Thanks for that - a good solution!
Hardcore Biker
Thanks for that - a good solution!
2 smoke lover
Interesting, How did one stop the exhaust gases causing problems in the cylinder bottom and top where the studs meet the different castingsOriginally Posted by wobbly
Compare Pornography now to 50 years ago.
Then extrapolate 50 years into the future.
. . . That shit's Nasty.
Forum whore
The studs were a neat fit in the overbored casting thru holes and you can see the groove for a Viton O ring just above the Exhaust cutout level.
Never had any heat issues with the gasket surfaces .
Hours of sim , and hours of TIG.
Fastest Pre 82 Post Classic 350 non streamliner on the salt ( 172 mph stuck in 5th pulling 12,000 ) , the second cylinder is in the Frepin frame now.
Not sure who's more scared of it with 100 Hp , me or Charlett.
He does record 13s around Hampton now , with this thing in it and +50mm swingarm I recon 10s easy.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
Low personal B.M.E.P.
I see the inlet side studs are cut away too. Got a pic of the inlet side of the barrels please Wob ?
Forum whore
Yep , my version of Kenny's factory OW , but faster.
Cant decide what would be scarier a TZ750 with 200Hp or a TZ350 with 100Hp.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
Low personal B.M.E.P.
Thanks for the pics Wob.
TZ750 with stock frame would not be pleasant. Where's the Nico Bakker been hidden ?
In some ways the Frepin isn't ideal either. From all i've heard Fred was building for light weight prioritised over stiffness.
And yeah, i know yours is stiffer than the originals.
2 smoke lover
It took me a little time looking at the pics to realise the water jacket had bin cut away to allow the welding for the exhaust ports, I take it they were patched up afterwalds?
Am I reading the code stamped into the top of the piston right and it's a different bore size?
Compare Pornography now to 50 years ago.
Then extrapolate 50 years into the future.
. . . That shit's Nasty.
2 smoke lover
Good spotting! what size reeds are you using? If I can ask Wobbly.
Compare Pornography now to 50 years ago.
Then extrapolate 50 years into the future.
. . . That shit's Nasty.
2 smoke lover
I forgot to ask this in my first Question. I noticed welding on the bottom of the cylinder is it a different stroke?
Compare Pornography now to 50 years ago.
Then extrapolate 50 years into the future.
. . . That shit's Nasty.
Anorak
top and bottom from memory
Kinky is using a feather. Perverted is using the whole chicken
Fair weather rider
I would definitely lead the auxilary ports around the studs.
This was done by DEA in a Vespa Smallframe cylinder. Very good design!
https://www.facebook.com/DeaEngineer...952237/?type=3
Forum whore
Bunch of questions and answers - the long stroke is from cranks I had made with Mallory added for balancing and is 58mm ( +4 Banshee based ) by Shunchi in Taiwan.
They do HotRods and a couple of others.
The bore is 61.5 using race H1 pistons.
Best combination of rpm and port power I could get for an odd 175cc cylinder size.
The cylinder is a 250G as it had the best ducts Yamaha could do in the RD based case stud layout.
A deck plate was added as the rods are special RD400 with Peek coated flat cages @ 115mm to get some case volume and 1.3 ratio , and another plate was added on the top to get the piston edge -0.8 down at TDC.
The crank has rollers on both ends with straight cut low ratio gears , so the clip slot is moved into the middle balls.
The reeds are RS125 Honda from VeeForce , same bolts as CR125 and are what I used offset in the TZ400 , replacing CR250 to get them back on bore center in the flawed CPI cylinder design.
Re the addition of Aux port ducts - sweeping around the studs may look efficient , but then you have an even bigger disparity between the main duct and the Aux duct length.
This smears out the wave front exiting at EPO even more in time and amplitude.
Wasted studs are the best solution - was done first on the inlet in Eckerolds last 350 privateer title TZ/Bimota by my hero Helmut Fath.
I believe the Baker went bare to OZ , Trev put the engine back in a Yamaha frame.
Question from me - when Dennis won the Shorai challenge at Hampton on the TZ400 there was a shitty condition YB3 from OZ with a young lady on board , I want it , the bike or the girl would do .
Who , where etc etc.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
Scooter boy
This brings up a thing that I've seen a few places but never understood.
Auxiliary exhaust ports lower than the main port seems to be something that is completely universal and I get the impression it has been tested to death and there is not much question that is what works best.
But...why? I don't think I've ever seen an explanation that makes sense (to my possibly dim mind). Usually something about smearing or distorting the wave front...but...since the auxiliary exhaust ducts are longer than the main duct, wouldn't that mean that if they were opening at the same height, the wave from the auxiliary ducts would be behind the wave from the main duct, and in order for them to arrive at the same time you would need the auxiliaries to be higher than the main duct and open first.
OR conversely, if there is some advantage to having the wave front from the auxiliaries behind the wave front from the main duct, couldn't you make the auxiliary ducts longer, and the port height the same, thus getting more time area and/or more space for transfer ports?
The best cylinders seem to not do that, so...I dunno.
Fair weather rider
On the DEA (and other) vespa smallframe cylinders the aux ports pass inside the studs, but include a bump on the outer edge to clear the stud. The wasted studs could easily be applied to these to remove that bump.
Patrick Owens
www.OopsClunkThud.com
Forum whore
I must have explained staggered Aux port theory 100 times , but here goes.
Its a twofold act.
Firstly - At EPO , we want the highest amplitude , and longest duration initial wave front ( yes its sonic ) entering the duct and subsequently the header.
This will generate the highest and longest negative pressure ratio at the Ex port around BDC if the pipe geometry is correctly timed.
To achieve this goal we want a single port with the most efficient Blowdown geometry ( ie area ) dumping into the smallest duct area possible.
This is helped immensely by lifting the duct floor ( Jan's genius ) and or necking down the duct exit area to achieve Mach 0.8 ( some tosser called Wobbly's innovation ).
Having the Aux ports lower achieves two goals , it restricts the EPO area , thus generating a high and wide initial wave front , and that wave front is coherent ie because
the Aux duct length is considerably longer than that of the main , this would smear out the high pressure ratio we are striving to achieve if it was active at EPO.
The area at the point the Aux side ducts enter the main is the greatest , and having a later timed high intensity "pulse" entering that area after the main one has passed would in effect create a double
camel hump pressure front that confuses the already complex pipe / wave interaction.
Thus the staggered Aux port is reduced effectively to the role of only dropping the Blowdown remnant pressure before TPO.
Lastly , having concurrent 3 port EPO generates huge Blowdown efficiency , and this kills the front side power , as the staggered transfers actually use remnant Blowdown pressure to
stall flow in the highest TPO , and having very low remnant Blowdown pressure severely reduces the transfer scavenging regimes ability at lower rpm's.
So there you have it SOTA is now staggered Ex and transfers that are subtilty interactive.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
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