All carburetor jetting hands on deck! - Yamaha ATV Forum
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post #1 of 33 Old 11-26-2018, 07:17 AM Thread Starter
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All carburetor jetting hands on deck!

So I met someone online in a Facebook Raptor 660 forum who because of where he lives where the atv sound laws are so strict and he said the sound of his muffler scared his son he was looking to trade his chrome flawless looking Duncan Racing Fat Boy 4 muffler (which they sell rebuild kits for and they come apart very easily to do so) for a bone stock raptor 660 muffler. But obviously he wanted to trade for one that was clean like his. Many people tried to trade him but there's were rusty etc. Myself wanting a slip on and love loud traded with him as my Raptor has very low hours on it and has been garage stored pampered before I got it my muffler looked new. So we trade. All went smooth. I put a new gasket in where the stock muffler connected.

I completely rebuilt my carburetor with Mikuni jets before this with my air screws set at 2.5 and 2. Where I'm at elevation of 500 feet location near Saginaw Michigan area code 48706.

My problem - I called Duncan Racing and as I'm sure some of you already know the guy who runs Duncan is a total asshole. I asked him for jetting tips on a stock airbox yes with snorkle, only thing different is the dual intake Uni air filter. He said "I don't believe in slip on pipes they don't work I don't know what to tell you about jetting. This was after he told me to download the instructions for the entire fat boy 4 exhaust system. After I told him I only had the muffler he turned into a prick. "oh your the guy who asked about buying just the header and midpipe like a month ago? Oh I'll reply to that email when I can".

So now I have no clue what jets to use. When I start it which it starts and idles perfect. Any punch on the throttle it pukes. It's not the parking brake or nuetral switcg. I have done both mods as described here in blue Trax. After I started talking to the parts guy at the Yamaha dealership he said just removing the snorkle off the airbox would make you need to reject.

So can soneone who knows about jetting one of these beaats please offer some advice. I'm sitting bone stock with 22.5"s and I whatever stock for the two carbs mains are " I don't remember right off hand".

If you purchase the entire Duncan exhaust there instructions are to up the jets to like 155 and 178 or something close using the 4th needle clip.

Well the spark plugs isn't the easiest to get to so if someone could give me advice on how to proceed I would so appreciate it. I want to ride this quad so bad and it just snowed here about 2 weeks away from the river behind me is going to freeze over. I bought two rear tires with stud slots for the ice. Can't use them though if this things gonna choke and puke when you give it has. I would very much appreciate help fellas.

JMH
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post #2 of 33 Old 11-26-2018, 10:11 AM
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heres my 2 cents. the guy a duncan may be an ass, i dont know but he is right. without airbox mods a slipon will only make it louder (adding the header and mid pipe wont help either) your raptor will only flow as much air as the the most restricted part will allow. in this case the air box. the 660 air box is very restrictive and will have to be modified if you want any performance gain. i suggest something like this https://www.ebay.com/itm/MoFlow-Airb...onmQ:rk:7:pf:0
i ordered the outers fabric and made my own ( i am way to cheap to spend that kind of money on something i was able to make in an hour)and added a k&n. it does a pretty good job of shedding splashes but would not hold up to deep water.
that being said i suspect your problem is in the rebuild of your carbs. i suspect that if you had the old muffler you would find it runs the same. adding that slip on would not cause jetting issues bad enough to create your problem
i could not even begin to count the number of carbs i have rebuilt and tuned but it is a lot and 2 years ago a picked up a really nice 660 for my wife and after one or two rides i figured out why i got it cheap, the carbs were leaking and it was boggy in the middle. i thought no problem i will rebuild the carbs. well 2 days later i got it done but they were the hardest carbs i have ever done. the main problem i found in hers and what i suspect happened with yours is the is the guts from the right carb ended up in the left carb and vice versa. as i was rebuilding them i started to do the same, it is really easy because as you work on them the left carb is on the right side because they are upside down. tuning, balancing, and setting the floats was also a real bummer. did you use a manual or just take them apart and put them back together. each carb is jetted slightly differently and handle different stages of throttle. ( this is why so many people changed to a single carb back when these were the hot ticket). i am not judging your skill just saying it is really easy to do. also double check the carbs in the boots they are a little tricky sometimes as well.
as far as the jetting goes i know the plug is no fun to get to but at least you dont have to pull the tank like i do on the yfz's. the plug is critical to getting the jetting. there is no magic number because each bike is different. the amount of vacuum the engine creates plays a roll in how much fuel flows through a jet. the tighter the engine the more vacuum it creates, the more fuel is pulled through the jet. so a 155 may be different in my bike as compared to yours so checking the plug is the only way to get it perfect. the header and mid pipe wont make that much difference so if you do the air box i would start with the duncan numbers and move from there. if you dont do the air box i would be surprised if you need to rejet at all.
i installed air mix screws like these https://www.ebay.com/itm/Raptor-660-...l3J:rk:10:pf:0
i think mine were mod quad but i am not sure. i found them critical for getting the tune exactly right. i have those or the flex jet screws on all 6 i my bikes and i will adjust them throughout the day as the air temp changes, especially when i am at the beach. if you dont have one i really like the clymer manual it was very helpful getting those carbs perfect.
i have only worked on mine and that is what i found. hopefully digger will be on in the next day or so, he really knows these machines and may have solved this issue for someone else. again i am not trying to knock your skills but that is where i would start if you brought it to me with the information given. let me know if you need anything else
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post #3 of 33 Old 11-26-2018, 02:47 PM Thread Starter
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Thank you for your reply and I have much to chat with you about if you have that much experience. I rebuilt this carb and went through it twice bro just to check if that is what happened. I am at work now but will be back later to chat some more.

