Trouble starting 79 550E

[Anonymous]

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 !

[kz]

Re: Trouble starting 79 550E

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 !

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?

[Bill + Karen]

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

[Anonymous]

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 !

[Bill + Karen]

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

[Anonymous]

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

[Bill + Karen]

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

[earlfor]

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]

[earlfor]

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

[Don Lobacz]

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.

[Anonymous]

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

[Anonymous]

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

[Dink]

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

[Anonymous]

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.

[KEITH KRAUSE]

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.