cam and piston combos???

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1/29/2019 11:02 AM

Hello all,

Just picked up a 17 yz250f.. the head has been ported already. Looking to gain some more top end and power..

any recommendations on Cam and Piston combos?? I think im gonna keep the valves stock to maintain some reliability...

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1/29/2019 11:09 AM

hc piston and stage 2 from hotcams paired with a good map will do pretty good

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1/29/2019 11:11 AM

kb228 wrote:

hc piston and stage 2 from hotcams paired with a good map will do pretty good

Any recommended Brands? Do you have experience with the hotcams on this bike?

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1/29/2019 11:13 AM

kb228 wrote:

hc piston and stage 2 from hotcams paired with a good map will do pretty good

TSCHAM101 wrote:

Any recommended Brands? Do you have experience with the hotcams on this bike?

Ive got cp carillo hc pistons and hotcams in both of my kawis. I really like them.

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1/29/2019 11:15 AM

Just remember running a hotter setup means quicker wear on the valves and piston. If your not racing, you might consider OEM for longevity.

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1/29/2019 11:21 AM

The 19 piston is hard to beat on the dyno...as was the oem 17.

And cam wise - we have some that I Feel are best on the market bar none. But - everything has its cost. The OEM valve springs are really suspect and close to problems on the 17 with stock cams.

So for any cam that really does much - I suggest improving the spring situation.

I haven't tested the latest dcr stuff - it might be ok - and what I had tested from web - was surprisingly not exceptional and also surprisingly similar to the stock cam profile of the 16-18. I think those who work more closely with web may have some grinds that are good by now.

The bikes are getting SO good that finding gains is getting very tough. At this point, juggling reliability and valve train stability with performance is on a very fine edge.




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1/29/2019 12:00 PM
Edited Date/Time: 1/29/2019 12:01 PM

Derek Harris wrote:

The 19 piston is hard to beat on the dyno...as was the oem 17.

And cam wise - we have some that I Feel are best on the market bar none. But - everything has its cost. The OEM valve springs are really suspect and close to problems on the 17 with stock cams.

So for any cam that really does much - I suggest improving the spring situation.

I haven't tested the latest dcr stuff - it might be ok - and what I had tested from web - was surprisingly not exceptional and also surprisingly similar to the stock cam profile of the 16-18. I think those who work more closely with web may have some grinds that are good by now.

The bikes are getting SO good that finding gains is getting very tough. At this point, juggling reliability and valve train stability with performance is on a very fine edge.




sooo.. what are you getting at? You have good cams, but I need better valve springs.. and the other cams you mentioned aren't as good? and I should stick with the stock piston?


Also.. I sent you a PM.

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1/29/2019 3:22 PM

Derek Harris wrote:

The 19 piston is hard to beat on the dyno...as was the oem 17.

And cam wise - we have some that I Feel are best on the market bar none. But - everything has its cost. The OEM valve springs are really suspect and close to problems on the 17 with stock cams.

So for any cam that really does much - I suggest improving the spring situation.

I haven't tested the latest dcr stuff - it might be ok - and what I had tested from web - was surprisingly not exceptional and also surprisingly similar to the stock cam profile of the 16-18. I think those who work more closely with web may have some grinds that are good by now.

The bikes are getting SO good that finding gains is getting very tough. At this point, juggling reliability and valve train stability with performance is on a very fine edge.




Which pistons did you try? PC and Twisted have one that makes good power.

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recmx.com

REC MX, JE Pistons, Wiseco, Rusk Racing, Yoshimura, Enzo Racing, Dubya Wheels, Asterisk, Rocket Performance, CCR Sport, & MMR

1/29/2019 6:54 PM

Derek Harris wrote:

The 19 piston is hard to beat on the dyno...as was the oem 17.

And cam wise - we have some that I Feel are best on the market bar none. But - everything has its cost. The OEM valve springs are really suspect and close to problems on the 17 with stock cams.

So for any cam that really does much - I suggest improving the spring situation.

I haven't tested the latest dcr stuff - it might be ok - and what I had tested from web - was surprisingly not exceptional and also surprisingly similar to the stock cam profile of the 16-18. I think those who work more closely with web may have some grinds that are good by now.

The bikes are getting SO good that finding gains is getting very tough. At this point, juggling reliability and valve train stability with performance is on a very fine edge.




moto314 wrote:

Which pistons did you try? PC and Twisted have one that makes good power.

define good.

