Running rich -it's not making sense

[jetmechmarty]

It's too cold to be out riding, so I put aside some time for tinkering. My SG has been rich since I did a carb overhaul a couple of years ago. Before that, my plugs were scary white.

When I did the overhaul, the jets were replaced with genuine Mikuni. The pilots are stock size. I don't remember what I put in the mains. 110 on 1&4 and likely something fatter in the middle. With the white plugs I had 120 in the middle. I used K&L kits with their float valves.

So, today I decided to see where my fuel levels are. 1, 2, and 3 are 5 mm from the top of the bowl. #4 is 7 mm from the top of the bowl as that's the one I had the post welded. The bike is running on the center stand with a block under the front tire. The levels are the same static or running.

I'm running rich, and the levels appear to be low. I get 28-30 mpg under normal operating conditions.




I'm not sure when I'll have time to work on it again, but I'd like to have a plan before I do.

[mack]

needles

What needles do u have. All tuning starts with those! U may have different carb bodies. The jetting follows the carbs passages not the motor. Also marty please give us the exhaust and intake configuration on the ride. K&l's have a smaller inlet size so I doubt that thats whats causing the colour however if you used K&L float needles, it goes a long way to explain the incinsistent float levels. they are absolute junk and must always be set manually. They will work but extra care must be used to get the shut off point within 2-4mm of the lowest edge of the carb body. (in line with the bowl washer +/-.

[jetmechmarty]

SG with stock airbox. Exhaust is Jardine 4 into 1. The slide needles are the same ones I was running when it was lean.

[trbig]

Fuel level in the bowls has nothing to do with jetting. Sounds like your float needs some tweaking. That being said, fuel levels will change running rich/lean. So you can mess with your float levels, or you can mess with your jetting to match your float levels.

OR... go fuel injection and tune it with a laptop? lol.

[jetmechmarty]

Fuel level in the bowls has nothing to do with jetting. Sounds like your float needs some tweaking. That being said, fuel levels will change running rich/lean. So you can mess with your float levels, or you can mess with your jetting to match your float levels.

OR... go fuel injection and tune it with a laptop? lol.

I think I'll leave the jetting alone. I'll change the fuel level next weekend and give it a go.

[BA80]

What do your plugs look like after just normal cruising Marty?


I have a couple of things in mind that could be a cause. Since the mains really do nothing but feed the needle jet/jet needle system up until about 3/4 throttle I would say that the pilot or needle jet/jet needle system is where the issue is.

What kind of mileage were you getting before the changes?

[jetmechmarty]

What do your plugs look like after just normal cruising Marty?

What kind of mileage were you getting before the changes?

It has been a while since I looked, but I believe my plugs are sooty. I used to get 35 mpg. The low fuel light used to come on at 100-105 miles. Now, it's 85-90 miles. I've been running like this for quite a while. Any jet changes were only the mains and if anything, I went smaller.

[BA80]

I am working on another members G carbs right now, he was getting lousy mileage too. Pulled them apart and all jets were aftermarket and the brass washers that go under the main jets were all gone. Had to hold the jet needle up with my finger to get the mains out because without the washer the jets will not hold them where they belong.

Also, he had 2 diaphragms with pinholes in them.

One thing you need to watch with the late carbs is SOME used larger jets in the middle and all the needle jets were the same but SOME others used all the same size jets but the 2 center needle jets had fewer bleed holes.

A couple 3 things to look at.

[motoman]

Marty, I had the same issue with my Venturer when I rode it to the 2014 Colo. West Rally.....to rich. Got back home checking my running fuel levels and they were low, very similar to yours. The K&L float needle's tiny spring doesn't hold the same tension and are very erratic in that sense compared to the Mikuni float needles. What I surmised and corrected is the low fuel bowl levels needed more draw to get correct fuel amount, and when it did draw fuel enough, it was more than needed. After some 1200mi. of putiing up with this(Pikes Peak climb was the worst and would hardly run anything above idle) and 33mpg, I adjusted float levels a few times in order to get fuel levels back up to 3mm down from carb body. Now they are 2mm down from carb body and a bit on the rich side. I haven't as of yet(my accident on the ST last summer still has me cutailed from correcting exact fuel levels). Even though rich, it did run super smooth under load at ALL rpm levels. Plugs were black, but with the Honda VF coils it fired perfectly. At this point, at least I figured out the rich issue. BTW, The Venturer is using stock OEM Mikuni pilot jets and 4 stock 110 OEM Mikuni main jets. Hope that helps with resolving your bikes rich running issue. Mileage wise, if all correct, my Venturer normally gets 38-41mpg on a LD ride at a constant 70-75mph with its stock final drive.

[BA80]

I am working on another members G carbs right now, he was getting lousy mileage too. Pulled them apart and all jets were aftermarket and the brass washers that go under the main jets were all gone. Had to hold the jet needle up with my finger to get the mains out because without the washer the jets will not hold them where they belong.

Also, he had 2 diaphragms with pinholes in them.

One thing you need to watch with the late carbs is SOME used larger jets in the middle and all the needle jets were the same but SOME others used all the same size jets but the 2 center needle jets had fewer bleed holes.

A couple 3 things to look at.

Should say needle jet......

[jetmechmarty]

OK. I really don't believe I have issue with pinholes, missing washers, or mismatched pilot jets. I already checked and rechecked that. The K&L float valves are the fly in the ointment. I probably have the originals someplace. Maybe I should put them back.

It won't cost me anything to futz with the fuel levels, but it will be at least next week. Yes. It runs great. It just has poor fuel economy and stinky exhaust. Every time I go for a ride I have to fill it up three times.

[BA80]

OK. mismatched pilot jets.

Not pilot jets, needle jets.......emulsion tubes.

Since it was OK before but not since the changes you made, the logical place to look is where you made the changes.

[bikerphil]

Maybe your air filter is dirty and/or the exhaust is carboned up/restricted, JAT

[jetmechmarty]

Not pilot jets, needle jets.......emulsion tubes.

Since it was OK before but not since the changes you made, the logical place to look is where you made the changes.

Yes. The only thing that was changed was the float valves. It's probably the issue.

[Bonz]

An SG will be 110 mains across the board, and the SG will have different a needle taper than the G from what I understand.

As has been said, float levels don't control an overall rich or lean condition, they control throttle response to the extent is it rich or lean when you roll into it. Float level too low (fuel level high) and it is rich at throttle application, float level too high (low fuel level) and it gets a lean stumble at throttle application and starves for fuel leaned over in a long corner. I learned this stuff from months of work grafting ZZR1200 downdraft carbs onto the ZRX side draft head. Carbs are carbs and the XS is no different.

Go with what you are thinking, try the old float needles. You can take some 3M label/adhesive remover on some terry cloth and clean the needle tips to try and remove that ring. It's not compressed rubber but usually gunk that has stuck itself to the rubber above and below where it seats giving the impression of an indent. Again, learned the trick re-using float needles in the ZZR carb graft onto the ZRX.