I used a clymer manual, set the floats using the clear tube method and they sit perfect right where they should be, I checked them on a bench with gasoline before reinstalling them. I was afraid I might of did exactly what you said which is why I tore the whole thing apart to check. I even replaced the rubber valves under the caps with brand new Mikuni ones. The rebuild kit for a dual was around $90. Now I have no idea what is going on. But it does sound amazing.

Hey dude, I am a DIY kinda guy to and am interested on how you made your airbox. Wouldn't mind copying the design if you don't mind sharing. I was told those screws bro were bad and would leak? IDK. LOL

No bro I get it, I used the clymer to, those books are amazing. I am going to order a pair of those screws, I bought one of those 90 degree screwdrivers, junk!. still impossible to reach the air screw and turn it without messing it up.

JMH

Last edited by jason9922; 11-26-2018 at 03:33 PM. Reason: Add more info
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post #4 of 33 Old 11-26-2018, 08:12 PM
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The Raptor is pretty corked up by the pipe, as cory already said the intake is holding it back as well. If you are looking for some power ditch the snorkel, and if you want more get a clamp on filter setup and leave the airbox lid off and then proceed with the jetting. This way you only have to go through this one time. DOn't leave the lid off if you plan on doing a bunch of water crossing though.

First off I agree the Duncan guy isn't being too friendly. Aftermarket header and midpipe on a 660 single exhaust is NOT worth the money. People with dynos have shared their findings and the power gains are not there. Larger diameter head pipes show gains with the full dual exhaust but not enough to talk about on single muffler.

I cant understand why Duncan Recommends the big difference in size between the two jets, most setups I have seen are 5 number size apart. 160/165 for example.

I would start with a 25 pilot and 165/170 mains(if you take the snorkel and or the lid off, otherwise leave the 22.5 and try 160 165) and see how it reacts. Jetting is not a fun process but is worth it in the end, step up the sizes until it runs good. You get good at pulling the carbs and get to know your machine. Once you get it dialed in its all fun! I usually dont mess with the needles until I get the top end running good. Use the needles to dial out and mid range stumbling after.

Another thing to make sure is not to get carb cleaner on the diaphragms on top of the carbs, it distorts them and can compromise the seals and make it unpredictable.

Its also a good idea to check the valves if you have never done so.. The 660 is notorious for the valves tightening up as they get hours on them.

01' Raptor 720, Stage 2, FCR'd
97' 250 Vitos Blaster
06' Rhino 450
94' Banshee T-5's, Vforce, ported, Cool Head, 2-1
06' Wolverine 450 - Stock!
06' LTZ 440
94' Vmax4 750, 96' 600 MountainMax, 07' Nytro(b00sTed)
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post #5 of 33 Old 11-26-2018, 09:11 PM
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i have had the screws in in for 2 years now and no leaks you just have to make sure the o rings go in correctly and they dont rattle out. put a little spit on them when you install them to avoid rolling the o rings. the lid was gone off of my 660 when i got it so i am just running an open box until i can find a cheap used lid to cut up but when i get home tomorrow i will upload a picture of a yfz lid and i think you will be able to see what i did.
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post #6 of 33 Old 11-29-2018, 04:05 PM Thread Starter
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Thank you fellas for all you replied. I appreciate it. It's just a mo-fo taking this carb off to rejet it and fellas I bought this and a warrior 350 1998 like a year and a half ago. We got really hosed on the warrior. Took the airbox off and the entire manifold fell right out of the atv. Grease packed in the rear caliper so we wouldn't feel it was smoked. The mess to replace all that. I have dialed in the valves on the Raptor but I did not turn the crank a couple times and re measure so I'll probably do that again. It's just my girl is so sick of me working on these things and after she seen me rebuild that carb so intricately. Yeah I didn't have any of the rubber on the carb when I cleaned it, thats a good tip. I rebuilt the whole thing using Mikuni stuff only. I took all the rubber, o rings, diaphrams and let them soak in a thin oil before I reinstalled them. Yeah I wiped them off they weren't dripping but you guys get what I mean. Making sure they do not dry out. I have them synced perfect, honed out every spot that air hits to almost a mirror shine including the two brass pieces. When I was done anyone who walked in thought it was brand new for sure. She was so excited thinking we were good to go after I installed it after rebuilding it to stock spec, new choke system plunger o ring kit, everything new. Then it falls on its face. I am going to get the adjustment screws, check the valves again, and do exactly what you guys said about jetting up. I have .25's pilots already and am going to order some 160 -165. Dynojet will not sell the needles separately. Really appreciate the help

