I'm confused

[mike-evans]

2001 YZ 250, My bike bogs at first touch of throttle when riding, smokes alot when started up and loads up while having to clear it before riding....and has alot of spooge...cylinder liner and piston has approx 4 hours on them, along with new crank seals, jetting is standard at PILOT 50,, MAIN 180 STANDARD NEEDLE CLIP SECOND FROM TOP (leaned out one clip). Once I get to half throttle it pulls like a train and hits hard.
Been doing a bit of reading and come to the conclusion that my pilot is rich due to it being factory jetting, so want to drop it down one size (52)..

Just phoned my local bike shop asking for the pilot jet, and he was saying it is probably not the pilot as Yamahas come jetted good? He said most prob rich main? Hes put me right off track now....any ideas guys?


*Yet to check my plug, just after an idea*

 

[IndyMX]

Your local bike shop is wrong. They always come a bit rich from the factory. I doubt that the factory knows exactly what elevation, temperature and whatnot every bike leaving the factory is going to be ridden at. So, they send em out rich.

If you have a 50 in there now, and want to go down a size, 52 is not the right direction. That's bigger.

Don't listen to the guys at the local bike shop, read the jetting guides, and read your bike.

If it's bogging, there's a reason. Try leaning out the pilot & needle a step at a time, one at a time and compare the results.

If it gets better, you know you are on the right track. Also, talk to others who ride in your area and see what they are doing.

For all we know, that guy at the shop only rides street and doesn't really know much about 2 stroke MX bikes.

 

[mike-evans]

Your local bike shop is wrong. They always come a bit rich from the factory. I doubt that the factory knows exactly what elevation, temperature and whatnot every bike leaving the factory is going to be ridden at. So, they send em out rich.

If you have a 50 in there now, and want to go down a size, 52 is not the right direction. That's bigger.

Don't listen to the guys at the local bike shop, read the jetting guides, and read your bike.

If it's bogging, there's a reason. Try leaning out the pilot & needle a step at a time, one at a time and compare the results.

If it gets better, you know you are on the right track. Also, talk to others who ride in your area and see what they are doing.

For all we know, that guy at the shop only rides street and doesn't really know much about 2 stroke MX bikes.

I always understood them to be jetted rich from factory as a precaution....
Sorry got it wrong, ment to say its a 55 pilot in there...so I'm looking at putting the 52 in :cool:

The guy who owns the shop (who I was speaking to), has a Dyno machine they use to set up trail bikes etc, and he said bring my bike down and put it on that is the only way to tell, just selling me his equipment so he could make money :pissed:

My mate took his DR there before for it to be set up on the Dyno machine, and it ran WORSE when he had it back, and ended up doing it himself....

 

[IndyMX]

Yeah, the only dyno you need, you are sitting on.

What runs fine on his dyno, in a nice climate controlled shop, may not run worth a damn out on the track/trail.

You might even be wise to carry a few jets with you when you go riding, if you are going places with different elevations than you are at at home.

 

[whenfoxforks-ruled]

Are you bringing the dyno with you riding? Drop that pilot smaller. Vintage Bob

 

[mike-evans]

When I drop the pilot, what shall I do with the air screw? Return it to factory to start with?

 

[BSWIFT]

Carefully count the number of turns on the air screw until it is fully seated(clockwise) and then return it to the same position. Make only one change at a time. If the smaller pilot jet helps, adjust the air screw in or out according to the reaction of the engine. Keep track of where your air screw is and if you change the pilot again, return it to where you started BEFORE you change the jet.
Jetting just takes time and patience. Best to have plenty of both. Read the jetting guide at the top of this forum thoroughly and you'll have it perfect in no time.

 

[1998RM250]

Then you turn the a/f screw clockwise, that would be making it run richer correct?

 

[mike-evans]

I removed the rad valve earlier to inspect my reeds and took photos of how black/oily/spoogey things are......rich?

 

[whenfoxforks-ruled]

Take the radiator cap off and start the bike. Do you see bubbles streaming in when revved? Does the smoke smell sweet? The pic just wreaks of a head gasket leak!

 

[mike-evans]

Take the radiator cap off and start the bike. Do you see bubbles streaming in when revved? Does the smoke smell sweet? The pic just wreaks of a head gasket leak!

Coolant in radiator does not loose a drop.

Its smokes, but its a blueish colour which I believe is the colour 2ts gives off?

Why do you think its head gasket?

Bike is on standard jetting which I think is rich??

 

[wake_rider]

Coolant in radiator does not loose a drop.

