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Thread: ESE's works engine tuner

  1. #32236
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    5th April 2013 - 13:09
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    Looking for tips on max safe width for RD400 intake port. I have some cylinders here that have been ported atleast 4 times by other tuners, now I'm supposed to give it a go. Drag racing application.

    I did them, or should I say tried to fix them... but it broke the intake skirts after about 12 1/4 mile runs.

    I'll post intake widths, I didn't make them any wider than previous porters. But because of piston failures, they must be too wide right now.

  2. #32237
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    20th January 2010 - 14:41
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    Quote Originally Posted by jonny quest View Post
    Looking for tips on max safe width for RD400 intake port. I have some cylinders here that have been ported at least 4 times by other tuners, now I'm supposed to give it a go. Drag racing application.

    I did them, or should I say tried to fix them... but it broke the intake skirts after about 12 1/4 mile runs.

    I'll post intake widths, I didn't make them any wider than previous porters. But because of piston failures, they must be too wide right now.
    For road racing the old numbers were .65-.75 with .7 being very reliable in my experience.
    You also need 2mm each side to seal according to bell.
    You can put your cylinders on the other way and the wear will move to the exhaust side.
    I can't remember what the TZ was that they ran backwards but that was the max practical limit on the model before using that available tech at the time.
    He googles G model
    Quote Originally Posted by Frits Overmars View Post

    Husa was of course exaggerating about the piston mileage in the Yamaha TZ250G but apart from that I must agree with him on all accounts.
    The TZ250G was remarkable. Power-wise its cylinder block was a big step forward, with better transfer ducts, smaller exhaust duct volumes and the huge inlet ports that were detrimental to piston life.
    The following year Yahama reversed the direction of crankshaft rotation by means of the jackshaft, but we'd already found a much simpler solution: we reversed the cylinderblock on the 'G': piston problem solved.
    Quote Originally Posted by husaberg View Post
    Although it might appear to be flippant, I actually wasn't Frits, it was out of McKellar’s Yamaha twins book, he lists 80-120 KM piston mileage and cranks not much more. With 53 Rear wheel hp 43mm inlet port width and a 4mm Sinusoidal port roof. More curving yet flat roofed transfers
    Slightly larger Front forks were added as well.
    The official recomended replacement of pistons on the G i believe was per race.
    Along with the Jack shaft and the changed bore and stoke the H was also the first year of the PV, it has bigger big ends, lighter crank wheels and a different crankshaft coupling resulting in less crankshaft flex.
    Base mounted cylinders 44mm intake port width 23mm ex port height and 55 HP. But of course more importantly much greater reliability.

    Funny enough as you know yamaha, eventually followed you. (and MZ)
    Quote Originally Posted by wobbly View Post
    I did the same trick of putting a bridge into the intake on a 350G - 6 port cylinder, as it now has reed boxes on the back.
    This allowed a much wider intake width, and then I added an extra pair of boost ports up each side of the welded in bridge.
    Works well.
    Hummel and Chevalier did some cylinders for the 250 with a bridged intake that worked well also.
    Quote Originally Posted by twotempi View Post

    I have a TZ250G with the inlet port about the same size as the bore. My solution was to weld a 6mm wide vertical bridge in the inlet port which was then shaped into an old cylinder that needed to be re-plated. Early days but this seems to give better support to the rear face of the piston to guide it down the correct hole .l My reasoning also included that since it was in direct line of the conrod there was little reduction in effective port area.
    Reversing the cylinder would mean new pipes etc so this solution have the least effect on the rest of the bike. Also wanted the bike to look "original". Also managed to find a stash of 30 "G" pistons which are 54.25 mm rather than 54.00mm !! And no - I do not want to sell any.
    Comments anyone ? ( Especially Frits Overmars )
    So the tz250G was 79.6%
    The TZ250H 78.5% and was reliable with the jackshaft. ie same as reversing cylinder
    Bridged 100%
    Last edited by husaberg; 15th July 2019 at 17:46. Reason: added stuff
    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

  3. #32238
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    1st May 2016 - 13:54
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    Vintage 2T
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    Quote Originally Posted by jonny quest View Post
    I'm Drag racing application.... but it broke the intake skirts after about 12 1/4 mile runs.
    I'm sure Top Fuellers & Pro-Stockers would Kill for 12 runs from a set of pistons!

    Cheers, Daryl.

  4. #32239
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    7th October 2015 - 07:49
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    honda ns 400
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    Lithuania
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    Wob, it is really interesting how different capacity engine react to piston radius. We tested seven different engines on dyno and ended with different cylinder height, but looks like 50cc needed most cylinder drop from factory settings.

    KTM Sx50 -piston radius 0,7mm Cylinder down 0.5mm from std (best max 14.2 hp)
    KTM Sx65 - piston radius 0.5mm Cylinder up 0,2mm from std (best rmax 18.2 hp winter, at 8500rpm 11hp )
    KTM Sx65- for World cup piston radius 1.0mm Cylinder down 0,2mm from std ( best max 17,33 hp summer, at 8500rpm 13,5 hp )
    KTM Sx125- piston radius 0,5mm ( not mached head) Cylinder up 0.9mm from std ( best max 31,8hp and same mid range like on std with max 28hp)

    We never compensate C duration losses when lowering cylinder, but only because if something goes wrong it would be not possible to rise cylinder again for tests, but maybe with restored C, engine goes even better.

