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Slavens CDI for 300sx with RK Tek Head

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Was thinking about getting the SX CDI from slavens for my 19 300xc. The site says to only use it with a higher compression head and mentions the SX or S3 head but still runs on pump gas. I'm guessing the RK Tek head tuned for 93 would work as well? 

I don't really need any more power but I figure a little more can't hurt :)

any one run this or a similar combo? Worth it? Seems like an easy enough and relatively cheap mod to try out. 

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I'm not sure what oem cdi slavens has stolen but my guess its an SX type cdi. It's more aggressive and should make more power than stock with the right head and pipe.

 

The RK head is a way better designed head than the stock or S3. I would keep your stock cdi and put that money towards the RK and tell Kelsey what kind of power you want.

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I have a slavens sx cdi and a slavens s3 head on my 250 xc and I really like it. Definitely woke the bike up. I saw a dyno chart of the s3 versus the rk tek somewhere on the forum, if im remembering correctly the s3 pulled harder.

Edited by andrewfrankl
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I saw a dyno chart of the s3 versus the rk tek somewhere on the forum, if im remembering correctly the s3 pulled harder.


At WOT..

WOT isn't where the RK shines IMO. What it did to my bottom and mid at part throttle is what made it so impressive.
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I’m running the 300 SX CDI (SXS14300390) that Slavens sales with an RK Tek head, Pro Circuit pipe and Lectron carb on my 2017 XC 300. Two of us have the same set and it works great.

It pulls harder off the bottom and revs out better too.

I wrote a review on an older thread that I’ll see if I can dig it up.

Update:

https://thumpertalk.com/forums/topic/1310056-2019-300xc-to-300sxs/

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7 hours ago, andrewfrankl said:

I have a slavens sx cdi and a slavens s3 head on my 250 xc and I really like it. Definitely woke the bike up. I saw a dyno chart of the s3 versus the rk tek somewhere on the forum, if im remembering correctly the s3 pulled harder.

People may give kels shit for downplaying dynos but he's right, a Dyno at WOT means nothing. You are almost never at wot, it's all part throttle stuff. The rk head actually has correct squish and you can run pump at really high comp ratios if you desire. But the great thing is you don't have to bump compression too much. Any head with higher compression is going to give you more pep. 

 

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People may give kels shit for downplaying dynos but he's right, a Dyno at WOT means nothing. You are almost never at wot, it's all part throttle stuff. The rk head actually has correct squish and you can run pump at really high comp ratios if you desire. But the great thing is you don't have to bump compression too much. Any head with higher compression is going to give you more pep. 
 
All the compression tests show rk head have a big increase in compression

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11 hours ago, 2strokenut said:

People may give kels shit for downplaying dynos but he's right, a Dyno at WOT means nothing. You are almost never at wot, it's all part throttle stuff. The rk head actually has correct squish and you can run pump at really high comp ratios if you desire. But the great thing is you don't have to bump compression too much. Any head with higher compression is going to give you more pep. 

That's a before / after on RK on a 300 XC (ala @KennyMc).  There's a significant compression increase  (190 -> 217) psi.

Luckily I have 'you know who' blocked, so I won't see his nonsense about how none of us are qualified to do compression tests.

13D3F94C-DAA7-4FBB-A816-35B3DA6E5D4D.jpeg.da2acb11d4939a515e7c28d697af4c49.jpegAB565395-EFDF-4697-8013-54531F7B0CF9.jpeg.3699732de8f53c76589294400289d6b3.jpeg

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JD Jetting (James Dean) dyno'd the RKTek vs the Slavens S3.  They are similar with the S3 looking a bit better. 

I know everyone wants to think there is some magic in the RKTek to justify the added expense, but my gut says they both do the same basic things.  They improve the squish area and increase compression.   One might be a little better than the other but for the most part they both probably improve power similarly.   The one place they may differ is how they handle lower octane pump gas.  I suspect RKTek might be a little better based on reading a number of reviews of both heads.   Also, with RKTek, it does sound like Kelsey will cut it differently based on what you want and that has a lot of value as well.

I've got an Slavens S3 sitting here waiting to be installed.   Maybe at some point this season I'll also pick up an RKTek head and try them back to back and try to give an unbiased report if there is any seat of the pants difference.  I'll be very surprised if one is just "meh" and the other is awesome.  I suspect at best I might have a little preference one way or the other but that they'll both be relatively the same improvement over stock.  But I'll keep an open mind.

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Doc

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2 hours ago, redrider144 said:

That's a before / after on RK on a 300 XC (ala @KennyMc).  There's a significant compression increase  (190 -> 217) psi.

