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Pwk jetting

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I bought a new pwk with factory 1999 cr250 jetting. I would have to double check but I think the main jet is 180.

I put this on my 93 cr250.

Does not seem as crisp and powerfull on top end as I think it could be.

So I lowered the needle by raising the clip from the middle to the top. It got better but still could be better.

Would I be correct to go to a smaller main jet and put the clip back to the middle to try?

It seems a bit boggy on 3/4 to WOT pulls, cleans it out sometimes eventually.

Elevation is around 2000ft +or-500

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I bought a new pwk with factory 1999 cr250 jetting. I would have to double check but I think the main jet is 180.

I put this on my 93 cr250.

Does not seem as crisp and powerfull on top end as I think it could be.

So I lowered the needle by raising the clip from the middle to the top. It got better but still could be better.

Would I be correct to go to a smaller main jet and put the clip back to the middle to try?

It seems a bit boggy on 3/4 to WOT pulls, cleans it out sometimes eventually.

Elevation is around 2000ft +or-500

 

99 CR250 came stock with a 190 main jet and a 42 pilot.  I don't know what the stock needle was.  the slide in the PWK was a 5.5 and the #7 does work better with a CR250 than a 5.5. 

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I just checked and I wrote on the side of the carb when I put it on, 48 and 180.

Maybe its for a 2000 cr250 but pretty sure its a 99 from partzilla. I didnt pick jet size . This us what they sent.

I might try a smaller main jet and look into the slide.

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I just checked and I wrote on the side of the carb when I put it on, 48 and 180.

Maybe its for a 2000 cr250 but pretty sure its a 99 from partzilla. I didnt pick jet size . This us what they sent.

I might try a smaller main jet and look into the slide.

 

If you have a 2000 carb, and you probably do, then Pro circuit recommends dropping to a 172 main for sea level jetting.  You might try going a bit leaner on the main (if you have a 180 in there.  You can make sure you have a 2000 carb by looking at the bottom of the slide and see what number is there, if it has a 7 then you have a 00 carb, if it has a 5.5, you have a 99.

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The 7 is leaner.

thanks. By the way, a little off topic to the thread.

 

Im swapping a PWK into a CR125, it has 7 slide, I see recommendations of putting the 5. Since the slide alone is not available for sale (or at least i see any), is this a minor mod in the performance or is it really noticeable? Thanks guys

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Im not sure the excact specs are for how much airflow is allowed at a given rpm range but I know if the 7 is to lean you can always run a richer needle. Im sure there is a 125 owner that has experience with the sensitivity of the slides on the 125 because maybe the smaller engine with less velocity getting sucked in may need a smaller slide cutout to make them work well.

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Thnaks for your answer, I appreciate contributions since if it is a minor change I wont be spending a fortune to get a slide to where I live, where mx is practiced by very few people

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thanks. By the way, a little off topic to the thread.

 

Im swapping a PWK into a CR125, it has 7 slide, I see recommendations of putting the 5. Since the slide alone is not available for sale (or at least i see any), is this a minor mod in the performance or is it really noticeable? Thanks guys

The #7 slide seems to be the dominant slide out there.  JD sells his pre-jetted pwk carbs with a #7 slide for the CR125.  However, reading through some of Eric Gorr's technical data, he recommends a #5 or #6 slide for the 125.  I have a JD pwk with a #7 slide that I was using on my 2005 CR125/144.  I have since changed for the yz pwk as it is a better fit, and I can still use the TPS in my ignition system.  Anyway, I have done some experimenting with different slides because I was having an "off idle hesitation" (OIH) with my best jetting settings using a #7 slide.  I found the #5.5 slide from oem 99 CR250 to remedy the OIH, but also found that 1/8 to 1/4 throttle was not as clean.  I'm currently having my best results with a #6 slide using an oem alternate needle from 2000 CR250 A685/294R in the 4th clip, with a 42 pilot, and 178 main.  Great throttle response, slightly spoogy.  

 

You can get different slides from JD Jetting, jetsrus.com, or you can order oem slides from different pwk equipped bikes.  2000 KX250 comes with #8 slide, 99 CR250 comes with 5.5 slide.  Or you can send a slide to RB designs and have a slide recut to a leaner number.

 

Update:  Just messing around with jetting again and find this to work better.  A685/294R #3 clip, 45, 178, 2 turns, #6 slide.  Previous setting was near the edge with 1 turn and 42 pilot.  This setting opens up the airscrew to midrange, and seems to run cleaner with no OIH.  I could use the A685/289R #3 clip which is 1/2 clip richer and this works well too.

Edited by magpie5
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The #7 slide seems to be the dominant slide out there.  JD sells his pre-jetted pwk carbs with a #7 slide for the CR125.  However, reading through some of Eric Gorr's technical data, he recommends a #5 or #6 slide for the 125.  I have a JD pwk with a #7 slide that I was using on my 2005 CR125/144.  I have since changed for the yz pwk as it is a better fit, and I can still use the TPS in my ignition system.  Anyway, I have done some experimenting with different slides because I was having an "off idle hesitation" (OIH) with my best jetting settings using a #7 slide.  I found the #5.5 slide from oem 99 CR250 to remedy the OIH, but also found that 1/8 to 1/4 throttle was not as clean.  I'm currently having my best results with a #6 slide using an oem alternate needle from 2000 CR250 A685/294R in the 4th clip, with a 42 pilot, and 178 main.  Great throttle response, slightly spoogy.