    Its difficult to to stick to one rule for duration with rounded piston, but with sharp at C this is really work. With bigger than 1mm radius, maybe something needed to be done with exhaust pipe, as those is harmonized with non rounded piston.

    Very first time testing on dyno was with full rounded piston 0.7mm on 65cc with some gains, but over 1mm no gains, reaction was very similar to your tests.
    But other variation, with full rounded piston more than 1mm, maybe could be much lower duration for C than A and B.

    Add SX 50 piston photo

    Cheers
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  5. #32240
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    23rd March 2015 - 21:24
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    Conti RX356 V3
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    just for clarification - what does cylinder up/down mean?

    up - e.g. raise it with different gasket beneath cylinder?
    down - e.g. turn it down on a lathe?

    was squish always kept constant?

  6. #32241
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    13th December 2018 - 18:06
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    youtube andreas länström
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    The rd project
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  7. #32242
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    18th May 2007 - 20:23
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    .
    Andreas I love your bike stand. I have one like that under my BSA but yours is more innovated.

    Click image for larger version. 

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  8. #32243
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    20th April 2011 - 08:45
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    Quote Originally Posted by TZ350 View Post
    Andreas I love the bike stand. I have one of those myself.
    What do you call this material? Pre-carbon?

  9. #32244
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    13th December 2018 - 18:06
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    Smile

    Quote Originally Posted by TZ350 View Post
    .
    Andreas I love the bike stand. I have one of those myself.
    Ha ha, piece of art.

  10. #32245
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    13th December 2018 - 18:06
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    Quote Originally Posted by Frits Overmars View Post
    What do you call this material? Pre-carbon?
    Yes natural carbon fiber.

  11. #32246
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    7th October 2015 - 07:49
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    Quote Originally Posted by koenich View Post
    just for clarification - what does cylinder up/down mean?

    up - e.g. raise it with different gasket beneath cylinder?
    down - e.g. turn it down on a lathe?

    was squish always kept constant?
    Yes you right I must correct.

    Up - how much raised cylinder from what we started with non rounded piston ( mainly from factory base gasket setting)

    Down - how much lowered cylinder from what we started with non rounded piston ( usually enough thinnest gasket )

    Squish kept constant and head volume too and this is little frustrating work.

  12. #32247
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    25th March 2004 - 17:22
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    Quote Originally Posted by jonny quest View Post
    Looking for tips on max safe width for RD400 intake port. I have some cylinders here that have been ported atleast 4 times by other tuners, now I'm supposed to give it a go. Drag racing application.

    I did them, or should I say tried to fix them... but it broke the intake skirts after about 12 1/4 mile runs.

    I'll post intake widths, I didn't make them any wider than previous porters. But because of piston failures, they must be too wide right now.
    Very carefully monitor bore wear everywhere and clearances. That will break off piston skirts. It might be you can get away with slightly crazy width but only while fresh.
    Don't you look at my accountant.
    He's the only one I've got.

  13. #32248
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    5th April 2013 - 13:09
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    These RD400 cylinders are at .655. They had .003" piston clearance, running ProX Blaster pistons. Maybe I just need to tighten them up to .0018"... and cringe, use Wiseco Forged.

    The side that didn't break has extensive wear on piston skirt. And you feel it rub on port pushing piston up and down in cylinder.

    There was no detonation.

  14. #32249
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    8th February 2007 - 20:42
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    Thanks for the piston radius info.
    My first reaction would be that if the cylinder reacts best with the radius AND then being lifted, this would mean straight away
    that the cylinder was way low anyway , and would be better being lifted even with no radius.
    If you plot in CAD what happens to the effective timing when adding a radius , it works out that the original timing is achieved
    when lowering the cylinder exactly half the radius ( using a 0.7 feeler gauge as a stop , to change the piston movement by exactly 1mm ).
    I have done alot of work on this in the kart engine and found that a full radius gives really good front side power increase - but at
    the expense of too much overev power.
    But I have just tested lifting the boost port as the latest Modena has it positioned 1/2 way between the A and B.
    This did exactly the opposite - really good overev at the expense of front side power.
    So Im thinking now that the radius , not cut above the boost , along with lowering the cylinder will give me mid range , then lifting the boost
    will add the overev.
    As you say , having to cut special heads to achieve this really is a pain.
    But hey , if it was easy everyone would be doing it.
    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.

  15. #32250
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    20th January 2010 - 14:41
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    Quote Originally Posted by jonny quest View Post
    These RD400 cylinders are at .655. They had .003" piston clearance, running ProX Blaster pistons. Maybe I just need to tighten them up to .0018"... and cringe, use Wiseco Forged.

    The side that didn't break has extensive wear on piston skirt. And you feel it rub on port pushing piston up and down in cylinder.

    There was no detonation.
    The RD400 already has a poor rod to stroke ratio std
    Longer rods will also give the skirts a longer life as it will decrease thrust on the faces.
    KTM200 118mm rods should work with what you have.
    Blaster pistons are a fair bit shorter than RD400 ones. Which will make it worse. .
    woosner do forged it175 ones. they also used to do single ring DT175 ones for long rod rd400's
    ALso oem Yamaha single ring pistons are available for the YZ175 NOS anyway. no idea re their lengths
    Plus TZ750 pistons were in similar sizes.
    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

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