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Detonation!


95blazer

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Well I was out at glamis this weekend, and within about 45 minutes my weekend of riding came to an end. :( After pulling the plugs I found the left one was covered in aluminum glitter, meaning I had detonation. After pulling the head I found a hole in the top of the left piston, and an indent in the top of the right piston(the beginnings of another hole). I have been running 91 octane at a 36:1 with maxima k2. I have vitos superstock pistons, vitos head gasket, stock head, and a +4 degree key. Should I need to be running a higher octane, and if so what? I am pretty sure this is the cause of the problem, I am just wondering why it happened all of a sudden. I am also pretty sure that the vitos superstock pistons did not cause this and would like to use them again if possible, is there any reason that I shouldn't? My next question is how to properly repair the engine. I just put a new crank in and don't want to risk ruining it, by having pison debris get into the bearing. How can I properly flush the lower end to ensure that I get all of the debris out of it? What else should I do during reassembly to ensure that there will be no ill effects from this meltdown? Thank you and any advice is greatly appreciated. Sorry for all the questions.

 

Derek

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Hey Derek it's Paul with the Blue Banshee. Did Scott get out on Saturday night? Anyway you might want to back your timing off a little or mix some race gas with premium pump gas. As crazy as it sounds you might want to rethink your oil fuel ratio. Too much oil can cause heat leading you into detonationville. I just added a milled head and advanced my timing 3 degrees before this last trip and ran fine with pump gas. Your jetting could still be a tad lean as well adding to the heat problem. The tempatures were pretty cool in the morning when we went on that run. There are a lot of factors compounding on each other leading down to a holed piston. Now what to do about it... your going to have to flush the bearings really well to be sure nothing is in the crank bearings. I would try to force a thick fluid something like grease through it and clean that out afterwards. Clean the mess up the best you can and then determine if you are willing to run the crank without a rebuild. If you want or need any help let me know.

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I detonated a piston due to improper squish, and a seperated crank. I didn't clean out the crank good enough, and shortly after rebuilding the motor, the crank let go. Catastrophic damage was the end result. I was not happy, and it cost me a bundle of loot in the long run. Be absolutely sure you clean everything out. And detonation can come from a few places, and once you get it back together, be sure to check your squish. And with your timing, and compession, I would be considering running at least a mix of race fuel....

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Hey Paul- Yeah Scott got out around 8pm, they were trying to mess with him because they told us we couldn't get him until 8pm, but he could've really gotten out at around 2pm. Still hadn't got his bike back.

 

Anyways, I think I am going to take the degree key out, and try to run it on pump gas. I am also going to check my compression after the rebuild, before I run pump gas in it. What ratio do you think I should run? I used to run yamalube 2r at a 32:1 ratio with no problems, and after my rebuild started running maxima k2 at the 36:1 ratio to be on the safe side.

 

What type of grease are you suggesting I use, how would I force it into the lower end, and how would I clean it out. I was thinking of filling it with gas and then turning the motor over a bunch of times to free the debris from the bearings, then draining it and repeating the process a few more times, would this work?

 

I will also purchase a few sets of jets, start out rich and work my way down until I find the magic number.

 

If you can think of anything else let me know.

 

Thanks,

 

Derek

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I would try some lithium grease and use gas to clean it up. Just make sure you do this in an area where there are no pilot lights or open flames. I used Yamalube 2R mixed with 91 octane at 40:1 with no problems. Now I run Belray MC-1 at 50:1 with 91. One thing you shouldn't do is turn the motor over while it has all the crap sitting in the bottom of the cases. If any did get in the bearings turning the motor is just going to help it work it's way deeper in the bearings. I would split the cases and inspect everything while it's apart. A tube of yamabond is cheap and knowing for sure there is nothing left in the crank is better than worrying about it during your first trip back out there. If you need any tools or a hand getting things repaired shoot me an email. I just helped another guy on this site get his motor squared away.

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I probably will split the cases just to be safe. I have only ridden the shee for 4 weekends since I replaced the crank and all of the seals on the lower end. I think I should be able to reuse the seals as they are in no way worn out. Thank you for all of the advice I will let you know how things go.

 

Derek

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