Rallyestefan Posted April 22, 2014 Share Posted April 22, 2014 Hey guys just wanted some opinions on the cause of failure on the engine. I have ran with a 990 carb and stock carb settings. Run 27/1 fuel ratio with castor 927 oil. There is loads of little pieces of metal on the inside. And a nice center burn mark on the piston. Any help greatly welcomed Cheers Quote Link to comment Share on other sites More sharing options...
Rossyra Posted April 22, 2014 Share Posted April 22, 2014 (edited) 27:1 a little bit of unusual mix but people run 32:1 without issue. How long had you been running that session and how old is the engine? Edited April 22, 2014 by Rossyra Quote Link to comment Share on other sites More sharing options...
Nitroholic Posted April 22, 2014 Share Posted April 22, 2014 I'm guessing the metal filings are what's left of your cylinder plating. Looks to me like the result of a mild sieze. Could have been an airleak or a problem with the fuel supply leaning off thye mix. Bit hard to tell. Not liking the uneven carbon deposits in the combustion chamber. Especially as the clear bits line up with the transfer ports Quote Link to comment Share on other sites More sharing options...
Rallyestefan Posted April 22, 2014 Author Share Posted April 22, 2014 It had a run in. Then had new plug and check. Then ran about 20mins in pratice. Then 1 heat of 10mins then failed 5 mins into 2nd heat. And sorry the mix is 28/1. The engine is 2 weeks old ;( Quote Link to comment Share on other sites More sharing options...
Rallyestefan Posted April 22, 2014 Author Share Posted April 22, 2014 Nitro man what do you mean by that could that be manufacture error from the head or wrong carb settings which it was running a 990 with low 1 1/8 and high 1 5/8. ??? Quote Link to comment Share on other sites More sharing options...
Pharrel Posted April 22, 2014 Share Posted April 22, 2014 I run my 990 carb with 668 settings. I remember they're low 1 1/4 and high 1 1/2. Works fine on 25:1. Quote Link to comment Share on other sites More sharing options...
Rallyestefan Posted April 22, 2014 Author Share Posted April 22, 2014 I used to run that sort of mix but was getting more build up so was told to lessen the mix. Which I have done. It's fine for abit then this happened. It's the 2nd engine to do it to which makes me question if it's a duff batch of heads or pistons??? Quote Link to comment Share on other sites More sharing options...
Rossyra Posted April 22, 2014 Share Posted April 22, 2014 Am I seeing things or does your isolator block have an enormous gasket on it? Was that factory fitted? What brand of engine? Quote Link to comment Share on other sites More sharing options...
Nitroholic Posted April 22, 2014 Share Posted April 22, 2014 Nitro man what do you mean by that could that be manufacture error from the head or wrong carb settings which it was running a 990 with low 1 1/8 and high 1 5/8. ??? No way to tell if it's manufacturer error.... and wrong carb settings is something only you can tell us! To have scraped all the plating off the barrel indicates the motor was on the way to siezing. The ring has picked up on the plating and shaved it all off. That isn;t normal...and is usually an indication of a lean mixture/overheat. That may not be down to the settings on the carb, as any form of air leak or fuel problem can reduce the fuel mix ( and the oil with it) leading to an overheat. As you say it's not the first time..but the second...I'd say that was more than bad luck I would also be inclined to wonder as the problem occurred just after you thinned down your oil ratio, which would have helped to mask an overheat issue by giving more lube. What brand of engine is it? I am also curious about that inlet manifold gasket. It looks home-made. Are you cutting your own gaskets from gasket paper? Quote Link to comment Share on other sites More sharing options...
Rallyestefan Posted April 22, 2014 Author Share Posted April 22, 2014 That's the standard gaskets fitted from the manufacture don't really want to say brand but it's a big one for most bashers. Obviously I only race with them and at the mo there not holding up to it and it's very costly. The carb settings were as said and fuel mix bang on as previos heads had failed last year and was instructed to adjust. Here is a different branded engine with same settings Quote Link to comment Share on other sites More sharing options...
the watchman Posted April 22, 2014 Share Posted April 22, 2014 The black on top of the piston looks to me like a carbon build up, is it a chalky substence? Its hard to tell from a picture, if that is the case i would pressume its a ignition problem, timing will be out in that case so i would look at flywheel/coil/crank. Quote Link to comment Share on other sites More sharing options...
