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Plugs backing out


oldskool

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With your compression and squish, I wouldn't feed that motor pump fuel.

Won't be feeding this one anything else. Its GONE!    I thought 93 octane was good for up to 160/165 psi of comp. I look at the plugs several times this weekend, hell they were already loose and they were consistantly dark,dark brown to black, so I felt like my jetting was rich(320 main)  at prolly 200ft

Now I got a  hole in the right side piston and a broke rod on the left side. A big ass hole in bottom case. Haven't gotten the crank out yet

All this was caused by running too low octane?

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Add fuel, Switch to race gas, get some measurements of your clearances on your domes........Much more to come, but it's a starting point.

 

Remember.........they all run like a raped ape just before they ventilate the pistons. If your backing plugs....STOP RIDING TILL YOU FIGURE IT OUT!

 

Yep. See Above folks ^^^^ Lesson learned. when a plug backs out......you don't put it back till you make some changes that will prevent it from happening again.

Won't be feeding this one anything else. Its GONE!    I thought 93 octane was good for up to 160/165 psi of comp. I look at the plugs several times this weekend, hell they were already loose and they were consistantly dark,dark brown to black, so I felt like my jetting was rich(320 main)  at prolly 200ft

Now I got a  hole in the right side piston and a broke rod on the left side. A big ass hole in bottom case. Haven't gotten the crank out yet

All this was caused by running too low octane?

Nope, Sadly all that was caused by you just tightening the plugs back up and lining up for another race. Well tuned motors don't blow. Motors with symptoms that indicate trouble don't blow if you park them. But if you whip a horse till it dies.....then you have a dead horse. (Sorry to hear about your horse.)

 

You never stated the hours on that motor. If you have a ring going down, or your rolling to the line with a cold motor, you can cold seize the motor and get parts hot enough to work like a glow plug and the motor will fire off too early causing detonation.

Kicking compression isn't as accurate as calculated. Octane rules of thumb aren't promises. Plus pump gas can be VERY unstable. If you didn't get the gas the same day.....it gets really risky with performance motors. I've seen pump gas go bad in just 6 days. A guy in our group had a 57 HP bike and ran it on premium pump gas. Next weekend we go to ride and he needs push starts every time the bike dies. He thought his brand new build had ate the rings......Nope. Premium pump gas went to shit. (In this economy who knows how long that premium is sitting in the tanks in the ground? I'm sure many of the hot cars are sitting dormant.)

 

So it could have been enough Octane originally.....but maybe it went bad. Who knows?  :shrugani:

 

So what are you building next? Big drag cub or Raptor 700?

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Yeah, you told me to park it. so I did for sunday and loaded up today to come home. When I got home my son was here and hadn't been on it since my 4mil build so I told him to check it out. well about 10 mins later and that was all shee wrote.

 Raptor 700, naw I got a 700xx slightly modded

Gonna do another 4mil banshee. I hope my crank is still ok.(don't know how to check it) Can my local Yamaha shop check it for me, they do engine builds.  If the crank is thrash, I got a vito's short rod i'm gonna use. Does the short rod take the standard piston?

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Yeah, you told me to park it. so I did for sunday and loaded up today to come home. When I got home my son was here and hadn't been on it since my 4mil build so I told him to check it out. well about 10 mins later and that was all shee wrote.

 Raptor 700, naw I got a 700xx slightly modded

Gonna do another 4mil banshee. I hope my crank is still ok.(don't know how to check it) Can my local Yamaha shop check it for me, they do engine builds.  If the crank is thrash, I got a vito's short rod i'm gonna use. Does the short rod take the standard piston?

 

WARNING: All the force your pistons saw during your dance with detonation was also shared with your crank and rod bearings. Proceed with caution.

 

No your local Yamaha dealer can't check shit and I would never let one build or even re-build a motor for me.  :evil:

 

We have site sponsors here. Get to know one. It'll save you hundreds in the long run. I'm a big fan of Cameron at REDLINE RACING. He knows his stuff, has his own dyno and isn't afraid to post the results of his work. Great guy....give him a call and just chat.

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NO pics for you joksters. I felt like a pallbearer as I pushed her in the garage. I'm in mourning.

Pastrykiller, can't a crank be rebuilt or is that a waste? I have one broke rod that I know. The crank turns freely, but is it still true?????????

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