How to tell if jetting is ok
Mar 19, 2002 | 12:05 PM
#2
Pro Rider
Joined: Jul 2000
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You will need to do several plug chops (or checks) to jet your R. This will be a long post.
1. Warm up your engine and ride it for a short while.
2. Find a place where you can run it wide open in 5th or 6th gear.
3. With a warm engine, get it tapped out, wide open throttle (WOT)and hold it there for a "10" count.
4. While still WOT, pull in clutch and shut off motor KEEP IT WOT UNTIL ENGINE STOPS COMPLETELY!!
5. Pull the plug out and look at it.
You're looking for a light tan/brown color. If it's black and sputtered on the top-end, it's too "fat" or "rich" on the main jet and you need to go smaller. Step down one size at a time until you get the tan/brown color you're looking for.
If it's white, it's way too lean and you need to go up in size on your main jet.
Depending on what has been done to your engine, you're jetting can be affected by other things also; ambient air temperature, humidity, etc.
A stock 86 R with stock carb has a main jet of .152 with the needle set in the 4th groove (from the top).
If you add a pipe/silencer combo and an aftermarket air filter, you will need to increase at least three sizes on the main jet to start.
If you have an all stock set-up, start with the .152 main and start your plug checks. You will need to do this several times until you get it "right" and it's a pain but you really need to do this. Once you have it, keep in mind that you will need to change jets periodically as situations change; if you go to higher elevation you will need to "lean" the main, lower elevation you will need to "fatten" the main.
Stock size main jets for stock carbs; .148, .150, .152, .155, .158, .160, . . . . . .
Main jets are inexpensive (about $4 each) so buy several of them and keep them on hand, along with a 17mm box wrench (to take off the plug on the bottom of the carb) and a jet-tool (or a 6mm socket) to remove/replace the jet. You can change your jets just by doing that, no need to remove or adjust the carb around at all, just pull the plug on the bottom, pull the jet and replace. Can be done in just a minute or so. Remember to shut off your gas before you start.
Good luck!
1. Warm up your engine and ride it for a short while.
2. Find a place where you can run it wide open in 5th or 6th gear.
3. With a warm engine, get it tapped out, wide open throttle (WOT)and hold it there for a "10" count.
4. While still WOT, pull in clutch and shut off motor KEEP IT WOT UNTIL ENGINE STOPS COMPLETELY!!
5. Pull the plug out and look at it.
You're looking for a light tan/brown color. If it's black and sputtered on the top-end, it's too "fat" or "rich" on the main jet and you need to go smaller. Step down one size at a time until you get the tan/brown color you're looking for.
If it's white, it's way too lean and you need to go up in size on your main jet.
Depending on what has been done to your engine, you're jetting can be affected by other things also; ambient air temperature, humidity, etc.
A stock 86 R with stock carb has a main jet of .152 with the needle set in the 4th groove (from the top).
If you add a pipe/silencer combo and an aftermarket air filter, you will need to increase at least three sizes on the main jet to start.
If you have an all stock set-up, start with the .152 main and start your plug checks. You will need to do this several times until you get it "right" and it's a pain but you really need to do this. Once you have it, keep in mind that you will need to change jets periodically as situations change; if you go to higher elevation you will need to "lean" the main, lower elevation you will need to "fatten" the main.
Stock size main jets for stock carbs; .148, .150, .152, .155, .158, .160, . . . . . .
Main jets are inexpensive (about $4 each) so buy several of them and keep them on hand, along with a 17mm box wrench (to take off the plug on the bottom of the carb) and a jet-tool (or a 6mm socket) to remove/replace the jet. You can change your jets just by doing that, no need to remove or adjust the carb around at all, just pull the plug on the bottom, pull the jet and replace. Can be done in just a minute or so. Remember to shut off your gas before you start.
Good luck!
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