One for the 250cc folk

[Rasmussen]

looking real good tiny, it`s definitely getting crowded in there. Sounds great too

[generatorshovel]

looking real good tiny, it`s definitely getting crowded in there. Sounds great too

I'm beat, for this year, can't sort the lean out condition Iv'e got , not without trying, I can assure you 

I'm maxed out with the needle jet/needle combo, any richer it won't burn the mix, mind you , it sounds good WHOOF. WHOOF'n on deceleration , I'm sure the blue flames would look good at night !

I'll try going back to a jet combo I know is good up until the main jet takes over, and supplement it with an adjustable power jet ?

Another worry is #1 cylinder running 100 degrees F hotter than the rest, until I put the gas carb on to purge the alcohol out of everything idling , all 4 pots run at the same temp ?
Tiny
Ps, Goggs, we will cya saltside, we leave thursday, plenty of room for beer and tucker now too !

[Rasmussen]

That sucks , but at the same time is very interesting, as a very bad leanout is exactly what I´m dealing with at the moment. Have just posted about it in my thread. We´ll get this fixed! no surrender

[gearheadeh]

Tiny, I like the idea of adapting the Holley float bowl. They make high flow and super high flow needle and seats for alcohol.
What have you done to eliminate that the seats are not flowing enough under high demand, Also- how about the upstream piping and the shut off valve. Are they able to keep up with the flow demands?
Hoping you do well, cheering for you.   

[wobblywalrus]

The advice given to me is to fill the tank up to the top before the race, use a high flow fuel valve like a guzzler, and a well flowing tank vent like a hose projecting up from the gas cap.  The solution might be something really simple.

[generatorshovel]

Tiny, I like the idea of adapting the Holley float bowl. They make high flow and super high flow needle and seats for alcohol.
What have you done to eliminate that the seats are not flowing enough under high demand, Also- how about the upstream piping and the shut off valve. Are they able to keep up with the flow demands?
Hoping you do well, cheering for you.  

Flow from the bowl, measured with drain removed, out of the float bowl(s) exceeds the 1.8 liter needs of my engine @ wot, by 300 ml
I'm using a Mallory 70 gallon / hr pump @ 3.5 psi
The problem I'm thinking, is once boost is at max (9 psi at the moment)the fuel requirements go up, the fuel/ air ratio remains the same, but the air is compresses, the fuel is not (liquids don't compress, even in the droplet state) so the quantity of air in the cylinder is increased, but being a draw thru system, the fuel is introduced before the air is compressed.
Starting with a #640 main, I rode,shot video of the gauges, upped the jet to 680, repeated the test, then upped to a jet drilled to equal a 710 main, there was no difference in the a/f ratio above 3/4 throttle with either of the larger jets, which leads me to think Ive reached the flow limits of the "good" mid range jetting in supplying more fuel at wot.
I cannot increase the flow past the needle and needle jet to enable enough fuel to pass thru the main jet,  between the needle & needle jet diameter/ orifice without changing the a/f ratio from 1/4 to 3/4 throttle, which the engine hates when it's too fat.
Sure, months of cutaway mods, needle mods may cure the problem, But I'm thinking some kind of adjustable powervalve added to the carb may be the answer.
Tiny

[Sam Green]

