Jetting?? Headder Only, Homemade Intake Filter

[bandit78]

I read up on jetting for dif mods but noting seems to be clear cut for my set-up.
Why not ask the community?

I currently have stock jet settings and seem to run super rich.
I foul plugs regularly. Points, timing/time chain all have been set/adjusted
properly.
Running headder only, no muffler or baffle (Bring the noise)
homemade intake filter....look at the pic and advise, BIG thanks in advance.

 

[Paulrxs650]

Hi
You definately need to rejet. At least turn your mixture screws in a few turns! At least you've got the plugs to go on which is a good start! Take a digi pic of the plugs as you work through the carb guide in the Tech section above. It helps me as my memory is not as good as it used to be the carb guide is excellent

Here's the link - read, read and read again

http://www.amckayltd.com/carbguide.pdf

 

[deadchef]

if you have valves and such set correctly with the mods you have and using stock carb settings i don't see how you could be fouling plugs. are you sure they aren't fouling from oil, maybe bad rings? how's the compression?

 

[bandit78]

if you have valves and such set correctly with the mods you have and using stock carb settings i don't see how you could be fouling plugs. are you sure they aren't fouling from oil, maybe bad rings? how's the compression?

compression is solid, Rings? no smoke blue/black so rings aren't likely.
could my fouling be caused by old coils? They are stock and higher engergy
could allow for more gap in the plugs...just my stinkin thinkin
I'm looking more for jet numbers/sizes for my setup I like the thought out diagnosis tho.
Thank you guys.

 

[5twins]

I'm guessing those funky looking "filters" are blocking the air jets around the outside of the intake bell which would cause a rich condition. Take them off and see if the plug fouling stops.

 

[Dakota_Lew]

I run a headers with pods on one of my 650's and i am using jets at #135, but i am also at 3300 ft elevation. If you plan on rejetting them regardless you might as well call Mercury up at 650 central and talk threw it with him and just order the parts from him. The man knows his carburetors!

 

[deadchef]

how sure are you that you are using stock jetting? like have you physically broke them down and taken a look at the numbers on the jets & needles? i'm not familiar with the bs38's but i think in general you should at least be up one pilot and two or more on the main jet. i do know that there is a rubber o-ring on the needle jet that can allow fuel to pass by if it's toast. are the floats set correctly? by the way, what plugs are you using?

 

[XSLeo]

With the variety of mods, the fuel you use, the altitude, and very many subtle differences between your bike and anyone else's it's impossible to say with any certainty just what jets you need. You need to read the carb guide section on carb tuning and learn how to tell what your bike is telling you. Once you figure out what your bike is telling you then you will know what you need to do.
That's why most say up one or something to that effect.
But your set up is going to be a tough one. Open pipes and basically no air filter are hard to tune too.
Leo

 

[bandit78]

great responses...
I ran awhile without filtration and bike did run a bit leaner (at least a little while longer between plug changes) so next good weather day i'll rip my "funky's" off and see if it makes a difference.
I used the carb guide's step by step to clean my carbs best i could, I'm for sure the jets are stock and needle is set to stock clip. Floats were quad checked for proper height.
I use mobil 1 4T 10/40, not sure on plugs at the moment srry, will check the shop tomorrow and update.

 

[bandit78]

chef, rubber o-ring on the needle jet? can't remember if I caught that when I broke them down last. Is it yellow? I'll rip them off first thing tomorrow and check that out.

bTW I came across a guy in Rock Hill, SC bout an hour from me http://oldskoolcarbs.com/ that will completely tear down and beadblast/mediablast/ultrasonic clean and tune for $225. wonder if anyone is familure with his work and could add 2 cents.
Thanks

 

[deadchef]

the o-ring is black. i'm not familiar enough with those carbs on how the needle jet is removed but it should be in the carb guide.

oldskool does a great job but you can do the same for a lot less if you have the time and gumption.

 

[DogBunny]

This is off the subject of jetting, but since you mentioned Mobil 1:
These engines do not have a proper filter, they just have "screens." Dirt and metal particles never get filtered, they are just held in suspension until you do an oil change. For this reason, the factory specified oil change interval is only 1,000 miles. Using expensive synthetic oils is therefore a waste of money in my opinion. Use motorcycle-specific 10W-40 when it's cold and 20-W50 when it's hot. Do not use auto oils, they are not compatible with your wet clutch.

 

[bandit78]

chef, plugs I use are NGK 5422/BR8ES ...haven't had an oportunity to ride with
my funky intake screens removed, but soon as I can I will and update.
will also speak with 650central's carb guru when able to get his input, thanks

 

[5twins]

8's are one step too cold, you should be running 7's - and not a "BR", I think that's a resistor plug. Use NGK BP7ES plugs.

 

[deadchef]

certainly take heed of 5twins advice on the plugs. after that toss on some foam air filters and give it a go. if your problems haven't been solved at least you've ruled out potential issues.

 

[bandit78]

twins, I'll pick up the BP7ES plugs today, I'll also get to work on a foam filter idea
that wont compromise air jet flow...thanks for sharing your knowledge

 

[meanstreakmark]

Has anyone mentioned that you can lean out your carbs a bit by LOWERING the fuel level in the float bowls? You accomplish this by adjusting the tangs on the floats...