Just how do you know you need to rejet and just how do you do it. As you may have guessed, I'm a new 2x owner
Danny
jetting why and how
great question:grin2: you can have several indicators of sick jetting. and lots of engine troubles that mimic sick jetting. most jetting troubles will be indicated by spark plug color and jetting/fuel mixture corrections will be verified by plug color also. a new spark plug has a snow white ceramic insulator on its firing end, when its in use it becomes colored by the combustion process inside combustion chamber. your 2 stroke/carbureted bike will have a tan to light brown color on insulator when jetting is happy. when it remains white or turns black it can indicate jetting or other troubles. either condition can have engine performance complaint symptoms. the white or lighter plug colors are called lean indications, the dark brown or black colors are called rich indicators. if your bike runs good and performs well, and your spark plug color is tan to chocolate brown your jetting is probably good and you are lucky as hell:yes: if not please check back any time for more information....and send pictures of your spark plug if you would like another opinion on its condition.:nerd:
great question:grin2: you can have several indicators of sick jetting. and lots of engine troubles that mimic sick jetting. most jetting troubles will be indicated by spark plug color and jetting/fuel mixture corrections will be verified by plug color also. a new spark plug has a snow white ceramic insulator on its firing end, when its in use it becomes colored by the combustion process inside combustion chamber. your 2 stroke/carbureted bike will have a tan to light brown color on insulator when jetting is happy. when it remains white or turns black it can indicate jetting or other troubles. either condition can have engine performance complaint symptoms. the white or lighter plug colors are called lean indications, the dark brown or black colors are called rich indicators. if your bike runs good and performs well, and your spark plug color is tan to chocolate brown your jetting is probably good and you are lucky as hell:yes: if not please check back any time for more information....and send pictures of your spark plug if you would like another opinion on its condition.:nerd:
imo , its the plug combined with on throttle action. fast throttle versus slow throttle openings.
The difference between one clip height on the needle is just that.
Slow jet as another test method others can mention.
main jet is full throttle in the high gears.in other words the bike is under max load and one size jet will offer the fastest revs .
what year is it?
The difference between one clip height on the needle is just that.
Slow jet as another test method others can mention.
main jet is full throttle in the high gears.in other words the bike is under max load and one size jet will offer the fastest revs .
what year is it?
Thanks for the replies.
More Info: It really screams when snapping the throttle open, but it seems to flatten out if just coming up to speed more slowly. I'm not in race mode just in ride mode. Hard to explain, but it's like it doesn't want to accelerate fully, like the plug is fouled or is fouling when riding. Haven't pulled it yet. Had it jetted by Mechanic Under warranty period in Dec. Ran Not So Well, after, but then ran better a week later, then turned into a screamer, then back to somethings not right.
It also has a fair amount of oil running down the Muffler. Would that be fouling the plug?
More Info: It really screams when snapping the throttle open, but it seems to flatten out if just coming up to speed more slowly. I'm not in race mode just in ride mode. Hard to explain, but it's like it doesn't want to accelerate fully, like the plug is fouled or is fouling when riding. Haven't pulled it yet. Had it jetted by Mechanic Under warranty period in Dec. Ran Not So Well, after, but then ran better a week later, then turned into a screamer, then back to somethings not right.
It also has a fair amount of oil running down the Muffler. Would that be fouling the plug?
now were getting somewhere!!
if your bike ran good and then ran sick without anyone rejetting carburetor it seems unlikely(but not impossible) that your trouble would be jetting. your symptoms can be helpful here. but before you start trying to rejet to solve a problem, did your performance complaint start after any repairs or modifications? is the air filter clean? fuel fresh and correct premix ratio? i always recheck these first. i drain fuel tank and mix up fresh fuel (not last years chain saw mix) and try running bike with air filter removed to isolate these easy ones. then if symptoms persist take a good picture of the spark plug and send it along with your next post if needed. and dont be afraid to add details of how and when performance troubles started if possible. check back as needed
if your bike ran good and then ran sick without anyone rejetting carburetor it seems unlikely(but not impossible) that your trouble would be jetting. your symptoms can be helpful here. but before you start trying to rejet to solve a problem, did your performance complaint start after any repairs or modifications? is the air filter clean? fuel fresh and correct premix ratio? i always recheck these first. i drain fuel tank and mix up fresh fuel (not last years chain saw mix) and try running bike with air filter removed to isolate these easy ones. then if symptoms persist take a good picture of the spark plug and send it along with your next post if needed. and dont be afraid to add details of how and when performance troubles started if possible. check back as needed
it is an 2018 250 XC-W.
It ran good on "old" gas (not that old - a few weeks), then filled it with 60:1 (per manual), it sucked. Then I added a little more oil to bring it to 50:1 (not that much of a difference - but just in case). Still no different.
That's why the post. Maybe some bad Premium? Too much oil - as in running down muffler?
But also wanted to learn how to jet correctly - not just correct this current problem.
Thanks again for all the info. Will take about 3 - 5 days before plug can be removed and I get back to everyone.
It ran good on "old" gas (not that old - a few weeks), then filled it with 60:1 (per manual), it sucked. Then I added a little more oil to bring it to 50:1 (not that much of a difference - but just in case). Still no different.
