2 head gaskets or just 1? PK80

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meowy84

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Jul 18, 2009
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I know this issue/question has probably been covered already but I can't seem to find the thread.

Anyways, as most do my slant head PK80 came with 2 head gaskets. I checked the piston/plug clearance with just one head gasket and my newly acquired NGK B6HS plug and there's no interference issues at TDC. Obviously just using 1 head gasket will raise the compression slightly which should give slightly better performance but that's not my motivation. Instead I figure 1 head gasket reduces the number of joints by one and so lessens the chances of a leak since the slant heads seem to be more prone to warpage.

What do the HT gurus say on the subject?
 
Mac

Mac

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Dec 3, 2009
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I am running PK80's also. One of mine runs better with the 2 gaskets, comes on the pipe real nice, when I tested it with one, it took a while to get full power, so I left it with two. My other PK80 likes one. I guess whatever works for your setup. I do recommend making the head true with some 400 wet/dry paper on a piece of glass. Just my opinion, not a guru here, it's easier not knowing too much!!

Mac
 
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Roadwarrior

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Apr 23, 2010
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I've only ever run 1 gasket on mine. I took the head off and lapped it flat, then assembled it with one new gasket. The only thing I find is that the compression is very high making my clutch want to slip, or back tire want to lock when I start it. Otherwise it runs very strong.
 
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meowy84

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Jul 18, 2009
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Thanks for the comments guys. Looks like the consencus is split on this one. I do want to avoid the clutch stress and the locking tire scenario. Plus I'm not after the most power that I can squeeze out of the thing so I'll probably use the 2 gaskets to begin with and do the old 400 grit lap and the aluminum paint trick right off the bat to minimize (hopefully prevent) any possible leaks. Too bad the slant head is a bit of a higher compression engine since I wouldn't mind a lower compression to minimize stress on the engine since I'm going after reliability and not performance.

By the way, anyone know what the 'normal' HT egines run for compression as compared to the slant heads? I assume the regular HT is typically in the 6 to 6.5:1 range????
 
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beentryin

beentryin

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Apr 24, 2010
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i did two to see what would happen. i lost alot of low end,and mid but motor ran smother on top end.so i went back to one for more low end power
 
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Dogtown Burner

Dogtown Burner

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Sep 15, 2011
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meowy84 said:
Thanks for the comments guys. Looks like the consencus is split on this one. I do want to avoid the clutch stress and the locking tire scenario. Plus I'm not after the most power that I can squeeze out of the thing so I'll probably use the 2 gaskets to begin with and do the old 400 grit lap and the aluminum paint trick right off the bat to minimize (hopefully prevent) any possible leaks. Too bad the slant head is a bit of a higher compression engine since I wouldn't mind a lower compression to minimize stress on the engine since I'm going after reliability and not performance.

By the way, anyone know what the 'normal' HT egines run for compression as compared to the slant heads? I assume the regular HT is typically in the 6 to 6.5:1 range????
Click to expand...
what is the slant comp rated at?. I have a reg ill trade ya
 
Al.Fisherman

Al.Fisherman

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Sep 9, 2009
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rustycase said:
Two head gaskets is not a gud idea.
...my 2cents...
:)
rc
Click to expand...
You say 2 head gaskets is not a good idea but never qualified your statement. Using 1 or 2 head gaskets is determined by your engine. First of all I lap ALL my heads before instillation. Then I go with 1 gasket. If there isn't too much compression to start the engine, I'll stay with 1. On the other hand if the compression is too much (like for my son @ 135#) then I'll add a second one (also considering other factors as performance). After determining the correct gasket set up then I will copper kote the gaskets and torque them down to specifications. Not knowing these engines when I bought my first (installed and ran out of the box), I have never had a blown head gasket after the first engine. In fact I have had ZERO issues with my last 5 of 6 builds.

https://docs.google.com/document/d/1GcesQihc7-mm3hJGf7UPiqOaRXZ8ekUT99QUZq2qXXE/edit
 
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rustycase

rustycase

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May 26, 2011
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Hey ALF,

Well, shows yah what I know! :)

...NO qualification... I would NEVER use two head gaskets.
Never seen a motor that called for more than 1.

I suppose if I needed lower compression for some reason I'd use thicker stock for the gasket.
...but the Husky out there in the yard runs somewhere's around 14:1 compression so I have trouble seeing where anything near a chinagirl might have too much... I better go back and read the entire thread to see if I missed something. Sry !
Best
rc
 
Al.Fisherman

Al.Fisherman

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rustycase said:
Hey ALF,

Well, shows yah what I know! :)

...NO qualification... I would NEVER use two head gaskets.
Never seen a motor that called for more than 1.

I suppose if I needed lower compression for some reason I'd use thicker stock for the gasket.
...but the Husky out there in the yard runs somewhere's around 14:1 compression so I have trouble seeing where anything near a chinagirl might have too much... I better go back and read the entire thread to see if I missed something. Sry !
Best
rc
Click to expand...
Now that's better, you qualified your post.. I myself have never seen 2 separate head gaskets used either, that's until working on these Chinese engines. Using 2 head gaskets is much like using a sandwich gasket (basically 2 gaskets with a filler) on some automotive applications. My son can't (at 135#) start his engine when running the one gasket, on a flat level road. Now on the hill we have in the front of the house is another story. I only use 2 gaskets if I have a problem with the piston hitting the head or I want to decrease the compression. But to each his own.
 
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rustycase

rustycase

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May 26, 2011
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Ahhh... i gotta disagree with that Alf.

A composite head gasket with a sandwiched core is bonded, (in most quality gaskets), and there is a compression ring integral with the design around the combustion chamber area... at least in all the head gaskets I have seen that I can remember... which probably ain't sayin' much ! lol

I don't think the racer guys use composite gaskets.
And people like you, who have lapped the cylinder/head surface, well gosh, you could probably do very well with a lite coat of silver spray paint !

If the kit CAME with two head gaskets I would consider it to be an error, or engineering blunder, such as the many other problems we love to hate abt chinagirls !

Best
rc
 
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