ESE's works engine tuner

[Grumph]

Peewee, both Keihin and Dellorto and Amal make float valves withe 4.2 and or 4.5 hole size.
Might be easyer to adapt one with no mods.
I have tried drilling / reaming them before, and could not get them to ever seal again.

It is a hell of a lot easier to use the big ones Wob mentions - if you're using gravity feed. And Husa's correct to say check the flow rate of the whole system - how big's your tap ? tank breather ?

I've always found it unneccesary to go bigger if you're using pump feed. I'll qualify that by saying electric or mechanical pump - and not on a kart...

[husaberg]

It is a hell of a lot easier to use the big ones Wob mentions - if you're using gravity feed. And Husa's correct to say check the flow rate of the whole system - how big's your tap ? tank breather ?

I've always found it unneccesary to go bigger if you're using pump feed. I'll qualify that by saying electric or mechanical pump - and not on a kart...

I am pretty confident that 65l/h should belts and braces
http://www.mikunioz.com/shop/df62-70...h-dual-outlet/

[wobbly]

The thing to get "right " with a fuel supply system is the ratio of pressure head to float valve size.
When you only have a tank sitting just above the carb , then the head can be as little as 150mm.
So in this case I had to demand from Lectron that they fit their so called "high flow " valves that are still only 3.5mm.
They were saying I didnt know what I was talking about , until I sent a phone video of a RZ400 racebike making 100RWHp on the dyno.
Doing an all gear run, the clear bowls were less than 1/2 full when clicking into 6th gear using the stock 3mm size.

Using a pulse pump on karts , the current system is to use a 3mm float valve ( 125 making 50 sprocket Hp ) but a return line to the tank is fitted from a Y on
the carb , this gives a head of around 400mm all the time.
And you MUST have consistent fuel bowl level all the time to get reliable jetting, when chasing the weather all day as I do.

Using full pump pressure ( 3.5 psi ) and a 2mm valve would overflow the bowl, as even the slightest bump would shake the floats and allow a high pressure "squirt " past the needle.
Jetski engines use this system, but they dont run over sharp bumps , with high vertical acceleration .

[peewee]

husa ive checked flow from tank more than once. 3.75L per min. more than plenty I would say. I had previously been using the 65L mikuni pump but since I recently made a new aluminum fuel tank I wanted to keep it simple and go gravity from tank directly to carb. and I did have problems with the 65L fuel pressure squirting past the needle and flooding the crankcase like wob said. I believe it was because I was using a 2.5mm valve. once I switched to a 2mm valve it didn't flood the engine nearly as bad. still I would rather just keep it simple with a short hose from tank to carb

wob ive never seen a keihin with removable float valve. ive never seen a delorto valve but im doubting it would screw into my lectron carb, that uses mikuni valves. maybe the needle itself would fit in the mikuni valve and allow me to drill the passage hole bigger ? hard to say without seeing delorto parts. ive got a pwk laying around but its needle diam (slightly over 6mm) is to large to fit in the mikuni valve, otherwise this may be a option. then again maybe I could grind down the four fins on the side of the pwk needle until it fits in the mikuni valve, the bore out the valve hole to 5mm or so.

also I have this other bowl with a stand alone inlet but its made for a jap bike with carb angled to the left side. my carb angles to the right and it hits the shock spring. so I would have to cut of the inlet side of the bowl and weld it back on to the other side of the bowl. this should solve all my problems but nothings ever easy with custom bikes

[lodgernz]

What about using a kart diaphragm/pulse pump and leaving the float valve as close to STD.

PS I would be checking the flow rate out of the tank as well.
http://www.mikunioz.com/shop/df62-70...h-dual-outlet/

...or use 2 pumps and no floats.

[husaberg]

...or use 2 pumps and no floats.

or do like they do with dry sumps and swirl bowls and use a pump around with a reservoir .
Pretty sure some of those big old race v8s used to use a pump around with two pumps.

Another option is the old school extra float bowl like they used to do with the old pomy shitters.

Some of the old pommy bikes and those with Dellortos used to use twin feeds to the carb.

Ages ago I posted a pic of one where Amal MK2 were converted to use remote floats on the Cosworth challenge
Plus one where a guy grafted on fuel bowl and needles off a Valiant to go on a Harley with Anal concentrics.

