cylinder gasket question

[Shayner]

i am doing a top end rebuild on my 787 out of my 98 speedster and i know it prob leaned out in the weeds last yr,upon tearing it apart there was a 0.4mm gasket there.
my question is......i want to put a 0.3mm to get more mixture in the cyclinders to help avoid lean out again or could i use a very common gasketwith a size of 0.6mm.

thanks :thumbsup:

 

[Dr Honda]

I'm totally lost with what you are asking.

If I reading it right... the base gasket has nothing to do with mixture. It sets the squash band, and if you go thinner... you can over heat the piston crowns.

 

[Shayner]

i figured with a thinner gasket the cylinders would run cooler....i guess ill put a 0.6mm in there instead.
thanks for the reply

 

[Dr Honda]

NO!!

Setting the squash band correctly will keep the engine the coolest. Too Thin = High compression, and over heating. Too Thick = improper quench, and can sill lead to overheating... but more importantly, you will loose performance. (up to 5 mph on the top end)

Check your manual, and set the gap to the proper spec.

 

[Shayner]

well as said in the manual the gaskets u can use are between 3mm to 8mm....if i loose a bit on the top end i guess i loose id rather it run a bit cooler....i just want this to be riliable this summer

 

[Dr Honda]

You aren't listening. If you want it reliable... do it right !!

Too big of a gap isn't good either. It needs to be set properly. YES... that means buying a few gaskets, and taking the top end apart again if needed.

If the gap is big... you loose performance... you will build carbon... the crown edges won't be properly cooled... and that can lead to a pre-mature death of the engine too.

Rotax/SeaDoo uses an exposed top ring... and things need to be right, or the engine will die.

 

[Shayner]

im trying but look at it from my end the dealership says 3mm and the manual says between 3mm to 8mm....im from the skidoo world and always ran a 6mm in my 800cc motor so thats why i am saying what i am. never had an issue with regular service.
one thing im thankful for is the reliable oil injection
i just wanted more insight,thanks for the info,ill do some more research

 

[Dr Honda]

First... the guy at the dealer is an idiot. He probably only has a 0.3mm gasket in stock, and doesn't want to order more.

Second... there is a 90% chance that if you run a 5 dot gasket... you will fall within spec.

Third... The book gives a range because there is a range. There should also be a section talking about properly setting the squash-band.


Finally... do what you want. You've been given the info, on the "how" and "why". If you want to do it wrong... that's up to you.

This is my final word on it.