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1/29/2019 7:05 PM

TSCHAM101 wrote:

sooo.. what are you getting at? You have good cams, but I need better valve springs.. and the other cams you mentioned aren't as good? and I should stick with the stock piston?


Also.. I sent you a PM.

Resend - I cant ever find that screen without email directing me.

OEM pistons perform exceptionally well on almost all 250fs on the market. The R&D behind them is insane.

Generally some head or cyl machining to get squish/quench as tight as possible is the best route couple with OEM pistons..

if given the time - I've been wanting to do a youtube channel posting some test results on head to head tests.
A piston shootout would be a good one...though costly.

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1/30/2019 4:39 AM

Derek Harris wrote:

The 19 piston is hard to beat on the dyno...as was the oem 17.

And cam wise - we have some that I Feel are best on the market bar none. But - everything has its cost. The OEM valve springs are really suspect and close to problems on the 17 with stock cams.

So for any cam that really does much - I suggest improving the spring situation.

I haven't tested the latest dcr stuff - it might be ok - and what I had tested from web - was surprisingly not exceptional and also surprisingly similar to the stock cam profile of the 16-18. I think those who work more closely with web may have some grinds that are good by now.

The bikes are getting SO good that finding gains is getting very tough. At this point, juggling reliability and valve train stability with performance is on a very fine edge.




TSCHAM101 wrote:

sooo.. what are you getting at? You have good cams, but I need better valve springs.. and the other cams you mentioned aren't as good? and I should stick with the stock piston?


Also.. I sent you a PM.

Derek Harris wrote:

Resend - I cant ever find that screen without email directing me.

OEM pistons perform exceptionally well on almost all 250fs on the market. The R&D behind them is insane.

Generally some head or cyl machining to get squish/quench as tight as possible is the best route couple with OEM pistons..

if given the time - I've been wanting to do a youtube channel posting some test results on head to head tests.
A piston shootout would be a good one...though costly.

Id be really interested in that kind of a youtube channel. Theres not much out there as far as technical info on engine modding

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1/30/2019 8:09 AM

Derek Harris wrote:

The 19 piston is hard to beat on the dyno...as was the oem 17.

And cam wise - we have some that I Feel are best on the market bar none. But - everything has its cost. The OEM valve springs are really suspect and close to problems on the 17 with stock cams.

So for any cam that really does much - I suggest improving the spring situation.

I haven't tested the latest dcr stuff - it might be ok - and what I had tested from web - was surprisingly not exceptional and also surprisingly similar to the stock cam profile of the 16-18. I think those who work more closely with web may have some grinds that are good by now.

The bikes are getting SO good that finding gains is getting very tough. At this point, juggling reliability and valve train stability with performance is on a very fine edge.




moto314 wrote:

Which pistons did you try? PC and Twisted have one that makes good power.

Derek Harris wrote:

define good.

More HP and torque than stock.

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recmx.com

REC MX, JE Pistons, Wiseco, Rusk Racing, Yoshimura, Enzo Racing, Dubya Wheels, Asterisk, Rocket Performance, CCR Sport, & MMR

1/30/2019 8:22 AM

Derek Harris wrote:

The 19 piston is hard to beat on the dyno...as was the oem 17.

And cam wise - we have some that I Feel are best on the market bar none. But - everything has its cost. The OEM valve springs are really suspect and close to problems on the 17 with stock cams.

So for any cam that really does much - I suggest improving the spring situation.

I haven't tested the latest dcr stuff - it might be ok - and what I had tested from web - was surprisingly not exceptional and also surprisingly similar to the stock cam profile of the 16-18. I think those who work more closely with web may have some grinds that are good by now.

The bikes are getting SO good that finding gains is getting very tough. At this point, juggling reliability and valve train stability with performance is on a very fine edge.




TSCHAM101 wrote:

sooo.. what are you getting at? You have good cams, but I need better valve springs.. and the other cams you mentioned aren't as good? and I should stick with the stock piston?


Also.. I sent you a PM.

Derek Harris wrote:

Resend - I cant ever find that screen without email directing me.

OEM pistons perform exceptionally well on almost all 250fs on the market. The R&D behind them is insane.

Generally some head or cyl machining to get squish/quench as tight as possible is the best route couple with OEM pistons..

if given the time - I've been wanting to do a youtube channel posting some test results on head to head tests.
A piston shootout would be a good one...though costly.

Whats your email? I will email you directly.

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1/30/2019 8:47 AM

moto314 wrote:

More HP and torque than stock.

how much are you claiming.

