Wet setting carbs. Anyone have specs they can share?

Hi,

I'm rebuilding my carbs. I just received a bunch of parts from chacal. (thanks!).

I have an '81 xj550 maxim and after I get the carbs all pieces together, I will build a PVC carb stand I saw in someone's write up so I can "wet-set" the float heights.

Now, I ordered a service manual, but it hasn't come in yet, which I was afraid of.

I understand my carbs to be mikuni bs28's.

Could anyone please help me out with some specs?
I am lookin for the proper float height and the height that fuel should be in bowls from the base of the carb( hope I make sense there.)

Once I get these ironed out, I will fabricate the YICS tool and use my new carb sync gauges to sync these suckas up and hopefully well be in business!

Thanks in advance!

 

Sorry, I thought you were after parts sizes, specs etc!
Regs.

 

Wet set, clear tube spec.
3mm +/- 1mm

Ghost

 

Get your valves in spec first or you won't have much success trying to sync.

Float levels: http://www.xj4ever.com/setting%20fuel%20levels.pdf

 

Thanks for all the help!

You're right, BigFitz, i have valve adjustments on my todo list. I need to get these carbs squared away first.

So, i got all of the guts put into the carbs.. insides are fresh and clean. 3 turns out on the mixture screws.

Now I am doing the wet-set float adjustments... Now, this is the setup i have.. What is the best way to verify i have the fuel at the right height looking at it from the front?

 

nevermind - I measured 3mm down from the top of the bowl and adjusted the tabs on all floats so they're all the same. I did this on all carbs.

I set the carbs back up on the bike and now it just refuses to start. Killed the batt trying to start - charged it up, and tried some more... no go.. All of that work and excitement for nothing. Brewed up quite the cuss storm.

At one point i had it running every time i started it, but it died after 5 mins and it would never start again, which is why i replaced the needles, needle seats, pilot fuel screws (they were in baaaad shape).

I just dont get it. Any XJ geniuses in Utah interested in helping out for a few bucks? If so, let me know.

Thanks!
James

 

Did you then verfy EACH CARB, individually, with fuel? Matching one carb's wet setting "dry" won't cut it. Gotta wet-verify each one individually.

Did you do a nice accurate bench sync?

Pilot screws on 2 1/2 or 3 turns out on all 4 to start?

Replace the spark plugs. NGK D8EA. If your plugs got gas-soaked, they won't fire.

 

Yep... I copied the PVC carb holder that I saw in a writeup, purchased an aux fuel tank and checked the fuel levels with the hose connected to the drain on on each of the carbs float bowls individually. Ive cut corners a couple times already in the past and been bitten. this time, i have tried to be as thorough as possible.

I did not do a bench sync. Do you just eyeball the equal opening of throttle plates? Doesn't sound to be if you mention "accurate".

The pilot screws are currently 3 turns out on all 4.

I will check plugs. Thanks for the part number.

After cranking and cranking and cranking i eventually got the bike to start. Then i put into gear and tried putting back into neutral and it wouldnt so i had to kill it. You may have seen this in another post.

After i got the neutral thing sorted out, i tried to start the bike, and it refused to fire. im worried about wearing out the starter.

I will look at plugs and hopefully i can get it to start within the first couple tries.

 

Verify your settings using a "Wet Test"

But, I have had great success "Measauring" Float Heights, ... 'Dry"

Using the BEST Carb to pass the Wet Set, ... I MEASURE the Height of the Float Material.
Once I have that Value, ... I "Set" the other three too that Measured Height.

Normally, the measurement will correct any error in the Heights of the other three, .. when the Floats are matched to the Height of the correct one.

The "Measurement" should place you within specs.

But,, the final analysis is the Clear Tube Method.

 

Thank you RickCoMatic.

I am pretty sure i have my carbs pretty closely matched with the wetset method. I will take them off again and dry measure them. Although, i thought they needed to be measured at an angle with the float tab just resting on the needle. Is it OK to measure with them laying flat on the tops as seen in the pics you provided? Much appreciated for that!

That is a nice float-height-measurement-tool you have yourself there. Can you or anyone by chance verify for me the dry float height of the bs28's? 21.5mm sticks in my mind likely from another thread, but so does 17mm.