Its smokes, but its a blueish colour which I believe is the colour 2ts gives off?

Why do you think its head gasket?

Bike is on standard jetting which I think is rich??

Your bike doesn't have a head gasket, rather two oversized o-rings and I've rarely had issues with these leaking without it being a warped head (probably not the issue).

I had a similar issue with my 99 yz250. Ended up dropping a size on the pilot, leaving the needle at stock position and stock main jet. I actually had the bike running a bit more crisp with a step down on the main too, but recently I've been riding more mx than woods, so I've kept the larger main since I seem to never have issues with breaking up as my current setup.

If you're having to let out your air screw more than 3 full turns, drop a size on your pilot. Stock setting is 1 1/2 turns out.

Don't take the settings for my bike as being correct for yours. Jetting is trial and error. Believe me, I understand your frustration with changing jets on that bike, too. There is not much room to get to the carburetor, and I usually have to pull mine out in order to change the jets. Every other bike I have worked the jetting on before you could usually just twist the carb with the bowl towards you and not have to take it out of the intake boot and reed block; not the same with these generation yz250's!

 

[whenfoxforks-ruled]

It could be rich, could be the way you ride it? Has the float valve ever been changed? What brand premix oil? Where is your air screw adjusted to for highest idle? You are in Wales, I like to start at the top, checking your head? That float valve can appear fine, and leak like my wallet in a dirt bike shop! And its a yearly replaced item. Lugging the engine around, as opposed to riding it like you stole it, will cause spooge build up. The silencer packing will need to be changed when jetting also.

 

[Uchytil]

Lugging the engine around, as opposed to riding it like you stole it, will cause spooge build up.

That's a statement most people don't understand but it's pretty much true. These are race bikes. They like to be wrung out. Not to say you can't jet it close enough to take care of drooling spooge. You need to get some jets, and plugs, and go testing. Then be honest how you ride. My chainsaw does not load up because I run it on the ragged edge :)

 

[mike-evans]

Fitted my new reeds today, adjusted the air screw to get the highest idle, but found it did not really make any difference , does this mean the pilot is to rich?

Im on standard jetting, and have a smaller pilot jet (next size down) ready to go in...

 

[whenfoxforks-ruled]

You could put like a 38 pilot in there, and as long as you do not run it for hours on end, will not cause issues. Warm it up, take it for a ride and see/feel/and hear what the engine is doing. The adjustment for highest idle, is just for pilot sizing, not race riding, it needs fine tuning still, after adjusting makes a difference/you have the correct size jet. The 50 is way big for a 250, in most applications! Personally, I hope you have some more pilot jets, 48, 45 and so on? It really is not difficult, once you get on the right path, and try it out.

 

[mike-evans]

You could put like a 38 pilot in there, and as long as you do not run it for hours on end, will not cause issues. Warm it up, take it for a ride and see/feel/and hear what the engine is doing. The adjustment for highest idle, is just for pilot sizing, not race riding, it needs fine tuning still, after adjusting makes a difference/you have the correct size jet. The 50 is way big for a 250, in most applications! Personally, I hope you have some more pilot jets, 48, 45 and so on? It really is not difficult, once you get on the right path, and try it out.

The only pilot jet I have is the 52 which I put in earlier, I can get more tho, but don't feel good going much lower....its hard to get out on the bike at the minute with the winds and rain here, and being in work, so its going to be a slow process...

 

[whenfoxforks-ruled]

I will box up some snow, and the cold, to trade if that is better? Try JD jetting, he MAY be able to help with an assortment of jets. He may have some killer needles also! The guys at your shop are going to believe you are insane? Keep going smaller till the air screw is effective. It really is not that dramatic. The first time, everyone goes through it. Your bike does not have to only run good, when its running out of gas, or getting ready to blow up. Jet it.

 

[mike-evans]

I will box up some snow, and the cold, to trade if that is better? Try JD jetting, he MAY be able to help with an assortment of jets. He may have some killer needles also! The guys at your shop are going to believe you are insane? Keep going smaller till the air screw is effective. It really is not that dramatic. The first time, everyone goes through it. Your bike does not have to only run good, when its running out of gas, or getting ready to blow up. Jet it.

Funny you should say that, when I fitted the 52 pilot, I was playing with the airscrew, and I thought I had it, idle at its best, but I was actually running out of gas, I give up then.

Do you get a BOG on both rich and lean conditions?
Is it possible to tell which by hearing it?