Luckily I have 'you know who' blocked, so I won't see his nonsense about how none of us are qualified to do compression tests.

13D3F94C-DAA7-4FBB-A816-35B3DA6E5D4D.jpeg.da2acb11d4939a515e7c28d697af4c49.jpegAB565395-EFDF-4697-8013-54531F7B0CF9.jpeg.3699732de8f53c76589294400289d6b3.jpeg

Is 190psi from your shaved sx head or stock head? Are you running pump on the new head? 

 

Edit, I see it's from KennyMc. If that is stock to RK, then a 27 psi isn't a huge increase, imo. I'll go back to one of my threads but I think my 300 stock was around 170ish and ended up at 205? But every gauge is a little different.

 Lets see your RK tek comp test Red.

Edited by 2strokenut
kant reed

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Guys, we have been thru this before.. 

It is NOT about compression.. It is about the overall chamber design. The RK Tek head is LESS compression than the SX Head or Mule Head...  

There is absolutely no comparison between the SX and the RK Tek head in the performance.

The dyno chart above is with the incorrect RK Tek head jetted incorrectly and it still matches the Slavens head.

You can believe whatever you want but when the rubber kits the dirt, the difference is VERY obvious on which one delivers.

There are dozens of threads that do a direct comparison between the two.. Here are a few of them to read.

https://ktmtalk.com/showthread.php?540137-Another-RK-Tek-head-review

https://ktmtalk.com/showthread.php?544841-Rk-Tek-vs-Sx-head-comparison

 

 

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1 hour ago, Doc_d said:

 

JD Jetting (James Dean) dyno'd the RKTek vs the Slavens S3.  They are similar with the S3 looking a bit better. 

I know everyone wants to think there is some magic in the RKTek to justify the added expense, but my gut says they both do the same basic things.  They improve the squish area and increase compression.   One might be a little better than the other but for the most part they both probably improve power similarly.   The one place they may differ is how they handle lower octane pump gas.  I suspect RKTek might be a little better based on reading a number of reviews of both heads.   Also, with RKTek, it does sound like Kelsey will cut it differently based on what you want and that has a lot of value as well.

I've got an Slavens S3 sitting here waiting to be installed.   Maybe at some point this season I'll also pick up an RKTek head and try them back to back and try to give an unbiased report if there is any seat of the pants difference.  I'll be very surprised if one is just "meh" and the other is awesome.  I suspect at best I might have a little preference one way or the other but that they'll both be relatively the same improvement over stock.  But I'll keep an open mind.

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Doc

Both the S3 or RK are much better than the stock or cutting the head, for sure. 

The thing is, we all spent over 10k for these bikes so I just find it weird that some people have a problem paying an extra 100 dollars for a head that's made in the USA and from a company that builds it to suit. I think that is pretty cool. You are hard pressed to find someone unhappy with the RK as well.

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21 minutes ago, HERA said:

Guys, we have been thru this before.. 

It is NOT about compression.. It is about the overall chamber design. The RK Tek head is LESS compression than the SX Head or Mule Head...  

There is absolutely no comparison between the SX and the RK Tek head in the performance.

The dyno chart above is with the incorrect RK Tek head jetted incorrectly and it still matches the Slavens head.

You can believe whatever you want but when the rubber kits the dirt, the difference is VERY obvious on which one delivers.

There are dozens of threads that do a direct comparison between the two.. Here are a few of them to read.

https://ktmtalk.com/showthread.php?540137-Another-RK-Tek-head-review

https://ktmtalk.com/showthread.php?544841-Rk-Tek-vs-Sx-head-comparison

 

 

Since your're here... Any opinions on the Slavens CDI running with the RK head? 

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15 minutes ago, 2strokenut said:

Both the S3 or RK are much better than the stock or cutting the head, for sure. 

The thing is, we all spent over 10k for these bikes so I just find it weird that some people have a problem paying an extra 100 dollars for a head that's made in the USA and from a company that builds it to suit. I think that is pretty cool. You are hard pressed to find someone unhappy with the RK as well.

 

Yep, I totally agree.  That's why in my post I tried not to discount the fact that Kelsey will tailor the head for you.  I should have also mentioned that I've always heard that Kelsey ships fast and responds to question.  That's why I am interested in trying both myself.

I'm fairly confident I will find they are both very comparable but I might find some slight differences that may make me prefer one over the other.  But it's kind of like looking for a steel 10mm bolt from one reputable manufacturer that will perform 100% better than a steel 10mm bolt from another reputable manufacturer.   I find that to be highly unlikely.  There may be some minor differences that may make you prefer one bolt over the other but at the end of the day their performance is likely 99% the same.

