Is this "surge" scenario common?

[Windsmile]

My Suzuki is a 1982 GS750T. It runs very well until the speed reaches about 65MPH and then the surging begins. What takes places feels like the brake is being applied and released every few seconds. There isn't any coughing, sputtering or the like...just slowing down and speeding up.

If you've had this problem, or know someone who has solved a 65MPH and up surging problem, I would appreciate your sharing what it was that stopped it from happening. Thank you.

 

[JEEPRUSTY]

Hmm well welcome
a massive welcome will soon ensue and you will find a tome of information.

Surging is caused by leaking o-rings or boots or a carb imbalance as I dimly recall. A combo of all three or just one.

There is a must do list in the welcome and the root cause is addressed by the list.

 

[spyug]

Welcome. As the Jeepster says , its a carb issue. If they haven't been cleaned in a year or two they will likely need a strip, dip and rebuild with new o-rings. Your intake boot o-rings likely will need changing out too and make sure your airbox is well sealed.

Refer to the carb tutorial for detailed instructions on proper carb cleaning if you're not up to speed on it.

Good luck.
Spyug

 

[hampshirehog]

Or it could be the fuel tank not venting or partially gummed up fuel tap.

 

[Steve]

..., its a carb issue. If they haven't been cleaned in a year or two they will likely need a strip, dip and rebuild with new o-rings.

I agree with the concept, but don't agree with the idea that this is something that must be done every year or two.

It really only needs to be done when you get the bike or if it has been sitting for quite a while. I just had the carbs off my wife's 850 while having some machine work done to the head and cylinders. They were cleaned and o-ringed six years ago, so I thought I might as well do them again, since they were off the bike, I had the parts and I had the time. Everything inside was spotless. All the o-rings were still in good shape, but got replaced anyway. Yeah, the "dip" cleaned the paint off the outside of the carbs, too, but it gave me a good excuse to do a better job painting them this time.

If you either keep fresh gas going through the carbs by riding every so often or properly treating the gas with Sta-Bil or Seafoam before storage, dipping the carbs should be a one-time ordeal.

Then, once the carbs are cleaned and back on the bike, proper adjustment will likely remove all your surging. If the bike is stock, as far as intake (stock filter or pods?) and exhaust, simply turning the idle mixture adjustment screws out a bit will help. If you have intake or exhaust mods, you will have to lift the needle a bit, too.

.

 

[BassCliff]

Hi Mr. Windsmile,

In addition to checking valve clearances, cleaning the carbs, and repairing the air intake system (intake boots, intake boot O-rings, sealing the airbox, etc), your symptoms could be caused by an inline fuel filter, if you have one attached to your fuel line. If the fuel system is clean an additional inline filter is unnecessary IMHO. It can cause fuel starvation at higher speeds or throttle openings.

Anyway, let me dump a TON if information on you and share some GS lovin'.

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

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!"....

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. Now let me roll out the welcome mat for you...

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!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

 

[Dogma]

Someone should mention making sure the carb vent tubes are correctly routed. I'm not sure where they belong on a 750T, but if they're exposed to "dirty"air, they can cause surging. If the airbox has a snorkel, make sure that's correctly fitted, etc.

 

[Windsmile]

Many thanks for your suggestions...

Many thanks for your suggestions...

First of all I'd like to say thank you for your suggestions and comments about the surging I'm having at speeds above 60 MPH. The good news is that I have a lot of two lane roads left to explore and I can do that at less then 60 MPH. In the meantime I'll check all of the usual culprits plus the specific ones mentioned in the threads.

Second, I'd like to thank you for your warm welcome. I took the suggestion to send in a picture of my 82 Suzuki GS750T, which, if approved, should be viewable soon. "Jim Braun" is the name to look for in the caption.

 

[Jethro]

Do you have an inline fuel filter installed?

 

[Steve]

I took the suggestion to send in a picture of my 82 Suzuki GS750T, which, if approved, should be viewable soon. "Jim Braun" is the name to look for in the caption.

No "approval" necessary, just post it here.

.

 

[Windsmile]

There isn't an inline filter so what I'll do is take a look at the screen that's attached to the petcock to eliminate that as a possibility. thank you for your suggestion.

 

[Windsmile]

There may be a picture attached.

There may be a picture attached.

I'm not sure I accomplished the upload successfully but I tried.

 

[Steve]

I'm not sure I accomplished the upload successfully but I tried.

Better. Thanks. :clap: :clap:

Better if you host your pictures on PhotoBucket or Image Shack or similar site, then copy the IMG link and paste it here. They will show up full-size that way.

.

 

[Eli69]

i've always heard that surging at speed is a sign of a lean condition. maybe try doing a spark plug inspection to see if that's the case. most of the problems suggested above would lead to a lean condition, plus many others.

 

[Windsmile]

Air or vacumn leak likey is the problem.

Air or vacumn leak likey is the problem.

I agree with you and others who have said much the same.

I didn't know if what I am experiencing was something others with similar engines have experienced so I threw the problem out there hoping it was something peculiar to the family of engine I have.

From the replies and links I've read I can tell there are some "go to areas" such as brittle O rings on the intake manifold however in my case that doesn't apply since my engine doesn't use that kind of manifold.

There may yet be someone who solved this very problem who will respond and if so I'm almost certain it will be an air leak and they'll point to where it's likely to be found.

But as I said earlier, the bike runs beautifully until 60+ so I can still enjoy the 2 lane roads for the time being.

 

[BassCliff]

Hi,

Your bike does not have intake boot O-rings, but the intake boots themselves can crack as the rubber ages, causing air leaks. Have you gone through the maintenance lists in your "mega-welcome"? Sometimes it's just a process of elimination. The airbox also has to be sealed up and the boots between the airbox and carbs must have no leaks. Is the snorkel still attached to your airbox? See the Air Intake Repair article on my website, it will be similar to your bike.


Thank you for your indulgence,

BassCliff

 

[Windsmile]

If you are referring to the connector hose between the air filter housing and the manifold to the carbs as the snorkel, it is attached. Once the the weather cools down I'll go through the intake system and begin to eliminate possible air and vacuum leaks.

 

[BassCliff]

Hi,

My left index finger is resting on the snorkel on the back of my airbox.

Some previous owners have been known to remove this to try and increase airflow through the intake system.

Thank you for your indulgence,

BassCliff

 

[Windsmile]

I believe the air induction system on the '82 GS750T that I have is a different design. There is a plenum that holds the filter which in turn connects to a distribution manifold via a short tube. That tube clamps to each of those two pieces.

 

[cowboyup3371]

How are the boots from the carbs to the engine? Have you properly dipped the carbs yet to rule them out?