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Attention bog fixers!

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I am still having trouble with my bog. Any advice would be greatly appreciated.

03WR250

Jetting

Pilot 42

Main 172

Pilot Air Jet 75

Needle OBELP Clip #2(top being #1)

Stock AP diaphram

The bike runs great when the rpms are up a little. No bog to speak of. It only bogs when I am low rpms and whacking the throttle. The stock Leak jet is a 90. I have the AP linkage adjusted as per these instructions.

The 90 leak jet bogged. I heard of great improvments from the 40 leak jet. I swapped it out. Still a bog. It did feel a little different, but still bog. I timed the squirt with the 90 leak jet using a stop watch. Consistently around 1 second. I timed with the 40 leak jet. Between .3-.35 sec. I read that .7 is the target range of squirt duration. I bought a 70 leak jet. Did not time it but still a bog. Feels more like the 90 LJ bog.

So I'm thinking that because the bog felt different with the 40 leak jet in it may be a rich bog(too much squirt) instead of the 90/70 lean bog(not enough squirt). My next step would maybe be to get a 50 leak jet and see what it feels like. My other option is to pay $250(Canadian) and have a company jet it for me. They say they use a fuel/air meter to read the exhuast or something like that. Sounds like a lot of money.

I've done search after search and read through the entire FAQ site(which is awsome by the way) and I'm sort of wondering if I'm missing something. Is there any thing that I'm missing? Any advice as to what I should do next? Am I going in the right direction?

Thanks

in advance.

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Do you still have the stock baffle in the exhaust? I ask this because your main and needle look to be set quite lean. The needle position has quite an effect on the bog, and I think I'd experiment by moving the clip down one or two positions.

I don't think upping your main jet size will affect the bog much, but you might get more mid and top power by going up to a 175 or 178.

I mention this because one of the key points in fixing the bog is to get the rest of your jetting just spot on.

Other than that, I think you are progressing in the right direction. You might also try adjusting your fuel screw if the 50 leak jet doesn't completely clear it up (after your needle position is tweaked a little that is).

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I did the YOT setup (#75 leak, .5 turn in on linkage from free play) and it works great. I had also previouly gone to 45 pilot and 172 main with fuel screw at 2-2.5 out.

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ThumperGirl, do you work as a mortician? What's with the body/foot tag for your avatar? :thumbsup:

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Another thing you can try is plugging the leak jet hole with a small ball bearing then putting the leak jet back in overtop of it (it wont go all the way in). This will give you a AP duration of about 4 seconds. From there you do the BK mod (do a search, it's been covered tons) which will allow you to adjust the duration of your AP squirt by simply turning a screw.

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I timed the squirt with the 90 leak jet using a stop watch. Consistently around 1 second. I timed with the 40 leak jet. Between .3-.35 sec. I read that .7 is the target range of squirt duration. I bought a 70 leak jet. Did not time it but still a bog. Feels more like the 90 LJ bog.

Something aint right here. With the #40 leak jet you should get a longer squirt duration than with the #90. You thinking is right about lean bog vs. rich bog but your timing numbers appear to be backwards. You may think about borrowing a video camera to get more accurate readings.

I agree with Barton, your jetting is pretty lean across the board. I would try the needle clip in position 3 and/or 4 to see if it helps.

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Another thing you can try is plugging the leak jet hole with a small ball bearing then putting the leak jet back in overtop of it (it wont go all the way in). This will give you a AP duration of about 4 seconds. From there you do the BK mod (do a search, it's been covered tons) which will allow you to adjust the duration of your AP squirt by simply turning a screw.

True in theory, but the BK mod is more difficult to do in the 2003+ models. I think that working with leak jets and AP diaphragms is the way to go on the newer models.

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I timed the squirt with the 90 leak jet using a stop watch. Consistently around 1 second. I timed with the 40 leak jet. Between .3-.35 sec. I read that .7 is the target range of squirt duration. I bought a 70 leak jet. Did not time it but still a bog. Feels more like the 90 LJ bog.

Something aint right here. With the #40 leak jet you should get a longer squirt duration than with the #90. You thinking is right about lean bog vs. rich bog but your timing numbers appear to be backwards. You may think about borrowing a video camera to get more accurate readings.

Yeah, I totally missed that. Maybe he transposed his results.

