Rejet Help - Stalling out in gear - SOLVED

[BushidoBrown]

Hey folks, I searched for existing threads on rejetting, but I feel like my situation had a mixture of issues from those so here goes:

I'm rejetting an 07 GS500f with a K&N lunchbox and an ebay slipon. I picked up a rejet kit from Buddha, and just finished reassembling everything. She cranked right up after priming so I was like . But alas that was short lived. Bogged and stalled out on the first test ride. Here's what i've observed so far:

147.5 main
Stock mid
20 pilot
1 washer on needle (oddly enough, there was already a washer on the needle even though everything else was stock )
3 turns on mixture screw

Right after rejet:
Cranked right up - smooth idle @1300
rev increase w/ throttle in neutral
In 1st under load stalled out at 3k rpms
Revs increase normally when clutch pulled in.

No leak @ intake boots - tested with carb clean around boots

follow up test:
Idle raised = slight hanging idle
Idle lowered = idles rough

at 67 deg. mild humidity - cranks w/out choke. Dies when choke is opened.
Pulled plugs - noticeably darker than before rejetting.

I'm assuming this means I'm running rich, should I back off the mixture screws?

Im also not sure what to do with the hose coming from the pair(?) system. It was attached to the stock airbox before, but it's not in any of the walkthroughs so i let it hang in the mean time.
Solved:
SHE LIVES!!!

My hunch was correct. Turns out I did not properly reinstall the slide needles on the diaphragm side of the carbs. On the CV carbs the plastic cap above the needle should snap into place. On the tutorials I read, they all talked about not forcing the needle so you dont damage it. That made me afraid to use too much pressure when putting them back together. Clicked them in, put the bike back together and bam: POWER EVERYWHERE! Newbie mistakes lol

Thanks to all you ladies and gents for helping me work through this. You're the real MVPs 

[Big Rich]

Both plugs are darker? Usually stalling when dropped into gear means you're running on one cylinder. With the engine at idle, pull one spark plug and see if the engine dies. If not, reattach the plug and try the other side (and don't touch any metal on the bike while holding the plug boot!).

[BushidoBrown]

Hmm, good question - I only checked 1 plug. Ill check the other and then try pulling each while running.

[BushidoBrown]

Ok, so upon further inspection the left spark plug is a little dark, but nowhere near the right one.

After I let it warm up some,  I pulled the left plug and the bike kept running. On the other hand pulling the right plug kills it.  Whats the best course of action here? Should I assume this was the case before rejetting or could this be a result of it?

sidenote: this is my first bike, so I'm learning from scratch here.

[Suzi Q]

Rejetting in and of itself would not cause a misfire unless you jostled something when removing the carbs. Looking at your previous posts, I can't get a feel for your history with this bike. Did you just buy it?

[Big Rich]

So it's running on the right cylinder only. Check the vacuum hose from the left carb to the frame petcock - if it's not connected the carb won't deliver fuel.

But knowing that you were in the carbs, take a look at what else could be wrong. Float level height, missing oring, etc.

[BushidoBrown]

@Suzi

I bought it last summer off craigslist as my first/learner bike.  Changed the oil, oil filter, and put in new spark plugs then rode till about march. Took it to a shop to get the carbs cleaned then because it has always bogged a little letting the clutch out.

Aside from cosmetic stuff, I've replaced the rear shock w/ a 04 Katana shock and upgraded the fork springs with .95kg ones (I'm about 235 w/ gear)

this is my first shot at real mods (Rejet, lunchbox, and slip-on)

@ Rich

I'll break it down again in the AM and see what I find. How do I check float height, Is there a good thread on that?

[Suzi Q]

Yeah so if you've been riding this thing without issue, it sounds like something changed. Check the things Rich stated. Here's a thread on floats:

http://gstwins.com/gsboard/index.php?topic=26604.0

Post '01: must be 13mm + - 1mm.

[Big Rich]

Good thread Suzi Q!

Bushido, at the beginning of that thread it mentions checking the height with some clear tubing. See how small the float bowl drain nipples are? You'll need some tubing that fits (tightly) over that. Raise the free end of the tubing above the carb, and open the drain screw. The fuel "should" come up to the same height as the float bowl gasket.

[BushidoBrown]

Ok, so here's some pics from the tube test:

Left

The left side has WAY more fuel than expected. The tube filled up to passed the bottom of the gas tank. What should I do here?

Now that I think about it, when I was taking the bike apart the left carb took way longer to drain than the right. I've seen threads where peoples floats are stuck, maybe that's the case here?

Right

The right one looks about right. Gasket line is about at the arrow.

[Endopotential]

Looks like the float needle / seat on your left carb is shot.  That much fuel going to the left carb would flood it, and kill the left cylinder.  You can try to re-bend the flange on the carb float, and just test it on a bench before putting it back on your bike.

I have an '07F and  did pretty much the same mods as you, and the same jet sizing.  Currently running great in that combination.

When you take your carbs apart again, also make sure that the choke cable runs smoothly back and forth. Sometimes it can bind at the plate at the front of the carbs.  If you can, also try to run the bike with the gas tank and air filter off (jury rig a fuel supply from a plastic bottle or funnel) to make sure your slides are moving appropriately with throttle changes.

