GS850G - Low Throttle Stutter - Excess Fuel Consumption

[vicimus]

This is a continuation of my GS850G Fuel Upgrades thread located here: http://www.thegsresources.com/_forum/showthread.php?t=158372

I figured I'd start a new thread with a new title.

Bike:
GS850G
V&H 4-1 exhaust
Stage 3 dyno kit (165 mains - the rest is stock besides larger slide holes and the air corrector that came with the dyno kit)
Emgo pod filters
Mixture screws - 4.5 turns out (as recommended by the dyno kit instructions)

I finally got back around to synchronizing the carbs last night. It was a pain in the ass to find the right settings, but I think all went well. The one thing I did notice is that the vacuum was around half of what I expected. Instead of the 11.25inHg on #1&4 and 10inHg on #2&3 I was aiming for, it was closer to 5-6inHg when they were finally synced. Is that because of the exhaust & air filter modifications, or am I just waaaay off of where I'm supposed to be?

I also tried adjusting the mixture? screws using the highest rpm method, but I couldn't notice any difference, so I just put them back to the 4.5 out that dyno recommended.

The problems I'm still having are a low rpm stuttering and stalling when I come to a stop light. I'm guessing I can fix the stalling just by increasing the idle stop screw.. but I'm worried about that. I've been moving that sucker around quite a bit since it revved up too high when I first started it, then decreased after that.

In addition to the stuttering problem, I took it out for a 25-30ish mile ride (just to get some road time in) and I went through half a tank of gas!! That's around 10mpg??

I never really got it above 4k rpm, with most of the time at around 1/4 throttle so I'm thinking it's just running waaay too rich on the pilot circuit? When I cranked back the throttle a bit it did have GREAT power and smooth running.

So which way do I turn those mixture screws to lean that out? In? Should that fix my stuttering? Are there any tips for the "highest rpm" calibration? What if at highest rpm it's still far too rich?

Wow, I tend to write a lot on these forums.. ha.

Anyway, any help would be really appreciated. Thanks all!

 

[crapwacker]

This is a continuation of my GS850G Fuel Upgrades thread located here: http://www.thegsresources.com/_forum/showthread.php?t=158372

I figured I'd start a new thread with a new title.

Bike:
GS850G
V&H 4-1 exhaust
Stage 3 dyno kit (165 mains - the rest is stock besides larger slide holes and the air corrector that came with the dyno kit)
Emgo pod filters
Mixture screws - 4.5 turns out (as recommended by the dyno kit instructions)

I finally got back around to synchronizing the carbs last night. It was a pain in the ass to find the right settings, but I think all went well. The one thing I did notice is that the vacuum was around half of what I expected. Instead of the 11.25inHg on #1&4 and 10inHg on #2&3 I was aiming for, it was closer to 5-6inHg when they were finally synced. Is that because of the exhaust & air filter modifications, or am I just waaaay off of where I'm supposed to be?

I also tried adjusting the mixture? screws using the highest rpm method, but I couldn't notice any difference, so I just put them back to the 4.5 out that dyno recommended.

The problems I'm still having are a low rpm stuttering and stalling when I come to a stop light. I'm guessing I can fix the stalling just by increasing the idle stop screw.. but I'm worried about that. I've been moving that sucker around quite a bit since it revved up too high when I first started it, then decreased after that.

In addition to the stuttering problem, I took it out for a 25-30ish mile ride (just to get some road time in) and I went through half a tank of gas!! That's around 10mpg??

I never really got it above 4k rpm, with most of the time at around 1/4 throttle so I'm thinking it's just running waaay too rich on the pilot circuit? When I cranked back the throttle a bit it did have GREAT power and smooth running.

So which way do I turn those mixture screws to lean that out? In? Should that fix my stuttering? Are there any tips for the "highest rpm" calibration? What if at highest rpm it's still far too rich?

Wow, I tend to write a lot on these forums.. ha.

Anyway, any help would be really appreciated. Thanks all!

Did you over oil your pods? Just a thought...

 

[vicimus]

Actually, that was another question. The description when I bought the pods said that it wasn't necessary to oil the one's I have, so I didn't. Were they full of sh*t, and should I oil them anyway?

 

[SqDancerLynn1]

Your most likely too rich DJ 165 is a big jet Try one of the smaller jets from the kit

 

[BassCliff]

Hi,

Is that 165 jet a Dynojet size or Mikuni size? (DJ and Mikuni use different criteria for measuring their jets.) Stock main jet for the 850 is a #115. For pipes and pods you'd normally start with about 4 sizes up, which would be a Mikuni #125 main jet. Did you change any other jets with the DJ kit?

These are the stock jets for the GS850 ('80+)
Main Jet = #115
Main Air Jet = 1.7
Jet Needle = 5D50
Needle Jet = X-5
Pilot Jet = #40

When you were synchronizing your carbs, did you set your idle at about 2000 rpm? Use the idle set screw or the throttle cable adjustment at the handlebar.

