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Discussion Starter · #1 ·
Dual purpose write up here. To help with tuning your carbs and to explain to you why Dynojet kits are a waste of money.

No pic for this one but in order to tune the low end or "pilot circuit" you'll either need a D-screw drive tip (from Motion Pro) or you can just cut a slot into the head of the pilot screw and use a flat head screw driver like I and others have. The d-screw tool comes with the Dynojet kit but as you can see there are other ways to get the job done.

The pilot circuit is really simple to adjust properly.

1) Start by running the machine for about 10min. Taking it for a quick spin is the best way to warm it up.

2) Assuming you've cut your screw or have the drive tip already take the left side panel off to allow your hand to get under the carb where the screw is. This is the easy pop-off panel.

3) While the engine is idling turn the screw out of the carb until the RPMs peak and start to come back down. You won't need to go far at all from peak PRMs. If you have a tachometer great but you don't need one and can hear the RPMs go up and down.

4) Now turn the screw back into the carb until you find the other side of peak RPM. You want to turn the pilot screw back in just until you hear the RPMs slightly go back down.

5) You're done! There is need to do a plug chop or any other home remedy test to confirm this setting. The low end is set. If you want to know what your screw is set at then carefully note how many turns it takes to turn the screw all the way in, mark down the number of turns and bring it back out. At a minimum be specific to the quarter turn.

EDIT: As I add later in this thread if you don't want to adjust your pilot screw but need to richen the low end you can also swap out the stock 45 pilot jet for a 48 and you will be quite close to want you need without any special tools or cutting.
 

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Discussion Starter · #2 ·
The mid range you can and should usually leave to the end. The Needle fine tunes the the mid range but the main jet affects the mid range also. Another thing that comes in the Dynojet kit is main jets. This is not a kit exclusive item and main jets can be cheaply purchased from JetsRus.com or for double the price at your dealer. An order of 4-5 different size jets shipped will be less then $20.

Adjusting the top end

1) You've got the low end set, now try out the top end by using the throttle. If you can hit the gas with no choppiness in the upper RPM range then you're ready for plug testing.

2) If you can not use the top end without chopping out then you've most likely added a pipe or a large snorkel or both and are too lean. Remove the carb and up the jet size to a 162. IF you can change the jet without removing the carb that's fine too. The plastic piece around the jet is an "over engineered" anti slosh devise and is not needed. Run it if you want but it's not in any of my carbs.

3) Reinstall the carb and with the engine warm try the full range of the throttle again. Is it smooth on the top end yet? If so then go to plug chops. If it's better but not great keep going up on the main jet sizes until you get the upper RPMs like butter.

4) Now that you've got the top end smooth install a new properly gaped spark plug. The proper way to test the top end is to now go out and run it at almost peak RPMs and hold it there for at least as few seconds if not more. The engine must be warm and the configuration of your intake and exhaust must be complete and together as if you were going on a ride.

5) After you've held the throttle at the upper RPMs kill the engine in that RPM range and let it die down, engine shut off.

6) Pull out the plug and look at the tip. If it's a nice light caramel color then you got it. If it's too white then you need to go up on your main. If it's bordering black then you need to go down on your main. Repeat steps 5 & 6 if you need to change the jet until you get it right.

7) You're done with the top end, on to the mid range.

EDIT: It appears that different years have different main jets. This could be due to several factors so if you want to be 100% sure what size jets you need look to see what you have in your carb already and order then next 3 sizes.
 

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Discussion Starter · #3 ·
The mid range is where Dynojet really sells the "snake oil". What they do is have you install an extremely weak spring and a larger needle to compensate. Neither of these parts are needed to properly tune your carb.

Tuning the mid range.

1) You've got the low and the upper ends set. With a warm engine in neutral pin the throttle quickly. Does it accelerate the RPMs smoothly? It may and you could be done but if there is a slight hesitation coming off idle then go to step 4. If it's more then slightly off in the mid range then you may need to add shims to the needle.

2) Pull the top cap off the carb, remove the needle holder in the slide and remove the needle. Using either M3 machine screw washers or #4 copper washers add one between the needle clip and the factory washer. This will richen the mid range. Pictured below is the washers I found at True Value for less then a buck and below that is my needle that I used with 3 M3 washers below the clip.

3) Reinstall everything and test the throttle again. Did it get better but not good enough? Then add another shim. If it's almost dead on except for a slight very low hesitation then move on to step 4.

