Jetting for full exhaust help!

[HondaSnake]

I just recently bought a full dg exhaust for my 85 200x. Can anyone help me with what size jets to put in it and if I should adjust the fuel air mixture screw. Thanks a lot!

[yaegerb]

do you have an OEM carb on the bike?

[barnett468]

I just recently bought a full dg exhaust for my 85 200x. Can anyone help me with what size jets to put in it and if I should adjust the fuel air mixture screw. Thanks a lot!


Hello

Jetting a bike properly is an art and difficult to explain. Your jetting requirements depends upon a few different variables such as cam air box/filter compression etc. If you can answer a couple questions it would make it much easier for someone to give you the best possible jetting suggestion.

A general rule is this. If your bike started and ram fine with no flat spots or loading up with the previous pipe and the new one is less restrictive and it still runs fine with the new pipe your jetting is very close but still slightly lean.

If it has a flat spot, mainly off idle wit the new pipe you are still lean but by a larger margin.

If it starts, idles and runs ok I would go up 1 on the main and raise the carb slide needle one position and leave the pilot jet alone.

If it is harder to start and doesn’t idle well then go up one on the pilot.

If it has a noticeable flat spot with the new pipe when accelerating than go up at least 2 sizes on the main and 2 positions on the slide needle. This should get you very close.

You will have to adjust the air screw slightly as needed if you know how.

Is your carb stock?
Is your air box assy stock?
Is your cam stock?
Was the pipe you removed stock including silencer/spark arrester?
Does your new pipe have a spark arrester?

Hope this helps

[HondaSnake]

Wow! Thats alot of good info. I really appreciate it! Everything on the bike is stock. Im not too sure what a spark arrester is so that one im.not sure of. The bike runs great and doesnt smoke a lick. The only problem i have is the kickstart spring is worn out so it has a hard time starting when the bike is cold. But once it warms up kicking gets alot easier. Do you know what size a stock main jet is for the 200x?

[yaegerb]

The starting point for stock engines with bolt-on modifications is to increase main jet size by at least 3 sizes and move needle clip down one position (richer). The starting point for modified engines with larger displacement is to increase main jet size by at least 4. Move needle clip down one position (richer). Pilot jet usually stays stock.

Since your mod's are mostly bolt on applications I would say start your jetting circuits 3 sizes bigger. Assuming you have a stock 24MM Keihin, your main should be a 110. So you need to go to a honda dealership and get a 112, 115 and 118 main jet. Start with the 118 (Fat) and work your way down (lean). I would also recommend getting at least two sizes larger for your pilot, but that's up to you.

How to properly jet is below.

1. Find a gentle slope that you can ride in 2nd or 3rd gear. Look for something that will put a reasonable load on the engine. This will be your “dyno”.
2. A basic outline of which jet is active at a particular throttle setting: Pilot Jet = 0 to 1/4 throttle. Needle = 1/4 to 3/4 throttle. Main Jet = 3/4 to Full Throttle. (Changing the Main Jet size won’t affect how your engine idles or runs at 1/4 throttle. Engine RPM isn’t what determines which jet is active - throttle position does)
3. Make the recommended jetting changes. Always start rich and work leaner.
4. Start and warm up the engine, then ride your ‘dyno hill’. Any point where you feel the engine stumble or hesitate indicates a tuning problem. Note the throttle position and modify the corresponding jet (1/4 to 1/2 throttle = needle. 3/4 throttle or more = main jet).
5. Only change jetting by 1 step at a time, and 1 circuit at a time (don’t change needle and main at the same time). Re-check after every change.
6. Once the engine runs smoothly throughout, you’re jetted!

[HondaSnake]

Awesome! Thanks alot for the info. Ill repost when i get my exhaust and start jetting.

[barnett468]

Wow! Thats alot of good info. I really appreciate it! Everything on the bike is stock. Im not too sure what a spark arrester is so that one im.not sure of. The bike runs great and doesnt smoke a lick. The only problem i have is the kickstart spring is worn out so it has a hard time starting when the bike is cold. But once it warms up kicking gets alot easier. Do you know what size a stock main jet is for the 200x?


