Need help with cylinder head and valves.

[BPT7594]

Hi, first post here.
I have purchased some performance mods for my PCX 125 esp 2014.
1/ Yuminashi high lift camshaft ESP, not the RR version, the first version, got it from a friend who bought it but never used it.
2/ New 58mm piston and PCX150/SH150 cylinder, my piston has 13 pin, which is originally a Honda Sonic 125 piston.
3/ Had my mechanic done some work on the cylinder head, I think he just enlarged the combustion chamber to fit the new 58mm piston surface, not so sure on the valve diameters, have to recheck on it, but the valve springs are the same.
4/ Modded stock exhaust. Where I live, there're shops who would mod the exhaust, so I modded it, basically take everything out and use a new core, wrapped it with some fiberglass.
My problem is this.
1/ Yuminashi has said that the first version of their camshaft needs/requires (I'm not so sure) a new set of rocker arms or I have to grind it (not too keen on grinding anything) because the cam lobe would touch the rocker in the middle. As careless as I am, I installed it without reading that first and my engine now has some sorts of ticking sound, just like Yuminashi said. Will this damage my engine? Because I commute almost everyday and having my engine's pulled out is almost impossible.
2/ Valve bounce. Like I said, my valves kinda bounce a little. Just like an old dirtbike that had one of those flat-slide carbs which rattles. But only when I whack open the throttle extremely suddenly, it rattles a little then nothing. I have read about this, my mechanic said that because the stock exhaust is too restrictive, which causes exhaust pulses to affect the valve springs. Yuminashi has a set of double valve springs. Would a set of too stiff valve springs affect the rocker arm or the camshaft in anyway? I planned to try a new exhaust header or pipe, about 32mm in diameter, or 30/28 and keep the exhaust pipe as straight as possible.
I know it's long but since I'm a noob, please forgive me.

[waspmike]

Well if you bought the 14100-KZY-25086 camshaft

You are correct as it says:

*The X250 ESP 8.6 camshaft has the highest lift possible in a PCX125 eSP head, and this camshaft can not be installed without the Yuminashi High-Lift eSP intake rocker 14430-KZR-000 & High-Lift eSP exhaust rocker 14440-KZR-000.

Now quite why Yuminashi don't simply sell the set all together as a kit instead of putting the requirement for the additional rocker arms in the "small print" is beyond me. Maybe to make the price of the camshaft seems competitive?

So you 'll have to buy some rocker arms.?

Edit: this is the key which I missed first time reading.

But only when I whack open the throttle extremely suddenly, it rattles a little then nothing.

You are experiencing detonation. Find the highest octane fuel you can or see if you can find a bottle of octane booster and see if that helps. Maybe the mechanic shaved too much off the head and your compression ratio is too high?

If you also get bounce at at high rpm 9000+ then yes you'll also needs some Honda Sonic double valve springs/retainers etc. (actually the first mod you should have done). I assume you can get those as you have a Honda Sonic piston. You don't have your location in your forum profile so I don't know if you can? I can probably dig out the part numbers as I think I have complete set somewhere.

[dasshreddar]

YOU need the hi lift rocker arms for that cam!(or grind(file)your stock ones... been there done that

[BPT7594]

YOU need the hi lift rocker arms for that cam!(or grind(file)your stock ones... been there done that

Thank you, I will order those rocker arms then. In the mean time, would it make too much damage to the stock rocker arms or the yuminashi camshaft?
By the way, did you happen to measure the maximum lift of the Yuminashi camshaft? I know they advertised it as 8.6 lift, but we must also take into account the rocker arm ratio, and my mechanic said at first sight he thought it was about 5.5 at maximum lift.

[BPT7594]

Well if you bought the 14100-KZY-25086 camshaft

You are correct as it says:

*The X250 ESP 8.6 camshaft has the highest lift possible in a PCX125 eSP head, and this camshaft can not be installed without the Yuminashi High-Lift eSP intake rocker 14430-KZR-000 & High-Lift eSP exhaust rocker 14440-KZR-000.

Now quite why Yuminashi don't simply sell the set all together as a kit instead of putting the requirement for the additional rocker arms in the "small print" is beyond me. Maybe to make the price of the camshaft seems competitive?

So you 'll have to buy some rocker arms.?

Edit: this is the key which I missed first time reading.

But only when I whack open the throttle extremely suddenly, it rattles a little then nothing.

You are experiencing detonation. Find the highest octane fuel you can or see if you can find a bottle of octane booster and see if that helps. Maybe the mechanic shaved too much off the head and your compression ratio is too high?

If you also get bounce at at high rpm 9000+ then yes you'll also needs some Honda Sonic double valve springs/retainers etc. (actually the first mod you should have done). I assume you can get those as you have a Honda Sonic piston. You don't have your location in your forum profile so I don't know if you can? I can probably dig out the part numbers as I think I have complete set somewhere.

