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Trouble starting 79 550E

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Have read most of the posts on carbs etc (and thanks)... I have a 79 550e that I'm starting for the first time in 2 yrs.. Removed carbs, used air and fine wire to clean main and 2nd jets.. Checked float bowls ok. Spark good on all four cylinders. Here's the trouble.. the bike will start and rev high by spraying carb cleaner, but will immediately die once the cleaner is used up.. I have new plugs in the bike. I'm at a loss at this point. Is this a symptom of weak spark? Timing off?.. One other thing, when the bike is running on the carb cleaner and I open up the throttle, the engine bogs and will only run on closed throttle. Help is appreciated !
 
Re: Trouble starting 79 550E

Calzuki said:
Have read most of the posts on carbs etc (and thanks)... I have a 79 550e that I'm starting for the first time in 2 yrs.. Removed carbs, used air and fine wire to clean main and 2nd jets.. Checked float bowls ok. Spark good on all four cylinders. Here's the trouble.. the bike will start and rev high by spraying carb cleaner, but will immediately die once the cleaner is used up.. I have new plugs in the bike. I'm at a loss at this point. Is this a symptom of weak spark? Timing off?.. One other thing, when the bike is running on the carb cleaner and I open up the throttle, the engine bogs and will only run on closed throttle. Help is appreciated !
Click to expand...

Have you changed the fuel in two years? if not I would.

Does the petcock work as it should? Are you sure the fuel goes down into the carbs?
 
It sounds to me like Karens bike when we first got it , I think your choke circuts are still plugged. This will require removing the carbs and more of the compressed air, small wire treatment. Safe Riding, Bill
 
Thanks for the replies.. It is new fuel, and I checked the bowls for fuel by removing the drain plugs.. there's fuel in the carbs. I'll check the choke circuits, once I figure out what those are !
 
On the right hand side of the carbs there is a tube that goes down into the float bowl. This is the inlet for the choke circut. There is a passageway in the float bowl that lets the gas into the area where the inlet tube is. Then it goes up the tube makes a turn to the rear of the bike and down to the choke assembly. Hope this helps, Bill
 
Bill+Karen
Thanks! that did the trick... two of four were blocked. cleaned the passages and reassembled and it started first try... Now.. the next problem. When I give it a little throttle it bogs.. I'm running individual pod filters with stick jetting
Tim
 
I have no experience with that, due to stock filters and I'm a chicken. My best advice would be use the search feature in this forum, it has been discussed often. Safe Riding, Bill
 
I suspect your 79 550 and my 79 750 use the same type of slide mikuni carbs. I have the same characteristic on my bike and there is nothing wrong with it. The bike will start fine on the enricheners
(choke circuit) and it will run on the enricheners. Try letting it run without touching the throttle and controlling the rpm with the choke. As it warms up, you should have to keep reducing the amount of choke to keep the rpm from climbing. When it idles at about 1000 rpm or so without any choke, very slightly feed in some throttle, if it sags, add a slight touch of choke. Balance the throttle and choke to keep it running at just above idle. Once warmed up, you can throttle freely and it should be fine. With the old slide mikuni's you will notice though that even when the engine is fully warmed up, if you instantly advance the throttle from low setting to wide open. there will be a bog. This bog is because of the design of the carbs. The slides are throttle position controlled which means air intake volume through the carb is increased before fuel flow is increased, so there is a momentary mismatch
in fuel air ratio until things can readjust. If you twist the throttle in a steady, progressive manner, you will never notice this characteristic.

Earl

[quote="Calzuki" Now.. the next problem. When I give it a little throttle it bogs.. I'm running individual pod filters with stick jetting
Tim[/quote]
 
Unless the bike has been fitted and running with stock jetting and pod filters for some time and the plug colors have been determined to be correct, I would keep a close eye on the plug colors and mixtures. Usually, changing from a stock air filter to pod type results in a leaner mixture and it may be necessary to richen up the carbs a bit.

Earl

[quote="Calzuki" I'm running individual pod filters with stick jetting
Tim[/quote][/quote]
 
Since the choke system had blockage, it would be safe to assume that some other jets are at least partially plugged. Pull and check the mains, pilots, and the emulsion tubes (the tube that the mains screw into). If there is a tar-like residue, it needs to be soaked in carb parts cleaner, brushed with an old toothbrush, sprayed out with Gumout and air-blown. Do not soak any rubber parts (the emulsion tube has a tapered rubber gasket). Check the jet needles to make sure that there is not a buildup on them (opening the throttle brings them up to where you can see/clean them without disassembly). All of this is on the assumption that there is no blockage higher up, as in the internal passages or the air-screw area.

One other possibility is that your carb mounting boots are old and deteriorating - this causes cracks and air leaks that will dramatically lean out the carb mixture.
 
Hey Gang

Just an update. The bike runs fine on choke, and by spraying carb cleaner on the boots I'm pretty sure there are no air leaks.

Apart from the bogging when I put the throttle on, I am sure I do have a problem with the petcock. She runs fine on prime, but when I switch to the run position it quickly drains the bowls.. I'll check into that tonight, and once its resolved I'll go back to working on the bogging problem.

Again, thanks for your input and suggestions.

Tim
 
Update .. the bogging and the petcock are related problems... I removed the petcock, and by sucking on the vacumn line was able to have fuel come out of the main fuel line.. So the petcock works. However, in running the bike I don't think that there is enough of a vacumn off the carbs, as the fuel doesn't flow in volume when on RUN or RES... So I think I'll have to remove the carbs again and check on cleaning out the circuits that create the vacumn.