Jolly_roger_uk Posted April 22, 2014 Share Posted April 22, 2014 I'm quiet shocked that an engine tuner would supply a gasket looking like that to be honest. It certainly looks like you've lost some plating from those pics. I agree with Nitro, looks like a semi seize Quote Link to comment Share on other sites More sharing options...
Rallyestefan Posted April 22, 2014 Author Share Posted April 22, 2014 All brand new on both of the engines, even new carbs and filters with outer wears. I haven't messed as 2nd engine to fail Quote Link to comment Share on other sites More sharing options...
the watchman Posted April 22, 2014 Share Posted April 22, 2014 That issolator block gasket does look really erm weird, it looks to be sticking out the sides (alot) and not stright, doesnt appear to be sitting flush either with the head ?? Can you post some pics of that block/gasket ? Give us a better clue. Quote Link to comment Share on other sites More sharing options...
Rallyestefan Posted April 22, 2014 Author Share Posted April 22, 2014 Quote Link to comment Share on other sites More sharing options...
RC1Gary Posted April 22, 2014 Share Posted April 22, 2014 Stef that last picture of the piston......looks like a lean seize to me bud........as ya know I'm an expert lol Quote Link to comment Share on other sites More sharing options...
sean-vrs Posted April 22, 2014 Share Posted April 22, 2014 ive seen a lot of this in the motocross world, a highly tuned engine and a leaner mix will give momentary better results, but as you are finding out you need to finish a race! racing is flat out a lot of the time i would run a higher oil ratio and detune the hsn a little Quote Link to comment Share on other sites More sharing options...
Rossyra Posted April 22, 2014 Share Posted April 22, 2014 That gasket doesn't look right at all, doesn't even look like the correct part. Quote Link to comment Share on other sites More sharing options...
Rallyestefan Posted April 22, 2014 Author Share Posted April 22, 2014 And the block removed Quote Link to comment Share on other sites More sharing options...
Rockhopper Posted April 22, 2014 Share Posted April 22, 2014 You need to measure the bore diameter then we can perhaps get an idea where that metal came from. I've never seen a engine seizure that's left the piston skirt looking almost undamaged like that one appears to be. Are the bits on top of the piston steel or aluminium? Quote Link to comment Share on other sites More sharing options...
norcoforever Posted April 22, 2014 Share Posted April 22, 2014 (edited) looks to me like the iso block with that gasket wasn't anywhere near sealed, leading to nearly a lean sieze/ failure if this is how the engine came it feels unfair for you not to name the tuner etc so that 1) they can defend themselves and 2) people may want to avoid them Edited April 22, 2014 by norcoforever Quote Link to comment Share on other sites More sharing options...
Rossyra Posted April 22, 2014 Share Posted April 22, 2014 Looks like it's been leaking on the bottom left side judging by the residue on the gasket. Quote Link to comment Share on other sites More sharing options...
Jolly_roger_uk Posted April 22, 2014 Share Posted April 22, 2014 Looks like it's been leaking on the bottom left side judging by the residue on the gasket. Plus I see what appears to be a split between the lower left hole in the gasket and inlet. Quote Link to comment Share on other sites More sharing options...
Rallyestefan Posted April 22, 2014 Author Share Posted April 22, 2014 It does tbh I noticed that. The bits are defo alloy fragments and melted to it both inside the head and top of piston but mostly exhuast outlet side. The engine is a obr well both are. ?? 1 Quote Link to comment Share on other sites More sharing options...
norcoforever Posted April 22, 2014 Share Posted April 22, 2014 It does tbh I noticed that. The bits are defo alloy fragments and melted to it both inside the head and top of piston but mostly exhuast outlet side. The engine is a obr well both are. ?? odd, neither of my obr's came with gaskets like that, but that does look like the culprit, my obr wasn't great either and died a death Quote Link to comment Share on other sites More sharing options...
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