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Post by wilmerpitt on Jul 10, 2024 5:38:30 GMT -5
Hi, found this page while looking for help and information why my Yamaha SR 500 1980 that I bought last year.
The SR had been standing still for almost 20 years, we changed oil a couple of times, cleaned up the bike and made it rideable. When starting, oil was leaking into the combustion chamber and put coal on the sparkplug.
We have sharpened and grinded the valves, changed valve guides, replaced all the piston rings, cleaned the carburator multiple times and set everything right timing wise with help from the owners manual.
Yet still when it eventually starts, the exhausts smells burning oil and the sparkplugs go greasy to the point where it doesn't always want to start. Some times it takes 2 kicks, sometimes more than a hundred.
I also changed the idle jet to a 22.5 instead of a 25 to make the mixing not as rich.
I use 10W - 40 oil as of now since I haven't been able to get it to work.
I am open to suggestions, I will be able to provide pictures on Saturday.
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Post by andy on Jul 10, 2024 8:11:31 GMT -5
Wilmer, I’m struggling to point you the right way but having recently done a top end rebuild I took extra time and care measuring,checking and double checking my work. Did you rebore or just glaze bust the cylinder bore ? Did you accurately measure the piston and bore to determine how much clearance ? Silly question but you put new valve stem seals in ?
I’m sure you don’t want to tear it all down again but if that’s the case I would rebore and replace the piston and carefully check the ring gaps and remember to butt the oil control ring end to end NOT overlap ( don’t ask me how I know 😳) . Valves and guides ? I replaced my inlet valve as it had worn a distinct step on the stem. I’m guessing you’ve possibly made a mistake in checking measurements/ clearances. Keep us posted and good luck 🤞.
Andy
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Post by andy on Jul 10, 2024 8:22:15 GMT -5
100% you’ve not overfilled the oil level ? 10/40 is thin 20/50 is what the Haynes manual reccomends ,thin oil won't help at all if piston/bore is worn,is it smoking excessively when it finally starts ?
Members, anyone else chime in if I've missed the obvious ?
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Post by wilmerpitt on Jul 10, 2024 10:59:57 GMT -5
Wilmer, I’m struggling to point you the right way but having recently done a top end rebuild I took extra time and care measuring,checking and double checking my work. Did you rebore or just glaze bust the cylinder bore ? Did you accurately measure the piston and bore to determine how much clearance ? Silly question but you put new valve stem seals in ? I’m sure you don’t want to tear it all down again but if that’s the case I would rebore and replace the piston and carefully check the ring gaps and remember to butt the oil control ring end to end NOT overlap ( don’t ask me how I know 😳) . Valves and guides ? I replaced my inlet valve as it had worn a distinct step on the stem. I’m guessing you’ve possibly made a mistake in checking measurements/ clearances. Keep us posted and good luck 🤞. Andy When replacing the piston rings I honed, glaze busted the cylinder bore and put new valve stem seals in, although I am not sure if I measured the piston and bore to the point of perfection but they we're measured. I was however struggling to get the oil control ring to fit, but since I got it in correctly that shouldn't be a problem? I have a feeling that I'm going to have to tear it all down again:D I will keep you all posted! |
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Post by wilmerpitt on Jul 10, 2024 11:01:53 GMT -5
100% you’ve not overfilled the oil level ? 10/40 is thin 20/50 is what the Haynes manual reccomends ,thin oil won't help at all if piston/bore is worn,is it smoking excessively when it finally starts ? Members, anyone else chime in if I've missed the obvious ? I've been thinking about this as well, the oil level is always measured to 2 liters, but because of me using too thin oil it might create wrong pressure, since i've seen an oil leak from the clutch bolt with the small screw in it. Also, it doesn't smoke all too much but during start it does smell like burnt oil. |
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Post by andy on Jul 10, 2024 13:18:36 GMT -5
Okay, I’m thinking cheapest option first, drain the 10/40 and put the 20/50 in. Have you done a compression test ?
I know we’ve all got a budget to work to but if the above doesn’t help it’s a tear down and at least double check bore and rings and any other work you’ve done. Compression test wants to show around 100psi.
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Post by andy on Jul 10, 2024 13:41:11 GMT -5
Meant to say, although up until my rebuild I was getting through a lot of oil although not too apparent on the plug colour or from the exhaust, I’m still baffled now 😳. What I did find out though was I had fitted the oil ring wrong and it wasn’t doing it’s job. Anyway back to your woes, if you’ve got the funds go for a rebore and new piston, be lucky and hopefully that’s not necessary.
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Petes2Wheels
Full Member
Out riding the country roads
Posts: 102
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Post by Petes2Wheels on Jul 10, 2024 16:54:38 GMT -5
I have just completed a top end rebuild on my SR as well. Lucky for me it started 2nd kick and hasn't missed a beat since. Though it is a tad noisy from the tappets. It has always been a noisy bike. For a 40yr old motorcycle have to expect some noises. To your issues, did you use a proper gasket kit? Also when doing the cylinder head, there is one gasket for one join then there is one that need to use gasket sealant. All torque settings done to spec?
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neal
Junior Member
We may need a bigger hammer.
Posts: 37
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Post by neal on Jul 11, 2024 5:22:15 GMT -5
Hey Wilmer,
+1 on suggestions by the lads. If the bike has been standing 20 years the valve stem seals will def need replacing, get oem items if you can, I remember previous members on old forum having issues with pattern seals. Good luck mate, sounds like you are going to be busy. Let us know how you progress.
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