I measured 21.5 on a cutoff q-tip and used that as a guage. I would much rather have a tool.

James

 

On the subject of plugs.... I didnt really know the condition of mine.

Here they are... they are not WET.. looks like carbon as if the bike had been rich.

note that the carbs have been rebuilt. I have only ran for 2 minutes maybe. It is a realllll pain to get started.



I cleaned the plugs up a bit:



I then performed a compression test - Here are the results:



Compression seems consistent. Although, im not sure what number range is typical on these bikes. Anyone shed some light on that for me?

Thanks!

 

The readings are pretty even, that is good, a 14 psi difference is the max allowance. Standard is 156---min 128---max 171. did you test with WOT & air cleaner removed ? Gauges do vary & the length of the hose, ect.

 

Isn't the compression spec for the 550's lower than the 156 that the 650's and 750's use?

 

That would be cool if it was..

 

Im done for the night working on the the bike. it refuses to start.. I pulled the carbs and checked the fuel height.

I know compared to the pic that RickCoMatic posted, this seems a bit higher..

Does this appear high to you in the bowls? They all are about this height. Could this be a cause as to why the bike wont start?

(I know, ruler is not level)


Thanks!!!!!!!!!!

 

In the photo the level looks pretty good. It also looks pretty clear. Are you using gasoline to do the wet set?

 

Personally I would get rid of the Champion plugs and go with NGK. About the only luck I have had with champion is in my lawnmower, but that hasn't been great either. Just a curve ball here, but when you have a no-start condition do you have spark at the plugs??? All 4 plugs???

 

I made a the Tool.
I took a Mechanics Pocket Ruler with a Sliding Clip and Epoxied a Toothpick to the Slider.
Painted the Toothpick with a Red Magic Marker to look good in a photo.

http://samuelpesantescircle.blogspot.co ... nless.html

 

Thanks Biggs, Yup, that's pure 87 octane in there in an aux fuel tank hanging from above..

Thanks Skyhawk. I had read a few places that NGK was the preferred for the XJ's. I used to run NGK only when i had both of my Honda Preludes. Bigfitz suggested NGK D8EA. As soon as i read his post, i hit Amazon and ordered them (yesterday). Should be here tomorrow hopefully.. I love Prime.

Thanks RickCoMatic... I re-did the q-tip after marking the height on it from my drafting ruler.

So, throughout the day at work today, i skimmed through different threads in the forums. I found the float height for my carbs (21.5) I believe i had it off a bit yesterday.

Anyways, when i got home, i remove the carbs and reset the float height.

Also, i put some antiseize on the drain plug and pilot screws. I currently have my pilot screws backed out 2 1/2 turns on all carbs.

I also attempted a "bench sync" with a paper clip. Really i dont think i knew quite what i was doing. I just did my best to make sure all butterfly valves lined up.

I then checked the wet-set and they appeared to be a bit closer to the height shown on the left pic RockCoMatic posted.

I put the carbs back on the bike, hooked up my aux fuel tank and tried to start it. It refused to start...

Finally sucked it up and used some started fluid and it TURNED OVER and was running. It ran pretty rough for a few seconds the i blipped the throttle a bit.
I turned off the choke and It idled about 1500rpm on its own then slowly began dropping rpms...

I shut the bike off. I then tried restarting and it started, but it was running consistently about 3000rpm on its own. The idle screw (knurled big screw) isnt even screwed in to touch the throttle plate.

I shut it off and started again and it runs at 3000rpm regardless of choke on or not.

Here's something odd to me, maybe someone can help explain... the bike was running about 3000rpm.. since i had a aux tank hooked up, i put an awl inside the vac hose that connects to the hose that goes to the petcock from the 2nd carb. I pulled the awl out and the rpms dropped to about 2500.

So, at this point, i can get it to start with starting fluid and the rpms are pretty high.

Could it be because i dorked around with trying to "bench sync" and screwed it up? Or could it be because i am using pods?

Or could it be because i need to sync the carbs with guages? I have them, but i still need the YICS tool i guess.

Any ideas appreciated. Oh and all the help everyone has provided has been great! Thank you!

 

There's nothing wrong with Champion Plugs.
I have thousands of miles running Champs.
When you get right down to it; Plugs are pretty basic.

The hype is all Madison Avenue.