Tuning Tips - Honda Foreman Forums : Rubicon, Rincon, Rancher and Recon Forum

ATJ_Number_1 · 03-22-2009, 04:03 PM

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.

ATJ_Number_1 · 03-22-2009, 04:20 PM

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.

ATJ_Number_1 · 03-22-2009, 04:46 PM

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.

JWJR · 03-22-2009, 11:05 PM

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

jrfonte1479 · 03-23-2009, 03:09 PM

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.

ATJ_Number_1 · 03-23-2009, 09:30 PM

QUOTE (jrfonte @ Mar 23 2009, 02:09 PM)

Quote:

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.

kymudder08 · 03-25-2009, 03:09 PM

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?

ATJ_Number_1 · 03-25-2009, 08:22 PM

QUOTE (KYmudder08 @ Mar 25 2009, 02:09 PM)

Quote:

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.

jrfonte1479 · 03-26-2009, 08:27 AM

QUOTE (ATJ_Number_1 @ Mar 23 2009, 08:30 PM)

Quote:

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.

ATJ_Number_1 · 03-26-2009, 04:55 PM

QUOTE (jrfonte @ Mar 26 2009, 07:27 AM)

Quote:

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.

03-22-2009, 04:03 PM	#1 (permalink)
ATJ_Number_1 Honda Lover Join Date: Jan 2009 Location: SE Wisconsin Posts: 291	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. __________________ '05 Foreman 500 4x4 ES Highlifter Spring Kit / 25" Duro Power Grips / ITP Black Steel Wheels Ricochet guards front to back / Warn front bumper (modified to hold fairlead) / Superwinch S2000 Pro Taper Fat Bars / Acerbis Uniko Hand guards Custom Intake / Uni Filter / SuperTrapp Mudslinger Exhaust No rip-off Dynojet crap!!! '88 CR250R PSI chamber w/ PC silencer Lowered gearing for woods racing For all your tuning needs check out the "Tuning Tips" Thread.

03-22-2009, 04:20 PM	#2 (permalink)
ATJ_Number_1 Honda Lover Join Date: Jan 2009 Location: SE Wisconsin Posts: 291	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. __________________ '05 Foreman 500 4x4 ES Highlifter Spring Kit / 25" Duro Power Grips / ITP Black Steel Wheels Ricochet guards front to back / Warn front bumper (modified to hold fairlead) / Superwinch S2000 Pro Taper Fat Bars / Acerbis Uniko Hand guards Custom Intake / Uni Filter / SuperTrapp Mudslinger Exhaust No rip-off Dynojet crap!!! '88 CR250R PSI chamber w/ PC silencer Lowered gearing for woods racing For all your tuning needs check out the "Tuning Tips" Thread.

03-22-2009, 04:46 PM	#3 (permalink)
ATJ_Number_1 Honda Lover Join Date: Jan 2009 Location: SE Wisconsin Posts: 291	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. Attached Thumbnails __________________ '05 Foreman 500 4x4 ES Highlifter Spring Kit / 25" Duro Power Grips / ITP Black Steel Wheels Ricochet guards front to back / Warn front bumper (modified to hold fairlead) / Superwinch S2000 Pro Taper Fat Bars / Acerbis Uniko Hand guards Custom Intake / Uni Filter / SuperTrapp Mudslinger Exhaust No rip-off Dynojet crap!!! '88 CR250R PSI chamber w/ PC silencer Lowered gearing for woods racing For all your tuning needs check out the "Tuning Tips" Thread.

03-22-2009, 11:05 PM	#4 (permalink)
JWJR Super Moderator Join Date: Aug 2006 Location: Southern Illinois Posts: 2,279	awsome write-up ATJ i'm moving this to the how to section. __________________ '08 Rancher 420 4x4 ES (Mine) -28" Maxxis Zillas -12" Machined ITP SS212s -Warn RT25 with 6ga wire Audio Tube will be getting made shortly '05 Foreman 500 4x4 ES (Dads) -26" Maxxis Zillas -NGK Iridium Plug -Carb Mod

03-23-2009, 03:09 PM	#5 (permalink)
jrfonte1479 Honda Red Wing Rider Join Date: Feb 2009 Location: se texas Posts: 804	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. __________________ 08 black 700 rhino (sold) 03 yellow 450s (sold) 07 black 500 (sold) i no longer own any hondas but they wont be forgotten especially the black 1 10 750 blue nocturnal brute

03-25-2009, 03:09 PM	#7 (permalink)
kymudder08 Honda Rider Join Date: Jan 2008 Location: Owensboro, Kentucky Posts: 86	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? __________________ black '07 500 foreman 4x4 26" ams swamp fox plus tires soon to come: 12" itp ss108s HL lift springs HMF exhaust (dno which one) jet kit NGK plug snorkle light kit

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