Hello

Good as long as it has no burbles or flat spots with your new exhaust installed as i mentioned in my post above then your jetting is extremely close and good enough for now. Yaegerb's explanation and technique are also good and will also get you there.

Try it on a hill as is, if it's fine you may still go up just one one the main and raise the needle by lowering the clip one position.

If it begins to burble when the whether is hot than it is slightly rich so lower the main 1 and lower the needle 1.

[HondaSnake]

Thanks barnett

[barnett468]

hello

not a problem, hope the info from one of us helps

[nb200x]

ok i didnt know you could change the pilot jet. my book just has an adjustment for it.I have a cobra exhaust, and i cant get it to start and run. itll pop just wont start.

[barnett468]

ok i didnt know you could change the pilot jet. my book just has an adjustment for it.I have a cobra exhaust, and i cant get it to start and run. itll pop just wont start.

Hello nb 200x

It would be best for you if you post your question as a separate new topic. You will get a LOT more help that way since EVERYONE will see it there. Also asking for help within someone else's topic is sometimes called "hyjacking" the thread or topic but don't worry about it since you are new and now you know now. I will try to help you in a few minutes.

OK Please read closely. I have a brief interrogation for you. Lol The more of these questions the sooner I and others can offer you suggestions and the better those suggestions so your results are completely up to you, ok? Just do them one at a time and you won’t be overwhelmed. Information is king, the more the better.

0. What model exactly is your bike?

1. Did it start and run fine prior to installing the new pipe, if not what was the problem before?

2. When did it last run good?

3. What pipe did you have and which one do you have now?

4. Can you get it running at all and if so how does it run then. Does it idle? Does it accelerate smoothly or load up [burble] or have a flat spot?

5. What Carb and jets do you have if you know?

6. Is it the original carb?

7. Did you change anything along with the pipe that cold cause the problem like carb or ignition etc?

8. How old is your plug and what does it look like?

9. If it’s dirty or dark brown then replace it we’ll look at it again later. We can tell if you are rich or lean by doing this.

10. Is your plug wet when it doesn’t start?

11. Does it spark when grounded to the head?

12 We are dealing with a very similar problem on the “atc 70 help going insane!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!” on the front page I give a very detailed carb start and run test there in my last two posts. Check that out asap. It should help you.

[HondaSnake]

Ok, so I installed the exhaust along with new sprockets and o ring chain. My local ship only had a 112 & 115 main and I got a 40 for my pilot. My stock setup was a 108/38. All I started out with was changing the main to the 112. I changed nothing else. The bike ran really well. Tons of power. I didnt really notice any flat spots. Should i really adjust anything else? Also, I've seen some air box lids drilled out. Is that better to do? More airflow more power? Thanks everyone.

[barnett468]

Hello

This is my suggestion only others will have good advice also.

If you can start your bike with no choke and ¼ throttle or less your pilot jet is slightly large.

If you need full choke plus throttle and it takes several pulls your pilot is too big.

If it starts with 2/3 choke – full choke and idles fine with choke off after about 1 minute AND you have no flat spots or burbles accelerating from a stop don’t touch the mix screw or pilot jet.

Since if runs perfectly your main is probably close enough just install a new or clean white plug and look at the color after an hour of general riding. If it’s dark or black and DRY not WET it is too rich on the main.

[HondaSnake]

Sounds good thanks

[barnett468]

Ok, so I installed the exhaust along with new sprockets and o ring chain. My local ship only had a 112 & 115 main and I got a 40 for my pilot. My stock setup was a 108/38. All I started out with was changing the main to the 112. I changed nothing else. The bike ran really well. Tons of power. I didnt really notice any flat spots. Should i really adjust anything else? Also, I've seen some air box lids drilled out. Is that better to do? More airflow more power? Thanks everyone.

Hello

As far as the air box goes I would just remove the lid and try it. If there is no lid now than more holes won't help you. I will at least sound faster.