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loss of compression when warm


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Ok I have another problem altogether... When the banshee is cold the compresssion is 110psi on both sides. When warm it drops to 100 on both sides. Do you think this and the other problem I am having are related?? What would cause a loss of compression after it's warmed up??

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im not sure what causes that. but mine did awhile back when i needed a topend. it would start just fine when it was cold, but when warm it was hard. on one occasion i had to be pulled behind a sand rail to start it after it would start atop a dune.

 

btw, whats your other prob?

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im not sure what causes that.  but mine did awhile back when i needed a topend.  it would start just fine when it was cold, but when warm it was hard.  on one occasion i had to be pulled behind a sand rail to start it after it would start atop a dune.

 

btw, whats your other prob?

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intermittant spark on left side.

 

I'm hoping I find a blown head or base gasket but I'm starting to think it may be a cracked head

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I would say its time for a new set of rings if not a complete top end job. Even at a 110 that would be low enough copression that I would at least trear her down and inspect it. If you had a base gasket leak she would of leaned out and blown up. If you would of had a leak in the head gasket it would of smoked a sweat smelling white smoke, and I have never heard of a head cracking. Wiseco recomends that you replace your rings every 100 hour of rideing. I bet they are just worn, and when they warm up it just increases the blow by.

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I would say its time for a new set of rings if not a complete top end job.  Even at a 110 that would be low enough copression that I would at least trear her down and inspect it.  If you had a base gasket leak she would of leaned out and blown up.  If you would of had a leak in the head gasket it would of smoked a sweat smelling white smoke, and I have never heard of a head cracking.  Wiseco recomends that you replace your rings every 100 hour of rideing.  I bet they are just worn, and when they warm up it just increases the blow by.

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I got a rough estimate as to what a top end kit would cost, $160. it does seem tha everyone I have talked to says I need a new top end kit. I tore the head off and looked at everything and the cylinder walls look good. I didn't see any kind of scoring. I did see what seems to be a wear mark on top of both pistons at about the 7 o'clock position on both sides. I don't know if that has anything to do with it.

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You're making my head spin with all these very similar or same post. Here is a simple way to check your rings.... but the head has to be on. You can put a tbls spoon of 2 stroke oil in the cylinder and do a compression test. If the compression increases a lot then your rings were leaking. Do both before the oil and after putting in oil at the same temp.. cold.

 

You may have a gauge problem too. Those compression gauges seem to go bad a lot.

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You're making my head spin with all these very similar or same post. Here is a simple way to check your rings.... but the head has to be on. You can put a tbls spoon of 2 stroke oil in the cylinder and do a compression test. If the compression increases a lot then your rings were leaking. Do both before the oil and after putting in oil at the same temp.. cold.

 

You may have a gauge problem too. Those compression gauges seem to go bad a lot.

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I took it to another shop before I took it apart and they found the compression was low when cold. They used a new gauge they had ordered for a customer and he let use it. still low compression.. 110 both sides. They said the same thing you did and the end result would be the same. I could have bought just new rings but since I'm going to have everything off might as well put ina new topend and do a little upgrading.

Edited by Handyman
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