4) This slight low end hesitation is most likely that stiff factory spring. As pictured below pull the spring out and with 2 thin strips of duct tape shorten up the spring 1 1/2". Cut the tape short, fold the tape to the inside of the spring and put the tape end in the cap, reassemble and try again. The length you need could be more or less so using tape allows you to test the spring at different lengths without cutting it.

5) When you find your desired spring length cut it. Bend the end of the spring so it's not pointing as sharp and install the cut end into the slide of the carb and the uncut end into the steel cap.

6) Your done tuning your carb! You can plug chop the mid it's not necessary.

I'd like to note a couple things here. First is that in my foreman I only needed to trim about 1 inch from the factory spring to get a perfect throttle pull. DO NOT try to replicate the Dynojet needle!!! They use a very weak spring and a bigger needle to make up for it. Cutting the stock spring to the same length as a Dynojet spring will not match it. By weight testing I've found that due to the different spring tensions you'd have to cut your stock spring to a mere 3 1/4" to match the spring tension of the Dynojet needle! You don't want to be anywhere near that with the stock needle.
 

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awsome write-up ATJ i'm moving this to the how to section. :goodjob
 

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just out of curiousity what main jet size did yours come with from the factory. im asking because you said up the jet size to 162 my 500 came with a 165 stock. and what kind of jets are you using keihin and dj are different sizes.
 

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Discussion Starter · #6 ·
QUOTE (jrfonte @ Mar 23 2009, 02:09 PM) index.php?act=findpost&pid=124156
just out of curiousity what main jet size did yours come with from the factory. im asking because you said up the jet size to 162 my 500 came with a 165 stock. and what kind of jets are you using keihin and dj are different sizes.
As the theme suggests I can't stand any products that the rip off company Dynojet offers so I use Keihin or generic equivalents. Mine came with a 158. I would be interested is what others had stock because Honda doesn't even list a 165 option for an 05 Foreman.
 

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you told me to check this out, but it looks complicated. lol. im not mechanically inclined when it comes to engines. and how do you know what size your stock jet is?
 

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Discussion Starter · #8 ·
QUOTE (KYmudder08 @ Mar 25 2009, 02:09 PM) index.php?act=findpost&pid=124288
you told me to check this out, but it looks complicated. lol. im not mechanically inclined when it comes to engines. and how do you know what size your stock jet is?
The jet size will be stamped on the jet it's self. Whether you get a kit or not you'll have to go in either way so if you take a look you'll know where you are. It should be a 158. That's what mine was and in HMF's help section they state that it should be a 158 also.

Regardless what you have, jets are real cheap so if you get 162, 165, 170, and 175 main jets you'll be covered for about anything and from jetsRus.com it should be less then $20 shipped!

Here's another tip! From my past tuning experience and what I've recently done with my Foreman you should be able to install a 48 pilot jet and not have to do any changes with the air fuel mixture screw ( the one I talk about the d-screw tip). Stock pilot jet is a 45 and 48 with the stock screw setting should be perfect. I'm running a 48 myself and you could toss that into your jetting order with the mains. Just go to their website and on the left you can use the "Parts Finder" to look up your machine so you get the right parts. I've been using them for a while and they are cheap, fast and reliable.
 

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QUOTE (ATJ_Number_1 @ Mar 23 2009, 08:30 PM) index.php?act=findpost&pid=124181
As the theme suggests I can't stand any products that the rip off company Dynojet offers so I use Keihin or generic equivalents. Mine came with a 158. I would be interested is what others had stock because Honda doesn't even list a 165 option for an 05 Foreman.
just to be sure i went outside and looked at the jet again and its a 165s it was the jet that was in it when bought new from dealer in 08.
 

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Discussion Starter · #10 ·
QUOTE (jrfonte @ Mar 26 2009, 07:27 AM) index.php?act=findpost&pid=124336
just to be sure i went outside and looked at the jet again and its a 165s it was the jet that was in it when bought new from dealer in 08.
I'm not doubting you and as a matter of fact Honda has at times tuned carbs different for different regions. There may be something to the difference in years too.
 

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I ordered 162, 165, 170, and 175 jets and when I pulled the main Jet out of my 08 Foreman it had a 165 already in it so I moved up to a 170 with a K&N Filter and a 2in Snorkel. These tips worked great for me I can't wait for the Hilifter park to be open again so I can ride it.
 

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I have the little....D shaped tool thing, but its just hand held.

I had a **** of a time trying to adjust it today, I couldn't tell if it was stripping it or actually biting.

