idling / starting "issues"

[tab1324]

I fixed up an 82 XJ last summer and rebuilt (cleaned) the carbs a few times. I never did anything other than the "bread tie" synch job on them and it ran pretty well all year. This year, it's running about the same. It start s little tough sometimes and you have to let it warm up a bit before riding otherwise you have to rev it higher and slip the clutch in first gear or it will kill.

So the question is - will a synch job fix this or am I looking at a jet or choke problem. The idle is "fairly" smooth at @1000 rpm. Could maybe be slightly smoothed out - jets or synch???

The other item owrht mentioning is that I have a quite dirty air filter. I need to replace it but haven't done so yet. Could this cause or contribute to any of the above?

I don't know what else to do to the carbs other than just replace the jets. I'm planning to get together with 2fast to synch the carbs soon so hopefully that will smooth out the idle.

Any suggestions?

Tom B.

[prometheus578]

Dirty air filter restricts the airflow, resulting in an overly rich mixture. What do the plugs look like? Carbon fouled?

[Ken Talbot]

Carb jets are simply bits of brass with a hole drilled through them. They really can't wear out, but they can get dirty. Ditto for the various small passages and orifices that the gas and air are supposed to pass through for he engine to run properly. When everything is clean, your bike shold be able to idle fairly smoothly down to 600 or 700 rpms, not that you would want to leave it set that low all the time. Tough starting indicates you may be looking at dirty passages or jets in the low end areas such as the choke circuit. For example, right at the bottom of the float bowl, there is a very small jet that controls fuel flow up the brass tube that sticks doen from the carb body to supply fuel for the choke. Being at the bottom of the float bowl, it is one of the first places to get plugged up. I'd say you're due for another go at cleaning the carbs.

[Snow]

An air compressor, a blowing tool, a couple screwdrivers, a small punch (for removing float pins), and an hour of your time can get stubborn carb problems cleared out quite nicely.

A buddy of mine has an '82 Nighthawk 450 that has run like crap for years. Lately it has been spewing gas from some little brass nipples between the carbs. So, we pulled the carbs off and removed the floats (don't want to damage these!). Next, I removed the jets and sprayed compressed air through each of them a couple times (look through before and after). Then I spray air through every single hole I could find. After that, we assembled the carbs and installed them.

I tell you what, I didn't really expect this to stop the leaking but it did. It also made it idle so smoothly that we thought the cylinders weren't hitting right. It's now got more power than it had over the last 5 years and starts very easily. Before it would take fiddling with the choke for about 5-10 minutes to finally get her started, now she just fires right up. On both cylinders even.

[Hepcat]

I couldn't resist putting my 2 cents in.

It's possible to "wear out" the jets. But probably only through egging out the holes when cleaning them. The first time I worked on a carb, I did just that. Dad came out to see what I was up to and noticed the dental pick I was poking into the holes. He let me finish that carb and then pointed out the error of my ways. From that point on I've only used a cutting torch tip cleaner or fine, soft (copper, aluminum, or brass) wire, and that's only when carb cleaner and air pressure fail (or air pressure is unavailable). It's amazing what an overnight soak in one of those little buckets of carb cleaner does, even after air pressure and tip cleaners.

I've taken a very fine drill bit to the passageway inside a jet once or twice if I couldn't get it clear any other way. But that's only a last ditch effort and you've gotta be willing and able to replace the jets if you're gonna try it. We did it on a 2 cylinder Honda 350. In order to balance both carbs we ended up enlarging the other hole with the same bit to match the first. Ended up working well when we changed air filters to allow a little more air flow.

Good luck!
Jon

[fxrer]

Ken,

I too have a persistent cold start problem with my SG. When cranking with the enricher full on, the bike will catch on one cylinder, then two. It will chug roughly for a few seconds, then catch on the third, then after maybe 30 seconds, at ¼ throttle, the motor will sputter and run roughly on all 4. When I push in the enricher, and give more throttle to compensate, the motor hums to life. When warm, the motor sings, runs very smooth, makes lots of power, and I only hear a light puffing/popping from one cyl (I think #2) on closed throttle deceleration. Plugs look perfect, light gray/tan color.