After I fitted the 52 pilot, I leave it idle, then grab the throttle, and its a bog then a good clear rev, can't tell if its a lean or rich bog, it smokes and plug is wet, so thinking its still rich?

 

[whenfoxforks-ruled]

Assuming, the bike is warmed up and cleared out. Yes, you may be able to hear the difference between lean and rich bog. Looking at the plug is easier. Stop the engine when it bogs, pull the plug, wet or dry? Riding it and feeling it takes a little trial and error also, not as much as hearing it! I still go to extremes on the jetting once in a while to double check I am going the correct way. Rich blew the story about temperature readings in the exhaust last week, a wide band O2 sensor is the only method of true jetting. And I still would go with the seat of pants for my science final exam!

 

[adam728]

50 jet is stock in a 01 YZ250, and most people agree it's too rich. I can't imagine running a 55 or even a 52. I run a 45 90% of the time in my 05, occasionally stepping up to a 48 for really cold weather (last ride was mid 20's).


You really need to:

• Go through the carb and make sure every bit of it is spotless.
• Set the float height.
• Make sure all the breather lines are clean and not clogged up. Do these first three before messing with the jetting.
• Does your bike use any transmission oil? Disapearing tranny oil can get sucked through the right side crank seal, burn with a ton of smoke, foul plugs, etc, mimicing rich jetting.
• Make sure the bike is up to temp before messing with the air screw and throttle response, meaning you've ridden it around some. Idling a few minutes and then reving it while sitting on the stand will get you no where when trying to work out jetting.
• A bog is typically lean. Blubbering is too rich. A hesitation, then "cleaning out" is too rich as well.

As was said earlier, all bikes are different. There's a big thread on another forum about what jetting YZ riders are using. I don't know your altitude or temps, but in most "normal" conditions (say 0-3000 ft, 50-80F) guys are finding generally
45-50 pilot
Stock needle on 2nd or 3rd clip from top
168-178 main

I typically run 45 pilot, stock needle 2nd clip from top, and 172 main, and I'm far from being too lean. Then again someone else with the same bike as mine might find they need to be 2 sizes richer.

 

[mike-evans]

50 jet is stock in a 01 YZ250, and most people agree it's too rich. I can't imagine running a 55 or even a 52. I run a 45 90% of the time in my 05, occasionally stepping up to a 48 for really cold weather (last ride was mid 20's).


You really need to:

• Go through the carb and make sure every bit of it is spotless.
• Set the float height.
• Make sure all the breather lines are clean and not clogged up. Do these first three before messing with the jetting.
• Does your bike use any transmission oil? Disapearing tranny oil can get sucked through the right side crank seal, burn with a ton of smoke, foul plugs, etc, mimicing rich jetting.
• Make sure the bike is up to temp before messing with the air screw and throttle response, meaning you've ridden it around some. Idling a few minutes and then reving it while sitting on the stand will get you no where when trying to work out jetting.
• A bog is typically lean. Blubbering is too rich. A hesitation, then "cleaning out" is too rich as well.

As was said earlier, all bikes are different. There's a big thread on another forum about what jetting YZ riders are using. I don't know your altitude or temps, but in most "normal" conditions (say 0-3000 ft, 50-80F) guys are finding generally
45-50 pilot
Stock needle on 2nd or 3rd clip from top
168-178 main

I typically run 45 pilot, stock needle 2nd clip from top, and 172 main, and I'm far from being too lean. Then again someone else with the same bike as mine might find they need to be 2 sizes richer.

55 is stock for 01 YZ 250 here in the UK/europe.
I've dropped to 52, going to try that. I bought a brand new 01 YZ 250 in 01 and only twice had rich issues, once when I was running the bike in when it was brand new (lugging it round to much) and blew a plug, and another time when I was out in the snow I blew a plug, so they do come slightly rich...

I have never blew a plug in the 01 YZ 250 I have now, plug is wet/black tho...tranny oil, I pretty much get out what I put in (750ml), sure you can't get every drop out?

What colour does burning tranny oil give out? Mine is a blueish colour...

 

[mxer9]

blueish. I would definitely suspect the right side crank seal

 

[mike-evans]

blueish. I would definitely suspect the right side crank seal

Its like a blueish/witte, I'll know when I change the tranny oil soon...

 

[whenfoxforks-ruled]

Burning oil has different colors, not a warning sign. White is usually steam, that along with a sweet odor point to a coolant leak. About the only safe method of determining a seal leak is a leak down test. Or, just change the seal. Personally, a lot of blueish smoke, change the float valve.