I'll glady line up a test of a piston of choice vs stock on a yz250f or ktm 250f

I haven't seen more than .5 hp on any piston ive ever tested on a 250f if the squish is standardized for the test. And I've tested a lot. In general - I see losses, be it small and OEM's are really hard to beat.
Back in the JE days at star - now that they are with wossner - I will share that star ran the std compression offering from JE and in all their testing with various changes they tried - it took a long time to match the OEM piston. Most of what they chased was durability for 15000+ rpm.

The new crf is an exception - but it needed a lot of help in the combustion chamber design to start with - if you own a crf a piston can do you some serious help

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1/30/2019 8:55 AM

Derek Harris wrote:

The 19 piston is hard to beat on the dyno...as was the oem 17.

And cam wise - we have some that I Feel are best on the market bar none. But - everything has its cost. The OEM valve springs are really suspect and close to problems on the 17 with stock cams.

So for any cam that really does much - I suggest improving the spring situation.

I haven't tested the latest dcr stuff - it might be ok - and what I had tested from web - was surprisingly not exceptional and also surprisingly similar to the stock cam profile of the 16-18. I think those who work more closely with web may have some grinds that are good by now.

The bikes are getting SO good that finding gains is getting very tough. At this point, juggling reliability and valve train stability with performance is on a very fine edge.




Do all 17's have this valve spring problem? Because I have a 17 with 77 hours on it and no issues yet. Just wanna know if I'm fine or should still replace as soon as possible.

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1/30/2019 9:04 AM
Edited Date/Time: 1/30/2019 9:11 AM

Using an off the shelf piston, the only place your going to find power vs OEM is in compression. Compression itself isn't a very efficient way to try to make horsepower.

What the race teams use is quite a bit different than what you buy off the shelf. Billet, diamond finish rings, ovality, gas port configuration, ect.

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Race Bike: 2018 KTM 350SXF

Other Bikes: 1985 CR80R, 1990 CR250R, 1998 PW80, Specialized Fuse Comp 29.

Sold: 2016 YZ250F, 2012 CRF250R

1/30/2019 10:54 AM

c0ncEpT wrote:

Using an off the shelf piston, the only place your going to find power vs OEM is in compression. Compression itself isn't a very efficient way to try to make horsepower.

What the race teams use is quite a bit different than what you buy off the shelf. Billet, diamond finish rings, ovality, gas port configuration, ect.

How do I get better throttle response, quicker/harder engine hit to go against torqy 450's a lil better?

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1/30/2019 11:34 AM

Derek Harris wrote:

The 19 piston is hard to beat on the dyno...as was the oem 17.

And cam wise - we have some that I Feel are best on the market bar none. But - everything has its cost. The OEM valve springs are really suspect and close to problems on the 17 with stock cams.

So for any cam that really does much - I suggest improving the spring situation.

I haven't tested the latest dcr stuff - it might be ok - and what I had tested from web - was surprisingly not exceptional and also surprisingly similar to the stock cam profile of the 16-18. I think those who work more closely with web may have some grinds that are good by now.

The bikes are getting SO good that finding gains is getting very tough. At this point, juggling reliability and valve train stability with performance is on a very fine edge.




I’m looking at freshening up my 2014, I was thinking of updating the crank to the 18, doing a gytr piston, and updating the oil nozzle or whatever that part was they recommended. This was also all before the ‘19 came out, so would going with any of the ‘19 stuff be better? I’m looking at reliability primarily, but if I can gain some overall power I would like to. Running race gas is fine, I tend to run AV gas anyway

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RPM Performance
CT
783

1/30/2019 12:58 PM

Derek Harris wrote:

how much are you claiming.

I'll glady line up a test of a piston of choice vs stock on a yz250f or ktm 250f

I haven't seen more than .5 hp on any piston ive ever tested on a 250f if the squish is standardized for the test. And I've tested a lot. In general - I see losses, be it small and OEM's are really hard to beat.
Back in the JE days at star - now that they are with wossner - I will share that star ran the std compression offering from JE and in all their testing with various changes they tried - it took a long time to match the OEM piston. Most of what they chased was durability for 15000+ rpm.

The new crf is an exception - but it needed a lot of help in the combustion chamber design to start with - if you own a crf a piston can do you some serious help

How tight does they set squish? 0.5-0.8mm? When you milling the head wouldn't it change cam timing?

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1/30/2019 1:40 PM

MadsDausel wrote:

How tight does they set squish? 0.5-0.8mm? When you milling the head wouldn't it change cam timing?

