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Fitted a K&N filter what rejetting?

  • Thread starter Thread starter dridgy
  • Start date Start date
D

dridgy

Guest
Hi guys i have a 1985 suzuki gs850

i have fitted a new k&n filter in the standard airbox as the old filter was dead.

the bike has a mid range flat spot.
i asked K&N if i need to rejet with this filter, they said its normal to rejet.

So can anyone give me a idea what to rejet too?

i have just taken off the carbs and the original main jet is 110

Any advice appreciated.
many thanks

dridgy
:)
 
From reading other threads it is my understanding that with just the filter and not a exhaust you should be good to go.
Do you still have stock exhaust?
You have a problem and I don"t really have the answer, hopefully someone here to help.
Have you oiled your new filter?
To Little or too much oil on the KN?
I have a 16 valve 750 and they run different but with just the KN it runs fine.
 
Crankthat said:
From reading other threads it is my understanding that with just the filter and not a exhaust you should be good to go.
Do you still have stock exhaust?
You have a problem and I don"t really have the answer, hopefully someone here to help.
Have you oiled your new filter?
To Little or too much oil on the KN?
I have a 16 valve 750 and they run different but with just the KN it runs fine.
Click to expand...

Yeah what Crank said, I have a 750E with a K&N (31 yrs old). Had to rejet when I added the pipe. Other then that no flat spots.
 
k&n

k&n

ahhh ok guys.

i have a stock exhaust.

maybe the carbs need a good clean then ?

is 110 main jet the normal size for this bike or could i go up slightly, the plugs do look a little white, maybe its running a bit lean.

thanks

dridgy
 
I have a chart with jet sizes but no reference with the 85 850.
The 82 took a 115 but the 85 may be a 110 for a reason?
A good carb rebuild would be great.
If you haven,t rebuilt the carbs before then they should be done as you may find your stumble from jets being dirty, or might not be related.
You may have a air leak also but a unoiled filter would cause same leanness as a air leak I would imagine.
I will dump some reading on you from a members website with carb rebuild guide, valve adjustment info (Another Priority) And some other great GS info.

http://members.dslextreme.com/users/bikecliff/

If you are anything like me that will keep you busy for a while.
If you introduce yourself in the gs owners area Mr basecliff should send you his mega welcome.
 
I would jump it up to a 115 these bikes are a little lean from the factory and you are adding a freer flowing filter
 
I would install 115 mains and shim the jet needle with radio shack washers. Stack the washers to equal the heigth of the spacer over the needle jet. Remove one washer from the stack and install as the spacer. Do this to all four jet needles.
 
update

update

Hi guys.
i fitted 115 main jets to the old suzuki.
i havent touched the spacer on the needles yet as i wanted to see what happend with just the main jets.

it runs better but has a flat spot when pulling away, as if its a cold enigine.
after it get past that flat spot it revs great up to the redline.

do you think i need to go higher on the jets?
is it worth messing with the needles?

the bike ran well before i laid it up for 18 months. then when i went to start using it again it ran crap, i found it was running on 3 cylinders so i replaced the coils, put in a new air filter and new plugs and caps, and cleaned the carbs, cleaned the tank and filter insides then put in a inline fuel filter and new fuel.

so now its almost there just gotta sort out the flat spot issue.
thanks
John
 
hi guys i have taken off the carbs again so i can shim the needles as suggested.
i have two types of washers available for shimming.
i have nylon washers and stainless steel washers, which one should i use?
metal or nylon?
or does it not matter?
thanks
Dridgy
 
dridgy said:
hi guys i have taken off the carbs again so i can shim the needles as suggested.
i have two types of washers available for shimming.
i have nylon washers and stainless steel washers, which one should i use?
metal or nylon?
or does it not matter?
thanks
Dridgy
Click to expand...
In the stock configuration, the nylon spacer will sit above the circlip, the stainless one sits below the circlip, just above the spring (its main function is to keep the spring from getting tangled on the circlip). What you need to do is to remove the nylon spacer and replace it with a stack of washers that is slightly shorter. It usually takes four washers to equal the height of the spacer, so putting in three washers in place of the nylon spacer might be enough. If you still have a bit of a flat spot in your mid-range, remove one more washer.

The good news is that if you only need to change the stack of washers on the needle, you do not need to remove the carbs from the bike. You can simply remove the tops of the carbs, pull the diaphragms up, then change the washer stack.

.
 
Greetings and Salutations!!

Greetings and Salutations!!