Hi Bob, sorry to hear the bad news, ya really don't want to go messing them new pistons up if you can't get it to fuel right.
Have you ever thought of going old fashioned and using the likes of a Wal Phillips Fuel injector.
https://www.google.co.uk/search?q=wal+phillips+fuel+injector+instructions&rlz=1C1EODB_enGB531GB532&espv=210&es_sm=93&tbm=isch&imgil=o8ZT3VzOS0nmnM%253A%253Bhttps%253A%252F%252Fencrypted-tbn3.gstatic.com%252Fimages%253Fq%253Dtbn%253AANd9GcTI_N1z959qIRV0sORZOMWi-CfYGxnTHc2pIa5iz7gZV6Op45R6%253B742%253B690%253BioG5FGAX7mW85M%253Bhttp%25253A%25252F%25252Fwww.racinglambrettas.com%25252Fhowthetdidit%25252Fwalphillips.html&source=iu&usg=__BdhjYjXbnRkOXVPWa7OojRq4PGE%3D&sa=X&ei=kCIJU4fdNbCO7QbDm4GAAg&ved=0CDUQ9QEwAQ&biw=1280&bih=963#facrc=_&imgdii=_&imgrc=o8ZT3VzOS0nmnM%253A%3BioG5FGAX7mW85M%3Bhttp%253A%252F%252Fwww.racinglambrettas.com%252Fhowthetdidit%252FWalPhillips11.jpg%3Bhttp%253A%252F%252Fwww.racinglambrettas.com%252Fhowthetdidit%252Fwalphillips.html%3B742%3B690

It's simplicity in itself, just a jet and a butterfly, Ok, I wasn't blown but I used one to get Methanol into my little 175cc LSR back in the 60s and 70s. A lot of the drag race guys used them on all types of blown machines. They are just gravity fed so the only thing you have to make sure of is that you don't turn the fuel on until the motor starts to spin. Also you have to make sure you turn the fuel off when you kill the motor. Just a thought my friend.

Regards Sam.

[generatorshovel]

Yeah Sam, 'ol Wall has entered my brain, I had a mate in the early 70's who used /em on his YDS5 250 yammy, that thing shattered eardrums, shook windows and frustrated it's owner, it was faster in 3rd than it was stock, but wouldn't pull any taller gears, and tended to spit broken chains onto the ground when dragging,,lol,,mamories,,,,,

I think I'll go with the power/thunder/adjustable jet idea at this stake, but I'll have to make it I think,,I already have a 90 degree barbed elbow on my float bowl drain plug, just waiting for another job, other than draining the float bowl, and checking fuel level at a glance.

[Sam Green]

When I got it from Wal, it came ready jetted for Methanol.
I fitted it, turned on the ignition and fuel and spun the rear wheel.
It went straight to a perfect tick over. haha
I never touched it all the time I had it.
It did run very rich but performance wasn't impaired. I had to drop the oil after two runs over the quarter and at the end of a full flyer.
What looks like smoke in the second picture is un burnt fuel coming out of the exhaust.

[generatorshovel]

After a winter rest, tuning has recommenced , disregarding the A/F gauge that was lying all the time (long story)
I went back to similar jetting I had when I melted the piston, but with a fuel pump this time, eliminating the risk of inadequate fuel supply to the carb.
After a flog today, 1/4 mile (or so) @ WOT in 6th I killed ign etc, and pulled the plugs (methanol fuel)
Opinions sought please
I think I'm close to the right side of safe(but not safe , yet), by the look of the plugs ?

[tauruck]

Wee bit lean.

[RansomT]

Wee bit lean.

Agree'd.

and keep an eye on those electrodes.  I had issues in the past with the Iridium's getting strange when boost is applied, they seem not to like the increase cylinder pressures over long distances.

[generatorshovel]

Wee bit lean.

Agree'd.

and keep an eye on those electrodes.  I had issues in the past with the Iridium's getting strange when boost is applied, they seem not to like the increase cylinder pressures over long distances.

Methanol

[wobblywalrus]

It might be worth it to do some research on plug type.  The high compression methanol motors I have seen did not use projecting tip plugs.

[generatorshovel]

Wee bit lean.

Agree'd.

and keep an eye on those electrodes.  I had issues in the past with the Iridium's getting strange when boost is applied, they seem not to like the increase cylinder pressures over long distances.

Agreed, I have new plugs on the way

It might be worth it to do some research on plug type.  The high compression methanol motors I have seen did not use projecting tip plugs.

http://youtu.be/ZA7NEwX_kjk

Another test 'n ' tune today, still leanish,
Tiny