• 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.

Weird high rpm surging returns,...

  • Thread starter Thread starter UncleMike
  • Start date Start date
U

UncleMike

Guest
Was working on Pat's (Gravity Tester) '83 750ES yesterday, and got some interesting, unexpected and frustrating results.

First, a little background:

When Pat bought the bike a few years back, it had a lean surge at cruising speeds that caused the bike to lose power and gain it, back and forth so it was like riding a wave. This was fixed by raising the needles one notch, although they had to be modified to do so. No more lean surge.

Pat had noticed when riding with me that his bike was slower than my 750T, and had a noticeable handlebar shake as well, so figured something needed fixin'.

First, he poured some Seafoam in the tank, which took care of a lot of the handlebar buzz. Yesterday, we re-torqued the headbolts to hopefully take care of a small oil leak, and then synched the carbs. Pat took it for a ride, and the lean surge is back, albeit less noticeable and at high rpms.

Valves are in spec.

I can't imagine what we did that would bring back the lean surge. Any suggestions?

Some additional info: We didn't wait for the bike to get fully warmed up before synching. It was by no means cold, but since it has an oil cooler, the needle never got above 160 degrees, even though it had been running for a long while.

ANY suggestions would be greatly appreciated. Pat's taking her out for another spirited jaunt this morning, and will report back.

Thanks,

Pat and Mike
 
If Pat's bike is stock, you shouldn't have tinkered with the jet needle positions. Only intake/exhaust mods warrant raising the needles.
The bike needs to be at "operating temperature" per the factory manual before vacuum synching. That means fully warmed up. Then the mixture screws can be set using the highest rpm method and then the vacuum synch.
If it's surging (most noticable at steady crusing speeds of course), then an intake leak is possible or the fuel isn't flowing correctly.
Does it help to crack the gas cap vent? Are any float bowl vent lines clear? Were the float levels checked? Were the carbs cleaned? Did you verify the jetting sizes? Is there a fuel filter involved or incorrectly routed/kinked fuel line? If removed, were the carbs "popped" into the manifolds correctly? Hows the air box sealing? Could be lots of things.
 
Keith,

Pat just called and said it's not surging anymore. But thank you very much, as these were all the things I needed to be reminded to check. I think we're going to run a few more tankfuls of fresh gas through there and re-synch properly this time.

Although the airscrew plugs haven't been removed, so we couldn't do the highest idle either.

Gotta do it proper next time.

THANKS!

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