squish questions and your experiences

Discussion specific to the 1995 - 2006 KDX200 (H Series) and 1995 - 2005 KDX220R (A Series) models sold in the USA
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ohgood
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squish questions and your experiences

Post by ohgood »

does modifying the squish band require higher octane fuels to prevent detonation ?

i'm all for SMOOTHNESS tuning, but care absolutely nothing about 'mo power' or high rpm riding. i'm basically just pleasure riding tight single track, and occasionally dualsporting (Camp n ride) the kdx220.

i'm pleased enough with the power and smoothness of the stock pipe/arrestor and the next carb on my bike. yes, i know there is more, but i'm looking at fuel economy and SMOOTHness at this point.

thanks !
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Sullyfam
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Re: squish questions and your experiences

Post by Sullyfam »

Yes modifying your squish will require you to run higher octane fuel (91 or better).

The OEM squish is designed to run on a wide range of fuels and while you can get better performance by modifying it, you will limit your fuel options.

If you are just wanting fuel economy then I don't see the point. It will cost you a $100 to get the head modified which is approx what 30 gallons of fuel. I don't know the marginal fuel savings between OEM and a modified squish, but my hunch is that's a life time of miles before you just break even.

In terms of smoothness, I guess. However, I have found that once your bike is set up for you and what you ride (i.e. suspension) modifications of me (fitness & technique) are the best bang for buck [emoji12]

Any other bike modifications I do are more cause I just wanna and there is nothing wrong with that [emoji106]


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royadams
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Re: squish questions and your experiences

Post by royadams »

The squish band has nothing to do with compression. It only shapes the fuel charge. When You tighten and reshape the squish, you cut the combustion chamber to drop the compression back down. It makes your engine run more efficient.
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Re: squish questions and your experiences

Post by Jaguar »

Roy, are you saying that after lathing down the head (so the squish band is tighter) then you use a dremel to expand outwards the combustion dome so that you decrease the squish band area?
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/
ohgood
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Re: squish questions and your experiences

Post by ohgood »

Jaguar wrote:Roy, are you saying that after lathing down the head (so the squish band is tighter) then you use a dremel to expand outwards the combustion dome so that you decrease the squish band area?
good question.

(i'm a machinist) you wouldn't need to use a dremel to re-shape the domed area of the head. just a radius tool (maybe a 1/2" r cutter or 1/4" r cutter would be preffered) and a little hand work to get the desired pocket removed from the head. i have tons of experience with lathe / mill work, but zero with head shaping, and zero knowledge of how/what/why/where for head pocket forming.

not that this matters as far as the knowledgable guys here alraedy know, just wanted to point you towards how it would be done very smoothly, and if needed, hand work could happen later.
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Re: squish questions and your experiences

Post by Jaguar »

does anyone know what the maximum squish velocity is with the RB head mod?
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/
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Re: squish questions and your experiences

Post by royadams »

You shave the head cut the squish and machine the dome. I would think you would have to be some kind of wonderful to cut the dome with a dremil. If you specify you want to run race fuel they can leave the dome a little smaller. Back in the day I worked at a bike shop and went to a week long coarse on 2 stroke performance. They have formulas for figuring port velocities and squish angles. I have long since forgot all that good stuff.
Last edited by royadams on 10:10 pm Apr 16 2016, edited 1 time in total.
jjavaman
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Re: squish questions and your experiences

Post by jjavaman »

You sure do ask a lot of rb related questions. I'm sure he doesn't give out his squish numbers or he'd be out of business pretty quick. You should cough up the bucks and get the carb and head mod done and you could measure/copy/mod to your hearts content!
97-220 with a PC pipe. 2015- RB carb and head mod
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Re: squish questions and your experiences

Post by Jaguar »

You sure do know how to make curious people feel "odd" about being curious. Maybe we should all just shut up and do as we're told and accept everything that the people in charge tell us. (yeah, right. when I'm f'ing dead)
Here's what he says on his site: "This mod will increase torque, snap, ride-ability and helps with fuel mileage too! "
Knowing that increasing the squish velocity is equal to advancing the ignition (as far as when the peak combustion pressure happens) I'll bet the RB mod increases squish velocity. If I don't get an answer in this thread then I'll start my own.

ps- most people have no clue what to do with squish numbers so there's no f'ing way he'd be out of business by giving them out. He's in business because he offers a good service at a good price. There's nothing super secret that he does.
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/
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Re: squish questions and your experiences

Post by Jaguar »

