New and Confused...


First off I would like to introduce myself and thank this awesome forum and all the people who contribute. I have been following for a few months now and it has been a big help. I am 37 and am getting back into riding after a year off. I bought a new 07 450 last November and rode it once before hitting a guy head on. The guy was going the wrong way on the track.... I am now just getting ready to ride again with the injuries still healing... and my question is this. I have the dreaded YZ bog. Other than that the bike runs great. I see all of these fixes for it and additional parts that it is confusing. I am thinking of sending my carb in to Zipty. For those who have used Zipty, do you think this will fix the bog or will I need to purchase all the ap/bowl accessories too. The jetting is stock, elevation 3000ft and other than the bog the bike runs/starts great. Also, I am not looking for more power and want to ride/race the bike close to stock, as it has more power than I can use. Thank you for your help!

Welcome to the forums!

Have a look in the CRF 450 forum. There is a sticky called ridiculous throttle response or something close.

Read the thread, do the AP mod ZERO bog.

I usually start with a smaller leak jet, and wire the pump arm. If I can't dial it out after that I’ll look at grinding the rivet.

Yamaha has a fairly detailed description in the manual on timing the squirt, which is important as well.

Good luck.

From my own experience I can say that the most bang for your buck for the YZ450 is the Zipty Racing carb mod. This is hands down the best money you can spend on the bike, IMO.

Actually, I would spring for the $160.00 mod that includes the new fuel screw, aluminum hotstart nut, and magnetic float bowl drain...but at teh very least do the $100.00 mod.

I have not found the need for anything else, except for proper jetting for your altitude/temp.

Welcome to the forums!

Have a look in the CRF 450 forum. There is a sticky called ridiculous throttle response or something close.

That's linked in the Common Threads sticky here in this forum. No need to go anywhere else.

Before you go modifying anything, though, let's see what you have. You say it bogs. When' and under what circumstances? If it does it in neutral when you snap the throttle open from idle to WOT, but runs alright when you actually ride it, then you have to wonder whether there's anything to fix. OTOH, if it stumbles underway when exiting corners and such, then maybe you should work on it a little.

One thing you have to learn coming from a two-stroke is to roll the throttle, rather than snapping it. It's an acquired skill that involves opening the throttle a little more slowly and a little less just at first, responding to the engine's willingness to take it. After a while, it becomes second nature, and it will sound as if your engine is responding instantaneously.

Next, set up your idle circuit. Be sure it's rich enough, but don't overdo it. Most '07's do alright with the original 45 pilot jet unless it's cold out and/or they're at low altitudes. If you can't get your idle mixture to trim out with the fuel screw between 1.5 to 2.75 turns out, your pilot needs to go one way or other.

If it still has what you see as an unreasonable stumble, check the pump timing per the manual, then check that the stream of gas from the AP does not hit the slide as it opens.

Still bog? Then you have a choice of trying the free AP mod or sending the carb off to Zip-Ty for their modification. The ZT mod does much more for the carb than just get rid of the bog, too, and it's $100 well spent, IMO.

Another vote for ZipTy - I have both my bikes modded with this and bog is gone and throttle response is perfect.

I would also spring for the R$D floatbowl as well as alum hot start nut and fuel screw all from ZipTy. Call and ask for Steve :banghead:

Thank you for your information!

My bike bogs/hesitates in neutral when quickly twisting the throttle. It also does it when cracking the throttle in first when trying to wheelie. When getting on the gas with low RPM exiting a corner. Other than the low RPM hesitation, the bike runs awesome. It does have a little popping on decel, but nothing to complain about. The bike runs great as jetted from 1500-9500ft. I do notice a little power loss in the mountains, but thats to be expected. I asked my dealer what it could be and they said the jetting is fine and the air screw does not need to be adjusted and to clean the carb. I have 5 hours on the bike and the carb and inner air boot are spotless. I have adjusted the air screw and it has helped maybe a little. I will try adjusting the AP. My concern is making it worse or unreliable. If I can send it in for 100 bucks and not have to worry about messing with it, I will send it in. I just don't want to make the bike unreliable...

I have been riding/racing for 30 years and this is my first four stroke. All in all this is by far the best bike I have ever owned. It has the most power and once I set it up for my weight and size it carves corners like no other.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now