Bogging

[yz rider125]

My 02 yz 125 boggs when i get on it till i get close to the power band. Also if its sitting at idle and i rev it up real quick, it bogs and then revs up. What should i do in order to eliminate it? I put in a #27.5 Pilot jet in but it still boggs. I'm gonna rebuild the top end before the end of march. any help appriciated. thanks

[yzernie]

How ws it running the last time you rode it?

Just to see if it is lean or rich turn the air screw all the way in. The idle should drop and maybe even stall. If that happens then the pilot jet is probably about right. if nothing happens, the pilot is probably to lean.

What are your temps there? The colder it is the leaner it will run.

Also check for an air leak.

[yz rider125]

Originally Posted by yzernie

How ws it running the last time you rode it?

Just to see if it is lean or rich turn the air screw all the way in. The idle should drop and maybe even stall. If that happens then the pilot jet is probably about right. if nothing happens, the pilot is probably to lean.

What are your temps there? The colder it is the leaner it will run.

Also check for an air leak.

The weather here is about 20-30 degrees. i heard that is one reason why its bogging but its been doing that ever since i bought it in september. thats when i got the leaner pilot jet. Tomorrow I'll use your advice and see if the bike stalls, to figure out if the correct pilot is in the bike and check for air leaks. I'll let you know tomorrow what happens. If it is the correct pilot jet and there is know air leaks then what do you think is causing the bogging?

Thanks
Justin

[stormbringer]

It can be bogging because it is too lean, bogging is not always caused by too rich conditions.

Since it is bogging in the low end, I would expect that it would foul plugs too often if it is too rich.

So if it is not fouling plugs, It is more than likely too lean.

Your problem could be your float level, or air leaks from crankshaft seals or intake seals. Check all these before you rejet.

If these are all good and it still bogs, try a richer pilot jet.

[TUK101]

If your bike was bogging before, and it is still bogging after going with a smaller pilot then it is more than likely too lean already. Go with a pilot jet 2 sizes bigger than the one that you originally took out and I bet it solves your problem. Are you running an aftermarket pipe?

[yz rider125]

Originally Posted by stormbringer

It can be bogging because it is too lean, bogging is not always caused by too rich conditions.

Since it is bogging in the low end, I would expect that it would foul plugs too often if it is too rich.

So if it is not fouling plugs, It is more than likely too lean.

Your problem could be your float level, or air leaks from crankshaft seals or intake seals. Check all these before you rejet.

If these are all good and it still bogs, try a richer pilot jet.

It hasent fouled any plugs. My manual says to "use main jet having lower calibration No." and "Raise the jet needle clip position (1 groove up). If that doesnt work the reverse above procedures." Wouldnt hurnt to try that would it?

[stormbringer]

From what you are describing it sounds like a lean characterisitc.

I would try a richer pilot (book mght call it "slow" jet) than the first, since the pilot jet and air screw control your 0-1/4 throttle position, and (from your description) thats where it is bogging.

[yz rider125]

Originally Posted by stormbringer

From what you are describing it sounds like a lean characterisitc.

I would try a richer pilot (book mght call it "slow" jet) than the first, since the pilot jet and air screw control your 0-1/4 throttle position, and (from your description) thats where it is bogging.

thats where its bogging at. Everything on the bike mechanically is stock except for the 1st leaner pilot jet from stock. im going to try all of these thing tomorrow and let you know the situation
thanks

[TUK101]

What elevation are you riding at? Also, make sure that your air cleaner is clean and well taken care of and not over oiled or you can cause some serious confusion with jetting. Does it bog less with the choke on? Does it run better when cold than when hot?

[yz125man]

MY old yz 125h did the exact same thing. Now I dont know if there is a big difference between my old yz and your newer one. But I found out it was my crankshaft seal. I put my ear up were the stater was and I kicked it over and I could here the air coming out of the crankshaft. I just popped out the old one and put a new one in. And it ran really good.

[yz rider125]

Originally Posted by yzernie

How ws it running the last time you rode it?

Just to see if it is lean or rich turn the air screw all the way in. The idle should drop and maybe even stall. If that happens then the pilot jet is probably about right. if nothing happens, the pilot is probably to lean.

What are your temps there? The colder it is the leaner it will run.

Also check for an air leak.

according to him the pilot jet is right. I warmed it up and let it idle and then turned the air screw all the way in and the bike stalled. the crank seal may have an air leak in it. what does this mean. Then i adjusted the idle srew just a hair and now its fouling plugs. i adjusted the idle screw back and still no luck running. I had to stop cause i have other things to do.

[TUK101]

The crankshaft seal is definately another thing to consider. The seals are reletively cheap and a pretty good insurance policy before you go and play with your jetting anymore. Good luck man, let us know how it goes. Another thing to consider too now that I am thinking about it is if it is really cold where you are, the bike wont run quite right and will be really cold blooded and boggy.