Future GS550 owner reporting

[roeme]

(...)Just to see if I am right: If the spark plug is wet, it could be weak spark, weak coil (also if cylinder 3 is just fine?), too rich mixture in general (or due to carburator float issue). ?(...)

- Weak coil: not impossible but unlikely if one of the two respective cylinders is firing. In this case, it is way more probable that the high tension cable, spark plug cap or in case of a cap with resistor that the resistor has failed, or the spark plug has fouled enough to short out (i.e. no gap anymore).

That, or an spark plug with an integrated resistor has been combined with a spark plug cap that also has a resistor. While usually there's still enough oomph to get a spark, it'll be weak and it doesn't take much of anything else being out of whack (see above), and you'll have no spark.

I haven't yet seen a weak coil (i.e. not enough to fire) on my bikes, they were either fine or dead. One bike was not not firing on a single cylinder in one case (coils were fine), the other bike wouldn't come alive and just stumble (one coil had failed, the other one was fine).

From my understanding, the transition from a coil working to failed usually happens quite quickly, not much in between. But maybe someone with more experience than me can chime in.

Too rich: can be due to
- needle valve not closing correctly because of fouling/contamination.
- damaged floats, but be aware that none of the 30year+ floats in my carbs have failed (yet?).
- float level setting wrong - but be aware that the tabs won't bend just for fun. Somebody would've tampered with it
- Air/fuel screw setting screwed(eheheh) up. Doesn't also happen by itself (again tampering), but all four would be wrong at the same time.
- clogged air passages, generally clogged up carb
- some more, but...

...don't assume that somebody has done shoddy work on the carbs. I suspect electrical. If you have one and know how to use it, take a multimeter with you, stick the probes in spark plug cap #1 and #3, measure resistance. Expect 15kΩ (spark plug without resistors, if resistors present, add 5kΩ per resistor) resistance. If you don't get continuity, or a much higher reading either the caps are bad or the coil has indeed failed (to distinguish you have to disconnect the plug caps and measure directly at the high tension cable). Intermittent reading is very likely a bad spark plug cap.

(All of this assumes VM22SS carbs).

Edit: resistance readings

[Luuk]

Thanks Roeme for the technical info. This Saturday we'll go and see what the GS is like. For the record, yesterday passed all tests, finally I have my motorcycle license. 👌🏼😁

[Luuk]

Hi Guys.
Now proud owner of an 1980 GS550E
Unfortunately the spoke version I visited was in a poor state. Luckily this 1980 version was close by. All 4 cylinders are running, rides well, good brakes and suspension. Unfortunately low compression on cylinder #4. Head nuts all torqued to spec. I'll see if Marvel magic oil will do any good 😉

For now I am happy. Due to oldtimer regulations here in the Netherlands I can only ride it starting from March. Currently stripping exhaust, front fender, to clean it all up. Fixed the play on the tank cap.

The guy I bought it from never had real issues and rode with it in the mountains in Germany.

(any good image sharing service to add multiple pics in a post?)

[steve murdoch]

Congrats on the purchase.
Before removing the exhaust i would apply some heat and/or lubricant to the bolts at the collars.

[roeme]

Hi Guys.
Now proud owner of an 1980 GS550E
Unfortunately the spoke version I visited was in a poor state. Luckily this 1980 version was close by. All 4 cylinders are running, rides well, good brakes and suspension. Unfortunately low compression on cylinder #4. Head nuts all torqued to spec. I'll see if Marvel magic oil will do any good ��

For now I am happy. Due to oldtimer regulations here in the Netherlands I can only ride it starting from March. Currently stripping exhaust, front fender, to clean it all up. Fixed the play on the tank cap.

The guy I bought it from never had real issues and rode with it in the mountains in Germany.

(any good image sharing service to add multiple pics in a post?)

Congrats. Funny regulations...but you don't want to run these old machines on salty roads anyway, kills them slowly.
Yes, we need pictures! For image sharing I usually recommend imgur.

As mentioned in the newbie thread, I recommend having the valves adjusted soon (unless you know they have been adjusted recently). Also check all the other stuff mentioned there.
As soon as this is done, you'll have one of the possible reasons for weak compression eliminated.

Congrats on the purchase.
Before removing the exhaust i would apply some heat and/or lubricant to the bolts at the collars.

Also, when remounting the exhaust, add high-temp anti-seize to the bolts, and DO NOT OVERTORQUE, the aluminium threads strip easily.

[Luuk]

[steveb922]

Nice! Same colours as mine, and looks pretty unmolested.

[2BRacing]

Congratulations Luuk, that is a fine-looking 550 you have there!

One new thing you need to be aware of, is that the tap on the fuel tank is set to "Prime" in the photo above. You should not leave it in that position for longer than about 30 seconds. In the "Prime" position, fuel is free to run from the tank to the carburetors all the time, even when the engine is not running. Fuel can overflow from the carburetors into the engine, diluting the oil.

You should turn the lever on the fuel tap so that it points downwards. This is the normal "Run" position, and fuel can only flow from the tank when the engine is running and the vacuum-operated diaphragm in the tap has opened to allow the fuel to flow.

When the lever on the fuel tap is turned towards the front of the motorcycle, this is the "Reserve" position to be used when the fuel level in the tank is low. In this position, the fuel can also only flow when the engine is running.

Spend lots of time reading all the good information here on this website, so that you become familiar with all the "do's and do not do's" of owning these great motorcycles.

[Luuk]

Thanks for the replies. Indeed I forgot to switch it back. The seller must have switched it to prime. Tank and seat are taken off now to see what we have underneath and to replace O rings and valve check this or next weekend.

[GSXR7ED]

Welcome Luuk!

Nice story and great lookin' 550. She looks Beefy...like a 750...that's what I got.

When you are permitted to ride, take pics with beautiful country side backgrounds!

Ed