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Am I running lean?

  • Thread starter Thread starter Caferacernoc
  • Start date Start date
C

Caferacernoc

Guest
Bike starts fine but takes a long while to warm up. Flat spot between 2500rpm and 4000rpm. After 4000rpm pulls clean to redline but feels low on power. No top end rush. See attachment for a plug check. As far as I know bike is stock. Stock pipes, airbox intact. Air filter good. No air leaks, THAT I CAN FIND. All four plugs look the same as the one in the attached pic.

Thanks.

John 1982 GS650GView attachment 17014
 
Somebody has to ask..... what maintenance has been done? Have carbs been properly cleaned in last decade?
This flat spot is still there when bike is warmed up? So even when you take off in first, you notice this ? Plug looks too new to tell me much. At next cold start up , determine if any cylinders aren't firing within 30 seconds or so.

Edit; make sure "choke" is fully disengaging at carbs when off; my bike will stumble in this rpm range unless choke is fully off.
 
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Greetings and Salutations!!

Greetings and Salutations!!

Hi Mr. Caferacernoc,

Most new members who join up here in the forum have a 30 year old motorcycle that needs 20 years worth of maintenance. So here's the drill. ;)

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.
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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!"....
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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...

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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
 
tom203 said:
Somebody has to ask..... what maintenance has been done? Have carbs been properly cleaned in last decade?
This flat spot is still there when bike is warmed up? So even when you take off in first, you notice this ? Plug looks too new to tell me much. At next cold start up , determine if any cylinders aren't firing within 30 seconds or so.

Edit; make sure "choke" is fully disengaging at carbs when off; my bike will stumble in this rpm range unless choke is fully off.
Click to expand...

Thanks for the information from everyone. Not my first bike, just my first Suzuki. This forum is fantastic!
The plugs have 500 miles on them. The valves have not been adjusted since I have owned the bike. Not looking forward to the "shim" business! But the bike is clean with 18K so it's worth it! It looks like the choke disengages properly. I'll double check. The carbs were supposedly clean when I got the bike. I know I have to pull them, just asking about being lean before I go to it. And yes, the flat spot never goes away completely although when the bike is really really warmed up, and it's really really hot out, it gets a lot better. My last bike had pods, this looks like a huge pain! Thanks again!
View attachment 17017
 
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Nice find! get some covers for swing arm pivot or your pivot bearings will suffer. Basscliff has the stuff you need to know, so take advantage. Checking valve clearances is intimidating the first time, but plenty of us have muddled thru it. On these engines, the clearance wears smaller, and since it starts out at like .003 inch, it doesn't have far to go.
As an experiment, next time it's warmed up, peel back the air filter element a bit and go for spin to see if additional air changes this flat spot.
 
tom203 said:
Nice find! get some covers for swing arm pivot or your pivot bearings will suffer. Basscliff has the stuff you need to know, so take advantage. Checking valve clearances is intimidating the first time, but plenty of us have muddled thru it. On these engines, the clearance wears smaller, and since it starts out at like .003 inch, it doesn't have far to go.
As an experiment, next time it's warmed up, peel back the air filter element a bit and go for spin to see if additional air changes this flat spot.
Click to expand...
The covers Tom mentioned are available through Boulevard Suzuki if you do not have a local source. I tried to get some through CL/parting out ads, but wasn't successful.
 
BigD_83 said:
The covers Tom mentioned are available through Boulevard Suzuki if you do not have a local source. I tried to get some through CL/parting out ads, but wasn't successful.
Click to expand...

Will do. Thanks.
 
For your carb problems, you should contact TheCafeKid on this forum.
Perhaps he missed THIS thread?

Eric
 
I didn't see where anyone answered your question so I will tell you that, from what I can see from your picture, it IS lean. Ray.
 
rapidray said:
I didn't see where anyone answered your question so I will tell you that, from what I can see from your picture, it IS lean. Ray.
Click to expand...
Yeah, it sounds that way, but if he peeled filter element back for test spin, he could convince himself- filter might be overly oiled and he said "it felt low on power"
 
Change the o-rings behind the engine carb boots and do a valve adjustment.
If the airbox boots are hard replace them too.
 
tom203 said:
Yeah, it sounds that way, but if he peeled filter element back for test spin, he could convince himself- filter might be overly oiled and he said "it felt low on power"
Click to expand...

