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loss of power. Fuel issue suspected ? Gs550e

ukjules

ukjules

Forum Sage
A problem for you guys - loss of power. Fuel issue suspected ? On gs550e 4 cylinder

After fitting a new starter motor the bike has run fine until ran it down to almost reserve and started onto 3 cylinders .
(I am sure it was just 3)

Status at riding:
Very smooth running for 30 miles but then lost power and felt like on 3 cylinders when nearing reserve . Filled up at a garage , no change but got home another 20 miles no probs with loss of power.
Charging system can be assumed ok as I get 14.5v running with handlebar tester.
No kinks in fuel line. Breather pipe on.

- one thing that had changed was I had to take off the fuel filter as broke so running without one for first time in years. This is the only change but was ok before this !!

Test when home:
Check plugs for spark. All good spark
Plug 3 was black !!!!! , the others were fine. This plug 3 being black is new and was not like that before.

Id say at tick over it's smooth it's when throttle up and into max that it feels likes it's on 3 cylinders .(Whatever jets do that work - can't recall )

Do I'm assume :
Off with carbs and check and clean carb 3 jets ? And don't as all know run old bikes with no fuel filter ?

Thoughts would be useful to spare me totally strippi
ng all my carbs ....
 
Gosh just me, I like cheap and easy first. I'd try a new plug in # 3. Sometimes, no clue how, a plug will fire in open air but not when under compression. Hate to remove and clean carbs then find the #3 plug was the problem.
 
I will do that tomorrow change the plug for another OR .....
NO I'll swap that plug for another on bike and see if it transfers.

I think (and I'm sure you do too) this is gonna be dirty jets on 3 due to no fuel filter.
 
P.s - as I have to put on a fuel filter anyway which is easier with carbs out as so tight and dealing with such difficult bends I'll treat as a maybe for now. Until exhausted all easy options.
 
Wouldn't want to change anything on cylinders that are doing fine .. A good used or new plug for # 3. Unless the filter inside the tank has been removed or damaged, I never saw the need for any other filter. Those things are so fine a gnat's butt couldn't get through it.
 
The filter isn't necessary, actually not recommended either especially on gravity flow system. The petcock screen and screens in the carbs should catch any debris. Personally, I've never had one on any of my GS's. Lots do though.
Just sayin.

If you swap plugs instead of replacing, a neat trick I learned from another form member here to clean old plugs without damaging them is to use a torch and heat the electrode till it glows red. This burns off any crud and won't damage plugs works like a wire brush could.

Good luck. Always something with these old bikes...
 
It’s interesting that #3 cylinder on my 1100 started giving me fits, I chased it for darn near a year until I replaced my ignition with a Dyna. End of problem for me, and I had had my carbs off no less than 6 times for full tear down and cleaning. Sooooooo you might consider that as well and do the checks on the pick ups and such.

V
 
- I am not using points , have an electronic ignition system. I'll get the name/make when I wake up. Been finding for 6 plus years like this.

This morning I'll swap / replace plug on a run. Will update. Remember all plugs good spark when testing.

More info.
Needed fuel when I took bike out but went to 100 miles on one tank before it started loss of power - 3 cylinders. When it started loosing power like on 3 cylinders I put on res but may not have needed too.

I stopped and filled up with quality fuel.

All plugs were perfectly clean with wire brush when I took it out. On return 3 was black and it was lacking power probably on 3 cylinders.

The carbs have been off and back on a lot due to changing starter motor. This now fixed and iv realised I can just get started out without taking carbs off !

I have never had a bad plug !! Must be lucky but never ever had one.

I have had dirty jets on other bikes and possibly this one but I don't recall.

I am slick with carbs and could in a morning have them all cleaned and ready to put back on..... But I really don't want too..... As I do agree it starts then off / on scenario. I think off / on 4 times is my record and prob didn't help on another bike.
 
