New to 4 cyclinders- Compression???

[pcaden]

Hi GSers,


I just got my hands on a 81 GS550 and I am trying to test a few things out before I get rolling on this. Bike only has 16K miles so I assume its okay but I always want to check. I have always had V Twin or parrallel twins (I have an XS 650 Bobber that I built). when I turn the motor on my V or twin, I hear a distinct breathing of the engine and some friction and my twin is in great shape.

Question: without taking my bike to a shop to get it checked out, should the engine make a noticable sound when I turn the rotor? It makes sound when I turn it, but it is very weak sounding and I am not hearing the breath that I hear out of my other bikes. Just curious as I do not have testing equipment.

Any help is appreciated.

Another unrelated thing, I see that the GS parts sites that I have been to have 14mm wire caps and 10-12mm wire caps. Why? I have a 81 GS550T maybe the different models. I am surprised how much the book doe snot say.

Anyway thanks,

Pnedac

 

[gearhead13]

Hi GSers,


I just got my hands on a 81 GS550 and I am trying to test a few things out before I get rolling on this. Bike only has 16K miles so I assume its okay but I always want to check. I have always had V Twin or parrallel twins (I have an XS 650 Bobber that I built). when I turn the motor on my V or twin, I hear a distinct breathing of the engine and some friction and my twin is in great shape.

Question: without taking my bike to a shop to get it checked out, should the engine make a noticable sound when I turn the rotor? It makes sound when I turn it, but it is very weak sounding and I am not hearing the breath that I hear out of my other bikes. Just curious as I do not have testing equipment.

Any help is appreciated.

Another unrelated thing, I see that the GS parts sites that I have been to have 14mm wire caps and 10-12mm wire caps. Why? I have a 81 GS550T maybe the different models. I am surprised how much the book doe snot say.

Anyway thanks,

Pnedac

You first 4 cylinder and you have an 1100 in your sig?
v-twins have a much longer stroke, more friction and more sounds, harder to turn.
If it makes noise at all its a good sign, run a cold compression check on it.
Wire caps or spark plug size? 2 valves have the bigger 14mm plugs and 4 valves have 12mm to make room for more valve area, newer ones have even smaller 10mm plugs.

 

[Steve]

You first 4 cylinder and you have an 1100 in your sig?

And he's asking about a 550.

2 valves have the bigger 14mm plugs and 4 valves have 12mm to make room for more valve area, newer ones have even smaller 10mm plugs.

The 550s and 650s, although they are 8-valve engines (2 per cylinder), also have smaller 10mm plugs.

.

 

[gearhead13]

And he's asking about a 550.

The 550s and 650s, although they are 8-valve engines (2 per cylinder), also have smaller 10mm plugs.

.

I just looked up an 81 550 and it takes a b8es, 14mm plug

 

[pcaden]

Gentlemen,


I certainly appreciate the feedback. I had a GS1100E and I actually never had to check the compression in the 3 years I had it. Goes to its credit of course so I am glad to be holding a 550 for restoration. I measured the spark plug and measured 14mm where it goes into the engine. I hope I have the right stuff pegged down. Anyway thank you, I went out again while it was quiet at night and I think it is fine. I get that it is sharing the turn with four cylinders instead of just two. I think after building my first bike it is all so fascinating now. Thanks for the help.

 

[Steve]

I just looked up an 81 550 and it takes a b8es, 14mm plug

So it's just the 650 with the smaller plug?

.