1980 XJ650 Carb Tuning

Alrighty gents, just came in after an interesting start. I've watched videos and read threads on how to do this but im guessing that i dont have the order of operations right. First question is do you leave the petcock open on the fuel supply for the whole time or do you shut it off once the bowls are full? (I also don't know how to tell when the bowls are full aside from every carb leaking fuel) I cant figure out how to get a stable level, when the petcock is open, the level climbs well above what it should. Is my fuel tank set too high? If i shut it off, by the time i get the air bubbles out the fuel level is too low because it all ran out. This is what im doing, I have cycled the drain plug and run fuel through a few times before measuring. I leave the petcock open, close the drain plug to let the fuel run out of the clear tube. Lift the tube up for measuring, open the drain plug and make sure no air bubble come out. The petcock is open this whole time and at some point, all carbs begin to leak fuel everywhere and the level in the hose rises and rises until it is coming out of the top of the hose. So i shut the petcock off, the fuel runs out of the hose, and the bowls finish leaking the excess fuel on the floor. Its a mess, but when i try to do the same procedure with the petcock off the fuel level isnt enough to even measure.

 

Your floats must be sticking open, you need to inspect them, doing it is just like the video. Watch it again...
Petcock stays on all the time until you remove the hose for setting the floats if need be , once you get the air bubbles out of the line lift the hose against the front of the bowl and that's the setting.
Reinspect your needles and seats, they may be installed wrong or something, maybe they are of low quality, you may need to replace them ?
Are you using a level, I don't see one one in the photo.
The correct measurement level of fuel in the hose when it is against the carb base is the most lowest level of fluid in the hose or the bottom of the curve of fluid in the hose.
Be precise as you can take your time.
I spent about 3 hours doing mine and on the last test I found a needle and seat that decided to leak then I replaced them all and did the whole resetting all over again. they leak intermittently. Then I took them off the bike again because I didn't like how it ran and reset them again. Carbs off and on three times this summer !

 

I have been at it for 5 hours, it is the same every time no matter what adjustments i make. The first carb spits fuel from the intake side passages and ruins any chance i have at getting an accurate level. I have checked the float and needle and it depresses the needle closed, and springs back every time. I have spares from a kit i got awhile ago but the ones in it look brand new. So i guess for the past 5 hours ive made no progress. I suppose i can try to replace the needles with the ones i have on hand, but this has been soul crushing.

 

Old viton tipped float needles are guarenteed to be perished after 10 years, let alone 30.
Also make sure that the spare tank you are using for a fuel source is spotlessly clean. Even a little fleck of rust can prevent a float needle from sealing.
Were the crush washers for the float needleseats replaced? Some are fiber, and those do fail eventually.

 

Here's a pic of the #1 float needle that seems to be not working. Silver with a black rubbery tip. Part if the issue is I don't know what the seller used to rebuild these and when. The rest of the bike is in good shape for its age along with the tank. I've checked for rust many times before and its still good and shiny. So do you gents believe that the float needles are the primary cause of the bowls overfilling? or is there something else I need to check? Ill replace all 4 just in case, but the #1 has been extremely all over the place reading-wise for obvious reason. No possible way to get a static fuel level. This has also probably sent the fuel floats off as well as i had been adjusting to the false readings for a bit before i realized there was no stopping #1 from leaking. (Oh and yes the carbs were leveled front to back, side to side that's why the zip tie was on top to get the front to back level good.)

 

did you do a wet set of the fuel levels in the carbs?
you may just need to adjust floats.
your needle assembly looks new. does the pin on bottom near clip have a springy action?
Setting the fuel levels

have you checked to see if you can stop fuel flow by holding up the floats to cloose the needles?

 

Sounds like you need to get a set from Len at XJ4ever part's
Needles and seats.
It's a huge learning experience and nice to have it working correctly when it's all said and done.
Don't use any ethanol fuel.

 

Just went out to test the #1 again by oversetting the float so it would close very early and it seemed to work for a second, it definitely took longer but alas it still overflowed. The float cant push the needle into the seat any further, its like they're not long enough or something isn't fitting right. I suppose i will try to get new ones. The xj4ever site has many part numbers so i'm not sure which one to get and aren't cheap. Due to budget constraints i will not be able to purchase these for some time.

 

I think that's what needs to happen-e mail Len and he will let you know what you need.

 

Before I email him can any of you identify the ones I'm currently using? Do they resemble the correct ones or no? I cant seem to find images of what the right ones look like, just part numbers that yield no image results.

 

That's interesting -viton perishes? It would explain why they leak with no visible sign of wear.

 

They look alright just likely low quality, doesn't really matter at this stage.

 

Time...Viton is not supposed to wear out, but the combination of age and wear agianst the needle seat adds up to eventual leakage.

 

screw in needle seats?
shouldn't they be slip-in with an o-ring seal?

 

if they were Mikunis, yes. Since it's a 1980 XJ650 I believe we are dealing with Hitachi carbs here.

 

I spoke with Len and for ethanol fuel they recommend the metal tipped valves. Also explained how the valves i currently have don't work because they get cocked at an angle when the float presses on them and they don't seal. This I recreated myself and was able to pass air through it quite easily. Hopefully this is the core of my problem and I can get the carbs working once i have the proper valves. 5 hours of checking incorrect wet levels has at least made me fairly quick on tear-down/adjusting/build-up.

 

Correct. Hitachi carbs.

 

I wouldn't recommend using ethanol fuel unless your bike is going to be a every day driver ,if non ethanol fuel is available in your area and your bike is going to be sitting for long periods of time it absorbs water.
There are some additives you can use with ethanol fuel to reduce the affect of the fuel but I'm not sure how well they work ?

 

Depending on location, NOT using it is not always an easy or readily available option. It is only recently that non-ethanol gas has become more widely available, thankfully.

https://www.pure-gas.org/ The map, while entertaining, isn't that easy to use. I use the list (links by state at bottom of page.) My bike is much happier running real gas now.

 

Just checked that map of gas stations and it seems I'm pretty distant from any of them. If fuel additive works I may do more research into them but I'm unsure an hour drive to VA beach is worth a tank of gas. In other news I busted budget and ordered those valves from Len because I wanna get this thing running in order to surprise my father. He was in the Air Force at Clark Air Base in the Philippines and raced a midnight maxim. Said the bike had to be torn apart many times due to their quality gas with dirt floating in it!