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Post by ian44ktm on Dec 8, 2022 19:54:24 GMT 10
Hi All. I've had a piston fail . I'm interested in opinions as to what went wrong. I'll give the background story and what I think the cause may have been. I have a 2010 Ranger which I've owned for about 20 months. It had 8000klm when I bought it , it now has 17000klm. I avoid highways for the most part and only do 100kph so I'm not holding up traffic. This was the case a couple of weeks ago. I was dooing 100kph ,only for a few k's, when it lost power but was still running 80kph. I know the brains trust will say I should have stopped straight away but I didn't want to be stuck on the side of the road on a hot day (Brisbane) only a few k's from home. Hindsight is a wonderfull thing as they say, at the time it could have been a dying spark plug or a blocked carb jet. There was no noise to make me think something drastic was going on. What I think happened was the top compression ring broke . About 30-40mm was gone and the top of the piston above that broken part of the Ring groove was mostly gone . Some of the alloy was melted on the top of the cylinder. Luckily it all stayed at the very top of the stroke and the cylinder only needed a light sand with fine emery and a hone. The carbs had 122 mains and 40 pilot jets. Fuel screw was almost 3 turns out. I was told by previous owner it had been tuned for the aftermarket exhaust. Twin pipes ,no cats. Plugs never looked lean but I had never done a chop test at 100kph. I now think it may have been lean on the main jet. I have put it back together today. Big thanks to Claire at Ural OZ. They had all the parts in stock and sent them quickly. I have installed a 130 main and 42 pilot , fuel screw 1 1/2 turns out . After a quick test ride it seems to be running well. More riding tomorrow to get my confidence back with it. Seat of the pants ,I may have gained a couple of ponies. New pistons ,rings ,gaskets ect. So the question is have I made the right diagnosis and if there are any carby guru's out there do my jet changes sound correct. TIA.............Ian  |
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Post by Wheels on Dec 9, 2022 15:45:49 GMT 10
Ian, I’ve seen exactly the same thing happen to a 2013 Tourist my wife owned. It had a 2 into 1 exhaust fitted with no carb jet change (not good). After repairs I fitted 130 mains, 45 pilots, mixture screws out 11/2 turns, 2 washers under the needle and drilled the slides out. After many chop tests to get it right (lots of jet changes) the end result was exactly the same as my 2012 Retro, which has modified exhausts and air intakes with 130 mains, 45 pilots, mixture screws out 11/2 turns, 2 washers under the needle, drilled slides and 54,400 kms on the clock. After a chop test, the plugs indicated both bikes were running slightly rich which is a lot better than running lean. You should be right with what you have, although I went with a 45 over the 42 but don’t think that will make a lot of difference. Definitely rich is better.
Cheers Wheels.
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Post by ian44ktm on Dec 9, 2022 19:14:27 GMT 10
Thanks Wheels. That gives me more confidence I've also ended up with 2 washers on the needles. What size drill did you use on the slides? I rode 60 odd klm's today for 3 hot/cold cycles. I'm happy with how it's running. I'll check head bolt tension and valve clearence tommorrow. Glad to have it back on the road again. I think the dog missed it even more than I did. ............Ian
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Post by Wheels on Dec 10, 2022 6:59:06 GMT 10
Ian, use a 7/64 drill bit but go steady. On the first two I did I used my fingers to twist the drill bit (no machine), it took a bit of time but ended up good. The second time round I used a slow rotating drill which was fine. The increase of hole size isn’t much but makes a big difference.
Cheers Wheels.
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Post by ian44ktm on Dec 10, 2022 17:26:55 GMT 10
Thanks mate. First job for tomorrow
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Post by danny1965 on Dec 11, 2022 14:09:56 GMT 10
Interesting. I have Dave's old 2010 Ranger. 2 into 1 exhaust. Have no idea what jets are in the carbs. What is a chop test? Also, what is drilling the slides and washers under needles? Yes, I'm new to Urals.
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Post by Wheels on Dec 11, 2022 15:21:07 GMT 10
Put simply, a chop test is killing the engine with the kill switch while the bike is cruising at a given throttle setting (1/4, 1/2, WOT etc). The spark plug when removed will give a good indication if the engine is running lean or rich at that throttle setting. I prefer to do mine after a short run at WOT.
Drilling out the carburettor slide and putting washers under the needle allows better throttle response. Not necessary, but correct jetting is important.
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Post by danny1965 on Dec 12, 2022 14:47:58 GMT 10
Thanks Wheels. I'll look into this stuff. Cheers.
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Post by Uralee on Dec 12, 2022 16:59:56 GMT 10
A few points of interest. Disagree if you wish but don’t tell me. 🤣
For post 2014 bikes…..learn what an overheating spark plug looks like because you can’t alter the mixture. Google is your reference.
For pre 2014…. Don’t get too obsessed with plug colour. Yes you can get some indications of mixture, but with unleaded fuel it is both difficult and variable, depending on the fuel additives. It takes a fair degree of experience to read mixture colour on a plug unless it is way out. Temperature signs are relatively easy….again, Google will show you.
Raising needles with washers. Anything more than 0.5mm will cause rich running right through the range even on the standard 122 mains.
I ran 122 mains with 0.5 needle lift and two into one exhaust for 90k km without issue.
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Post by danny1965 on Dec 13, 2022 16:54:52 GMT 10
Thanks Lee. I don't know what I'm doing here. All advice is appreciated.
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