08 YZ450 Bog

[krzyaszwhiteboy]

My 08 450 is having a bog problem. I do not know if this has been happening since new and I just noticed it today or if it just started. The bike has about 9.3 hours on it I think. In neutral it has a bog if I pull it WOT but I understand that is normal due to programing. Today though when pulling off the track riding back towards the pits there were a couple of ladies there that my buddy was trying to impress and I decided to show him up so I decided to pull a wheelie. I was going fairly slow and in first and just ripped it WOT and it bogged bad. I had to let it off pull it a little then rip it. I did however end up pulling a decent 35 foot wheelie though. Is my jetting off or is this just something that is going to be there. It's not that big of a deal I was just curious.

[YamahaDude450F]

i had the same exact problem on my 08, it is now completely fixed. The most noticible improvement came from doing the o ring mod. next came from the boysen powerblade (works WONDERS for the bottom end too). Those two mods along with a boysen quickshot accelerator pump, #48 pilot jet, new fuel screw, twin air filters, and cutting out the screen on the air filter cage the bike completely rips with NO bog or hesitation. So long story short...it can be fixed, good luck! ooo and by the way, with this setup i have found that quarter mile wheelies are a walk in the park!

[krzyaszwhiteboy]

I was thinking about the o ring mod but I thought that it was not very effective for the 08, but I could be totaly wrong and misinformed

[KTM RULES]

all carberated bikes do that, the only bike ive seen that can go from 0 throttle to flat out with no bog at all os the 08 fuel injected suzuki

[YamahaDude450F]

i agree my bog was terrible from stock...but it is gone now, i am at about 600 ft elevation and with those settings it runs perfect. It is possible that i am just lucky to get rid of the bog. But i read the same thing about the o ring mod being ineffective for the 08's but i figured its easy enough to give it a shot and it worked beautifully

[Slinkyman16]

correct jetting works wonders for the bog. i know before i rejetted my 07 i had a bad bog off idle.. after i rejeted it, its almost impossible to get it to bog in nuetral.

owe since your buying things for you carb. pick yourself up a extended fuel screw.. best 20 bucks you will spend.

[Windseeker]

owe since your buying things for you carb. pick yourself up a extended fuel screw.. best 20 bucks you will spend.

As a matter of fact I bought two of them from Ride Eng - the blue and the red. Although they both came for YZ450F they were different in size and shape and most dramatically, differed from the stock fuel screw! They did not work, could not be fixed and were affected by the engine vibration - so they are gone and back is good old tiny carb screwdriver...

?

[Ga426owner]

As a matter of fact I bought two of them from Ride Eng - the blue and the red. Although they both came for YZ450F they were different in size and shape and most dramatically, differed from the stock fuel screw! They did not work, could not be fixed and were affected by the engine vibration - so they are gone and back is good old tiny carb screwdriver...

?

I do not know about Ride Eng...but Zipty Racing fuel screws work and you must have one in order to get the most out of your carb performance:thumbsup:

[krzyaszwhiteboy]

correct jetting works wonders for the bog. i know before i rejetted my 07 i had a bad bog off idle.. after i rejeted it, its almost impossible to get it to bog in nuetral.

owe since your buying things for you carb. pick yourself up a extended fuel screw.. best 20 bucks you will spend.

I actualy just bought a pc fuel screw that morning. I didn't put it in until I got home from riding though. I will make life easier it seems.

[Ga426owner]

I was thinking about the o ring mod but I thought that it was not very effective for the 08, but I could be totaly wrong and misinformed

All 4strokes have a bog period end. You notice now because you are used to the new bike and accelerating quicker. There are many ways to fix it and it can be fixed, as mine is.

1st the jetting must be spot on. MJ, Needle jets, Pilot jets and leak jets

2nd

I recommend either/or both

ZipTy Racing Carb mod

and/or the R&D Float bowl with the Adj leakjet

I have not had great success with Boysen Quick shots or Oring mods as they only address 1 part of the problem.

[YamahaDude450F]

Agreed about the Zipty fuel screw, the stock fuel screw is absolutely ridiculous to adjust

[zacw]

I am having the same problem on my brand new yz... Whenever I hit a few bumps it bogs off and turns off. But I heard that it is just a jetting thing... Plus it's really hot here...