However, on the good news side I was able to start and run the bike quite well with the petcock on PRIME.. In fact, it runs quiet smooth and without bogging on prime, so at least the jetting with the pod filters is not too out of whack..

More on the carb vacumn line later.

Thanks, Tim
 
the pod filters may be the reason why the vacuum is so low, can you return to stock airbox? quite a few members have found exactly the same problem when trying to run pod filters
Dink
 
I have the same problem.

I have the same problem.

After cleaning my carbs my bike runs the same way. I did a total tear down, diped em, new O-rings, and blew everything out with air.

I have not ballanced them yet, and I assume that this is the reason. I have a ballance guage set, just not enough time to spend on my bike as of yet.

My wife and kids are going to her folks for Thanksgiving on Tuesday.

As soon as I get home Tuesday evening I'll be running into the garage.
 
Even if you had a brand new set of carbs and a petcock, you would still be running too lean. A motorcycle with pod filters and stock jets is going to run VERY lean. You may get away with it if you just go on shorter trips,but if you went on a long ride the engine will be much hotter,your plugs will be white or glazed white and you risk piston damage,valves,etc...Pods make a HUGE difference in air intake,and I've never seen any bike run decent until the main jet size is increased and the jet needle is raised up. 'Bogging' can be caused by too lean a mixture, not just too rich.
When I was 17 my uncle gave me a 6 year old Yamaha 305 twin, totally stock except for pods.I rode all over town for months, but just short trips.One day I went for about 25 miles and pulled up to park.I turned off the key but the engine kept running.It ran for about 20 seconds.It was running so lean and hot that for those few moments it did'nt need spark to ignite the gases.I was innocent up to that day, then I entered the wonderful world of jetting. And later that week I had the bike jetted right, and it ran a lot stronger. Do yourself and the bike a favor,re-jet. KK.
 
Thanks for the advice.. Had a chance just before thansgiving to run the bike a little bit longer, an 8 mile loop. Clearly there are still a few bugs.. she runs fine with the petcock on prime, but runs out of gas on main/res.. So I've still got to fix the vacuum on carb #2... Question: is the vacuum strong enough that you can feel it ? ie. can you put your finger on the vacuum hose with the bike running and feel the suction? or is it normally too weak.

The other thing I noticed is that she won't rev past 6500.. again, probably a fuel flow/mixture thing..

And I will definitely look into getting larger main jets... Any idea where they can be purchased?

Regards, Tim
 
I would imagine you can feel some vacuum at hose. Be certain hose has no cracks, if in good shape(I'd replace anyways) then I doubt it's your carb. Check for any dirt in petcock,also I hear the diaphram in petcock fails sometimes,I don't know if you can buy one or if you must buy entire petcock, but I bet if hose is good, and petcock is clean,then it's the diaphram. And besides larger mains, you will need to raise the jet needle.Move the clip down 1 position to raise needle, should get you closer to correct mixture in low to midrange, sometimes you need to raise it more. Every bike I have ever seen that is stock but had pods needed AT LEAST 1 position richer at needle. Remember this is assuming your needle position IS stock,you need to check with a manual or dealer to know what your stock clip position is. The needle actually has the most influence in typical driving.The main jet BEGINS to take over at about 2/3 throttle and completely takes over fuel flow at 3/4 throttle and beyond. This is according to my factory shop manual and the operation of your carbs is same as mine. You can buy mains at dealer, or any parts shop(may have to order). Generally,to test needle/midrange you run bike (somewhere safe) at 1/2 throttle for about 1 minute, then shut off throttle,pull in clutch lever,and turn off key immediately.Check plugs for a 'tan' color on the porcelain around center electrode. If a'gray' or darker color, then you are too rich. If a 'white' color, then you are still too lean. To test mains the procedure is the same, except you run at full throttle,so please find a safe place.Also, I wonder if you have the correct heat range of plug. Check to see that plug number is stock.Someone may have put in a 'colder' set of plugs to try to compensate for a leaner engine set up.Also, take a rag, the plugs will be way hot. But first make sure petcock is flowing fuel correctly or jetting won't be accurate. Good luck,let us know how things go. KK.
 
IF you are hooked up to the correct vacuum outlet (#3 carb, right next to the throttle cable connection) and it is not blocked, then you should get adequate vacuum with 3 exceptions:

1) That cylinder has a problem with compression - a motor is basically a big air pump that gets a supercharged kick during combustion. If that air pump is not working correctly, then there won't be the vacuum at the inlet (carbs). Example: if the intake valve is not closing all the way, the pressure of compression will bleed back into the intake tract and nullify the vacuum.

2) There is an air leak in the intake tract. Cracked boots are the most common cause, but I have also seen loose clamps, missing synchro-hole bolts and even holes in carbs(!).

3) Synchronization for that carb is way off. If that slide is up more than the others (and it doesn't take much), the extra air can dramatically lower vacuum.
 
In posting the previous, I was noting the vacuum takeoff as it is on my GS1000, but the 550 carbs are more similar to kz650 carbs (22mm?). I just looked at a pair of kz650 carbs and the vacuum is off the front (motor-side) of #2 carb while the bowl vent comes off the back of the carbs. Is that how yours are?
 
Thanks for the updates.. Did a bit more work on the bike yesterday, and its really starting to come together nicely. Had to buy a rear caliper which I did via ebay. It arrived ok, and I now have a working rear brake.. The only remaining thing will be to fix the jetting and the vacuum, which is off of carb #2 for the 550.

I contacted motorcyclecarbs.com and they have the sizes I need for jets etc. Anyone have any experience with those folks?

Thanks for all the advice.
 
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