I think my compression is a little lower, because my mechanic carved out to make the combustion chamber a little larger to fit the 58mm surface of the piston. I'll try to use liqui moly octane booster to see if it helps. From where I'm from we only have RON 95 as maximum. I'm from Vietnam btw.
Is the honda sonic double valve springs and retainer interchangeable with my stock ones ? Yuminashi's set is 44.77$, if it's true I can save a heck of a lot of money .
I think you're talking about this one? I have the number for the parts, but getting my hands on it is a different story.
http://mototh.com/en/page/76

[waspmike]

^ yep that is the correct page they are the same length as std. PCX. You need all the bits 7,8,9 & 10.

Found the receipt, one set for one valve is 197 baht. #9 is the most expensive part at 142 baht.

E10 has a higher octane than normal gasoline/petrol if you have that.

[BPT7594]

^ yep that is the correct page they are the same length as std. PCX. You need all the bits 7,8,9 & 10.

Found the receipt, one set for one valve is 197 baht. #9 is the most expensive part at 142 baht.

E10 has a higher octane than normal gasoline/petrol if you have that.

Literally cannot thank you enough. You're a lifesaver. I'll see if I can get my hands on those parts.
By the way, how did you find out about this? I take it that you've done some fiddling too . how are those valves holding up for you?

[waspmike]

I haven't done it yet. I bought one set to compare with the PCX 150 springs as on the V1 PCX125 the guys here use Sonic double valve springs as sometimes the valves bounce before the speed limiter takes effect.

I had a customer with a PCX that revved to 11,000. So he claimed.

from the good old days?

166cc kit
CBR150 throttle body
CBR250 Valves
Std. Airbox
OVER Exhaust
Sonic valve springs

He said 130 KPH?

[BPT7594]

Also will I need parts number 1 and 11? Not really sure what that is.
Revving to 11k rpm is insane
About the cbr 150 throttle body.. just buy it and slap it on?
Did you do some work for him on the cylinder head to fit in the cbr250 valves? What diameters are those btw?

[waspmike]

You already have parts 1 and 11 on the bike now.
I confess i don't know what size the V2 (new) 125 has for a throttle body. Yes, but you'll have to modify the inlet tract to match the bore and don't forget the injector!

I don't know who did his cylinder head. Your guy should be able to do it? I don't know what the CBR valve sizes are. If the CBR250 is in Vietnam a Honda dealer should be able to show them to you?
I did find this:



From here http://www.rickramsey.net/CRF250L.htm

[BPT7594]

You already have parts 1 and 11 on the bike now.
I confess i don't know what size the V2 (new) 125 has for a throttle body. Yes, but you'll have to modify the inlet tract to match the bore and don't forget the injector!

I don't know who did his cylinder head. Your guy should be able to do it? I don't know what the CBR valve sizes are. If the CBR250 is in Vietnam a Honda dealer should be able to show them to you?
I did find this:



From here http://www.rickramsey.net/CRF250L.htm

Can I have your facebook address? Talking about engines with this speed is killing me . Finding someone who's ready to guide me like you is hard.
My guy should be able to do some work on the head.
However, my friend who also owns a PCX, wants to keep the pcx125 esp head and valves, just pop in the new sonic springs to keep the compression ratio high. Then the 164 bbk and so on. I can try to bore up the SH150/PCX150 cylinder and buy the according piston and camshaft from yuminashi. Keep the cost down a bit . Already have a big bore 8 hole injector in my engine. I'll see if I can bore the throttle as well.
Again, can I have your facebook address? Maybe can you buy the sonic springs for me? In Vietnam there's no sonic, so I'll have to get it from thailand.

[waspmike]

Ah. I don't do FarceBook. If you went to an old fashioned dealership I would be the old guy in the back wearing a white lab coat:-(

Have you looked at Mad Max Bangkok?

What are you using for a variator?

I don't have a philosophical problem with getting to some parts but as I don't do Papal I don't know how you could compensate me.

[Oyabun]

I have found absolutemotorcycleparts.com. com a quite good source for buying pcx/sonic parts from Thailand. Check their pricing and delivery to Vietnam.
As for 60mm pistons I've checked one what is marketed for a Yamaha 150 bike and sold for dimes on fleabay but the pin to crown distance is different so I doubt it could be used.

[BPT7594]

Then I would be the 22 year old engine modding fanatic .
Yeah it truly is a problem. Guess I'll do as Oyabun said then.
I'm running a modded SH150 variator, the clutch bell is drilled, it was made by my mechanic. Pretty good stuff, I'm 85kg, 1m75, and I can get to 100kph in like 11s or so, the guy knows what he's doing but he's a little conservative on putting plug and play aftermarket parts on engines, he prefers to personally mod it himself and keeps them secret, which is great in a way, but a pain in the a** in every other way.
One more tiny question. Can a double valve spring set or generally a too stiff valve spring damage or increase wear on the cam lobes and the rocker arm (that's the thing I'm seriously worried about, my friend had a heavily modded, and I mean crankshaft modding, yamaha LC135 with too stiff springs, rocker arms broken in middle of a drag, did not end up too well).
I don't race, but may do some long distance riding with a little bit of sudden wide open throttle. I don't need my cam and rocker arm or valve spring set to be reliable in 5 or 6 years but with an engine rebuild every 30000km, can the camshaft and rocker withstand the stiff valve springs? I take care of my PCX pretty regularly.