JMH
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post #7 of 33 Old 11-29-2018, 04:15 PM
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be careful if you are using the dyna-jet kits. they are ok but you have to use the entire kit, needles, jets and adapters. i spent a year chasing an over fueling mid throttle bog on a yfz. i dont remember weather i had dyna jet jet and another needle or the other way around but long frustrating story ditching the dyan jet stuff fixed my issue. i went with the factory racing needle and factory jets. the tricky part was i did not do it, i bought it that way and it was only after rebuilding several yfz carbs i noticed something was not right
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post #8 of 33 Old 11-29-2018, 04:51 PM Thread Starter
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Yeah I was gonna try and score the kit 2 needles but cannot get just them so I'm just sticking with Mikuni, what jet size you suggest I start at? Elevation 500 feet How many turns on air screws? Everyone throw in what they think on this. I can lose the stock lid and snorkle I will be riding on ice and through a little mud but not much at all.

JMH
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post #9 of 33 Old 11-29-2018, 05:15 PM
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so clearly tech is not my strong suit. lol. i spent an hour uploading pictures of the air box lid to the wrong thread. look in the raptor 700 thread under raptor wont rev. it is the first thread and they are there. i would move them but it was tough enough to get them there.
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post #10 of 33 Old 11-29-2018, 05:26 PM
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i am assuming digger meant 25 (not 125)- 165/170 with the lid off and stock 22.5 160/165. those look like a grate place to start to me. mix screws at 3 on the left and 2 on the right
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post #11 of 33 Old 11-30-2018, 04:14 PM Thread Starter
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OK cool, that is what I ordered, I ordered .25 pilots to along with the 160 165 and I also ordered the 165 -170 for when I can afford to get the pro mod air filter setup. I also ordered those air screws you can turn by hand. I would rather just leave the lid and snorkel on because I'll never know if I'm going to hit a lot of water or huge puddles and don't want to have to worry about it. This is nutts trying to adjust these screws. I'm over it. I'm getting very aggravated with this 660 altogether to tell you the truth. I have to say this is not one of the better designs I have messed with when it comes to anything mechanical.

JMH
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post #12 of 33 Old 11-30-2018, 05:37 PM
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now you know why 660s are 1800 bucks and the 700s are 4 grand lol. dont give up other than the second gear issue in the 01s they are actually great machines once you get them tuned. one i got mine dialed i have not had to touch it. just wait until you have to put a clutch in it. they turned a 20 minuted job into a 4 hour job but thats for another day. mine has hot cams, a full big gun and the air box done and it hangs with my yfz pretty well, at least on the bottom end. the super cool thing with the 660s is when we are at the dunes my wife can pretty much stay in 3rd all day. it has torque to the moon.
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post #13 of 33 Old 12-01-2018, 06:29 PM
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Quote:
Originally Posted by jason9922 View Post
OK cool, that is what I ordered, I ordered .25 pilots to along with the 160 165 and I also ordered the 165 -170 for when I can afford to get the pro mod air filter setup. I also ordered those air screws you can turn by hand. I would rather just leave the lid and snorkel on because I'll never know if I'm going to hit a lot of water or huge puddles and don't want to have to worry about it. This is nutts trying to adjust these screws. I'm over it. I'm getting very aggravated with this 660 altogether to tell you the truth. I have to say this is not one of the better designs I have messed with when it comes to anything mechanical.
Don't get too aggravated, they all have there stupid issues. Carb setup sucks but the great news is once you get it dialed in you dont have to screw with it much.. Looks like you are on track to getting it going. I run mine through big puddles but am just cautious in the deep water..

This is one of the more shallow holes that day, and the only reason I was stuck is I cut a tire on a rock 5 minutes before..

