XJ550 BS28 Carb Float Height Debate

The Clymer manual says in the paragraph to measure 2.0mm from the top of the Float Bowl. But in the picture, it shows to measurement on the side of carb and 2.0mm from the bottom of the carb body. Which one is the correct one? I have asked my riding friends their opinions and its about 50/50. Need some more opinions for a tie breaker!

 

Carb body.. since you can't see the top of the bowl when it's fitted for wet setting - as far as I recall

 

Carb body. Like @a100man mentioned the top of the bowl is "inside" a lip on the base of the carb body so you can't measure from that surface. When taking into consideration the thickness of the lip and the gasket, I doubt there'd be much difference.

 

This is my current dilemma. I had to swap my original carbs for a spare set due to too many leak issues (tees, float pins, etc.) After getting the cleaned and refurbished ones wet-set on a level workmate bench set up, I installed and found even with enrichment screws 3 turns out the bike ran far too lean, albite in cold (50F) weather. Measuring the float levels on the bike on the centerstand, I get the following (photos). To add to the discussion, the bike, even when "levelled" on the centerstand by putting equal thickness wood slats under both wheels, has the carb bases tilted forward. I'm assuming the measurement should be center to the carb bodies per the red line. I'm very pissed right now that these seem off compared to me tedious and thorough bench level set, esp #1. I really, rally hate pulling carbs off and and on all the time to deal with the stupidity of having to guesstimate float tang bending ad nauseum.

 

Do the wet set off the bike, get it right before reinstalling the carbs.

 

Yup, wet set off bike once and be done. How are you determining that it is running lean? If super lean after wet setting and turning screws three turns then you have another issue i.e. vac leak or wrong jets.

 

The written paragraph of measuring from the top of the float bowl could it be a misprint? I will put a pic of how it's written #9. Thank you for your input.

 

What I find strange is, if you look at from the backside, the top of float bowl is visible with the gasket on top. The lip is not in the way, just the sides and front. So is the manual a possible misprint? I measured the bottom of the lip to the top of the float bowl. it is exactly 1.5mm. That is a big difference when my target is 2.0mm. Here is a picture. Thanks for help.

 

The fuel level is actually from the bottom of the bowl up so 1mm is not a huge difference, also the spec is 2mm +/- 1mm so in theory it shouldn't matter much. The pic they use is basic so I think they just typed it up as top surface as float bowl, the pic does not indicate the lip.

I've just set mine based on the base of the carb body, never had an issue.

I'll go back to my main question, what makes you think it is super lean? If it's that lean, 1mm difference in the fuel level isn't going to help.

 

I don't have a lean or rich issue, I just wanted to know the answer before I do a rebuild next week. The manual for the XJ550 is contradicting where to measure the 2.0mm from (side body or top of bowl). I also have a 1986 Maxim-X and it's manual says specifically to measure from the side carb body. Thanks for the input.

 

Sorry @Derrek Woodard , another member jumped in the conversation and I thought it was you continuing the thread. My bad, carry on!

 

But I DID the wet set off the bike, painstakingly, and with the carbs level. But when on the bike, they, by default, are not level, they angle forward a little. My photos show the clear tube held near the rear of the carbs, if they were held near the front of the carbs the gas meniscus would be close to level with the gasket.

 

Actually, my bad for hijacking the thread, but my issue is the same as Derrek's. I wet set at 2mm, based on the "lip" not the gasket, and its definitely lean. Maybe the measurement should be based on the gasket. I looked for vac leaks and could find none.

 

When on the bike and on the center stand, about all you can do is "sanity check' the bowl levels IMO. Its my opinion that the level even with an angled carb has to be compared to where the line of the main jet/emulsion tube is.
On my HS32 carb, that is down the center. So when the carb is at an angle the main jet pretty much stays the same (or close enough). I had an issue with my bowls and was checking my levels while on the bike. Here is my levels (we set XJ650 @ 3mm on the bench)
You can see how I drew a line from the bowl level across the carb. If you look at the center line of the carb where the emulsion tube is, its pretty darn visually close to the 3mm. This I call a "sanity check", not a method to set the wet level of course. I had a small level and wish I had taken a picture but I was able to hold be bubble level up to the carb to look at the alignment of the tube and the carb. My issue was the bowls were not filling fast enough due to the type of screen in the carb I had. I would run 10 mins, then it would go lean. stopped the bike, checked bowl level and they were noticeably low. I consider myself one of the lucky ones. Once making sure my floats were straight (not one float higher than the other), dry setting it put me within spec wet setting it.

 

So, for those XJ550 owners on here, what's your general opinion of the levels seen in these photos? Do they look correct to you, or "close enough"? If so, I've got a feeling that there is either a vaccum leak I cannot find or something else strange going on. She's very lean, and screws are way, way out. Once fully warm, the problem diminishes but does not disappear. Before someone mentions it, shaft seals are good.

 

Levels look a bit low 1-2mm maybe (#3 looks worst) - how are you detecting a 'very lean' condition?

 

I know I cant tell how far off they are from the pics, you would have to measure, I would say as a "sanity check" that does not look that bad. As I mentioned, its not the method to really tell exactly what it is. But you can stay its not far off if its not correct.
Lean at idle with the idle mixture screws out?

 

That's why I am leaning towards the 2.0mm measured from the top of the float bowl as my clymer manual states. I think measuring 2.0mm down from the carb body is the misprint.

 

In your case, maybe the 2.0mm measured from the top of float bowl is correct as the manual states. The gasket alone is 1.0mm, the lip is another 1.5mm and then another 2.0mm down from the lip? I am still leaning toward measuring from top of bowl.

 

Yeah, 3# look low partly because of the camera angle; most of the pics I tried to "line up" the bowls centre to the camera but not that one.

 

So I know its lean because even at 4+ turns out:

1. Starts and idles with choke on, dies without it until semi-warm
2. when starting out semi-warm, stumbles and hesitates unless choke is 1/2 on, runs OK with choke 1/2 on until hot
3. Idle speed (no choke) is low when semi-warm and gradually creeps up when bike is hot; idle is 1500 while decelerating but 1200 when stopped
4. Overall condition improves as bike gets hot, mostly no stumble and quick acceleration but still "off" as its a little "crispy" and not as smooth as with the old carb set
5. Plug chops at hot idle: 1 and 2 generally white; plug 3 just a little tan, plug 4 a little more tan but none quite into the sweet spot.

I know this bike well as I have owned and operated it almost every season for 36 years, so I know its not getting enough fuel in the mix. Check my (new) avatar, that odo rollover was 2 years ago.

 

Just one more wrinkle - somewhere is a manual or other document that shows the "dry" method, which IMHO is easier to do and had not failed me in the past, but it is also subject to interpretation. That one had the carbs off the bike, but upside down with the bowls off and gravity holding the floats against the pins. The measurement was without the gasket and measured from the carb body to the top of the round part of the float. If I recall the measurement was something like 17mm. The last time I rebuilt the carbs about 5-6 years ago, that's the method I used and it did not fail me. If someone has, or can find, that document/diagram, it would be great.

 

https://www.xj4ever.com/setting fuel levels.pdf