yx 4 valve heads?

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hahah, thought soo mate, and I just had a look at you 122 4 valve you made, made your a champ haha keep up the good work!!!!
 
sean01 said:
milling machine...awesome...
iv been looking at getting one but its hard to find one thats at a decent price unless you settle for a china one, but apparently they have a fair bit of play in them.

what mill did you get and where from if you dont mind me asking...

im looking for 1 to setup and do case boring, piston fly cuts, seat cutting, deck machining and boring...
as well as other things...
Click to expand...

I bought one off my boss, I work for a machinery company. He gave me a pretty sweet price :) Its one of the small single phase chinese ones. I think It'll be good enough for what I want, case boring and decking heads and stuff.
 
Ok, we start with maths. Stock 4v head 2x 21mm intake valves, area = 692 square mm.
Stock 2v head, lets say Takegawa super+R, 29mm intake valve, area = 660 square mm
mmm, looks like the 4v head has a larger intake valve area more than 5%
Looks like the exhaust is similar,,,Bigger is BETTER.
I can also keep in mind that my(China) 4v head is less than a third of the (Takegawa)price, therefore, I can build 3 or more engines for the same price as 1.
Therefore,,,,,,,,If there is a little malfunction with the head,,,,,,,,,,I can push it to the pits, and insert the spare before the next round. At my age I only go for fun anyway. If the Take engine has issues,,,,,get ready to blow an overseas trip for the repair bill, and they do break.
Ok word from AKUNAR, cylinders are no issue. Piston has an issue. CBR piston (up to 67mm:)has 15mm little end, and is 2mm shorter than stock piston. They have bushes manufactured to overcome this, but the obvious solution is the correct size rod. They have given me a choice of rod lengths, but unfortunately for me I have no idea how long a standard yx 160 rod is. I intend to grab a 160 engine in the near future. Does anyone have a 160 crank in bits ? Or know of a specs page on the web?
Enough said, time to get onto Akunar, order the 67mm cylinder, and piston. And strip that head.
The crank can wait for now.
4 VALVES ARE BETTER THAN 2,,,,,,,,,,if it doesnt blow up on the dyno
 
There is more to it then Bigger valve area.

But you got a point with the price ... Maybe compare it to a Tb V2 .. where the price is actually reasonable
 
tormentandglory said:
I bought one off my boss, I work for a machinery company. He gave me a pretty sweet price :) Its one of the small single phase chinese ones. I think It'll be good enough for what I want, case boring and decking heads and stuff.
Click to expand...

yeah i may just end up with a china mill to start off with...then move up from there..

tassie01 said:
Ok, we start with maths. Stock 4v head 2x 21mm intake valves, area = 692 square mm.
Stock 2v head, lets say Takegawa super+R, 29mm intake valve, area = 660 square mm
mmm, looks like the 4v head has a larger intake valve area more than 5%
Looks like the exhaust is similar,,,Bigger is BETTER.
I can also keep in mind that my(China) 4v head is less than a third of the (Takegawa)price, therefore, I can build 3 or more engines for the same price as 1.
Therefore,,,,,,,,If there is a little malfunction with the head,,,,,,,,,,I can push it to the pits, and insert the spare before the next round. At my age I only go for fun anyway. If the Take engine has issues,,,,,get ready to blow an overseas trip for the repair bill, and they do break.
Ok word from AKUNAR, cylinders are no issue. Piston has an issue. CBR piston (up to 67mm:)has 15mm little end, and is 2mm shorter than stock piston. They have bushes manufactured to overcome this, but the obvious solution is the correct size rod. They have given me a choice of rod lengths, but unfortunately for me I have no idea how long a standard yx 160 rod is. I intend to grab a 160 engine in the near future. Does anyone have a 160 crank in bits ? Or know of a specs page on the web?
Enough said, time to get onto Akunar, order the 67mm cylinder, and piston. And strip that head.
The crank can wait for now.
4 VALVES ARE BETTER THAN 2,,,,,,,,,,if it doesnt blow up on the dyno
Click to expand...

has anyone seen any flow figures for these heads.. its all good to have flow area but if they dont flow then wats the good of them...
but in saying that i recon they would be better...

yeah i got pin boots here to convert 15mm pin piston to 13mm rod..

also you could probly work out the 160 rod length from the 150...
the 150 and 160 run the same piston and same barrel...ie pin height is the same and the bore height is the same...
150 has 53mm stroke the 160 is 57mm stroke so that is 4mm difference.
measure the the 150 rod and take 2mm of it....(stroke is longer so rod must be shorter)(and 2mm is half of 4mm between centers, but maybe shouldnt be calculated)

HMMM does that make sense... lol i know what im trying to say but not sure if thats understandable...

lol i have a 160 crank and rod here but it is a tad bent...but it could basically prove my theory above..
 
ok, well i measured my bent yx160 conrod...
between centers it measures 95mm (give or take a mm)
i dont have a `150 crank to compare so can someone else post the length of a yx150 conrod..
 
