She Runs, But sputtering se-fla

[2bhappy]

I like the look of your bike with the wrong seat. I think it looks a lot better than the original. Very nice work. Beautiful paint.

Marc

[Viking500usa]

ok guys, after a rough running/ short warm up ride with no problems, I figure tomorrow I'll sync and colortune. tomorrow came and #2 and #4 are leaking gas- mostly #4 bad, I can see it with the airbox bottom off. cant figure it out. as I mentioned, Ive rebuilt the carbs (triple clean and a flush, only replaced paper - re-used all old metal parts), rebuilt the petcocks, I was getting ready to replace the rubber in the vacuum diaphram that came in the petcock kit. Made sure there was ventilation to the bowls, and almost possitive the lines are not kinked. Measured floats dozens of times - both sides of float. The needle is not getting kinked, I checked the travel path on all- looks great when testing dry.
One weird thing I noticed is #4 carb will drip fuel with petcock on prime. shut it off and it stops.

thanks for the help !
Don 79sf

[TopCatGr58]

Okay Don,

Prime just bypasses the Octy and sends fuel directly to the carbs, so IF your carb is leaking in Prime, then that points to the float valves! You said you didn't replace them. Did you look at them very closely to see if they had a little depresses ring around the tip? Per Prometheus, after years, a slight groove can get worn in the needles, which can prevent them from sealing properly. Also, did you take a drill bit and turn it backwards in the valve seat to clean up the mating surface, along with using some carb cleaner and Q-tips? You might be able to clean or smooth out the surface of the float valves with some very fine emory cloth, 1000 grit sandpaper or such? But they aren't that expensive, and "Prom" highly suggests replacing them!?

T.C.

[Ken Talbot]

On a Special, the petcocks control the flow of fuel out to the octopus, which is where the vacuum control happens to shut off fuel flow when the motor is not running. I figure you're looking at one of two scenarios:

1 - you have both a leaky octopus and at least one leaky float valve. If either of these is doing its job, there will be no fuel leak. IF there is a leak, both are bad.

2 - you might have the fuel supply hooked up to the wrong "T" fitting on your carbs. The top "T" on the early carbs is a float bowl vent while the bottom "T" is to supply fuel to the float bowl. If fuel is supplie dto the top "T", it is not being controlled by the float valves.

[Viking500usa]

Thanks for the tips guys, you are all great !
I did notice a very slight ring on the float needles, I thought I cleaned it up with a gas dampened rag. havent run a bit to clean the seat yet. paranoid I guess. I tried testing the float valves by turning the carb bank upside down and connecting a 2 lines to fuel the carb. didnt see no gas at all ! Im gonna try to clean the needle and seat up, try again. I dont mind if I need to buy new ones, think I saw some on partsnmore.com... I know I got the fuel t's right, so I got a lil more work to do....
Thanks again guys !
Don 79sf

[Viking500usa]

Ok, Back. I ran a bit backwards on all the float seats, checked the float needles with magnifying glass, saw the ring, it was very very light, sanded it out with 900 grit, reassemble. rebuilt the diaphram, had to read here that one side squeezes through hole.
I think I forgot to turn to prime when I tested the carb banks upside down. thats why I saw no fuel ?
So, If this doesnt work, My guess is I gotta buy new float needles and seat...?
thanks,
Don 79sf

[prometheus578]

small hint.

Testing carbs up side down:
"Carbs needles didn't leak when tested, but still leaked on the bike."
When you hook up the hose and turn on the fuel, remember that you still have air in the last few inches of fuel line to the carbs. You may not see fuel leaking immediately and think that the seal at the needle valve is good. But during this time, what is happening is that your piping is filling up and you're passing air out your valve. (How often have we all had to hear about that? My Ex used to complain about that all the time... particularly in elevators)
Be that as it may... after hooking up the fuel line and turning it on, "blip" the floats once or twice to get the fuel right up to the needle and seat. Dry with compressed air or papertowel and THEN watch for leakage.

[prometheus578]

Oh, sorry

Clean the seats with chrome polish and Q tips. You should remove them to do this, as you have that small screen underneath and don't need it loaded with polish. Usually, it's just the needles that have to go. I've replaced very few seats.

