yx 4 valve heads?

[tassie01]

The feelers have gone out for the Keihin FCR downdraft kit, I guess all I have to do now is wait a few days, and if no luck get on it again.
Ignition is sorted, small outer rotor stepping advance curve digital CDI, would use nothing else here.
Would have to say that they would be definately one of the best bugget upgrades you can get for pit engine, far an away better than any inner rotor kit.
As for the camshaft, well, still working on this, we all know that the best real way to get an engine to really go is to get a fast camshaft. For the 211cc 4v project, keen to use the stock cam, for now, I think. Got to remember that Mr Big 211cc probably will never see 10 000 rpm, and would probably suit the stock cam. Can have another made up later, if I dont see the big HP numbers.
There are some pics of cams posted, lifan 150, takegawa R20, and the 4V YX, my fast cams are installed. Who can guess the donor bike for this experiment, see pics.
I have an old jailing 120 here, with an Akunar cam, a digi ignition, and a crappy lookin oval carb. It eats 140's for dinner. I can definately see the merit of a reprofiled cam.

 

[wogtaz ryder]

When do you plan on dynoing this thing??

Will be great to see what numbers you can get .

if it holds together for a good run i reckon around 25hp atleast.

 

[tassie01]

The bitz are being gathered from all over the world right now, not sure how long. I guess it will be 8 weeks. Things will progress pretty quickly when the stroker kit, and crank come together.

 

[sean01]

yeah stock cam will be fine, but it would be even better if you can get the lobe sep changed..

 

[wogtaz ryder]

A reminder: I stock the 66mm pistons, in case you ever wear out your 65.5mm setup, or NEED the extra 3cc
If you ever need more power than 192cc, we'll add a 63mm stroker, for 212cc, 215cc with the 66mm bore.

Contact this man , he has alot of the Akunar parts you mite need in stock . he is in the USA .

Let him no about your build and he will give you some damn good advice.

http://www.firepowerminis.com/index.html

 

[tassie01]

Finalising order for Carb, Suppier, Show and Go, Australia
Finalising order for Camshaft, Supplier, OOR,Uk.
Waiting parts Akunar, Thailand, Stroker pin, piston kit, gasgets and cylinder
Waiting parts, Seinor Member, Australia, small outer rotor Digital ignition.


Talked to reco-machine shop for case boring job.
Yet to order heavy duty cam chain
Yet to order complete engine gasget set
Yet to get an engine
Can get quality bearings, after I crack the new engine open.

 

[tassie01]

Ok, jobs done Sunday, finish port the exhaust, and polish.
Lighten, smooth off edges, polish and ballance exhaust valves. Both of the exhaust valves weigh in at 11.73 grams a piece. They are measured to be within 0.01 of a gram each, thanks to a mate who has paint weighing scales.
Interesting note, intake valve 1 weight 14.12, valve 2 weight 13.85 grams. Does not take rocket science to tell you that the difference in weight could factor into differing wear rates in the forked rocker arm ends, contributing to the shocking rattling noises that these engines make. Best to be the same weight.
Time to wash the head, and start putting it back together, been a good little fill in job while I wait for the other parts.
pics posted

 

[tormentandglory]

How much weight did you get off the valves? I lightened and polished the valves in the dirtmax head, I took a LOT of metal off them. A few grams each. And I got stuck into the rockers to, about 6 grams off each. I'll be running takegawa valve springs to. They're slighty smaller diameter, so I should be able to get some metal off the retainers as well.

 

[tassie01]

Hey yea, the valves stock are the best I have ever seen out of china, only managed to get about 0.7 of a gram off each one. Weight difference was about 0.25, which was surprisingly good. I did not take any off the bottom of the stem, like I usually would in a 2V. I have done quite a few multi cylinder 4V's, and they all have this thicker than the stem step behind the back of the valve. My guess is it helps improve flow around the valve, in a deep port. All the takegawa valves go thin at this point, on the 2V's. Most of the jap 2v's are like this also. In a shallow port, thinning the valve stem improves flow around it. Ever seen thinning of the stems in a 4V ?
Also didnt worry about the guides here, they don't really protrude into the port very much.

Didn't think to lighten the rockers, cheers. Just looked at the retainers, they are pretty chunky, paricurly inside below the valve spring step, really thick on top also, and could do with some time in the lathe. Everything takes twice as long, 4 of everything.

 

[sean01]

better question...
how and where was the material you removed.... pretty sure that these are 2 piece valves...
and if you only faced the valves to lighten them then your going to have 2 different installed heights and 1 spring will need more shims than the other...
should got some stainless blanks and made your own

 

[tassie01]

0.7 gram was removed from the valve face(inside combustion area) and overall valve diameter was reduced, and rounded a poofteenth 0.5mm. On the stem side of the valve, the sharp edge on the inside of the seat was rounded, and then polished up the stem
Valves were reinserted, after a big wash up, and the seats were very lightly hand lapped with 1000ppmm paste, mainly to check for damage, thankfully everything was spot on.
Should not have to change shims, but will check for sure, yes, it has shims on the valve top, no adjustable bits on the rocker.

 

[tormentandglory]

I have done quite a few multi cylinder 4V's, and they all have this thicker than the stem step behind the back of the valve. My guess is it helps improve flow around the valve, in a deep port. All the takegawa valves go thin at this point, on the 2V's. Most of the jap 2v's are like this also. In a shallow port, thinning the valve stem improves flow around it. Ever seen thinning of the stems in a 4V ?

There are 4v engines around with tuliped valve stems. The zx2r valves that i used in my 4v are 4mm stem, necked down to about 3.25mm. I've seen plenty of car engines with the reduced stem diameter to.

 

[Peter1230]

will a gpx160 4 valve kit fit a 155z

 

[sean01]

cant see why not... as i havent seen any gpx160's come factory with a 4 valve head so id say there the same item

 

[Peter1230]

same with the V2 head?

 

[wogtaz ryder]

Yes. but i think you will need the Yx cam cover thing its called , because the Z one is different. unless the V2 heads come with one..

Yx 150
Yx 160
Z 155

All have Same size Cylinder/pistons

Thats why the Z engines have 160 marked on them .

 

[sean01]

V2 head requires the matching piston also because the valves are larger... with out it and youll be in trouble.... lol ill post a pic of a 160 i got and i suspect he did the same thing...

but yeah.. the 155z also have different tappet covers and cam cover

 

[tormentandglory]

I haven't measured one yet, but I suspect that the "high comp" piston supplied with V2 kits actually isn't high comp at all, because the valve reliefs are so big. They need to be bigger than stock, but not that big. I'm gonna recut the reliefs in the stock piston next time I do a V2 build.

 

[sean01]

ok heres the pics...not a pretty sight... this dude must of just spent a crap load of cash on this engine...lol i bought it off him for $20

 

[DvDRip]

whoa holy crap that's some nice destruction, do you know what exactly happened there? trick valve tho