• Required reading for all forum users!!!

    Welcome!
    Register to access the full functionality of the GSResources forum. Until you register and activate your account you will not have full forum access, nor will you be able to post or reply to messages.

    A note to new registrants...
    All new forum registrations must be activated via email before you have full access to the forum.

    A Special Note about Email accounts!
    DO NOT SIGN UP USING hotmail, outlook, gmx, sbcglobal, att, bellsouth or email.com. They delete our forum signup emails.

    A note to old forum members...
    I receive numerous requests from people who can no longer log in because their accounts were deleted. As mentioned in the forum FAQ, user accounts are deleted if you haven't logged in for the past 6 months. If you can't log in, then create a new forum account. If you don't get an error message, then check your email account for an activation message. If you get a message stating that the email address is already in use, then your account still exists so follow the instructions in the forum FAQ for resetting your password.

    Have you forgotten your password or have a new email address? Then read the forum FAQ for details on how to reset it.

    Any email requests for "can't log in anymore" problems or "lost my password" problems will be deleted. Read the forum FAQ and follow the instructions there - that's what we have one for...

  • Returning Visitors

    If you are a returning visitor who never received your confirmation email, then odds are your email provider is blockinig emails from our server. The only thing that can be done to get around this is you will have to try creating another forum account using an email address from another domain.

    If you are a returning visitor to the forum and can't log in using your old forum name and password but used to be able to then chances are your account is deleted. Purges of the databases are done regularly. You will have to create a new forum account and you should be all set.

carb work recommendations

  • Thread starter Thread starter rideOn
  • Start date Start date
R

rideOn

Guest
i'm in sc and the temps have gone from 80/90 to 60/70. my 850 wants to stutter between 3-4k rpms. these are my thoughts and i welcome suggestions.

next paycheck i am replacing o-rings, intake boots (with new clamps) and new air filter (original). the previous owner put on a 4 to 1 exhaust, but i have no dough to fix that now. he also put (rumor has it) bigger jets and i don't know the size. i'm thinking factory jets to benchmark, and then go from there. i also plan to re-wrap the baffle.

oh, and shims for the valves.

thoughts?
 
Last edited:
Well, since you KNOW it already has a different exhaust and it will HAVE to be re-jetted, there is absolutely NO sense in putting stock in there "for a baseline". My son's bike has a header and stock airbox (K&N filter inset), so it's a bit like yours (click on "#2 son" link in my sig). I have 120 main jets in there and it seems to be working rather well. I have not taken the time yet to do proper plug chops to verify jetting, but it starts easily, warms up quickly and pulls well at any engine speed, so it's at least close.

First thing to do is to get your carbs apart and actually see what's in there, then we can do some more-intelligent guessing. :D

.
 
i agree that 120's are a good baseline, i have a 4-1 and pods on my 750 with 120's so with your bigger displacment you should start there and order some 122.5's along with it incase you needa go bigger
 
i don't know what's in it now. they're cheap enough to swap all of them out
 
Today, 01:18 PM Steve Well, since you KNOW it already has a different exhaust and it will HAVE to be re-jetted, there is absolutely NO sense in putting stock in there "for a baseline". My son's bike has a header and stock airbox (K&N filter inset), so it's a bit like yours (click on "#2 son" link in my sig). I have 120 main jets in there and it seems to be working rather well. I have not taken the time yet to do proper plug chops to verify jetting, but it starts easily, warms up quickly and pulls well at any engine speed, so it's at least close.

First thing to do is to get your carbs apart and actually see what's in there, then we can do some more-intelligent guessing.
Click to expand...

I agree with Steve on upping the mains two sizes for the pipe and would also suggest bumping your pilot one size if you are still running the stock airbox. I have a similar set up on my 1000 and my plugs read slightly rich, no decell popping, close enough for me. Slightly richer is always better than leaner IMHO.
 
rideOn said:
i don't know what's in it now. they're cheap enough to swap all of them out
Click to expand...
OK, before you go taking everything apart, put some new spark plugs in and do some plug chops. Don't know how? Look at BassCliff's site, there are instructions there on how to do that.

Now, before you go ordering parts, let's say that you order up some 120s and 122.5s. While you are waiting, you do your plug chops and find that the mixture is close, but just a tad lean. You open your carbs and find 125s. You just wasted money on TWO sets of jets.

First things first. Follow Nessism's advice: "To measure is to know."
1. Check the mixture with new plugs.
2. Open the carbs to see what's in there
3. Adjust accordingly.

And, if you find that urge to get rid of some money just overwhelming, let me know, I'll PM you my address. :-\\\


.
 
twr1776 said:
I have a similar set up on my 1000 and my plugs read slightly rich, no decell popping, close enough for me. Slightly richer is always better than leaner IMHO.
Click to expand...
yep, i'm getting me some decel popping. she cranks very fast and idles well, so i never thought about pilots. the big problem going on is the 'flutter' between 3-4k rpms. above and below that range, everything seems ok. i don't see a height adjustment for the main needle, so bigger mains make sense. i'll get those valves and new boots done first and go from there. ??
 