I ended up doing away with the PAIR system and all the vacuum lines on mine, including the stock petcock.  Lots of good threads on that mod.

Welcome to the club!

[BushidoBrown]

Thanks Endo! It's been great till this weekend Looking forward to it running right.

Question for you:
When you say test the carb with the rebuilt flange on a bench what do you mean by that?

Update:

I pulled it back apart to check out the left float.  The height is correct-ish at about 12-14mm (measured looking through a plastic ruler). When i tilt the carb it and the needle move freely. I opened up the other one for reference and seems to be in sync with the right carb.

Put it all back together and the left cylinder is firing intermittently now. Not sure if jiggling (technical term) the float did something.  I started to tear it down again and took a look at the tube before pulling the carb and now the left carb fuel is leveling in the right place. I don't trust it though.

Gonna look for leaks in other places check out the choke cable.

[The Buddha]

Grrrrr damn man, I have O rings sitting in my charlotte house, I'd have tossed in those if you had told me.
Anyway they're not too bad to buy 1-2. Try and match it up at the local auto parts store. I just got back to Columbia from charlotte and am not going there for weeks again.

Cool.
Buddha.

[Endopotential]

Question for you:
When you say test the carb with the rebuilt flange on a bench what do you mean by that?

I meant that before going to the trouble of installing it back on the bike, you can leave the carb sitting on your workbench and fill up the fuel line with a funnel or something, and test the float level that way.

Important to get an idea of what kind of an angle the carbs sit on the bike; I'm not sure the bowls sit perfectly level in situ. 
FYI, most Iphones have an angle/inclinometer built in so that's a quick way to check rough angles.

There are those white plastic disc things at the top of each carb.  If you got rid of the PAIR system, make sure you cap them off well to prevent vacuum leaks in the system.

[The Buddha]

Question for you:
When you say test the carb with the rebuilt flange on a bench what do you mean by that?

I meant that before going to the trouble of installing it back on the bike, you can leave the carb sitting on your workbench and fill up the fuel line with a funnel or something, and test the float level that way.

Important to get an idea of what kind of an angle the carbs sit on the bike; I'm not sure the bowls sit perfectly level in situ. 
FYI, most Iphones have an angle/inclinometer built in so that's a quick way to check rough angles.

There are those white plastic disc things at the top of each carb.  If you got rid of the PAIR system, make sure you cap them off well to prevent vacuum leaks in the system.

The angle they sit on the bike is irrelevant, that's why they have those 2 air chamber floats.
But yes on all the other stuff. Vacuum leak as all the rest.
Cool.
Buddha.

[BushidoBrown]

I meant that before going to the trouble of installing it back on the bike, you can leave the carb sitting on your workbench and fill up the fuel line with a funnel or something, and test the float level that way.

Ah i see - working smarter there.

Update:
So after messing with the left float more, it seems to no longer be overfilling


I got some new plugs and after running for a minute or so with the choke open there aren't black like the ones from last night.

Now the less than desirable -
The left cylinder is still firing intermittently. In addition, she doesnt want to idle w/out the choke anymore. I also noticed that open choke is only revving to 3500 as opposed to 4k. If I close the choke she dies, and if I try to give it gas she dies.

Found a tear in the T shaped gasket/hose that runs from the carbs to the vent hose. Carb cleaner on it jumps the revs, so it seems like a leak. That seems weird though, because i thought air was flowing out there. Gonna replace that piece though

Random thoughts:
I ran the bike a few times without the airbox just to see how it was responding to throttle - the slides are sort of fluttering instead of sliding open smoothly and uniformly. is that normal?

Still getting an arc on both plugs.

[Big Rich]

I'm not familiar enough with the later carbs to be much help, so somebody else will have to chime in on that. But as far as the slides fluttering - that's normal on CV carbs in my experience. Especially at lower rpms.

[BushidoBrown]

Ok Progress:

I gave the carbs another good clean. Used compressed air through all the jets and channels. Patched the leak in the vent hose with some electrical tape till that part comes in.

Now she runs perfect at 4k w/ the choke and she'll idle at about 1300. Left cylinder is playing nice again too

Throttle = smooth climbing through the rev range.

Now though, when i release the throttle the revs drop to about 700 rpms where either it will fight back up to idle or slowly die off.

Thoughts:
Im running it off a funnel - runs better in prime mode, not sure whats up there.

I think i read on another thread that idle rpm drops after turning the throttle are a rich condition. Thinking about switching back to stock pilots and seeing what happens.

[J_Walker]

just as I was about to chime in about the later model carbs..  sounds like you got it though.

as far as prime mode goes. if you have a inline fuel filter, just remove it... if not, look down into the gastank with a flash light, there's a screen/meshy like thing for the primary petcock, is that clean? I have an old tooth brush broken in half screwed to a metal rod, that I have used for scrubbing at the  screen a little bit to make sure it isn't clogged. only other thing maybe is the vacuum line has something clogged/blocking it. you can pull it off and cut half a Qtip, and with a coat hanger, CAREFULLY push the qtip through.

[BushidoBrown]

Never occured to me to check the vacuum lines

Good call, ill see what i find