[Oyabun]

Double springs are not necessary stronger. They have two major benefits usually.
Each spring has it's specific spring rate - and resonant frequency. By using two different springs engineers can eliminate the single resonant frequency issue and make a slightly stronger spring what is progressive (the cam profile does not get a hit trying to compress the spring, but a more curved resistance profile) to the pushing of an aggressive cam profile.
The spring you're talking about has been designed for a similar displacement single cylinder with a redline at 10.500 and designed for factory reliability. I doubt it would be too stiff.

[BPT7594]

Double springs are not necessary stronger. They have two major benefits usually.
Each spring has it's specific spring rate - and resonant frequency. By using two different springs engineers can eliminate the single resonant frequency issue and make a slightly stronger spring what is progressive (the cam profile does not get a hit trying to compress the spring, but a more curved resistance profile) to the pushing of an aggressive cam profile.
The spring you're talking about has been designed for a similar displacement single cylinder with a redline at 10.500 and designed for factory reliability. I doubt it would be too stiff.

Thank you. I would try it then.
My mechanic told me something about the rocker arm being different. He said that the roller rockers on new esp engines cannot run with too stiff springs, while the old no roller rocker will do just fine. I'll try doing something risky for once.

[waspmike]

I used to build oval track racing engines when I was younger, 19/20 so that's OK. By 22-ish I was crawling around inside ship engines!

I suppose we have to think about lift when worrying about coil bound springs. You say the lift of your cam is 8.6mm. The free length of the Sonic springs is 1mm shorter than PCX but there is still around 13.5mm+ of compression. This has to include the initial static compression but I suspect it will be Ok. The only way is to assemble and try. But if it will work with stock springs and Yuminashi don't say you need special springs then it will.

Thai camshafts only have maximum 6.0-6.2 lift. As they don't use high lift rocker arms. Also we have 70mm pistons here to fit PCX 150. They have , if I understand the info, pin to crown of 13,14 or 15. they come in sizes every 0.5mm from 50 to 66 with one type but to 70 with the other.

Thai cams range between about 1000-1200 baht , maybe a tad higher now. So that might be cheaper than two rocker arms?

Oh decisions decisions?

[Oyabun]

I used to build oval track racing engines when I was younger, 19/20 so that's OK. By 22-ish I was crawling around inside ship engines!

I suppose we have to think about lift when worrying about coil bound springs. You say the lift of your cam is 8.6mm. The free length of the Sonic springs is 1mm shorter than PCX but there is still around 13.5mm+ of compression. This has to include the initial static compression but I suspect it will be Ok. The only way is to assemble and try. But if it will work with stock springs and Yuminashi don't say you need special springs then it will.

Thai camshafts only have maximum 6.0-6.2 lift. As they don't use high lift rocker arms. Also we have 70mm pistons here to fit PCX 150. They have , if I understand the info, pin to crown of 13,14 or 15. they come in sizes every 0.5mm from 50 to 66 with one type but to 70 with the other.

Thai cams range between about 1000-1200 baht , maybe a tad higher now. So that might be cheaper than two rocker arms?

Oh decisions decisions?

Oh those ocean liner engines. I still smell the fumes of pakura while literally shoveling that mud out from the cylinders...

70mm pistons sound a bit too big in a pcx. As far I can remember I've seen 62mm at max - as the cylinder head bolts would be in a way. I might be missing something though. Do you have any links where I could check installations like that. As per my quick back of the envelope calc it would give a displacement close to 222cc.

Also 13 and 14 mm sounds like a piston pin diameter to me. The pin center to crown distances are more in the 18-21mm range as I've seen so far.

Can you recommend any webshops I could order any of the cams you have mentioned? Those seem to be really good bang for the buck. Do you know if they are reground or billet?

[waspmike]

I'm running a modded SH150 variator

How much did the guy machine off? I have an SH150 variator, might try the same That is one advantage you have with SH150 being made there.

[BPT7594]

Well I had to machine my Sonic piston to avoid piston valve touching. And I have tried the largest possible diameter exhaust tube, as straight as possible, no help with the valve bouncing.
I think I'll try it. 1 set of Sonic springs like you said and 2 yuminashi rocker arms. Shipping motorcycle parts from Thailand without knowing somebody with good experience is hard and costly . I tried to contact Hispeedpiston in Thailand for some clutch shoes but after an invoice, no response.
70mm is a bit too much. One of my mechanic's customer has a 65mm, modded crankshaft, he has to convert the fuel supply system from fuel injection back to a NSR125 SP carburetor .
I'll update the results as soon as possible. Thank you for your help.
I guess you are also from Thailand?

Hispeedpiston made a racing cam for the PCX, 5.5 lift. google them, they're quite famous I guess. They also make, wait for it, pistons . You can get the piston that are made for the sonic, 13mm piston pin, so you don't need to mod the connecting rod. In Vietnam we don't worry too much about it, we drill the connecting rod pin .