When adjusting the idle mixture screws, turning them in (clockwise) leans out the mixture. Turning them out (counter-clockwise) richens the mixture.

And I found this on some guy's website:

Plug Chops-Highest RPM Methods
(by Mr. tkent02 and Mr. psyguy)


Thank you for your indulgence,

BassCliff

 

[vicimus]

Is the main jet even having an effect on low rpm riding? I'm talking under 1/4 throttle to just over 1/4 throttle. I barely had it above that.. though when I did, she sure was fun

 

[vicimus]

@BassCliff - It was the 165 from the dynojet kit. I didn't realize they were different than standard mikuni jet sizes.

I did synchronize at 2k rpm, though I definitely had some issues where it would rev up to 4k and I'd need to keep adjusting the idle stop screw (definitely overheated at some point to judging by the discoloration on my #1 exhaust header now.) #3 & #4 were giving over 12-15 inHg at first while #1 & #2 continued to show around 5 inHg. When they were all even-ish it ended up being more towards the 5 inHg side of things.

Actually, while I'm on that subject... I read on here that they should all be EVEN instead of the two outer carbs being higher when using pods because it's the airbox that creates that difference? Is that bogus?

 

[Guest]

Your most likely too rich DJ 165 is a big jet Try one of the smaller jets from the kit

Same one I have in my 850.

 

[Guest]

The DJ kits are for the K&N pods. You'll be fat all the way around with those cheapo pods and the stage three DJ kit.

 

[salty_monk]

Your most painless way to cure the problem is to either switch to the K&N pods or buy the cheaper V&H ones that Ape sell.

Dan

 

[vicimus]

Is there a good way to test if it's the filters? Would running with no filters help me troubleshoot?

 

[vicimus]

Anybody? Before I spend another $130 on filters?

 

[Guest]

Anybody? Before I spend another $130 on filters?

Cant hurt to try as long as you dont run it for miles. Run it without the filters and see what happens.

 

[vicimus]

Guess I'll try it around the block tomorrow morning and see how she runs.

@Octain, you said you have the 165's from the DJ kit? Do you have aftermarket exhaust and K&N filters too?

I was thinking if it still runs poorly with the pods off completely, that I'd try decreasing the main jet size and see if that helps.

 

[TheCafeKid]

Where are you guys getting these instructions? 4.5 turns out is rediculous! That's the top end of adjustability boardering on wide open. There is the reason your bike is sucking gas. Put the pilots at two and a half or three turns out, max. Stock pilot jets. Use em. Adjust the needle clip down untill the surging and popping go away. Either the third clip from the bottom or one above or below. Four and a half turns is recockulous. You're like the third person I've seen post that and I'm thinking someone made a misprint in your instructions. Mine say 2.5. Everyones I've see. Say 2.5.

 

[vicimus]

@TheCafeKid - Check out the 3rd image in this posting. http://www.thegsresources.com/_forum/showthread.php?t=157035

The last part mentions 4 - 1/2 turns out. I read that as 4.5 turns, though I guess it's more likely read as 2 turns. I've already re-adjusted down to 2 turns with a highest idle adjustment after that. Since I haven't gone on any longer rides with those settings, I've no idea if the gas is still getting consumed as fast. I do get some popping in the exhaust now though and my stuttering problem is still there along with poor idle & stalling.

The plan is to try running without the pods (short distance so I don't get crap in there) to see if that helps the stutter, then if that doesn't help I guess I'll pull the carbs again to make adjustments, starting with re-measuring the floats.

Should I be playing with the messing with the needles first, or downsizing main jets?

Pilot jets are stock.

 

[vicimus]

Ok, so we've finally got a few nice days coming up and I hope to get this thing running right, or it's off to the dealer to buy a new bike and off to craigslist with this one. Such a shame after working on it for so long and being so close, but I'm missing out on riding!

So... this morning I pulled off my pod air filters completely and it still stumbles at low rpm. I'm assuming that eliminates the pods as the cause of my problem.

According to the dynojet troubleshooting guide, I'll be checking my floats again and raising the needle up one notch. We'll see if that helps over the next few days.

 

[Guest]

Where are you guys getting these instructions? 4.5 turns out is rediculous!

DJ, duh!!
Mine is set "around" 5 turns out.
Must be an 850 thang..

 

[vicimus]

I took the carbs apart this evening to check the float height, and a few of them were way off... adjusting those and it runs much better. It still stutters, but not nearly as bad, and I can cruise without much stuttering. I'm hoping a sync will fix it right up!

Now the bad news -- that float post that I "fixed" with epoxy is totally f'd. The epoxy is like rubber now.. not steel, and it's only been a couple weeks!

 

[Guest]

I took the carbs apart this evening to check the float height, and a few of them were way off... adjusting those and it runs much better. It still stutters, but not nearly as bad, and I can cruise without much stuttering. I'm hoping a sync will fix it right up!

Now the bad news -- that float post that I "fixed" with epoxy is totally f'd. The epoxy is like rubber now.. not steel, and it's only been a couple weeks!

What brand of epoxy did you use?