You stated you added a (new?) starter and removed an old fuel filter. Those are the clues.
Did it run properly before the new starter? Before you disposed the filter?

If it was running good, then you changed only one thing and it immediately started running poorly, well there's your answer (probably).
But I couldn't glean enough info from your initial post.
 
Starter not the issue that sorted.
Yes it ran fine before starter. It is not a regulator issue either

Details after as informed. Yes removed fuel line with filter to just a new fuel line. Ran fine till fuel got low then went on 3 cylinders and is like that still . One plug black. All plugs spark fine in test.

Update question :
But surely if it seems to 'tick over' smoothly seemingly on all four cylinders and it seems to splutter in medium to high revs it would point to jets ? I can't remember but different jets support different rev bands ? It could be the higher rev ban jets blocked on carb 3.

What's think ? But yes will do plugs first !! And report. Will do now !! Await results

P.s thanks as always for assistance
 
That's what I thought at first but I have filled up to brim.and zero change , continued on 3 cylinders (which I think Is no 3)
Madly I didn't pull off leads to check ...only just thought of that.

Plug 3 and 1 swapped. 3 being the one that was black. No need to remember all this I'll update.

- run with plugs swapped and see if issue follows.
- if in 3 cylinders find which one by pulling leads. How I didn't think of that yesterday is beyond me.....
-additional spare plug / plugs at the ready just in case

We are doing the cheap easy tasks first until I start on the horror of carb cleaning.
 
Diaphragm in tap is leaking fuel down vacuum line to number 3 cylinder. Try for a short run, 50 mile or so with vacuum spigot capped and vacuum pipe to number 3 cylinder plugged to seal vacuum. Run with tap on prime, but make sure to turn tap to run when parking bike. That will hopefully stop fuel flow to carbs.
 
@ UK GS nut
That is a very good shout and I seem to remember this exactly same thing happened to me on my Europe tour and you yourself assisted in the fix... (I may be wrong ) It turned out to be exactly what you have just said !!!! I had to spend a week in Amsterdam in a tent with the carbs out in a field.... A wonderful time I had there but distracted in the wonderful city. Pic attached. (Sept 2016) Good times.
I can remember someone from this forum commenting on my cup of tea...... On my work area.

I will make that the next test...

BUT - new results just.
Ran the bike and pulled leads off at tick over.
Bike lost power in 1,2 cylinder.
3 and 4 it barely changed ? Remember three was the black spark plug.
With this test I had swapped plug three with plug one..... The plugs may be a red herring

Should I test the coil ? Easy to do and jnhave spares.

What's think ?
 

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You can switch the coils to see if the problem follows.

Don't see any mention of valve clearances. If you haven't checked lately, now is a good time.
 
What is the center to center mounting dimension? I seem to recall that the 1980 550E petcock had some odd feature, a tickler maybe?, not sure if that's important, but I do know that it was unique. Most 1980 GS's used the leverless petcock, which is 50mm spacing. Most other GS's use 43mm, or maybe it's 44? Can't remember. There are various petcocks on the market from the likes of K&L which should work. Just make sure the fittings point the right direction and that the height of the petcock doesn't hit your carb tops.

Edit: and I missed the part where you tell us how long since your last valve clearance check...
 
Not enough info to diagnose online, but this summer the petcock on my 1100G became a problem. Fuel starved below just half a tank.
Decided after 30,000 miles the screen was clogged, so I replaced the petcock with one off eBay. Works great now.
 
The valves recede into the head with mileage, so the clearance goes down. Running perfectly for months/years is immaterial. I'm not saying the valves are the problem, but they could be, and I know one thing for sure: they must be checked regularly, or your engine may be damaged.
 
Do what??? You say "I can't pin down which plug is black", Heck post pictures and I'll try to pin it down for you... Your first post said "Plug 3 was black!!!!" the others were fine. This plug 3 being black is new and was not like that before. I don't understand what you're trying to say.
 
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