Looking at the before and after head pictures at http://www.kdxrider.net/forums/viewtopic.php?t=2444
and from the following email from Ron I'd say the RB head mod shaves off some of the mating surface, lowers the angle of the squish area, and increases the combustion volume to keep the cranking pressure from rising too much. That would serve to increase the squish velocity, something that decreases the time from spark to peak combustion pressure. So without adjusting the timing plate it would be akin to advancing the timing. If you disagree then just reconsider Rons own words on his site: "This mod will increase torque, snap, ride-ability and helps with fuel mileage too! "
Here is Rons response to my email: "Our mods are for premium pump gas and there is only certain things we can do to the 200 heads to help clean up the combustion without pinging and detonation problems for pump gas by squish angle reconfigured and machined combustion chamber. We have no MSV specs for you. We pretty much maintain the stock finished volume with maybe a 2 to 5 pounds increase in static compression"
For anyone that wants to MX a KDX then it's probably best to tell him to keep the same squish angle in order to not increase the velocity much.
If you want to calculate the squish velocity then go to www.torqsoft.net/squish-velocity.html
Performance CDI -- KDX motocross mods -- the SR KDX -- expansion chamber analysis---> http://www.dragonfly75.com/moto/
ohgood
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Re: squish questions and your experiences

Post by ohgood »

jjavaman wrote:You sure do ask a lot of rb related questions. I'm sure he doesn't give out his squish numbers or he'd be out of business pretty quick. You should cough up the bucks and get the carb and head mod done and you could measure/copy/mod to your hearts content!


please read my post. i'm looking for ridabilty IMPRESSIONs and EXPERIENCEs, not squish numbers, profiles of head pockets, or or compression numbers. i DO NOT want to copy anything (nor can I without a lathe) or undercut his business.

EDITED::::
i see where you got the impression i was going to copy RB's work, when i mentioned the machining specific part earlier. the intent of that post was to define the smoothest (and easiest) way to remove material, in the most uniform way, NOT to try and copy RB. he did the research, he gets the $$$. simple as that. :)


the reason i'm asking here is ... my buddy is sending off his beta 300 rr head to have squish calculated and modded, and we may share shipping costs.... AND SINCE RB IS ON VACATION RIGHT NOW i can't get replies about him modifying my old 33mm carb OR my head...

hence my questions here, where a lot of people have used his services.

have you personal experiences with his modified head ?
if so, does it need higher octane ?
does it increase or decrease fuel milage ?

feel better ? :-)
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Re: squish questions and your experiences

Post by C George »

I don't want to speak for RB but I believe I recall him saying that the basic 220 head mod he does runs off pump gas.

And I can't see where slightly more compression / efficientcy would hurt a thing.

I'd stay with the stock 33mm carb and as you already know ,,, The 220 is one of the "smoothest " two strokes out there.

Remove your kips ball and spring for even smoother power :)


XX - Our heads require better fuel but that was my decision
05 KDX-220R / 06 KDX-225R / Maxima 927 / Millenium Tech / Ron Black / PC , FMF / Many 220 engine mods / 40 + yrs. of riding dirt bikes 🤟🤟
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squish questions and your experiences

Post by Tioli »

If you want smoothness then the RB head mod may not be for you.

By making the squish more efficient it’s going to increase and localise the initial explosion so I would say sharpening it up will be noticeable in a non-smooth way.

BTW I have the RB Heads for 200 and 220 run full advances on 98 Ron and never heard any pinging or seen signs of it on the plug or piston. You could say its asking for the slots to be extended for a little more advance if you’re in to that sort of thing :grin:
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http://www.trials.com.au/forum/viewtopi ... &start=160

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ohgood
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Re: squish questions and your experiences

Post by ohgood »

C George wrote:I don't want to speak for RB but I believe I recall him saying that the basic 220 head mod he does runs off pump gas.

And I can't see where slightly more compression / efficientcy would hurt a thing.

I'd stay with the stock 33mm carb and as you already know ,,, The 220 is one of the "smoothest " two strokes out there.

Remove your kips ball and spring for even smoother power :)


XX - Our heads require better fuel but that was my decision

I've already gone from pwk33 to pwk35, mostly because the 33 was worn out, but secondarily (is that a word?) because it's the next step mod usually referred to for 220 owners.

ANNNNND

I completely forgot about doing anything to the kips. I'll be pulling the ball/spring today and testing if I like them removed. Thanks for reminding me !

My main concern is increasing snappiness (traction losses) and fuel economy. After riding a couple of ktm's with VERY twitchy throttles, I realized that hill climbs are more difficult with that kind of throttle response. I much prefer the lazy stump pulling roll-ons that my kdx does, for now.
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Tioli
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squish questions and your experiences

Post by Tioli »

If hill climbs is your problem get a auto clutch. You can stop any where any time and just take off with out the slightest hint of wheel spin.
If one of the group gets stuck it's easy for me to just go down where ever they are park best I can help them out get back on and take off as if it's flat.
You can stop on a steep slope and just hold it there with the slightest bit of throttle no brakes.

Im to old with loose knees which made hill climbs difficult. Now it's like cheating.
2001 KX125 with a 1997 KDX Tioli Hp motor

My KDX journey starts at the bottom of this page:
http://www.trials.com.au/forum/viewtopi ... &start=160

Trials.com.au / Forum / All about...me! / My long time friend the prancing horse / page 9
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