But I am throwing random shit out there
KISS is get a bigger needle and seat fitted better still get a custom bowl made with additional capacity and a bigger float and needle valve and better floats

Using a pulse pump on karts , the current system is to use a 3mm float valve ( 125 making 50 sprocket Hp ) but a return line to the tank is fitted from a Y on
the carb , this gives a head of around 400mm all the time.
And you MUST have consistent fuel bowl level all the time to get reliable jetting, when chasing the weather all day as I do.

Using full pump pressure ( 3.5 psi ) and a 2mm valve would overflow the bowl, as even the slightest bump would shake the floats and allow a high pressure "squirt " past the needle.
Jetski engines use this system, but they dont run over sharp bumps , with high vertical acceleration .

BELL

Most road race karts use motorcycle engines equipped with conventional float chamber carburettors, which of course means that some type of fuel pump must be installed. The pump which I recommend is a pulse type unit manufactured in America by Outboard Marine Corporation. The type 'AY' pump (Part No. 385784), designed for 60-100 hp outboard motors, is the most readily available and easily capable of supplying the required fuel volume for even the hottest TZ250 engines. To ensure a good strong pulse, the pulse tube connecting the crankcase with the pump must be short (i.e., no longer than 4in) and of small internal diameter. (Most fittings require >/4in bore tube.). If you find the pump will not supply sufficient fuel (this usually only occurs when pulse tubes longer than recommended, and very wild inlet port timings approaching 200°duration, are used), you can fit a small 150cc auxiliary fuel tank to gravity feed straight into the carburettor fuel inlet. The auxiliary tank fills at low rpm and keeps the carburettor full at high speeds when pump pulses are weak. Common plastic tubing is best for the pulse line as it is much stiffer than neoprene tube, hence it conveys a stronger pulse to the pump.Unlike automobile carburettors, motorcycle carburettors will not tolerate even very low fuel pressure before they give way to flooding. Being designed for gravity feed operation, their float system is not capable of shutting off fuel flow through the needle and seat at a pressure as low as 1 psi. Therefore, when a pulse pump is fitted, you will have to incorporate a fuel by-pass line, and also perhaps a pressure regulator, in your fuel system. (FIGURE 5.7). The by-pass line should be of the same internal diameter as the fuel line, and installed such that it is at a level approximately 6-12 inches higher than the carburettor fuel inlet. It must tee-off within one or two inches of the fuel inlet and discharge excess fuel in the top of the fuel tank. These precautions will ensure the fuel will not take a path of low resistance and return to the fuel tank, starving the engine.

Personally I would rather just place a simple restriction on the feed and return lines rather than change a seat or fit a proper regulator.
Just as they used to do on waste gate controllers with a needle tap valve.

PS are you sure its 100%the supply that was the issue on the Yamaha with Lectrons and not the vibes upsetting the floats and levels adding as well?

[wobbly]

The Yamaha with the so called high flow 3.5mm Lectron seats when rerun on the dyno with load control , would pull for 10 secs at peak power in 6th.
When watching the clear bowls the level would drop a little and stay there, whereas before they went below 1/2 full - very scary.
That RZ had a long stroke Banshee crank rebalanced with Mallory, and did not have any discernible vibes.

What thread is needed Peewee, I will measure the Dellorto ones I have here.

https://www.dellorto.co.uk/shop/dell...-needle-valve/

[F5 Dave]

The thing to get "right " with a fuel supply system is the ratio of pressure head to float valve size.
When you only have a tank sitting just above the carb , then the head can be as little as 150mm.
So in this case I had to demand from Lectron that they fit their so called "high flow " valves that are still only 3.5mm.
They were saying I didnt know what I was talking about , until I sent a phone video of a RZ400 racebike making 100RWHp on the dyno.
Doing an all gear run, the clear bowls were less than 1/2 full when clicking into 6th gear using the stock 3mm size.

Using a pulse pump on karts , the current system is to use a 3mm float valve ( 125 making 50 sprocket Hp ) but a return line to the tank is fitted from a Y on
the carb , this gives a head of around 400mm all the time.
And you MUST have consistent fuel bowl level all the time to get reliable jetting, when chasing the weather all day as I do.

Using full pump pressure ( 3.5 psi ) and a 2mm valve would overflow the bowl, as even the slightest bump would shake the floats and allow a high pressure "squirt " past the needle.
Jetski engines use this system, but they dont run over sharp bumps , with high vertical acceleration .