I have cleaned the carbs several times, most recently last summer. I paid special attention to the enricher “plungers” and the cavities they fit into. The problem goes away for awhile, but then gradually reappears. I am running 4 oz of SeaFoam in the tankful now.

The specs in my manual note a “starter jet” size of 25. For an E model, it is 40, and for an F and SF, it is 32.5. Where is this “starter jet”? Can I get a larger one? Any other thoughts?

Thanks

[Ken Talbot]

Fxrer - have a look at this. I finally found the picture I posted a while back showing a jet at the bottom of the float bowll that often gets overlooked when the carbs are cleaned:


This jet supplies fuel to the tubes that supply the choke or enricher circuit.

If you get any sediment at all in the float bowls, guess where it settles?

[fxrer]

Hey Ken,
Wow, what a great picture! Crystal clear - looks like about 3 megapix, on “hi” resolution? What model is that float bowl? Standard, or Special? Is there a difference? I have had my carbs (SG) apart umpteen times and I never saw that jet. And I’m sure I had the gaskets separated from the bowls, because I dipped the latter in cleaner at least twice. From the picture, it looks like it is installed into the mating surface of the float bowl, and would be underneath the gasket? If so, how does the gas flow there? Is it removable? What’s the best way to clean them?
I guess if the SeaFoam shows no improvement, I’ll have to pull my carbs off again (grrr!), remove the floats and clean the #### out of those suckers!

[Ken Talbot]

The floatbowl in the picture is from a standard, but the specials are the same.

The fuel gets there from the hole with a sort of collar around it that you see immediately below in the picture. The hole is not quite at the lowest point of the bowl, but it is so low that it is very prone to collecting fine sediment.

There is a hole in the gasket for the brass tube that sticks down from the body of the carb, so you should be able to see into and clean this jet without removing the gasket.

Wearing eye protection, spritz a bit of carb cleaner or gasoline down to the jet. Because the jet is so far down, it is almost impossible to poke it clean with a piece of wire, but a dental pick will get you in there. You should also be able to press the rubber tip of an air gun to the hole at the bottom of the bowl and blast any last bits out.

(BTW - I originally shot this at 6 megapixels with my Fuji S7000, then cropped, resized, and saved to 'low quality' to get it back to a more reasonable file size for downloading.)

[fxrer]

OK Ken, thanks for that lucid explanation. I have a spare set of carbs, pulled off a float bowl and sure enough, I could see the hole, and way down into it, the jet. I knew of this passage before, but I just never that there was that tiny little jet down there. I am sure I spritzed cleaner through these holes, maybe just not enough. Is that the “starter jet” which is size 25 on my bike, and larger for earlier models? Can it be changed for a larger one? (I can’t imagine how).

I think I can pull just the bowls off my carbs without removing the entire bank. I will then spray those offending little boogers.

As you explained, fuel flows from the bottom of the bowl, up through that jet, through the brass tube, and into the enricher passage way. Any other places in the passage that are prone to get dirty and cause a problem?

In this process, I also checked my petcocks, and have some questions. See next thread. Any Ideas?

Thanks again!

Rick

[fxrer]

Sucess!

Ken,

That did the trick! I removed all the float bowls and sprayed those jet passages with carb cleaner. Two jets were clogged and I cleared them with a fine needle. Put it all back together, and the bike starts from cold instantly, like it did when new. Wish I had known about this 10 years ago!

Thanks a million!

[Ken Talbot]

Another satisfied customer! That's what we like to hear....

[satanloses]

Hey Ken I bought "kits" from Partsnmore and I seem to remember the gasket covering the top of this starter curcuit jet do i need to cut the gasket to allow it to be open?

[John]

The long slender brass tube that protudes down into the bowl area is the pick up tube for the starter curcuit. The hole in the gasket must be open to allow the tube to enter the small well in the bowl it self.

[satanloses]

Sooo It had to be open for me to get the Bowls on? Correct