Last edited:
i wil do the chops this weekend. do i just need one set of fresh plugs or a new set for each rpm range? if only one set is needed, do i need to carry along a brush to clean the plug between chops?
 
rideOn said:
i wil do the chops this weekend. do i just need one set of fresh plugs or a new set for each rpm range? if only one set is needed, do i need to carry along a brush to clean the plug between chops?
Click to expand...

Use your old plugs, what changes color is the deposits on the plugs, with new ones there's little to see unless it is very rich. You don't need to clean the plugs.
 
less money, mo better. i'll report back here when i get some readings and maybe everyone can hepp me interpret.
 
Yesterday, 02:42 PM rideOn yep, i'm getting me some decel popping. she cranks very fast and idles well, so i never thought about pilots. the big problem going on is the 'flutter' between 3-4k rpms. above and below that range, everything seems ok. i don't see a height adjustment for the main needle, so bigger mains make sense. i'll get those valves and new boots done first and go from there. ??
Click to expand...

Checking your valves and replacing the intake boots and o-rings is definately the way to go before you even start on checking the jetting. Have you checked and/or sealed the airbox? Also check the airbox to carb boots and make sure they are still OK. The stock needles do not have the adjustment notches in them but do a search on shimming needles and you will find out how to do it with the stock needles. I shimmed mine with the Radio Shack washers (2 I think), and went 1 1/2 turns out on the pilots. The plug chops are the best way to see exactly what you have on the mix for each circuit once you have done the necessary valve adjustment/boots/etc. I am not a carb expert but that is what worked for my 1000.
 
twr1776 said:
Checking your valves and replacing the intake boots and o-rings is definately the way to go before you even start on checking the jetting. Have you checked and/or sealed the airbox? Also check the airbox to carb boots and make sure they are still OK. The stock needles do not have the adjustment notches in them but do a search on shimming needles and you will find out how to do it with the stock needles. I shimmed mine with the Radio Shack washers (2 I think), and went 1 1/2 turns out on the pilots. The plug chops are the best way to see exactly what you have on the mix for each circuit once you have done the necessary valve adjustment/boots/etc. I am not a carb expert but that is what worked for my 1000.
Click to expand...
i wanted to head for getting everything good and tight first...good advice. that's on the list 3 weeks out (when i get some dough). my single has a carb with a needle height adjustment for mid-range, but i couldn't find anything in the forum links or my manual for the gs. for now, when i'm in that 3-4k range, i push the choke over about 1/3 and it smooths out nicely.
 
rideOn said:
... when i'm in that 3-4k range, i push the choke over about 1/3 and it smooths out nicely.
Click to expand...
Good troubleshooting. :clap: :clap:

That shows you that it's running LEAN. You still want to check your valves to make sure the engine is breathing right, then you can adjust what it's breathing. You will need to make sure there are NO air leaks, especially between the carbs and the engine. Does your bike have o-rings in the intake boots? What shape are the boots in? ("Round" doesn't count.) If they are not soft and pliable, they could be the source of your air leak.

Now, concerning that "3-4k range", ... what is your throttle position when you are doing this? What I mean is, is it just barely open, as in cruising down the road? Is it open about 1/4, 1/2 or even full open? Diagnosing jetting problems has more to do with throttle position than it does engine speed. Example: going down the road at 25-30 mph in fifth gear (about 2k rpm) will take more throttle than sitting in your driveway, in neutral, and going for 5-6k rpm. Especially for repeatability when doing your plug chops, you should mark your throttle so you can SEE where it is, and you don't have to guess.

Here is how I marked my wife's throttle when I was working on it:
IMG_3646.jpg


The marks are:
Idle
1/8
1/4
1/2
Full

.
 
Steve said:
Good troubleshooting. :clap: :clap:

Now, concerning that "3-4k range", ... what is your throttle position when you are doing this? What I mean is, is it just barely open, as in cruising down the road? Is it open about 1/4, 1/2 or even full open? .
Click to expand...
not sure. i'm fixin' to ride it 15 miles to the house. i'll make notes....but not while i'm driving! :eek:
 
Last edited:
Steve said:
Good troubleshooting. :clap: :clap:
Now, concerning that "3-4k range", ... what is your throttle position when you are doing this? What I mean is, is it just barely open, as in cruising down the road? Is it open about 1/4, 1/2 or even full open? .
Click to expand...
in any gear, under 3k rpm, no problems that i've seen up to about 40mph. at 40-50 mph, 3-3.8k rpms and 3/8 throttle (best estimate per your diagram) very uneven with popping on decel. any thing above 50mph, 4krpm and 1/2 throttle up, runs great. good pocket about 60mph. there is decel pop at this level, also.
 
You are still pretty much on the pilot circuit at those low throttle openings. How far out are your mixture screws? They should be somewhere in the range of 2 to 3 turns out from lightly-seated on a stock bike. Try that and report back.

.
 
You must log in or register to reply here.
Back
Top