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Possible Detonation or something else?


ryguy27

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Recently purchased a banshee a few weeks ago, and from advice from folks on here I've been going over everything making sure its 100%. The compression was showing 175 and 170 with a cool head. From what I was told it was due to the domes that were in it. I purchased 22cc domes to get the compression down to run pump fuel. I have only started it up with the fuel that was in it, and rode it up my lane and back. It runs great, starts first kick. I just pulled the head off to swap the domes and found the top of each piston to be blackish brown burnt marks that do scrap off with your finger. The sides of the pistons through exhaust port look fine with no visible scarring, and same for the cylinder walls, from what I can see. My question is was this caused by previous owner running pump fuel with such high compression and can I clean the tops of the cylinders with something? and is this something that I should be worried about after doing the 22cc domes swap. It had 20cc domes in it currently. 

 

2001 banshee

FMF Fatty pipes, power core 2 silencers

V force reed valve

Pro design 2 into 1 foam filter

PD coolhead

TORS eliminated

Keihin carbs

 

post-48554-0-90340800-1415032808.jpg

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Ok. One problem. Those pistons do show a lean condition or a bit too much heat. Ideally the piston tops will show at least a wash pattern near the transfers where fresh incoming fuel washes off the piston. Those show quite alot of heat. This isnt exactly what you should see but it gives you an idea. https://www.google.com/search?q=banshee+piston+wash&client=ms-android-sprint-us&hl=en-US&source=univ&tbm=isch&tbo=u&sa=X&ei=i9hXVP-VHoqiyQSJn4L4DQ&ved=0CBsQsAQ&biw=598&bih=287

Edited by RadarRacing
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Yeah it all makes sense, I installed the 22cc domes , all went well, Thanks tricked carbine ! I am putting it back together tomorrow and doin a compression test and then hopefully start on the jetting process, also noticed the gaskets on reed valve were splitting so it was probably sucking air there as well , so I bought them today and will replace!

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Yeah it all makes sense, I installed the 22cc domes , all went well, Thanks tricked carbine ! I am putting it back together tomorrow and doin a compression test and then hopefully start on the jetting process, also noticed the gaskets on reed valve were splitting so it was probably sucking air there as well , so I bought them today and will replace!

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My opinion is you need to clean this cause they can cause rust in your engine if your that type of rider that goes out and rides 1 every two months and your better off going to get your bike ported and they'll clean your pistons for you too your pistons are like that due to the compression how the previous owner had it

Wtf?
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My opinion is you need to clean this cause they can cause rust in your engine if your that type of rider that goes out and rides 1 every two months and your better off going to get your bike ported and they'll clean your pistons for you too your pistons are like that due to the compression how the previous owner had it

Are you fucking retarded?
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