Ok, maths, 4v head with a pair of 21mm intake valves has about 692mm2 valve area. A2v head with 1, 29mm intake valve has 660mm2 valve area. Not alot of difference, about 5%. I am no guru of engine science but I would have to assume that 2 smaller valves may run more stable at high revs, than a large single valve. The 4v intake has a larger port volume also, which could mean that it has the capacity to flow more at high revs. Somone may put me straight here.
Selected piston for the build is a 67mm honda CBR, with 15mm pin diameter. Akunar will supply this, with a pair of little bushes to support the stock 13mm pin. I also have the option of boring the little end of the stock rod to 15mm. The CBR piston has a top of pin to deck height of 11mm, so it is 2.3mm short of the standard piston. This is overcome by using a 1.5mm offset crank bigend pin. Add 1 mm to CBR piston for the bushes, add 1.5mm for extra stroke, ends up with a probable piston protrusion from the cylinder of .3mm,,,,,,,,the best part is that the engine now has a bore of 67mm and a stroke of 60mm,,,,,,210cc.
Maths done time to order the bits,,,,,,with thanks to Akunar
I can show pics of the 4v head port work, if anyone is interested
 
Hey, cheers guys for measuring your bits,,,,,,,,,,95 mm is nothing to be ashamed of
 
tassie01 said:
Ok, maths, 4v head with a pair of 21mm intake valves has about 692mm2 valve area. A2v head with 1, 29mm intake valve has 660mm2 valve area. Not alot of difference, about 5%. I am no guru of engine science but I would have to assume that 2 smaller valves may run more stable at high revs, than a large single valve. The 4v intake has a larger port volume also, which could mean that it has the capacity to flow more at high revs. Somone may put me straight here.
Selected piston for the build is a 67mm honda CBR, with 15mm pin diameter. Akunar will supply this, with a pair of little bushes to support the stock 13mm pin. I also have the option of boring the little end of the stock rod to 15mm. The CBR piston has a top of pin to deck height of 11mm, so it is 2.3mm short of the standard piston. This is overcome by using a 1.5mm offset crank bigend pin. Add 1 mm to CBR piston for the bushes, add 1.5mm for extra stroke, ends up with a probable piston protrusion from the cylinder of .3mm,,,,,,,,the best part is that the engine now has a bore of 67mm and a stroke of 60mm,,,,,,210cc.
Maths done time to order the bits,,,,,,with thanks to Akunar
I can show pics of the 4v head port work, if anyone is interested
Click to expand...

ok im a little lost in the above...
you say"Add 1 mm to CBR piston for the bushes" wats this all about...
and please dont bore the little end on the conrod... it will more than likely split open in that size engine

and what base crank are you using..

im building a similar engine but using the yx150dt crank which has 60.5mm stroke and is slingerless...
to fit it all that has to be done is run the yx150/160 main bearings on it and change the timing gear and then find a piston that is 63mm with 10mm pin height or fit a shorter conrod... the standard piston hangs out the bore 4mm.

there is always the option of running a CNC conrod...im pretty sure akunar sells them..
we have one in a 196cc engine
 
Ok, draw 2 pistons,,,,,,1 that has a 13 mm pin, and 1 with 15. do it on graph paper to make it easier.
th3 13 mm piston pin piston is stock, and the 15 is the CBR. Draw them with a horizontal line through the pins. now draw the pin bushes on the 13mm pin, now draw the top of pin to deck(piston top). CBR is 11mm, YX is 13.2, can you see where that 1 mm comes from now?
Stock crank from 160 engine will have the offset pin fitted
 
Thats a big engine. What ignition are you gonna use? I'd recommend a lifan 150 ignition, or you'll be cracking cases like eggs. If you're going to that much trouble, is it possible to fit bigger valves to the 4v head? I can't remember how much room there is between the inlets. That head should work well on a sensible size engine, but 200+cc is getting pretty serious. I don't think it'll flow enough. As a rule, in a 2v engine, the inlet valve diameter should be close to 1/2 the bore size. If you do the maths to relate that formula to a 4v setup, I reckon you'll be down about 10% of what is ideal. I'd recommend 23 or 24mm inlets.
It'll be an extreme grunter, but not much rev. Be careful with compression to, I wouldn't be going much higher than 9.5:1. 10:1 max or you'll be leaving a trail of broken engine parts and oil on the track.
 
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tassie01 said:
Ok, draw 2 pistons,,,,,,1 that has a 13 mm pin, and 1 with 15. do it on graph paper to make it easier.
th3 13 mm piston pin piston is stock, and the 15 is the CBR. Draw them with a horizontal line through the pins. now draw the pin bushes on the 13mm pin, now draw the top of pin to deck(piston top). CBR is 11mm, YX is 13.2, can you see where that 1 mm comes from now?
Stock crank from 160 engine will have the offset pin fitted
Click to expand...

yeah i can now tht you say it like that,
i thought the 11mm pin height was including the pin and pin bushes..
so really its a 12mm pin height working off the conrod small end..

also whats happening about valve reliefs in the piston.
and what compression are you chasing..

its going to be a case killer for sure unless you get yrself some sort of decomp setup.
 
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