 

You can get different slides from JD Jetting, jetsrus.com, or you can order oem slides from different pwk equipped bikes.  2000 KX250 comes with #8 slide, 99 CR250 comes with 5.5 slide.  Or you can send a slide to RB designs and have a slide recut to a leaner number.

wow thanks for the great answer! Im taking tips

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BTW my 38 pwk as comes from a kx250 somewhere 98 - 02. Twist top and TPS, not very common from what I have checked, cutted the TPS off. It weights at least twice in comparisson with the stock TMX.

Edited by AdrianTenerife

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BTW my 38 pwk as comes from a kx250 somewhere 98 - 02. Twist top and TPS, not very common from what I have checked, cutted the TPS off. It weights at least twice in comparisson with the stock TMX.

Are you sure your not confusing the power jet solenoid with the TPS?  That is a 98.  You will have to block the power jet circuit by removing the bowl, then remove the power jet on the rim of the underside carb body, and plug with a small set screw (4mm stainless) you can get from the hardware store.  You can also remove the power jet solenoid and replace with a 8mm fine thread 1.00 bolt cut to size.

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attachicon.gifImageUploadedByThumper Talk1380150261.993547.jpgattachicon.gifImageUploadedByThumper Talk1380150403.546010.jpgattachicon.gifImageUploadedByThumper Talk1380150451.622648.jpgattachicon.gifImageUploadedByThumper Talk1380150471.180784.jpgattachicon.gifImageUploadedByThumper Talk1380150502.439481.jpgattachicon.gifImageUploadedByThumper Talk1380150524.462438.jpg

 

I know this is kind of going backward in the thread here, but I found these socket head bolts at bolt depot.com in metric8 x (1.00 fine thread), and had wanted these before, but could not find in the local hardware store.  I thought I'd post some pics of how cut and filed these to replace the power jet solenoid.

 

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Are you sure your not confusing the power jet solenoid with the TPS?  That is a 98.  You will have to block the power jet circuit by removing the bowl, then remove the power jet on the rim of the underside carb body, and plug with a small set screw (4mm stainless) you can get from the hardware store.  You can also remove the power jet solenoid and replace with a 8mm fine thread 1.00 bolt cut to size.

 

My god, I have been thinking for months that it was th TPS !

 

I just cut the cables away. Mine is the first one in the pic with the selenoid system of the second one. Thanks a lot!

 

The power jet in the carb body air flow should be cut as close to the rim as possible right?

 

About the jet next to the float taking gas from the carb, should it be cut as well?

 

 

013-2.jpg

Edited by AdrianTenerife

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Dont bother with the slide until you have the jets figured out. Get it to idle, then it needs to pull wide open throttle (which is where you defined your problem). The slide will tune 1/4 to 3/4 throttle, not what your complaint was about.

Does it ull clean or does it just not rev out? Clean meaning not burbly, but crisp. Or does it just gaining rpm? Burbling is rich, some call it 4 stroking. Not revving out is lean up top. Only chainge the main, nothing else. Other changes come later.

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I revs, I think. Just when on a wide open pull kinda seems burbly like it takes to ling to " get on the pipe" eventually it does and if I keep it wot it will stay there but if I let off and try again its "off the pipe " and have tp hold it open for a bit again to ( I think ) clean it self out.

Like trying to accell in to high of gear maybe but I know it not top high a gear.

I just moved and still have to get my extra bike parts and jets unpacked and organized in the garage asap or I would have already tried something

Thanks for all the help. I just thought that if lowering the needle helped than a smaller jet is the next step but I dont have alot of experience with jetting

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Dont bother with the slide until you have the jets figured out. Get it to idle, then it needs to pull wide open throttle (which is where you defined your problem). The slide will tune 1/4 to 3/4 throttle, not what your complaint was about.

Does it ull clean or does it just not rev out? Clean meaning not burbly, but crisp. Or does it just gaining rpm? Burbling is rich, some call it 4 stroking. Not revving out is lean up top. Only chainge the main, nothing else. Other changes come later.

The slide has most effect from 1/8 to 1/4 throttle, but will change the whole jetting curve in a minor way.  The Needle range is from 1/4 to 3/4.  If your jetting is on, but otherwise rich from 1/8 to 1/4, then time to think about a leaner slide.

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My god, I have been thinking for months that it was th TPS !

I just cut the cables away. Mine is the first one in the pic with the selenoid system of the second one. Thanks a lot!

The power jet in the carb body air flow should be cut as close to the rim as possible right?

About the jet next to the float taking gas from the carb, should it be cut as well?

 

ImageUploadedByThumper Talk1402766957.240297.jpgImageUploadedByThumper Talk1402766996.611334.jpg

 

Sorry, don't mean to jack the thread.  This info is already on another thread.  Image 1, remove the power jet and replace with SS set screw, in the half moon location on the rim of the bottom of carb body.  Image 2, option to replace solenoid with a 8mm x 1.00 fine thread bolt.  I used a hex head, but the other standard type bolt cut down to size will work fine.

 

Once the power jet is blocked, the brass fitting that protrudes out the side of the venturi has no effect.  Otherwise your jetting will be messed up.

Edited by magpie5
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