Jump to content
Sign in to follow this  

rm125 93' running lean, but bogging?

Recommended Posts

Hey guys, im trying to get my jetting right, for some reason my spark plug porcelin is mostly all white, and black unburned premix around the top of the metal.. I did a run through on 4 of the gears pinning it before i checked the plug, noticeable bogging in 1st and 2nd gear, so im kinda confused whats next..

My jetting specs

-Main jet #360 stock, use to be a #340 and that was a little less leaner

-Pilot jet # 55 stock, was a #35 when i got the bike

-stock needle with clip at the far bottom

-pro circuit platinum pipe

-32:1 w/91 premium pump gas

-clean air filter

-recent top end done like 3 months ago (6hrs max on it so far)

-tried moving the air screw 1 1/2 turns out, and even 1/2 a turns out, neither adustment made a difference

-my weather is like 72-83 in cali

-stock NGK 8 sparkplug

-repacked silencer

I have no air leaks around the rubber that connects to the reeds, the air box, and the left side flywheel case, i tested it with carb cleaner, and no idle change what so ever??

would changing the main jet to a higher number fix it?? If i check the Left side seal, would i need to split the case, or need some special tool?

will put pics up soon of my spark plug.

any guidance would be apreciated.. thanks

Edited by rafael707

Share this post


Link to post
Share on other sites

my 91 does does alomost the same thing. Ive found its something to do with the clutch on mine. If I pull the clutch in ever so slightly itll get rid of all the bog and my plugs look fine. I cant seem to adjust it away so i just deal with and ride the clutch in the lower rpms/gears.

I know some of the questions your gonna get from here are-

compression?

were in the range is it bogging?

and pics.

Share this post


Link to post
Share on other sites

Well bogging is usually a lean issue, I would start with one bigger on the pilot. When you say you have clean air filter I assume it is oiled as well?

When you turn the air screw in, can you turn it all the way in? I mean will it stay running with it turned all the way in? if so you defiantly need to go bigger on the pilot. I would stop running it so lean or you will be putting a new top end back in very soon.

Share this post


Link to post
Share on other sites
my 91 does does alomost the same thing. Ive found its something to do with the clutch on mine. If I pull the clutch in ever so slightly itll get rid of all the bog and my plugs look fine. I cant seem to adjust it away so i just deal with and ride the clutch in the lower rpms/gears.

I know some of the questions your gonna get from here are-

compression?

were in the range is it bogging?

and pics.

compression is good, i get bogging towards the end of my 1st and 2nd gear, sometimes a lil on 3rd. Im deffinately not going to keep riding like this, i know the bike is lean, since the plug doesnt want to change to a different color other than white.. pics comming soon

Share this post


Link to post
Share on other sites
Well bogging is usually a lean issue, I would start with one bigger on the pilot. When you say you have clean air filter I assume it is oiled as well?

When you turn the air screw in, can you turn it all the way in? I mean will it stay running with it turned all the way in? if so you defiantly need to go bigger on the pilot. I would stop running it so lean or you will be putting a new top end back in very soon.

You know what, my filter is clean but NOt oiled.. is that bad?

Share this post


Link to post
Share on other sites
You know what, my filter is clean but NOt oiled.. is that bad?

YES! oil it and then ride it and see how it rides. Oil help traps dust from the motor also make sure you are using grease to seal around the edge of the filter. You don't want any dirt in your engine. Go to your local shop and ask for filter oil and filter grease.

Share this post


Link to post
Share on other sites
YES! oil it and then ride it and see how it rides. Oil help traps dust from the motor also make sure you are using grease to seal around the edge of the filter. You don't want any dirt in your engine. Go to your local shop and ask for filter oil and filter grease.

will do, but i dont think that will help my lean issue.. thanks though

Share this post


Link to post
Share on other sites
will do, but i dont think that will help my lean issue.. thanks though

Oil in the filter will allow less air flow, so by no oil = more air. IE more air into the carb means leaner running engine.

Okay lets say this, since I opened up my sons air box on his KLX110, now the bike won't run correctly unless I go up one size on the pilot jet. More air now flowing into the box now allows more air to flow into the carb which now cause a bog IE lean running bike.

Very small changes in the amount of air or fuel your bike gets has a big effect on how it runs. Like one clip position move on the needle has a big effect just like 1/2 turn on the air screw.

Share this post


Link to post
Share on other sites
Oil in the filter will allow less air flow, so by no oil = more air. IE more air into the carb means leaner running engine.

Okay lets say this, since I opened up my sons air box on his KLX110, now the bike won't run correctly unless I go up one size on the pilot jet. More air now flowing into the box now allows more air to flow into the carb which now cause a bog IE lean running bike.

Very small changes in the amount of air or fuel your bike gets has a big effect on how it runs. Like one clip position move on the needle has a big effect just like 1/2 turn on the air screw.

thanks for the explanation, ima get my filter oiled up, and see what happens.

Share this post


Link to post
Share on other sites
thanks for the explanation, ima get my filter oiled up, and see what happens.

Don't forget to use grease to seal around the edges, all the oil in the world won't help if you have a big gapping leak on the edge.:thumbsup:

Share this post


Link to post
Share on other sites
Well bogging is usually a lean issue, I would start with one bigger on the pilot. When you say you have clean air filter I assume it is oiled as well?

When you turn the air screw in, can you turn it all the way in? I mean will it stay running with it turned all the way in? if so you defiantly need to go bigger on the pilot. I would stop running it so lean or you will be putting a new top end back in very soon.

Well today i turned the air screw all the way in, and it still started.. so i guess i need a bigger pilot jet, i hope im headed in the right direction to fix the lean issue.. still need to get oil and grease for the air filter.

Share this post


Link to post
Share on other sites
Please read the link. It will save you a lot of aspirin for your head aches.

read it, still needed a better standpoint.. i know now i need a bigger pilot..

Share this post


Link to post
Share on other sites

so this is how my spark plug looks, which was tested on a new piston, less than 2 hours on it, sorry took so long to upload.

magbhy.jpg

and this is my old piston that i just took out

es6eww.jpg

6s7400.jpg

nve2yw.jpg

73dnv9.jpg

73dnv9.jpg

does the piston look really bad??

Share this post


Link to post
Share on other sites

not horrible but ive seen way worse ran. For sure looks like there is getting dirt in there. The airfilter is the thing im most anal about... I wash and re oil after EVERY ride no matter what and always make sure its properly oiled and make sure to look down in your intake boot from the airfilter to the carb, there always seems to be dirt that falls down in there. did you wash the piston wash off? that could tell you how your jetting is/was

Share this post


Link to post
Share on other sites

so based on my spark plug reading, how big should i go on my main/pilot jet?

my pilot is a #55 and my main is a #360, and my needle clip is at the far bottom, still running lean.

I have a hard time believing that 1 up on both my jets will make hardly a difference, so would 2 or 3 up be better?

@vamped, unfortunately i did was the piston by accident, not relizing..

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  

×