[grayracer513]

With extremes of heat, as with altitude, the engine tends toward richness, so there is a possibility that it's loading up, particularly if you're yanking on the throttle as you romp through the whoops.

However, since your problem is in the bumps, it's also possible that your float level is low.

[mrmathers08yz450]

I have about 6 hours on my new yami...i'm at about 7,000 elev. with moderate temp. I'm getting a bad bog. Its horrible on the trails that i ride ranging from 6,000 to 12,000 feet. I've contacted the dealership that i bought it at and they have no answers. I've went lean as well as richer and can't figure it out.

155 MJ, 48 pilot, 1 1/2 turns out on fuel screw, clip position 2.

I think before i let it bother me to much i'm going to purchase a Dr. D exhaust but i could use some help for shure.

[Ga426owner]

This bog disease must be contagious....my 03 that had no bog at all(it has been ZipTy'd, jetted etc...)has mysteriously developed one also, mainly when opening up the throttle quickly. At first I thought it was a JD Jet issue...yep got that too but after going back to stock it is even worse. I am thinking either my squirt duration or float level has somehow changed.....and it plain stinks. This is the only thing I am looking forward to with EFI.......?

[grice]

my 07 does it as well, I hear the r & d float bowl works wonders I am going to try it and see how it goes.

[William1]

The lean bog is because when you nail the throttle, not enough vaccum exists to suck in a comensurate amout of fuel. To cope with this, the FCR has the AP. You can set the AP up to provide plenty of fuel at low engine speeds as typically experienced by a woods rider or you can set it up for MX where teh rpms are significantly higher. If you run MX and the bike has been fine all along, then I'd leave it be. You do not want to have a 'rich' bog. All the bikes from Yamaha have the FCR's setup for high rpm running. Those of us that tend to ride more on the pokey side, need to tweak the AP. That all said, you should, on all FCR's, check, confirm and if needed, set the AP timing screw so the squirt just misses the slide. For more info regarding the O-ring mod, leak jets and AP timing, here is a thread I started:

O-Ring Mod and AP Tuning

I would suggest reading the thread, and check over your AP before investing any money in any add-ons.

[bigred455]

What you need to do is set the AP timing ,along with greasing the linkage and swingarm etc,this should be done. The service manual explains how to set up the AP screw. Shim up the front of the carb slide with something that measures 1.25mm thickness. Turn the AP screw in until you have freeplay and come out just till the freeplay ends,I go another 3/4 OUT,a LITTLE EARLIER. I am not ragging on anyone,but I never seen so many bog problrms in my life before.Roll along in 3rd or 4th gear medium rpms CHOP THE THROTTLE THEN OPEN IT. If it doesnt bog leave it alone,if you do, set up your AP screw ,pilot, and fuel screw. I set my fuel screw at 1 3/4 STOCK FUEL SCREW and I leave it alone, this is my setting from summer to fall. I really do not see the fuss with fuel screws it is not that sensative:crazy: , most aftermarket fuel screws are junk . I leave my fuel screw alone and change out pilots from summer to fall. Most of the after market fuel screws do not even react from a turn.

Another thing is if you get a little pop pop from chopping the throttle after a hard run it does not mean you are lean,.Infact I like to hear this,THE MOTOR IS TELLING YOU ARE VERY CLOSE. Anyone ever hear the factory bikes,it is rare they chop the throttle,but if you pay attention when they do, it is very pronounced,the pops on the factory bikes. I am not happy until I start to hear this.

[William1]

Fuel screw, pilot jet have almost nothing to do with any bog. They affect idle and after idle, in a diminishing amount, up to 1/8 throttle.

Setting the AP with measurements is great for initial approximate settings. You can only accurately set it by visually seeing the squirt. You then deal with any remaining bog by selecting the correct leak jet for the type of riding you do. Small for the slow stuff, large for the fast.

Never test for a bog when on the stand/in the garage. Nailing nearly any carburetter engine from idle will bog, you are simply asking for too much from a carb when air quantities and velocities are too low. Only test for a bog when actually riding.

[grayracer513]

Never test for a bog when on the stand/in the garage. Nailing nearly any carburetter engine from idle will bog, you are simply asking for too much from a carb when air quantities and velocities are too low. Only test for a bog when actually riding.

Not to mention the fact that the ignition timing is quite different in gear than in neutral.