• 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.

Rejetting question

  • Thread starter Thread starter bill761mac
  • Start date Start date
B

bill761mac

Guest
I have a 1983 GS1100L. I moved from Utah which has a sea level of 4600ft to now North Carolina with a sea level of 770ft. Bike is jetted for 4600ft. It runs good here with no throttle issues. Its very responsive. I have noticed louder Knocking than ever, I'm guessing thats from running a little lean. I checked the plugs and they look normal. I stopped running the bike until I got some advise from this forum. Only thing that has been added to intake/exhaust is a mac 4 into 1.

Question: Should I rejet the carbs even if it is running as good as it is (besides knocking)? If I do rejet couldn't I just go back to factory mains? Do they need balanced after a rejet? All 4 carburetors were cleaned and balanced last year. I know the mac 4 into 1 will have some differences but hoping not much. Any help is appreciated.

By the way, If anyone knows of a mechanic in the Greensboro NC area that wants to help work on my bike I will gladly pay them. No shop around here wants to touch it. And I don't have a garage anymore to work on it. New apartment complex said no way. But wont they dont see wont hurt.

thank you to any replies.
 
Your CV carbs should not need rejetting, that is one of their benefits.
The knocking is timing-related. Either retard the timing by a couple of degrees, or move up one octane rating on the gasoline you are feeding it. Most likely you have a different mixture in the fuel you are using, which is causing the knock.
 
Did you rejet when you put the 4-1 exhaust on it? If not you should have. I definitely would not ride it if it's knocking. That is a good way to tear some stuff up in a hurry. Lean mixtures are very dangerous for your engine. You can burn a valve or a piston real fast. How do your pipes look? Are they nice and chrome or blue? If they are blue that is a sure sign of running way too hot and lean.
 
Thank you Koolaid, Being your a senor member I will lean more towards what your saying. Im running 93 octane always have. unless 93 is different here in NC than it is in Utah. Wouldn't surprise me. I am leaning torwards the timing, will retard the timing and go from there. So CV carbs don't need to be rejeted? That is awesome. Everyone I have talked to said it has to be rejet.
Once again GSresourses has saved me money.
 
GSX1000E said:
Raise your main jets by at least 2 steps. BTDT
Click to expand...
Since you are already running 93 octane, this may be the proper solution.
Personally, I believe it to be timing. Before spending the money on the jets, try retarding the timing. One or the other should solve the issue.
 
there is very little adjustment on the timing plate plus you have an electronic advance model.
you could always file the slots a little to get some more retard....
could be carbon build up boosting the compression....maybe?
 
blowerbike, have you heard of anyone needing to rejet CV carbs for elevation changes?
 
koolaid_kid said:
Since you are already running 93 octane, this may be the proper solution.
Click to expand...
Since higher-octane "premium" fuel burns slower, you need to advance the timing several degrees to get it to complete its burn in time.
With stock timing and "premium" fuel, the mixture is not being completely burned, robbing you of power.
My suggestion here is to go with the factory-recommended "regular" fuel.


bill-mac, your bike came from the factory with 115 main jets. With your MAC header, you might need something in the range of 120-125.
My suggestion is to remove the carbs and see exactly what you actually have in there, then decide what you need to do.

.
 
Steve, the issue is knock, which is usually pre-ignition. What is your opinion on that?
 
Spark knock can be caused by running too lean. He never said if the carbs were rejetted following the exhaust upgrade. Which probably they were not. Too hot of a heat range on the spark plugs can cause that too. Im sure the knock is not new it is just getting worse and now he is noticing it. Which mayhem is soon to happen inside his engine.
 
Last edited:
koolaid_kid said:
blowerbike, have you heard of anyone needing to rejet CV carbs for elevation changes?
Click to expand...

Nearly 4000 ft less elevation is a bunch. I think he may be on the lean side, CVs or not. Cheap and easy to jet up a bit & maybe save a motor. I would see what's in there, & follow jbthomp's advice.
 
A quick plug read is in order.
Bill, what color are your plugs?
 
I agree. Who ever installed the pipe should have gone up about 2 sizes on the mains, but that does not mean they actually did the work.
Bill, you really need to pull a main jet and see what size it is.
 
koolaid_kid said:
blowerbike, have you heard of anyone needing to rejet CV carbs for elevation changes?
Click to expand...

honestly all my work has been local but in my opinion i would think the CV's would need the same adjustments as mechanical carbs with large altitude changes.
maybe the changes won't need to be as large compared to RS seriers miks but still i think adjustments/jetting would need a little help.
 
Perhaps this is the scenario:
Pipe installed at 4000 ft. Since the air is thinner up there, the fact that the jets were not changed did not show as much, perhaps even compensated for the fact that they were too large for that elevation.
At sea level now, so the fact that the jets are too small is more evident.
Sound plausible?
 
Sorry guys for the late response, I work a lot of hours.

I have read all the responses. thank you to all. I decided to rent a garage and get this done. I am going to start with checking to tappet clearance, why not just get it out of my way for now. This weekend I will take the carbs off and see what size the jets are. I have a set of 115 that I can put back in and go from there. Yes, I rejetted them after the mac 4 into 1 I installed. Im not that far out of the lope lol. I am not new to maintenance and can interpret a manual very well which I have. I'm a turbine guy. Just not great at older recip bikes. Thanks for all the info.

I'm still open ears to all the knowledge on here. I appreciate all of it.
After all that has been said you think going back to 115 mains are a waste of time? You think I can, with them installed just play with the mixture and get it right?

Will post more info as I go, as I work around my schedule. Would like to post a pic of the bike but the quality is to high for the site to take. I have done a lot of work to her. A lot of you might not like it because it is deff no longer stock. Nice flat black paint job too.
 
Thanks for the info, bill. We were just speculating because we did not have thei information.
How many sizes did you go up on the mains when you installed the pipe?
I would certainly not go back to stock, you need to be 2-3 larger than stock to start.
What color are your plugs? That will tell you if it is indeed a lean condition causing the knock.
After that, it will be time to do some plug chops.

AFA the resolution of your pictures, an app such as paint.net will allow you to reduce it to any resolution you want and still look excellent.
 
You must log in or register to reply here.
Back
Top