01' Raptor 720, Stage 2, FCR'd
97' 250 Vitos Blaster
06' Rhino 450
94' Banshee T-5's, Vforce, ported, Cool Head, 2-1
06' Wolverine 450 - Stock!
06' LTZ 440
94' Vmax4 750, 96' 600 MountainMax, 07' Nytro(b00sTed)
06' Vmax 1200
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post #14 of 33 Old 12-03-2018, 08:33 PM Thread Starter
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So I haven't gotten my jets yet but was just wondering, if I only changed that Duncan slip on, with the snorkle on and everything all stock including the jets, I should be able to get this thing idling ok and maybe the issue was the snorkle not being on. NOPE! Everytime I have it idling and give it has it pukes. Backfires here and there. My raptor is an 04 660R with about 100 hours on it all maintained by Yamaha dealer but they hadn't touched it before I bought it for a while and dude left gas sitting in the carbs. We paid $2100 and he threw in a little utility trailer. SMH I shouldn't have traded my stock muffler for that Duncan. Hard to keep messing with this thing I just want to ride it. The thing is, I have KFX450 Front shocks with dual rate springs along with a triple rate spring for my rear shock (all going to jogacca to be redone and set up for my specific weight, a +2 dura blue axle, a set of +2 Alba A arms, an 11 way steering stabilizer and a brand new set of hole shotz that are on the warrior 350 right now. All these carb running problems are really bothering me since I've spent all this money and will be spending another $500 easy to jogacca before it's done. I should be passing all the 2 strokes and yfz450"s once I get it dialed in! That's if I can ever get it dialed in. Miserable in Michigan......
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post #15 of 33 Old 12-03-2018, 08:35 PM Thread Starter
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But when all said and done I'll have almost 3gs into this quad which should be running and moving feeling pretty awesome
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post #16 of 33 Old 12-04-2018, 07:40 AM Thread Starter
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Hey Diggerz,

So what do you think I should do to just end all these troubles? Try out those 160 -165 jets using no airbox lid? Or just say the hell with it and get one of those one piece air boxless setups with the net going around the filter? I actually have these two plastic side pieces that fit into the areas that are open under to the rear of the gas tank. I guess they are kind of rare. BUt with those in place I wouldn't worry about anything getting to my air filter. I will be trail riding and riding on the frozen river with my girl who will be driving the warrior 350 so it's not like I'm going to be going creek riding. Lol.. I just want to once and for all get this over with . I wish there was a mechanic nearby I could pay to do the jetting because I don't have hours to spend on it.

JMH
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post #17 of 33 Old 12-04-2018, 09:53 AM
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there is no easy fix for this you need to run it some shut it off and check the plug. if you are close you may be able to move your needles up or down one clip depending on what you plug looks like. are you sure you are setting the idle high enough. if it is to low you can get a flat spot. describe the flat spot a little better. is it only in the shop with a full throttle chop. or does it do it when you are riding. have you taken the pipe apart to make sure the sparky is not plugged. confirming it ran perfect after you did the carbs and when you changed the pipe is when the trouble started? as for leaving the banshee's and yfz's in the dust with nothing but a slip on you might be a little optimistic lol. my 660 has hot cams, airbox and a full big gun and it will hang with my yfzs climbing dunes and will sometimes get the hole shot but on flat ground by the time i hit 3 the yfzs and banshees are long gone. dont get me wrong the 660 is a great machine in its own right it is just a different design than the yfz 350-450
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post #18 of 33 Old 12-04-2018, 10:29 AM
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just went and dug my carb stuff out my set up for sea level is dyno jet needles on the 4th clip dj146 left carb & dj 148 in the right. three turns out on the screws and stock pilots. i used the screws from nitro 4 strokes
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post #19 of 33 Old 12-06-2018, 11:34 AM Thread Starter
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Yeah I was being optimistic. But guess what I have diggerz...... AN R1 engine with the complete harness and gauges.... So that kinda why I was getting cocky lol. But it's going to be years before I can mess around with that. I appreciate all the answers Cory. Can't tell you how much I appreciate all the help you guys have given me.
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post #20 of 33 Old 12-06-2018, 11:38 AM Thread Starter
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question? Does anyone know if keihin carburetor air fuel screws will fit Mikuni or know of any fuel mixture screws that will fit the BSR33-H1 carburetor that aren't $25 apiece? I see $10 ones but none are specific to the raptor. I'm just getting the screws messing with those OEM ones is rediculous. Oh and btw. I've never gotten to ride this four wheeler more than 30 feet. I know it's pathetic. But I don't want to ruin something riding it the way it is.
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