Hi Mr. dridgy,

I didn't have to rejet when I bought a K&N air filter for my stock airbox. Did you spritz it with a little oil? Is the whole air intake system tight, no air leaks? (I.E. new intake boots and O-rings, airbox sealing, etc.) See the maintenance lists in your "mega-welcome" and check out the "how to" guides on my little website. These bike do not like leaks in the air intake system. The engine will run lean, idle funny, and have performance issues. OK, now it's time for your S.W.A.G. :)

If you are here you probably have a 30 year old motorcycle that needs about 20 years worth of maintenance. You'll find all kinds of helpful tips, procedures, manuals, etc, in the links below. Let's get started.

Let me dump a TON of information on you and share some GS lovin'. :D

I just stopped by to welcome you to the forum in my own, special way.
big_hi.gif


If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....
hat1.gif


Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. This is what NOT to do: Top 10 Newbie Mistakes. Now let me roll out the welcome mat for you...

carpet.jpg


Please Click Here For Your Mega-Welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike! :D

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff
 
hi

hi

hey yeah, i have taken out the needles and i puchased some nylon washers and also some stainless steel washers. so what would be the best ones to use when i take away the nylon spacer to shim the needle?
shall i use the nylon or stainless washers?

thanks

John
 
Use the stainless. Should take 3-4.
Measure the nylon spacer. This gives you your baseline. Then make the stack thinner than the spacer. Adjust as required.
 
hey

hey

Thanks ill use the stainless ones then.
ill let you guys know how i get on.
Thanks
John
 
needle settings

needle settings

I have an '81 850G, and have been wrestling with my stage 3 rejet (yes, K&N pod filters, 4-1 exhaust. And, no, Ive no time for negative responses, i.e. "you should just of left it stock!" Only information please, not opinions) for a time now. I decided to try out 6 Sigma Racing. They have no phone #, and are very vague in their email responses.
Does ANYONE have any experience rejetting an '81 850G w/pods & 4-1 manifolds at sea level?
Any concrete settings for the various adjustments, I can start from? Everything is in great shape, new o-rings, intake mani's, good petcock, clean carbs, strong spark.
The instructions have me moving the needle clip down one (toward the pointy end). This puts it on the third clip down. No mention of changing out nylon washer on top of needle. Also, they have me turning out the pilot jets 4 1/2 turns. They only have 5 turns on them.
Now, for more fun. The PO had put on the pods and exhaust mani, and said he "rejetted" the carbs. It turns out, all he did was drill out some aftermarket 160's. No needle or pilot adjustments. The stock jets are numbered by fuel flow, and most aftermarket, by jet opening diameter. I was sent a few different sizes, the largest at 135. Visibly WAY smaller then the jets the PO had put in, and the bike would hardly run. Eventually, I was sent 170's, which had my bike roaring, but too rich.
After messing with pilot settings, and re-installing the carbs, I had flooded my crankcase by leaving the petcock on prime by accident.
OK, oil and filter change.
Now its not even starting. So.... you can see why rejetted carb settings would help.
Thanks a bunch.
 
Last edited:
chrisbock said:
I have an '81 850G, and have been wrestling with my stage 3 rejet (yes, K&N pod filters, 4-1 exhaust. And, no, Ive no time for negative responses, i.e. "you should just of left it stock!" Only information please, not opinions) for a time now.
Click to expand...
Strictly information? Not on your life. I'm going to start with an opinion. :p

It is my considered opinion that you would have gotten quicker response by starting your own thread, instead of tagging on to a thread that was already resolved. :o

Now for the information:
Stock jets on an 850 are 115 mains, 40 or 42.5 pilot fuel jets (depending on the year) and 180 pilot air jets.

The general rule of thumb is to add 2 or 3 jet sizes for a pipe and 3 to 5 sizes for pods. Since you have both, you will need 5 to 8 sizes larger than stock, or 127.5 to 135 main jets. Your pilot jets will probably not need to be changed, especially if you have 42.5 pilots. You will need the needle raised from the stock position, but you have non-stock needles, so you will have to do your own experimenting. Leave the clips where they are for now, you will test them later. Set your mixture screws out about 3 turns for a start, then start your testing process of plug chops to see what you have and what you need to change.

Good luck.

EDIT: by the way, all those jet sizes are Mikuni numbers. I know that DynoJet uses different numbers, I have no idea what Sigma 6 uses.

.
 
Last edited:
Awesome! Thank you very much. I had just figured out how to post a new thread, after I had replied to this thread. Sorry 'bout that.
Is there a good number of turns on the pilot jets? Everything I've found says 'do not alter unless for cleaning, counting number of turns till lightly seated'
being a nube, I didn't count the turns during disassembly. Also, the jet numbers you mentioned are the same as the original jets I was sent, 127.5 to 135's. They were visibly smaller then the PO's jets, maybe 2/3 the size, and I'm guessing that they weren't numbered as Mikuni, by airflow, but were probably numbered by inner dia.
 
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