[skids]

Re: Oh, sorry

In fact, you can toss those stupid screens, replace the fuel hoses with new (in case you have any doubts about the need for the screens anyway), and install inline filters. I agree with the polishing recommendation as 900 grit paper could rough it up a bit too much. Don't leave any q-tip fibers in the process! One more thing...you said you rebuilt the petcocks. I don't know if you got a new "wavey" ring in the kit, but if you didn't, you can re-bend the ring so that it makes for a better seal in there.

Originally posted by prometheus578
Clean the seats with chrome polish and Q tips. You should remove them to do this, as you have that small screen underneath and don't need it loaded with polish. Usually, it's just the needles that have to go. I've replaced very few seats.

[Viking500usa]

Has anyone seen the thread on where I can buy new float needles ?
I thought I saw new floats @ mikes xs, same style as mine. but they all say they're for 650 models. same with the floats needles that look pretty close. will any work for the 1100? I have the screw in style float seat.
Just point me in the right direction. thanks !
Don 79sf

[TopCatGr58]

Hey Don,

MikesXS has the #48-5019 "set" which is needle and seat, screw in type for Mikuni BS38 style carbs, which is what you would want to get. They only sell the Viton tipped Float needle by itself without the seat! I would think(there I go again), that you could use the Viton tipped ones in place of the full metal ones, but Prom may have more learned info on this!?
T.C.

[prometheus578]

Any brand of bike shop will sell float needles. There are only about 5 or 6 different styles. Vitron or plain tipped, some have wire guides mounted to them, and some are longer than others.(fatter, too, I believe) I tried once swapping a vitron tipped for a plain one in one of my XS850's, but fuel then gushed out. But, then again... the replacement was a different style and longer(or shorter), can't recall. I was hoping to offset this by bending the float level tab differently, but it didn't take.
I see no reason why a rubber tip can't interchange with a metal tip, as long as the length and width of the needle are the same.
I'm home now, but first read this post at work right before closing. I wanted to check the book to see which float we used and then check the float needle box to see if there was another number that was comparable.(also to see if there was a change between rubber tipped and plain between the years of our models.)
Anyway.. long story short....I couldn't find the box of carb needles! Will check again in the morn, and then call the vacationing mechanic and accuse him of stealing them.
I don't know what Mike'sXS sells them for, but our shop charges $4.95 a needle. XS650 needles could very well be the same ones... or they could not. I'd need to check the application guide before shooting off my mouth.
The bike in question is a '79 SF, yes?

[mro]

needle and seat

From TC and others posts, I ordered MikesXS's 650 carb parts.

got needle, seat, gasket, for jets and three piolt needles.

cleaned and installed the parts. Finished adjusting the valves about 2 hours ago.

forgot to bench test carbs and just put them in.

no leaks and the XS fired right up and idled at 1000 RPM

let it warm up a minute and went for test drive.

Not bad, but need to vac sync carbs.


No BS, just good XS



mro

PS
Thanks for all the good advice this site provides
As soon as I get back ahead money wise will send a donation

[prometheus578]

"Oh, quit needlin' me, will ya?"

Well, seems the other mech took the needle box home for the weekend, and then took off, so I can't compare differences between plain and vitron tipped.
What I can tell you is that the '78-'79 E, F and SF take the all metal needle (K&L #18-8956)
The "80-'81 G, H,(standard), SG, SH(special) LG, LH,(Midnight special) take the vitron tipped needle(K&L#18-8944)
The vitron apparently has a wire clip on it that hooks to the float. Not sure, but I can only imagine that the clip is in case the vitron forms to the seat and sticks, the float will pull it back.

[Viking500usa]

Thanks for the help guys ! your knowledge is invaluable. I'll order me a set of what Tkat suggested and tinker with what I got. And next time I'll wait a bit longer for the gas to flow when testing the floats upside down style=)
I see theres alot of 650 parts that look interchangeable, maybe the floats? who knows?... lol
Merry Christmas and/or Happy Holidays with XS
Don 79sf