Doc

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32 minutes ago, HERA said:

The dyno chart above is with the incorrect RK Tek head jetted incorrectly and it still matches the Slavens head.

 

 

Yes, it's all an Internet argument at this point, but I find it curious you are questioning James Dean of JD Jetting's ability to jet a bike.  You might want to shoot for a different talking point on that one.  Because if James Dean can't get your head jetted correctly, then I'm going to say the chances of any of your customers getting them jetted correctly is exactly 0%.

Doc

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7 minutes ago, Doc_d said:

 

Yep, I totally agree.  That's why in my post I tried not to discount the fact that Kelsey will tailor the head for you.  I should have also mentioned that I've always heard that Kelsey ships fast and responds to question.  That's why I am interested in trying both myself.

I'm fairly confident I will find they are both very comparable but I might find some slight differences that may make me prefer one over the other.  But it's kind of like looking for a steel 10mm bolt from one reputable manufacturer that will perform 100% better than a steel 10mm bolt from another reputable manufacturer.   I find that to be highly unlikely.  There may be some minor differences that may make you prefer one bolt over the other but at the end of the day their performance is likely 99% the same.

Doc

I don't know about that comparison lol but I think you get what you pay for in this instance.

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50 minutes ago, 2strokenut said:

Lets see your RK tek comp test Red.

1.  I don't have a stock head to compare to (my XC head has been squish corrected).

2.  My SX head is also not as delivered from the factory (also shaved)

3.  I'm not in the mood right now to publish any personal compression comparisons bc I don't feel like giving him and his proxy army a platform to shit all over my measurements.  Anything I post, he will just turn it against me to attempt to discredit me.

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6 minutes ago, redrider144 said:

1.  I don't have a stock head to compare to (my XC head has been squish corrected).

2.  My SX head is also not as delivered from the factory (also shaved)

3.  I'm not in the mood right now to publish any personal compression comparisons bc I don't feel like giving him and his proxy army a platform to shit all over my measurements.  Anything I post, he will just turn it against me to attempt to discredit me.

 

ED80z03X4AA31OG.jpg

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15 minutes ago, Doc_d said:

 

Yes, it's all an Internet argument at this point, but I find it curious you are questioning James Dean of JD Jetting's ability to jet a bike.  You might want to shoot for a different talking point on that one.  Because if James Dean can't get your head jetted correctly, then I'm going to say the chances of any of your customers getting them jetted correctly is exactly 0%.

Doc

As I mentioned... It was the WRONG HEAD he tested... it was NOT right for the application.  So it was not a head that would have been sent if ordered.  

Jetting could not be more simple once you add the head.. There is no issues getting anything jetted correctly.. The head addresses the MIS-FIRES which is the SOURCE of the jetting problems people are having.. There has never been any problem getting ANY healthy carb to meter correctly once you get rid of the mis-fires.

THIS concept is very important: You can NOT properly jet a bike on a wheel dyno.. I know this might ruffle some feathers.. but there are too many variables on the dyno (yes, I own a state of the ART Dyno Facility) You can get close for WOT jetting with a wheel dyno but anything off of peal RPM and WOT will not be optimum. It should also be noted that to properly jet WOT at peak RPM on a dyno, you MUST HOLD the engine at PEAK RPM for sustained periods, not this fast sweep test that are shown. 

The idea of a dyno test is to SIMULATE real world operation.. Anybody riding their bike on the dirt like any of the dyno runs? 

Once you make a dyno run that is indicative of the real world, then you will see what is working and what is not.. Again, near impossible to simulate any on-off-on-off-on part throttle running on a wheel dyno. Engine dyno, yes, wheel dyno... not

As for jetting... We can spin that around many ways.. 1st off while James is surely good at jetting he is not the only one that is and some of us have been jetting 2 stroke much longer than others..

Just because somebody makes a jetting product does not make them the "authority" on it without any argument. Does it? If that were the case, since I have been making heads longer than anyone.. I would also be the  authority and anybody questioning my findings or products would be crazy.. right??  Yet here you are questioning it....

Ya see it goes both ways..

Again.. in the end  it does not matter what any dyno chart says or does not say.. What matters is how ANY product performs in the real world, in this case, the DIRT!  And on the DIRT, there is no comparison.. It is like comparing a Mercedes to a VW... There is that big of a difference.. believe it or not..  There are dozens of threads comparing the 2, the results are ALWAYS the same.. NO COMPARISON.. 

Edited by HERA

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