Planet Minis

slow600 · 08-19-2007, 09:32 PM

what is the proper way to check piston/valve clearance using clay. is it as simple as installing piston with clay on top then assembling top end to roll over by hand then inspecting? if not, what is the proper procedure? also, whenever installing metal head gasket do the rubber oil passage seals still used or not. thanks

slow600 · 08-22-2007, 03:55 PM

checking to see if the valves will hit the piston. using a much thinner head gasket than what the kits come with. ill figure it out eventually.

Kurlon · 08-22-2007, 06:52 PM

Run a bead of clay across the top of the piston, from valve relief to valve relief. Put head and gasket on, torque down, and slowly turn the motor over BY HAND a couple times. Pop the head off, and measure the impressions in the clay. You want the thinnest spot to be .040" minimum.

slow600 · 08-22-2007, 08:02 PM

thank you, i feel more confidend now. "stock" tb head gasket is approx 1.5mm. i am told they run pretty low compression. just got in today my 1mm and .38mm copper head gasket. just waiting on a few more things.

firepower354 · 08-22-2007, 08:46 PM

Silver solder is less likely to get stuck in the rings, valves, etc and is much easier to measure when squished.

Kurlon · 08-22-2007, 08:57 PM

On the other hand, you need to consult a conversion chart to take the measured thickness and convert it to a real clearance. Silver solder has some elasticity to it, after being squished it springs back slightly. As long as you don't go nuts packing the cylinder with playdoh, keeping it out of the rings/etc is cake.

slow600 · 08-23-2007, 05:15 AM

even as a worst case though, i could just pull the cylinder and piston to clean if needed to right?

Kurlon · 08-23-2007, 06:51 AM

Ayup.

jRob409 · 08-23-2007, 07:10 AM

I have tried using a "normal" o-ring in place of the big square one before. Dab some silicone on the o-ring when you put it in. I havent had much luck getting the copper head gaskets to not leak compression and oil. I tore my 108 back apart over the weekend to find it had been leaking compression past the top 2 studs.

Kurlon · 08-23-2007, 08:44 AM

I haven't had any issues leaking compression with copper gaskets, and have yet to have a motor that doesn't mist oil regardless of the gasket type used. I take my time with copper gaskets though. The head and cylinder get scraped, scrubbed, and finally cleaned with brake cleaner before assembly so there is no oil or other residue present, including finger prints. The gasket gets cleaned as well, after being re-annealed if this is it's second or time being compressed. (Toss after that.) I don't use any sealant and have yet to have a problem even with engines running 300psi and up.

slow600 · 08-23-2007, 09:52 AM

that answers my next question, i was gonna spray both sides with some high temp copper sealant. used the stuff way back in the day when modifying a stock head gasket. i always clean my stuff really well before assembling, so hopefully i will not have problems. so should i install the o-ring on the oil passage or not?

Kurlon · 08-23-2007, 12:06 PM

No, unless you can get an o-ring that is thick enough to make a seal without being so thick it deforms thanks to the thinner gasket. It's easier to just run without it.

dax · 08-23-2007, 12:44 PM

When claying the engine it is good to apply a thin coat of light oil to head and valves. Then the clay will stay on the piston (if the piston is clean).

Kurlon · 08-23-2007, 01:19 PM

Good idea. If you're going this far and the piston ISN'T clean... clean it. : )

08-19-2007, 09:32 PM	#1 (permalink)
slow600 2nd Gear Member Join Date: Feb 2007 Location: springfield missouri Posts: 519	checking piston/valve clearance what is the proper way to check piston/valve clearance using clay. is it as simple as installing piston with clay on top then assembling top end to roll over by hand then inspecting? if not, what is the proper procedure? also, whenever installing metal head gasket do the rubber oil passage seals still used or not. thanks

08-22-2007, 03:55 PM	#2 (permalink)
slow600 2nd Gear Member Join Date: Feb 2007 Location: springfield missouri Posts: 519	Re: checking piston/valve clearance checking to see if the valves will hit the piston. using a much thinner head gasket than what the kits come with. ill figure it out eventually.

08-22-2007, 06:52 PM	#3 (permalink)
Kurlon Super Moderator Join Date: Feb 2005 Location: Windham, ME Posts: 8,301	Re: checking piston/valve clearance Run a bead of clay across the top of the piston, from valve relief to valve relief. Put head and gasket on, torque down, and slowly turn the motor over BY HAND a couple times. Pop the head off, and measure the impressions in the clay. You want the thinnest spot to be .040" minimum.

