Yamaha 5hp 5BS Piston Rings

ajstars · 16 February 2013, 11:15

Hi, so I have purchased some new Yamaha genuine piston rings for my Yamaha 5hp 5BS air cooled engine but I don't know which is which. One of the rings is green on the outer edge - is this the top ring or the bottom ring? I guess one is specifically for oil wiping?

steve66 · 18 February 2013, 12:56

Hi are they the same thickness?

ajstars · 18 February 2013, 13:00

They do look to be. It was only the colour/coating that I could see was different.

ajstars · 18 February 2013, 13:01

Yes I think so it was only the colour/coating that seems to differ -
Apologies double posted!

steve66 · 18 February 2013, 13:46

I wouldnt have thought it matters, being a 2 stroke and 100/1 they wont have a lot of oil to scrape.
Steve

ajstars · 18 February 2013, 13:51

Ok thanks. Is it worth getting it honed too prior to fitting? I can't see any physical wear though! I'm just hoping the problem was the rings! Problem was similar to that of a failed reed valve but it doesn't have one as its a three port design! Apparently exhaust coming out of air intake!
The old rings seem really loose around the piston.

steve66 · 18 February 2013, 14:03

I personally wouldnt. Your technically removing a little more of the cylinder. I would put them in rebuild it and run in at a minimum of 50/1. I think its absolutely suicidal running motors at 100/1 even though the manufacturer says its ok. You wont see a difference much of a difference between running 50/1 and 100/1

ajstars · 18 February 2013, 14:15

Ok thanks, I shall give it a shot - fingers crossed. Thanks for the help.

yam man · 18 February 2013, 15:44

Some rings have t1 and t2 writing on them.

T1 = 1 and facing upwards
T2 = 2 and facing upwards
Hope this helps

ajstars · 19 February 2013, 08:49

1N and 2N are printed on my rings (good spot, thanks). The 1N is green whilst the 2N is the black ring. Any ideas?

yam man · 19 February 2013, 08:56

1n top and 2 n bottom writing facing crown of piston. Locate rings in piston lactate pins this so the rings won't spin a catch a port forward facing arrow pston to exhaust

yam man · 19 February 2013, 08:57

# port

ajstars · 19 February 2013, 09:07

Thankyou

steve66 · 19 February 2013, 09:34

Good advice Yam man

ajstars · 19 February 2013, 18:12

All working except it won't go above idle without stalling!

steve66 · 19 February 2013, 18:17

Carburettor needs a good clean or check carb gasket or inlet for leakage.

ajstars · 20 February 2013, 15:03

Thanks for all the info, I will check for leaks! Just a thought as its air cooled should I be using a different premix oil or will standard quicksilver 2 stroke oil do the trick?

ajstars · 23 February 2013, 16:54

Yam man has helped out loads - so thanks to his advice the engine is now running. I have stripped down the carb and rebuilt it but it still won't accelerate. I can't find any air leaks - if I spray carb cleaner all around the carb it still idles on. Only when some gets into the air intake does it splutter.
I'm stuck for ideas now. If anyone fancies a go at fixing it I would be forever in their debt!

ionutfg · 23 April 2020, 11:53

Hi ! Recently i purchased an yamaha 5bs 661 5 hp 2 stroke air cooled and when i disasambly i found the engine was rebuild but he used an broken piston.Can somebody help me with a piston code ? Maybe something equivalent ? I will atached photos..I try to find a piston for about 2 month...

Chric007 · 06 July 2020, 22:53

Hi did you manage to locate the piston part number im look for rings and gaskets myself and can't seem to find a supplier who stocks there's . Kind regards