Jump to content
Sign in to follow this  

rich or lean

Recommended Posts

The science is mixed in somewhere between snipe hunting and nuclear fusion.

Share this post


Link to post
Share on other sites

Cuz no-one has answerd, i will offer what i can:

Lean will run hotter, and will leave a spark plug white

Rich will foul plugs(2-stroke) and you can smell fuel(4-stroke)

And both lean and rich conditions will affect power adversly.

The reason no-one responded is more likely because you have offered absolutly no info. What do you ride? What year make model? Where do you ride...Temp, humidity, elevation? What are your current settings...main, pilot, fuel screw turn-out? What mods have you done...airbox, exhaust engine hop-ups? Why do you ask?...what is leading you to believe you may have one or the other condition? Offer some more info like what i have outlined here and you would be surprised at how many good, knowledgable people want to help out!:banana:

Share this post


Link to post
Share on other sites

this wasnt a question about my bike it was a general question .like "if your bike does this ,its lean ""if it does that ,its rich".

was told you cant tell by plug .yes i searched but you get 30000000 pages of everyone who used the word rich or lean .i guess the only way to tell if if you have a dyno then youll know .

Share this post


Link to post
Share on other sites

You don't need a dyno to tell if you're rich or lean. There was a thread on here just a couple of weeks ago where someone went through the whole jetting procedure making use of riding and plug chops to get jetting correct. I'll try and find it when I have a bit of time and post link to it here.

Share this post


Link to post
Share on other sites

If it's running lean and you pull the choke out and it runs better, you were running lean. If it runs worse you are probably too rich. This works better for a street bike with a progressive choke lever, but could be a helpful tool for a dirt bike.

Share this post


Link to post
Share on other sites

Being you have provided so little information about the bike and what throttle position, fule used 2S/4S and so on, all I can say is if the bike is lean, the sound is dry/flat, and it can manifest as a bog. Rich sounds wet and will '8 cycle'.

your bike may exhbit none of these and still be mis-jetted. A 2S may run hot if a little lean or foul plugs if a little rich. A 4S will seem fine though a dyno or stop watch will be more telling. You want to get it exact, you use a wide band A/F sensor and either a data logger or dyno.

Reading the plug with pump fuel (in the USA at least) is pointless unbless you cut the plug, even then it is often futile.

Share this post


Link to post
Share on other sites

if your running rich the plug will be fouled on a 2stroke and on a 4stroke it will smell like gas and both will have trouble starting, too lean the bike will run hotter, it will have trouble starting, and the plug will look close to new condition.

Share this post


Link to post
Share on other sites

One thing that's not discussed here is engine longevity. A lean condition can shorten the life of the engine. On the other hand, if you're running super rich, you can get cylinder wash, which will also affect the life of the motor when it's extreme.

Share this post


Link to post
Share on other sites

too lean will cause damage to any 4 stroke engine..slightly lean will give great performance....to be safe and sure that all questions of damage can occure run it slightly rich..the spark plug is by far the best indicator of air/fuel ratio...get into the habit of checking plugs often

Share this post


Link to post
Share on other sites

It is near impossible to cause engine damage with a 4S running too lean. Plug reading with pump fuel is pointless as the additives make it nigh impossible to get an accurate take on A/F. Use a wide band instead.

Share this post


Link to post
Share on other sites

ive actually had pretty good success comparing lean to rich conditions by looking at the plug on my 05 crf250r

if the bike is running lean i tend to notice a lot of popping, especially on deceleration.

and the tip of the plug will be failry light if not white.

rich conditions you definitely can smell the unburned fuel more, harder starts, some bog. and the plug will be dark or black. these color changes can be noticeable in the tailpipe, more so with rich conditions.

what you should really be aiming for as far as color of the plug is a nice golden color.

best way to get a good plug reading is to go run the bike hard, stop and pull the plug out with put around time.

Share this post


Link to post
Share on other sites

I bought a wideband setup to tune with about 6 months ago.

It's a great tool - wish I could have got something affordable like this 20 years ago.

What becomes obvious very quickly is that plug reading or seat of the pants feel are very innacurate.

Mine is still really a bit rich around 3/4 throttle due to not having the right shape needle, however the plug looks very lean even though it's not.

Economy, response and performance are greatly improved and the jetting specs are considerably leaner than the specs normally posted for my bike.

Share this post


Link to post
Share on other sites
I bought a wideband setup to tune with about 6 months ago.