One thing I noticed is that my idle didn't seem to change at all when adjusting it, at one point the gold colored screw was poking out of the hole, I think I went way too far, didn't even realize it. Luckily it didn't fall out.
 

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Discussion Starter · #13 ·
QUOTE (lucky644 @ Apr 5 2009, 01:43 AM) index.php?act=findpost&pid=124781
I have the little....D shaped tool thing, but its just hand held.

I had a **** of a time trying to adjust it today, I couldn't tell if it was stripping it or actually biting.

One thing I noticed is that my idle didn't seem to change at all when adjusting it, at one point the gold colored screw was poking out of the hole, I think I went way too far, didn't even realize it. Luckily it didn't fall out.
It is possible that with your mods the stock pilot jet is almost maxed out. What I mean by that is you were able to turn the screw all the way out because the range of adjustability was maxed. You likely couldn't experience a drop in RPMs on the turn out because your pilot just couldn't produce anymore fuel. This isn't necessarily a problem yet.

2 things you can do here:

1) Buy a 48 pilot and step up to a wider band of adustability where you will feel both ends of the RPM test. If it was a customers bike I would do this to insure they had full adjustability for future mods but is not totally necessary.

2) Save some money and time and do part of the test. The idea of the RPM test is to give a person a positive feel of their parameters. You can't find that "turn out" RPM drop due not enough fuel provided by your pilot so just look for the "turn in" RPM drop. In your case I would set the screw at 3 turns out with a warm engine and turn it in slowly until you hear a slight drop RPMs. At this edge of the slight drop is where you want your setting to be.




I've admittedly never seen the d-tool dynojet provides. Would it be possible to see a picture? Is it hex shaped like a screw driver tip? Sorry for the troubles, let me know if there is anything else I can offer.
 

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Its a D shaped tip, with a rounded end, so you cannot insert it into a screwdriver or anything, it doesn't grip.
 

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the little dyno jet tool doesnt fit to good. take a pair of pliers and crimp the flat side of it a little more and it works better
 

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Ok guys heres one for yall! I installed a snorkel exhaust air filter then ran the 170 jet like hmf said! I checked the plug too rich! Went down to 165 still to rich! Now back to factory which is 162 should i keep going down? Do i get a hotter plug maybe? Is this common or what? got the low end pretty good, just right at max rpms on the high end still a little choppy and the fact of runnin it around checking the plug and well its black! I guess ill down jet more but dont want to rob of power!
 

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Discussion Starter · #17 ·
QUOTE (bayou_nut @ Apr 6 2009, 08:16 PM) index.php?act=findpost&pid=124899
Ok guys heres one for yall! I installed a snorkel exhaust air filter then ran the 170 jet like hmf said! I checked the plug too rich! Went down to 165 still to rich! Now back to factory which is 162 should i keep going down? Do i get a hotter plug maybe? Is this common or what? got the low end pretty good, just right at max rpms on the high end still a little choppy and the fact of runnin it around checking the plug and well its black! I guess ill down jet more but dont want to rob of power!
Are you using a new plug everytime? Also what size or type of snorkel are you running? How did the machine run before you did any mods?

Sorry I missed this post.
 

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Well the snorkel has 2 inch most of the waty then about eight inches of one and a half to the air box. The plugs i used was first a new factory plug with different jets. Second was a iridium ngk with different jets. Now today will try a little hotter one number down. I have it about half and half right now with a 162 jet what i mean is half of it is caramel color then toward the fire bracket i guess u can call it (the little piece that is bent on the bottom of the plug) is a little black. Im almost there i guess well i hope all this taking apart the carb is getting out of hand. At this point just tryin everything to try to fine tune this puppy!
 

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Hows the plug look?



Thats after I adjust this knob to change idel. I couldn't find the low end part. I have the jet kit but bought it before I seen this. I just need to install the actual jet once the carb is removed.
 

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Discussion Starter · #20 ·
QUOTE (ILockert @ Apr 20 2009, 05:19 PM) index.php?act=findpost&pid=125641
Hows the plug look?
Too be honest not too bad. Has this plug seen some miles?

QUOTE (ILockert @ Apr 20 2009, 05:19 PM) index.php?act=findpost&pid=125641
Thats after I adjust this knob to change idel. I couldn't find the low end part. I have the jet kit but bought it before I seen this. I just need to install the actual jet once the carb is removed.
That knob won't affect your jetting in anyway so your plug color should be the same as before. I'll have to update this thread with some pics but that plug looks good enough that I wonder if you need to change the jet at all. Is the top end smooth running?
 
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