Until it starts dusting the head. Then back it down .001-.002

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Race Bike: 2018 KTM 350SXF

Other Bikes: 1985 CR80R, 1990 CR250R, 1998 PW80, Specialized Fuse Comp 29.

Sold: 2016 YZ250F, 2012 CRF250R

1/30/2019 1:57 PM

TSCHAM101 wrote:

Hello all,

Just picked up a 17 yz250f.. the head has been ported already. Looking to gain some more top end and power..

any recommendations on Cam and Piston combos?? I think im gonna keep the valves stock to maintain some reliability...

The old " she's been ported and polished "

If you haven't lokked in a intake or exhaust runner and seen the work but just took the sellers word,

It's not ported

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1/30/2019 1:59 PM

moto314 wrote:

More HP and torque than stock.

Derek Harris wrote:

how much are you claiming.

I'll glady line up a test of a piston of choice vs stock on a yz250f or ktm 250f

I haven't seen more than .5 hp on any piston ive ever tested on a 250f if the squish is standardized for the test. And I've tested a lot. In general - I see losses, be it small and OEM's are really hard to beat.
Back in the JE days at star - now that they are with wossner - I will share that star ran the std compression offering from JE and in all their testing with various changes they tried - it took a long time to match the OEM piston. Most of what they chased was durability for 15000+ rpm.

The new crf is an exception - but it needed a lot of help in the combustion chamber design to start with - if you own a crf a piston can do you some serious help

MadsDausel wrote:

How tight does they set squish? 0.5-0.8mm? When you milling the head wouldn't it change cam timing?

Yeah,quad riders mil the head around hete,likes it's a sb chevy,then it runs slower and they are dumbfounded

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1/30/2019 3:16 PM

wideopen198 wrote:

Do all 17's have this valve spring problem? Because I have a 17 with 77 hours on it and no issues yet. Just wanna know if I'm fine or should still replace as soon as possible.

There was a stretch in 2016 where we saw a lot of new bikes make it less than 10 hours with a pro usage.

I have seen some really bad things on brand new heads with machining too - and I think this possibly was part of the issue on those low hour bikes.

So what I say is - if it's running good and has more than 20 hours - you got a "good one". The valve seats and guides were done right etc - and while I always suggest people replace valve springs every top end (highly overlooked - oem springs are cheap) - sounds like your still going strong.

at 70 hours - from a racing perspective - the valve guides, seats couldn't possibly be still in spec. Since avg consumers have no desire to pay to fix this - it's one of those deals where you just risk it and keep running it.

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1/30/2019 3:22 PM

moto314 wrote:

More HP and torque than stock.

Derek Harris wrote:

how much are you claiming.

I'll glady line up a test of a piston of choice vs stock on a yz250f or ktm 250f

I haven't seen more than .5 hp on any piston ive ever tested on a 250f if the squish is standardized for the test. And I've tested a lot. In general - I see losses, be it small and OEM's are really hard to beat.
Back in the JE days at star - now that they are with wossner - I will share that star ran the std compression offering from JE and in all their testing with various changes they tried - it took a long time to match the OEM piston. Most of what they chased was durability for 15000+ rpm.

The new crf is an exception - but it needed a lot of help in the combustion chamber design to start with - if you own a crf a piston can do you some serious help

MadsDausel wrote:

How tight does they set squish? 0.5-0.8mm? When you milling the head wouldn't it change cam timing?

as concept said exactly.

All the way to mechanical limit.

.030" is about as tight as you can go - often .033" on a bike that isn't torn down a lot. About .8mm

If the piston profile is heavily developed for a perfect fit with minimal rock - and the main bearings are ktm style, maybe a tad under .030 is rok.

On adjustable cam bikes - you have to move them back to their previous spot (if they were what you wanted) and on the ktms - depending on what your running you either have the cam ground accordingly for your squish change or DCR makes some adjustable cores you could move.


My bigger point was some aftermarket pistons move the squish/quench closer as part of their changes - and this is an important element to their performance - and rightly so - can make them a good piston - but apples to apples vs oem usually the oem piston design (profile, shaping underneatch etc) is the best under heat and load - plus flat pistons have idealized burn path vs many of the high dome stuff. The aftermarket drove the OEMS to be better - but in doing so - the OEMS really made some good stuff.

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1/31/2019 9:40 AM

Well all this is nice to know.. but what should I do?

Maybe a 270 kit?

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2/16/2019 10:40 AM

Photo
So this is a very good piston?
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