It's a great tool - wish I could have got something affordable like this 20 years ago.

What becomes obvious very quickly is that plug reading or seat of the pants feel are very innacurate.

Mine is still really a bit rich around 3/4 throttle due to not having the right shape needle, however the plug looks very lean even though it's not.

Economy, response and performance are greatly improved and the jetting specs are considerably leaner than the specs normally posted for my bike.

Interesting. Where did you get your wideband setup? I've been thinking about something like this for a while, but I don't have any reference as to how effective any particular setup has been for others.

My problem with tuning it by feel/sound has been exactly what you describe....it can't be accurate like a wideband IMO, no matter how good you are at carb tuning. Maybe somone will disagree with me on this....

It seems that seat of the pants tuning always ends up running richer than were recommended by my jet kit, which I'm assuming was tuning using a wideband. It runs really strong with the recommended settings, but I'm wondering if I wouldn't get more longevity out of the engine by going a bit richer, as I've always been under the assumption a lean condition leads to shorter engine life.

Share this post


Link to post
Share on other sites

If you're rich:

-you probably have a nicer bike than I do

-you've got hoochie mama's in the backyard pool at all hours of the summer

If you're lean:

-you have a low body fat percentage

-you might be a crack head

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

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

Reply with:

Sign in to follow this  

  • Similar Content

    • By SNORE125
      Anyone else have 130 main and 38 pilot jets already in the carb I took the wifes ttr 230 carb apart to add the bigger jets and this bike from 05 that I bought new already had them in it? I was reading that they came with a 125 main and a 36 pilot.
    • By Charles Joseph Miron
      Hello all.  Need a helping hand here..  
      I bought an older TT225 and am not about to spend almost $600 on a new carburetor for it. So I'm hoping someone can help me out with an idea of what (other than original carburetor) style, type and brand I should go with..  I'm also having a bit of trouble finding info on this bike.  It's a 1986 Yamaha TT225.  
      Thank you in advanced
      Charles
    • By Br0ck
      Hey guys, I went on vacation all summer and let my bike sit (2002 CR250). When I got back I ripped it apart and cleaned carburetor and put it back together and it started fine and ran alright, but idled really high. I adjusted the idle screw and realized it was a ridiculous amount of turns out. I can't remember exactly how many but id say 6+ turns out. My killswitch was a POS and didn't work anymore so I replaced it with an oem replacement. My last ride I crashed the bike pretty bad and I was off the bike for 2 weeks. I can't get the bike to start ever since I got installed the new killswitch. I think I wired it right I just replaced one wire at a time and it looked pretty straight forward. I verified it by testing spark while holding it in I was getting no spark but with it in running position it would spark. 
      Anyway I am just looking for some base settings for the Mikuni TMX to get my bike running again, my carburetor has a 35 Pilot and 380 Main jet which appear to be stock. I am located in Edmonton, AB, Canada which is about 2500ft and usually ride between 10-25 celcius.
      Thanks for any replies. 
    • By Goon Rides
      Hey guys... so I have a problem... I took the bike at Cal City, broke it in, and while I was doing so, the bike was bogging in first gear (Yes, first gear). Also it doesn't idle at all. I have to keep blipping it otherwise it'll stall. So I adjusted the screw circled in image 1. Well I was listening to the sound of the of the bike, yet the rpm's weren't increasing, and it was still stalling. So then, I unscrewed the screw in image 2, well I found out that it was fully twisted to the right. So then, I twisted it to the left, still nothing; it was still stalling... where's the idle screw? I am sure that the screw in image 1 is for the air/fuel mixture screw, and the screw in image 2 is the idle screw, just broken? I don't know, any and every help would be appreciated.


    • By Zach7018
      So Ive decided its time to pull apart my favorite machine and freshen it up, and I'm looking to make some improvements in the process. I already have a 3x3 mod and a JD jet kit done and it seemed to have changed the world. The stock bike just plain sucked and now its a lot better. I never expect 450 race bike power here but I know there is a little more and I'm wondering if the juice is worth the squeeze. I already plan to add a header and exhaust, an FCR39 carb and stage 1 hotcams. After some research it really seems like those places are where the gains actually come from, so would it be worth it to throw a 434 big bore kit at this bike or just stick with what I already mentioned and a new stock bore top end??? Also my rides are often solo and pretty isolated,how much of a reliability headache can I expect with these mods? 
×