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Yes I did get the timings backwards. barton knew what I meant and Rick is a hawk eye.

barton; I have the stock US exhaust and a GYTR insert. No air filter/box mods but I may remove the screen and get a fire proof filter. We have played with the pilot circuit and found the 42 to be best(and JD said that a 42 or 45 shopuld do the trick for my area). We also moved the needle down by raising the clip because we felt it was a little rich. I say we cause I had some help from my local shop guys(Xtreme Toys if any of you are from the London, Ontario area, 519-457-8697). I tried both ways but I couldn't tell if it was lean or rich. When removing the insert it seemed to open the bike right up. It revved so much easier and faster. So i think that I still have some more jetting issues to work out. Should I get that perfect before I continue with the bog?

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If you got .3 to .35 sec ap spray time with a 40 leak jet and around 1 second time with a 90 leak jet, something is screw up. May the stopwatch you are using. :thumbsup: I'm wondering if you are if you have the ap timing screw backed out so far that the spray is hitting the slide before you are actually seeing it. There is no way you can have a shorter time with a 40 vs. 90 leak jet without limiting the ap diaphram travel. I have a 35 leak jet in my bike with a sleeve on the end of the diaphram rivet that shortens the travel 28 thousandths(.028) and get between .69 to .7 sec ap squirt times. You guys don't :awww: about the sleeve, it has worked excetional ever since I have did it. Poor county boy's saved 80 bucks p-38 mod. :devil: I don't remember the last time I had bog that a fuel screw adjustment would not cure, and a minor hesitation at that. Your ap timing screw is backed to far or you have dried out dead ap diaphram.

Your jetting is also lean unless your are in some high altitude conditions or in the middle east desert heat.

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So i think that I still have some more jetting issues to work out. Should I get that perfect before I continue with the bog?

Yeah because the AP squirt is only part of the bog problem. Make only one change at a time, and test each change. I'd raise that needle one or two positions, then try several fuel screw positions, testing for its effect on the bog. Given your squirt times, you'll probably end up with the 50 LJ, but the fuel screw and needle positions are very important contributors to the solution.

Don't forget to get the bike fully warmed up (10-15 minuttes of riding) and test it under load. I see more and more people who worry about the bog in neutral and on the stand, and I'm not sure I see the importance of being bog-free under those conditions.

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Instead of all this guessing, why don't you run it on a dyno type machine with a fuel mixture analyzer - you'll get your mixture curve along with HP and torque numbers too. It doesn't cost much to do a few runs on the dyno ($24 for me a while back around my area), why guess at what's going on with the mixture? :thumbsup: If the engine tuner doing the dyno runs is good, he should tell you what you'll need to do to fix your jetting afterwards - it's also pretty obvious from the mixture curves what you need to do...

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Just curious, would a dyno tell you anything about AP operation? My guess would be no. Obviously ideal for PJ, Needle, and MJ tuning but won't help with the bog. Right?

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There's merit to what av has suggested. Most of the guys complaining of bog had pretty much whacked out jetting.

I agree with getting the overall jetting done first, then look at the bog. The fastest way there is a dyno and butt sniffer.

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"butt sniffer" :thumbsup:

The dyno will not tell you how your AP is working, but it WILL tell you what the curve looks like when you crank the throttle from closed to wide open under load. IIRC, typically there is a dip in the curve at the beginning indicating either too much or too little fuel in the transition phase (i.e. when the AP should be kicking in) - you can see what's going on as the curve smooths out when the engine catches up and revs out. The graph shows the mixture from idle to WOT and where the problem areas are - if the "butt sniffer" and your engine tuner do their jobs properly. :devil:

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Barry, I got my leak jet at Thousand Oaks Yamaha. Any Yamaha shop should be able to order it up for ya. I don't believe they are stocked at the shops, but I had mine in a couple days from the wearhouse.

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i use different jetting setups depending on winter or summer and found what works good for me is move the clip all the way down on the needle and it takes the bog out

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Moving the clip all the way down because it is a half assed way. The needle barely effects your jetting as far as curing the bog, it instead deals mainly with the mid range.

Use the proper jets, do not mask a problem by "half assing" it, your bike will thank you.

I think it has something to do with the needle on the OP. Your ENTIRE jetting circuit must be dialed in (including the duel screw) to get rid of the bog. Also note that you can fine tune the squirt duration by turning the screw on the cam linkage. Tightening down the screw pushes down the rod a bit, and makes the squirt shorter (less travel for the AP). Loosening the screw makes the squirt longer.

You want to shoot for about a .6. Try using a video camera as it is more accurate. I;ve also found that a 40 leak jet is too long. I'm swapping out to a 50 this week.

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