I have a 1980 rm125 and I have a 140 main jet on it is that the right jet or if not please tell me the right stock jetting.

Manual says - VT 1100 88-96 main Jet both nr.165, slow Jet 42

For VT C2 and 1100T main front 175, rear 180 , slow 42

For 97 main both 178 , slow 42

You can read Nr. on Jets, they are small

Hi unless some one changed the main jets they should all be #110 mains, the diaframs and needles if stock are all the same.

Black smoke indicates a too rich fuel mixture. Be sure the air cleaner is clean. Install a new spark plug. Check what size the main jet is. The prior owner may have installed a larger than stock main jet. There will be a number stamped on the side of the jet. Call the dealer and ask what the stock jet number is for your bike and then tell them what you have. Go back to stock.

Intended for motorcycles with a stock engine using the stock airbox, air filter and stock pipe. Stage 1 kits are fully adjustable to allow the use of a well designed aftermarket pipes and stock replacement air filters like K&N. Stage 1 kits are designed to improve throttle response and driveability and in most cases power increases of approximately 5% throughout the entire power range can be achieved.


STAGE ONE INSTRUCTIONS
1. Remove the vacuum slide from the carbs. Remove the stock needles & spacers, noting the order of
assembly. Locate the slide lift holes (Fig. A), with the slide drill DD# 14 supplied, enlarge your slide lift
holes. The picture may not show your slide exactly, enlarge your slide lift hole or holes depending on your
model. Do not drill any new lift holes. Do not drill the needle hole.
2. Install Dynojet needles on groove #4, using all stock spacers. Install the Dynojet washers (2 per
needle) above the E-clip.
3. Remove the stock main jets and replace with the Dynojet main jets provided. If you are running with
stock exhaust, use the DJ110 main jets. With an aftermarket header or slip-on with high flowing baffles,
use the DJ116 main jets. Be sure that the jets you are changing are the main jets.
4. Locate the fuel mixture plug (Fig. B), if you see a screw head, proceed to adjusting procedure. With the
DD #5/32 drill bit provided, carefully drill thru the plugs. Note: the mixture screw is directly underneath this
plug, be ready to pull back on the drill the instant you break thru. Use screw provided to secure and
remove the plug. Carefully turn mixture screws clockwise until they seat, turn out 3 turns.


For further info on this, visit: http://www.dynojet.com/jetkits/motorcycle/honda.aspx

You can find the manual for the model you are searching for. Follow the 1st column "CC" to find 650cc models and you can find your specific model after that.

Thanks for asking.
Regards,
Arvind S Iyer

The bike may have the wrong spark plug in it. The stock plug is NGK, CR7HSA. You may want to go to a hotter plug > CR6HSA. It is also possible that a prior owner installed a bigger main jet. Check the main jet size. The jet will have a number stamped on one side. Stock is #92. A #98 jet would be a richer jet. Please rate my answer. Thanks.

you need to change the big main jet. the stock size will be stamped on the jet. Go for one or two sizes bigger. Your motorcycle shop dealer will help you out when you buy the jets.

your factory jets should be ok with stock carb and exhaust,unless it came from way down south or someone changed them.factory jets are main jet #380,pilot jet #30

The stock main jet is 127.5. The stock pilot jet is 32.5 The stock jet needle is 0-8. The sizing on the needle refers to the taper in diameter.

No one can tell you what jet size to use unless they know exactly what exhaust and jets you have now. The best thing for you to do is go back to a known good configuration. If it has never run right since you had it, go back to stock (make sure it runs right with stock settings now!) and start your adjustments from there. Change one thing at a time and do performance testing between each change. Dyno runs are best, but timed runs might work too, depending on your application.

Carburetors supply a mixture of gasoline and air to the engine. The gas comes out of little things called “jets” (usually a pilot jet needle jet and main jet). If you modify your airbox or exhaust to flow more freely you get more air going through your system. This often means that there is not enough gasoline so the engine runs badly. “Rejetting” means replacing or modifying some of these jets so as to supply gasoline differently than stock, usually more gasoline than stock. If done correctly, this allows your engine to generate more power, run a little cooler, start and run smoother and get worse mileage. ,,,