08-22-2007, 08:02 PM	#4 (permalink)
slow600 2nd Gear Member Join Date: Feb 2007 Location: springfield missouri Posts: 519	Re: checking piston/valve clearance thank you, i feel more confidend now. "stock" tb head gasket is approx 1.5mm. i am told they run pretty low compression. just got in today my 1mm and .38mm copper head gasket. just waiting on a few more things.

08-22-2007, 08:46 PM	#5 (permalink)
firepower354 Advertiser Join Date: Oct 2006 Location: Flint MI Posts: 11,002 My Mood:	Re: checking piston/valve clearance Silver solder is less likely to get stuck in the rings, valves, etc and is much easier to measure when squished. __________________ If it has my name on it I did it;) FirepowerMinis.com Custom FPM parts and engines. Parts and service for all makes. Honda Trail Bikes parts and accessories. Pitster/Piranha/Thumpstar bikes, parts, engines and accessories.

08-22-2007, 08:57 PM	#6 (permalink)
Kurlon Super Moderator Join Date: Feb 2005 Location: Windham, ME Posts: 8,301	Re: checking piston/valve clearance On the other hand, you need to consult a conversion chart to take the measured thickness and convert it to a real clearance. Silver solder has some elasticity to it, after being squished it springs back slightly. As long as you don't go nuts packing the cylinder with playdoh, keeping it out of the rings/etc is cake.

08-23-2007, 05:15 AM	#7 (permalink)
slow600 2nd Gear Member Join Date: Feb 2007 Location: springfield missouri Posts: 519	Re: checking piston/valve clearance even as a worst case though, i could just pull the cylinder and piston to clean if needed to right?

08-23-2007, 06:51 AM	#8 (permalink)
Kurlon Super Moderator Join Date: Feb 2005 Location: Windham, ME Posts: 8,301	Re: checking piston/valve clearance Ayup.

08-23-2007, 07:10 AM	#9 (permalink)
jRob409 2nd Gear Member Join Date: Nov 2004 Location: NE Kansas Posts: 503	Re: checking piston/valve clearance I have tried using a "normal" o-ring in place of the big square one before. Dab some silicone on the o-ring when you put it in. I havent had much luck getting the copper head gaskets to not leak compression and oil. I tore my 108 back apart over the weekend to find it had been leaking compression past the top 2 studs.

08-23-2007, 08:44 AM	#10 (permalink)
Kurlon Super Moderator Join Date: Feb 2005 Location: Windham, ME Posts: 8,301	Re: checking piston/valve clearance I haven't had any issues leaking compression with copper gaskets, and have yet to have a motor that doesn't mist oil regardless of the gasket type used. I take my time with copper gaskets though. The head and cylinder get scraped, scrubbed, and finally cleaned with brake cleaner before assembly so there is no oil or other residue present, including finger prints. The gasket gets cleaned as well, after being re-annealed if this is it's second or time being compressed. (Toss after that.) I don't use any sealant and have yet to have a problem even with engines running 300psi and up.

08-23-2007, 09:52 AM	#11 (permalink)
slow600 2nd Gear Member Join Date: Feb 2007 Location: springfield missouri Posts: 519	Re: checking piston/valve clearance that answers my next question, i was gonna spray both sides with some high temp copper sealant. used the stuff way back in the day when modifying a stock head gasket. i always clean my stuff really well before assembling, so hopefully i will not have problems. so should i install the o-ring on the oil passage or not?

08-23-2007, 12:06 PM	#12 (permalink)
Kurlon Super Moderator Join Date: Feb 2005 Location: Windham, ME Posts: 8,301	Re: checking piston/valve clearance No, unless you can get an o-ring that is thick enough to make a seal without being so thick it deforms thanks to the thinner gasket. It's easier to just run without it.

08-23-2007, 12:44 PM	#13 (permalink)
dax 1st Gear Member Join Date: Jun 2006 Posts: 156	Re: checking piston/valve clearance When claying the engine it is good to apply a thin coat of light oil to head and valves. Then the clay will stay on the piston (if the piston is clean).

08-23-2007, 01:19 PM	#14 (permalink)
Kurlon Super Moderator Join Date: Feb 2005 Location: Windham, ME Posts: 8,301	Re: checking piston/valve clearance Good idea. If you're going this far and the piston ISN'T clean... clean it. : )

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