds like a wind up. . .

Any other ideas for fabrication?

Hi Dave; I've been pondering the same thing (using the same reed block) to provide better downdraft carb options (i.e. RGV carbs) and offering better clearance for building a full airbox.
the plan was to weld on two internal wings (and grinding them to the correct shape) then filling and shaping the cavity with rubber resin.

...I used to use the rubbery stuff that is used to fit car windows. You can model it with a wet finger and it stays somewhat elastic.

Thanks Frits. That's a very interesting solution; have you found any issue with reaction to fuel or heat?
(I'm guessing not as you wouldn't suggested it in the first place)...

[F5 Dave]

Hmm, I have some of that stuff from when I had a car. That was in the late 80s so maybe it might have gone off by now. Never would have thought it would have coped but heck I'm game to give it a try, thanks for the idea. Might even splash out for a new tube.

[2T Institute]

Horizontal splitters work by directing intake flow at the reed tip where it bends the easiest, loses the least amount of inertia. As a test hit a reed petal with compressed air from your air cleaning nozzle you'll be surprised how much it moves.

[wobbly]

I have done plenty of reed blocks fitted with alloy wing shaped splitters and then filled the cavity with Devcon.
The Devcon also can be shaped with a wet finger, so it doesnt stick.
I make the wing from 5mm plate with a full front radius tapering to a point that sits under the petal tips.
The real trick with the wings is to position the foil offset vertically a few mm, this forces the flow in a bent manifold to equalise
the lift on all the reed petals instead of pushing most to the top.
In a back to back on a flow bench test this gained around 12% of flow at the same pressure drop, and was worth around 2 Hp in a 44 Hp old KX125 - this is why dead straight intakes/downdraft work so well.

[F5 Dave]

Ahh, ok more good ideas to try. Must admit I thought the various bars were just a carry on from Enid Boyson trying to come up with another marketing gimmick back in the late 80s, what was it the 'Boyson bar'? But again I'm happy to be proved wrong.

My 32mm RGV carb is downdraft straight shot, but my 36 KX carb I will run with a bend to start with & progressively straighten to see what angle I can get away with, but it is unlikely to be totally straight as the pilot cct at the front & could flood at some point.

The lower reed will have some part of the crank to climb over but I want both parts of the reed to flow so the wing is starting to make a bit more sense now I think about it.

I think the 32 & the 36 will require different approaches, fortunately I have two 1KT blocks out of my old 350 barrels + a grogous one to cut up if needs be.

Thanks.

[Frits Overmars]

...The real trick with the wings is to position the foil offset vertically a few mm, this forces the flow in a bent manifold to equalise the lift on all the reed petals instead of pushing most to the top.....this is why dead straight intakes/downdraft work so well.

The wings also lessen another problem with bent manifolds. Without the wing the flow will centrifuge to the outside which will overload the outside reeds so they need to be thicker than the inside reeds that seem to have eternal life. These hard outside reeds create a lot of flow resistance. The soft inside reeds would offer less resistance to the flow, if only there was any flow to speak of on the inside of the bend...
Adding the wing (preferably curved) allows the use of softer outside reeds and makes better use of the inside reeds' flow area.
But nothing beats a dead straight inlet tract without a wing.

[gamma500]

Hey guys!

I found some nsr500 engine pics! http://www.geocities.jp/noda_keni/h/...0/00nsr500.htm

[F5 Dave]

Very interesting. Look how tight those webs are packed in there, Honda seem to have kept their love of high ratios.

& I apologise for misspelling Eyvind as Glenn pointed out, memory must be failing.

I can see two different blocks coming on for the different carbs & thus manifolds, thanks for the ideas 2T, Wob & Frits.

[F5 Dave]

Hey here's an odd one. I pulled out the piston from a mates GG dirty bike with 72mm bore. He bought it low hours & has ridden it quite a bit. Piston shows some wear but pretty good.

But checked the ring end gap: 0.3mm! Hells teeth. That's tight for a 300. It didn't look like anyone had been in there before so we have a bike with decent hours on it & rings are super tight close. std spec is 0.5 with 0.8 limit. Wonder how close they were from new?

I would have thought this close on a big bore would have closed the tips up & bulged them. Above ports are perfect with no scoring & cylinder in general looks sweet.

Putting a Wossner in this weekend. Did one in mine a few months back & I went to the bother of filing the end gap to 0.5. Wonder if I should bother?

Are these clearances over protective?

[wobbly]

Very old rule of thumb was 4 thou per inch of bore, so at 72 its near as damn it 3"= 12 thou = 0.3mm = perfect ring gap.

[Frits Overmars]

At 01.30 AM it took me some thinking to kick out the inches and the thou's. But I finally worked it out.
That rule of thumb says: ring gap = 0,4% of bore. Jan Thiel found this to be critical; we use 0,5% of bore as a minimum.
Using too wide a gap may loose you some power. Using too tight a gap may turn the ring into a very effective oil scraper which can lead to a giant seizure.

[F5 Dave]

yeah I just had a look at Wiseco figures & seems ok & manual seems over conservative. So I wonder how tight it must have been when new to be 0.3 now?

my 50 loses a good 2hp when the ring wears much past 0.3

[husaberg]

Hey guys!

I found some nsr500 engine pics! http://www.geocities.jp/noda_keni/h/...0/00nsr500.htm

Hondariffic

There was a while back a set of NSR500 cases on Ebay if memory serves me correct.
i have some pics off a forum if i can find the pics i will post them.

They were a little out of the bucket racers budget though.
There were also some Honda cylinders reputedly from a NSR500 available as well later on.

[F5 Dave]

Shiny rods aren't they?

[2T Institute]

HRC by-passed all the C,B and A kit stuff with the NSR 500. Never seen rods that long on a 125cc HRC cyl.