That's why the post. Maybe some bad Premium? Too much oil - as in running down muffler?
But also wanted to learn how to jet correctly - not just correct this current problem.
Thanks again for all the info. Will take about 3 - 5 days before plug can be removed and I get back to everyone.
CORS 187
Thanks for the blow up. I understand how they work. Just not how to properly jet it and when to jet it.
What is the bike doing that requires a re-jet. How do I know I'm going in the right direction in jetting. Do I change Main or Jet first and what happens when I do. Which changes what kinda thing that I can feel, hear, etc.
Thanks again for all the posts.
Thanks for the blow up. I understand how they work. Just not how to properly jet it and when to jet it.
What is the bike doing that requires a re-jet. How do I know I'm going in the right direction in jetting. Do I change Main or Jet first and what happens when I do. Which changes what kinda thing that I can feel, hear, etc.
Thanks again for all the posts.
It may be easier for you to start from scratch on your jetting question. Your original post and questions were more of a information seeking request. But you were not sure if jetting was your issue, but how do you know by symptoms. Kind of like calling your physician and asking for a diagnosis without an examination. A good doctor can guess but if you want to be certain you really need to run some tests. As I explained previously, any number of performance issues can mimic jetting issues. And if your bike ran well with jetting at current setting and developed performance issues it may not be a jetting problem as jets don’t wear out or change sizes on their own. They can become restricted by non fuel debris or vibrate out or loosen themselves from vibration. If you are able to remove and clean and inspect carburetor you may want to check float level and clean carburetor and remove and clean jets and record jet and needle numbers and verify correct part numbers. Your description of your sluggish throttle response sounds like a possible rich part throttle condition, but a loose or partially unscrewed main jet can cause that symptom also. Better to check basics first before rejetting. But if everything else looks alright, drop the needle 2 clips and retry it. Check back as needed
Thought about a partially plugged jet. I know if a tiny bit of dirt gets into or obstructs a jet, it won't run at all or run very poorly.
Found that out the hard way with my weed eater. No matter what I did it would not run. Ran perfectly till it didn't. A tiny piece of dirt in the jet did the deed. After buying a new one.
Think I will put in an inline filter before the carb, just in case.
Found that out the hard way with my weed eater. No matter what I did it would not run. Ran perfectly till it didn't. A tiny piece of dirt in the jet did the deed. After buying a new one.
Think I will put in an inline filter before the carb, just in case.
Thank You all for all the suggestions.
It's been way too cold to take it out and run it or even work on it. 48 is the high for the last week and upcoming weeks.
I also know that cold affects jetting, so will have to wait till it at leasts gets to 60 deg. If I don't and getting it running good now, then I'll have to re-ject anyway when it gets warmer.
I've seen the YOUTUBE vids on jetting (not all of them), but they all say how to not when to (if your bike is doing this then do that).
Yes, my question is the basic one: How do you know when you need to mess with the carb. Not just how to mess with it (seperate question - can do that part). That is my original question to begin with. When running not as good as it should, just what symptoms tell me to mess with the jetting. Hard starting, won't rev up freely, revs freely when fast accelerating, but not when slowly accelerating. Those kinds of questions.
Thanks again for the replies.
It's been way too cold to take it out and run it or even work on it. 48 is the high for the last week and upcoming weeks.
I also know that cold affects jetting, so will have to wait till it at leasts gets to 60 deg. If I don't and getting it running good now, then I'll have to re-ject anyway when it gets warmer.
I've seen the YOUTUBE vids on jetting (not all of them), but they all say how to not when to (if your bike is doing this then do that).
Yes, my question is the basic one: How do you know when you need to mess with the carb. Not just how to mess with it (seperate question - can do that part). That is my original question to begin with. When running not as good as it should, just what symptoms tell me to mess with the jetting. Hard starting, won't rev up freely, revs freely when fast accelerating, but not when slowly accelerating. Those kinds of questions.
Thanks again for the replies.
It took a bit of study to understand your question, but I think I got it. The simple answer is always the best answer. How do you know what proper jetting feels like and how to fix it when it’s defective. Our approach was previously to troubleshoot your symptoms which were unspecific in nature. I think the answer you need is simple if you look this way. We old school tuners speak a language derived from our experiences of tuning motors. Sometimes it’s difficult to explain but easier to just tell you what to do. If you could relate your symptom or complaint with a picture or description of your spark plug we could go about the process of jetting your bike. But you would like to learn how and why we change jets, needles and slides and why this is done. I learned these skills by tuning race motors for the past 40+years and would be glad to help. But I did a lot of trial and error to learn how and what to change and why. I’m hoping to do a mini seminar on the forum soon in a new thread so as to assist others on the forum with learning and also to allow some of our other forum mates an opportunity to chime in with their wisdom on this subject. Will add more details soon. Please take the time to read my previous suggestions on your thread as well, as I think I gave you your corrective measure in previous post
Thank you for the update and kind words. We all enjoy a problem solved. Now if only I could figure out how to solve all my motor headaches that easily, that would be great. Pop in any time to say hello and send pictures of your latest motoring adventure. Best of luck
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
-
?
