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Jetting question, different than normal

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I have learned to properly jet thanks to this forum. As I read through tons of post, I noticed a couple of times how it was brought up about jetting different for the woods or open. I don't understand this. I assumed that only a small range of jets would work. I can't recall what I have in now, but I assume I could only go 1 size either way???? So how does one jet for the woods.... or have I misunderstood?

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Dirt bike Jetting is by altitude, and air temp usually.

Moisture content in the air and barometric pressure not so much in a typical dirt bike.

Woods, street, Bonneville or desserts would make no difference IMO.

Edited by adnohguy

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Dirt bike Jetting is by altitude, and air temp usually.

Moisture content in the air and barometric pressure not so much in a typical dirt bike.

Woods, street, Bonneville or desserts would make no difference IMO.

I wish I had marked those post. Saw it 2 different times

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I wish I had marked those post. Saw it 2 different times

I may look for it, but if I recall they were talking about jetting for low end grunt.  This made no sense to me

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I may look for it, but if I recall they were talking about jetting for low end grunt. This made no sense to me

Sorry but Maximum low end grunt would happen from way more than just jetting....

Added Compression, proper camshaft and a Pro Com CDI box are your # 1 sources for low in grunt....

(Of course your carb would need to be jetted properly)

Want more? A big bore and a stroker crankshaft

(280cc) are now easily doable. = more than double stock factory HP

AND you can have it from idle to the stock limiter...

But you will need better suspension for sure and clutch upgrades.

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I found one of them;

 

Quote

"you couldn't be more correct. Jetting is tricky, so i never suggest my setting is best for all. We live in different locations, with those locations dictating whats optimum. I ran the 132 main jet at my first time out. Then I went to Coeshow'S jetting. Honestly i felt little change. I stayed with coeshow's because i got a nice tan brown plug. Wanting to make it stronger, I dropped down to a 110 and that was way too lean...almost fried my engine. in the woods i use the 110 main jet with a power ring. It works fine! From my experience, if you know you're going to open areas to ride, stick with mains ranging from at least 118 to 132. Wood riding, reduce your main jet...how much?...Well that depends on your condition and what your bike likes. I will not say what your bike like, because for sure it will be different from mine, an yours will be different from his. what i will suggest is a range that your bike will most likely perform best in. Woods riding 110 to 118 main jets. Open territory 118 to 132."

 

This is what confused me. As I understood jetting, there was one optimal setting for my bike. I am wondering if 1, I have misunderstood the post, 2 if I have misunderstood jetting, 3 This is not the normal, but we will not assume it wrong on his bike

Edited by 1gr8bldr

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Is lean consider to be grunt stronger than rich?  And engine temps need be considered.... it would seem opposite to me because woods riding gets less air to cool the head of a hotter lean jet. 

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To clarify, all that I say is intended to spur explanation. Because I don't know, not that I do know. I probably have a strange way of asking questions. This is how I learn..... 

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Is lean consider to be grunt stronger than rich?  And engine temps need be considered.... it would seem opposite to me because woods riding gets less air to cool the head of a hotter lean jet. 

 

For a given set of conditions "Lean and Mean" will usually get you peak power.  It also gets you peak heat.  When we used to race sleds we would reach down and give the main "T"handle on the Tillotson a small twist to close the gap on extremely tight races.  It was enough to get you that extra power to close the gap or even get ahead.  However, if you forgot to twist it back you were rewarded with a nice hole in your piston.

 

Air density is forever changing, even as we ride in the course of a few hours.  Trying to jet a bike for "best" power on the lean side will ultimately result in a mixture that is too lean in many circumstances.  Air-cooled engines are notoriously difficult to jet because the head temperature varies wildly.  There are also many other factors.  If we set the main for peak power at WOT we will find it is too lean to give adequate A/F ratio and power/response while riding and twisting the throttle.  Sometimes we jet for highest peak power but then find we are too lean or too rich in the over-rev area.  If we fix the over-rev area we are then too lean or too rich and lose peak power.  It is always a compromise.  Jetting for static power on a dyno is not the same as jetting for dynamic riding conditions.  The same goes for timing curves.  If we set jetting and timing for peak power on a dyno it may be way off once we get on the street.

 

Mike Coe quit at a 120 main because he felt that was the safest option for all of us.  I'm sure he also did a lot of riding and testing to determine that would be his best recommendation.  The chances of wrecking a CRF230 engine by way of too-lean jetting is quite a stretch.  It is such a docile engine that would require some very odd circumstances.  I guess if we leaned it out enough and had it running under load at WOT with inadequate air flow it would eventually quit.  I can assure you there are thousands of XR200s out there with a too-low float level (and therefore too lean) and they are not failing.

 

From Mike:

 

"It was worth more than 1.5 HP!! With the 132 the A/F mixture was @ 11.0:1 and the power would level out at 16HP. After going down to a 125 and then the 120, the engine pulled cleanly all the way to the rev limiter and 17.83HP. This was on a bone stock 230 with "power-up" mods. I could have gone even leaner and picked up a little more power, but decided to stay a little conservative."

 

Mike Coe told me Honda ran the 223cc prototypes for 72 hours at WOT before they were considered adequate for production.  Even with the stock intake restrictor these engines are super-lean fro the factory and we have no failures to speak of.

 

Consider the old MOPAR Lean-Burn System from the late 70s.  These engines were running with A/F ratios in excess of 17:1.  Though the power was pretty miserable the engines held up just fine.  Of course they had water to remove the heat.

 

Overly-lean jetting on a docile engine like the CRF230 usually results in loss of fop-end power, not engine destruction.

Edited by VortecCPI
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To clarify, all that I say is intended to spur explanation. Because I don't know, not that I do know. I probably have a strange way of asking questions. This is how I learn.....

No problem at all, asking questions, getting all opinions, and then using the information that you gathered is the way to learn the basics and then use that info on your bike to test what option suits your riding style and conditions such as air temperature and elevation.

Silly me, I incorrectly assumed that you were already using the STARTING point proven to be ideal jetting for a box stock, Un-corked 230f. (45 pilot, 120 main, needle clip in the 4th from the top slot (or 2nd from the bottom)

Idle mixture screw adjusted for fastest unless speed)

I should have clarified those settings first before my rant on actual ways to transform your 230f into a smile making, torque producing, head turning, trail weapon.

Hopefully this makes things more clear about my intentions?

Good luck, please let all of us know how it turns out.

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