The old dynojet100 I use doesn' have a brake but the all gears run has been a very valuable tool. Many times it has shown a weakness in carb feed on different bikes.

On the flatslide 24mm mikuni one might choose to use for buckets, the float jet can be any size, but the horizontal drilling that feeds the float jet is like 2mm.
Have to drill out a brass ball bearing and then the horizontal hole. But that breaks through so you have to devcon the outside where it breaks out and drill again. Then block where ball was.

This restores power to all gears.

Gee you have me worrying about the 35mmPWKs fitted to my 100hp 496 RZ.

[Grumph]

[QUOTE=husaberg;1131097847]

Personally I would rather just place a simple restriction on the feed and return lines rather than change a seat or fit a proper reguhat.

My personal favourite setup for multiple carbs on methanol is pump feed - usually a Facet 4 - 6LB pump - with a return line T'd off very close to the carbs.
In that return line I fit a Hilborn idle bypass - usually with the 2nd softest spring in the kit.
This gives a measured 1.1 - 1.2 psi at the carbs. Which motorcycle gravity feed carbs will accept happily.
Used with 3/8in bore fuel lines this system has enough capacity that I've never seen fuel starvation on a dyno.

[katinas]

Again positive tests with KTM SX 65 "rounded piston" on track. Today first place in qualification, at first round of European junior championship in Ukraine.

[Frits Overmars]

Again positive tests with KTM SX 65 "rounded piston" on track. Today first place in qualification, at first round of European junior championship in Ukraine.

Well done Katinas

[katinas]

Thanks Frits very much for your insights and advise.
First tests was in Belgium and boy has opportunity to try two bikes: one 18' KTM out of the box, other old bike with new rounded piston.
Very interesting, after tests boy said that he really want new 18' KTM chassis with old rounded piston engine in, so the new engine piston was rounded 0,8 mm, cylinder lightly tuned (cleaned) and lowered 0,4 mm. Head copied to piston roundness and restored volume.
I think is the basis to try this on others engines and maybe try to left sharp piston edge just at C. But it would be more difficult to modified the head.

[peewee]

The Yamaha with the so called high flow 3.5mm Lectron seats when rerun on the dyno with load control , would pull for 10 secs at peak power in 6th.
When watching the clear bowls the level would drop a little and stay there, whereas before they went below 1/2 full - very scary.
That RZ had a long stroke Banshee crank rebalanced with Mallory, and did not have any discernible vibes.

What thread is needed Peewee, I will measure the Dellorto ones I have here.

https://www.dellorto.co.uk/shop/dell...-needle-valve/

I have some great news for anyone that use these shitbox lectrons. last night I got looking at the needle in that stand alone inlet bowl, turns out its a 3.5mm mikuni oring (push in) style float valve. the needle was nearly the same length as the needle in the screw in type valve, although its a bit larger diam. so I grinded down the wings until it just slipped into my 3.5mm style valve. the new needle allows a much larger valve hole, nearly 4.5mm. so I hogged out the hole to 4.37mm to start with and put it to the bench test against my 3.5mm (bored out to 3.6).

with carb fully assembled as it would be on the running engine and 1.9l fuel in the tank it was .115L per 15sec with 3.6mm hole and standard needle. with hole bored to 4.37mm and rubber tip needle, flow was .228L per 15sec. nearly double . for both tests the 6 holes around the sides were bored to about 2.5mm or slightly larger. im going to punch out the center hole to about 4.5mm and test again. I think this modified valve may work like a peach for what I need. first two photo is with the 4.37 hole and grinded down needle. other two photo show the valve I got the needle from and it compared to the standard needle

wob ill figure out what the thread size is and get some length measurements. maybe theres something even better that would work but maybe this grinded down rubber tip needle and the hole bored to 4.4mm or so may do the trick. unless the rubber melts off once it touches methanol or nitro

[peewee]

well I think this is about as much as im going to get from this valve. bored the hole to exact 4.5mm and made it funnel in quit a bit which may not of done any good but why not give it a try. slightly over 2.3L per 15sec. a small flow increase over the 4.37mm hole. maybe if I can bend the tab arms alittle and let the needle drop away from the hole slightly more then maybe it can give more flow, as long as the floats can still push the arms up enough to stop the flow.

[TZ350]

Great work peewee...