It was overly oiled when I got it but I cleaned and re-oiled it lightly. No change.
And today I tried it with the filter cover cracked open. Flat spot was worse.
 
chef1366 said:
Change the o-rings behind the engine carb boots and do a valve adjustment.
If the airbox boots are hard replace them too.
Click to expand...

Going to order the o-rings today and the swing arm bearing covers. Read the basscliff tutorial on the valve adjustment, and prepare for a big weekend!
 
Caferacernoc said:
It was overly oiled when I got it but I cleaned and re-oiled it lightly. No change.
And today I tried it with the filter cover cracked open. Flat spot was worse.
Click to expand...
The extra air from having the airbox open made the problem worse, so it does sound (and look from the picture) like you are running a little lean. Do you have any hanging idle/rising idle issues?

The flat spot might be helped by shimming the needle as it sounds like you are flatlining in the transition zone from pilot to needle jet.

I wouldn't worry about shimming/re-jetting until you get the other basic maintenance done. With the stock airbox and pipes, you should be right on for jetting with a stock carb setup.
 
BigD_83 said:
The extra air from having the airbox open made the problem worse, so it does sound (and look from the picture) like you are running a little lean. Do you have any hanging idle/rising idle issues?

The flat spot might be helped by shimming the needle as it sounds like you are flatlining in the transition zone from pilot to needle jet.

I wouldn't worry about shimming/re-jetting until you get the other basic maintenance done. With the stock airbox and pipes, you should be right on for jetting with a stock carb setup.
Click to expand...

I have a slight hanging idle. As in it takes a little too long for the idle to settle after you rev it in neutral. The main thing is this: You are cruising in 3rd gear at 2500rpm. You give it a good throttle twist. It surges briefly, then loses power for a second or two. Then "wakes up" at 4000rpm and pulls clean to redline. However, that pull to redline does not feel like 60bhp. And the power at 8000rpm feels the same as 5000rpm.
I'm hoping carb cleaning, new O-rings, and valve adjustment does the trick. But if I have to do something I feel a bigger main jet over needle shim.
Plugs are clean and white.

Thanks everyone!
 
Caferacernoc said:
I have a slight hanging idle. As in it takes a little too long for the idle to settle after you rev it in neutral. The main thing is this: You are cruising in 3rd gear at 2500rpm. You give it a good throttle twist. It surges briefly, then loses power for a second or two. Then "wakes up" at 4000rpm and pulls clean to redline. However, that pull to redline does not feel like 60bhp. And the power at 8000rpm feels the same as 5000rpm.
I'm hoping carb cleaning, new O-rings, and valve adjustment does the trick. But if I have to do something I feel a bigger main jet over needle shim.
Plugs are clean and white.

Thanks everyone!
Click to expand...
You were going to hear this from someone sooner or later, but the throttle position is more important than RPMs.

3rd gear at 2500 rpm is basically lugging the engine, and on my 650 that would be about 1/8th throttle; still on the pilot jet. If you crack it open there, and it bogs, that's more than likely going to be an issue with the needle. The mains aren't going to kick in fully until you are close to wide open throttle.

That's not to say that you are getting great fuel delivery in the upper range if you have no power, but it could be an air leak (i.e. too much air) giving you grief, not fuel issues (i.e. too small a main jet)

Get the air leak (manifold boot o-rings are suspect) solved, and I'd bet a beer you see an improvement in that transition zone. In fact, all of the basic maintenance should help out with your sense of low power and leanness.
Post some more pics as you go along, so we can follow your progress.
 
BigD_83 said:
You were going to hear this from someone sooner or later, but the throttle position is more important than RPMs.

3rd gear at 2500 rpm is basically lugging the engine, and on my 650 that would be about 1/8th throttle; still on the pilot jet. If you crack it open there, and it bogs, that's more than likely going to be an issue with the needle. The mains aren't going to kick in fully until you are close to wide open throttle.

That's not to say that you are getting great fuel delivery in the upper range if you have no power, but it could be an air leak (i.e. too much air) giving you grief, not fuel issues (i.e. too small a main jet)

Get the air leak (manifold boot o-rings are suspect) solved, and I'd bet a beer you see an improvement in that transition zone. In fact, all of the basic maintenance should help out with your sense of low power and leanness.
Post some more pics as you go along, so we can follow your progress.
Click to expand...

I agree. I will check the petcock and float levels too.
 
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