MK65 Head and Cylinder Sadness

I have a new MK65 and a new 70 high comp head. This is the same setup I've used in the past. I have thousands of miles on my other MK65. I cannot get the head to seal on this new kit. I have tried three different new head gaskets, copper spray, several sets of new hardware, had the head decked, hand decked the cylinder with sandpaper on glass - and still leaking in the same place on the flywheel side. I'd love some ideas of how to resolve this issue. I don't want to give up on this kit. Pro advice needed. Thanks.

Re: MK65 Head and Cylinder Sadness

Overpriced Parts /

use a puch hi torque head modded a little so the piston don't hit

Re: MK65 Head and Cylinder Sadness

Hey Ken. What hi torque head would you recommend? And, how will this fix the cylinder issue? I'm fairly certain the issue is the cylinder itself is not flat at the head area, even after my polishing.

Re: MK65 Head and Cylinder Sadness

^ I never mentioned that in my first post. Important info.

Re: MK65 Head and Cylinder Sadness

campeona del mundo /

do you have access to a mill? sounds like the only option is to deck it with a mill/lathe to guarantee it's perfectly flat.

Re: MK65 Head and Cylinder Sadness

I think you're right, Will. I don't have access, but I'm sure I can find a machine shop around that can do it.

Re: MK65 Head and Cylinder Sadness

Overpriced Parts /

a hi torque head gots 2 compression rings on it but most likley only one will seal .

More clamping force then a "flat head'

Re: MK65 Head and Cylinder Sadness

Compression rings. I like the sound of those.

Re: MK65 Head and Cylinder Sadness

Before taking the cylinder in to be decked I would buy one of these and get your head turned in a lathe to accept it.

Re: MK65 Head and Cylinder Sadness

Overpriced Parts /

These will do the trick you may have to remove a little of the inner ring if the piston hits

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Re: MK65 Head and Cylinder Sadness

I'm taking both to a machine shop tomorrow. These two better get married.

Re: MK65 Head and Cylinder Sadness

I've used the stock hi torques with the inner ring removed on a 70 k-star... super sealing and moderate compression... Nice and safe but still have power. I imagine with an MK you could get the squish a little better since it travels closer to the top of the cylinder deck.

Re: MK65 Head and Cylinder Sadness

i ended up using a tomos a35 head cut for the kit by moped factory.

Re: MK65 Head and Cylinder Sadness

Yeah,I am using a moped factory head on mine, and it seals fine.

Re: MK65 Head and Cylinder Sadness

I'm going to have to try a moped factory head. I've tried two new heads and now another MK cylinder and I'm in the same place. I'm almost in disbelief that two cylinders can do the same things. Baffling.

Re: MK65 Head and Cylinder Sadness

Actually, I spoke too soon.Mine now has a very tiny leak. It is nothing that I am going to worry about.It hardly gets my finger wet when I run it under the head, and jug.I had a 50 metra, and it leaked really bad in-between the head, and jug.That is a cool thing about metra's.They can take a beating. Did you seal up that decomp hole in the jug?

Re: MK65 Head and Cylinder Sadness

Yeah, I sealed up the decomp on both cylinders. Both are leaking, so now I'm back to thinking this is a head issue. I think the 70 high comp is not a good head for the MK. We'll see how this moped factory head works out.

Re: MK65 Head and Cylinder Sadness

Okay. I still can't figure this out. Remember: after new gaskets, three new heads, and two different cylinders - I still have a leak. Dammit. Hardware is tight. I even cleaned up the metal base gaskets, thinking that this is the only constant that I had not tried to adjust. No luck. Seriously, dudes. Anyone have ideas? The base area is flat too. I thought that this could maybe cause issues. Never have I seen a head leak like this.

Re: MK65 Head and Cylinder Sadness

Try a copper head gasket just for a minute... it's pretty F'n soft. Maybe this is a bad idea... IDK. Sounds like a good trouble shooting one to me. Are you sure it's not just the carb cleaner vaporizing and getting sucked back into the carb?

How'd you seal up the decomps?

Re: MK65 Head and Cylinder Sadness

Hmm. Do you know where I might find one of those copper head gaskets? I would totally try that. The idea on the carb is good, but the way the Mallosi filter is pointed, i would think that I'm okay. Also, here is the interesting thing: when I pull the head off, it is wet on the bottom portion of the gasket\cylinder every time. The rest of the surface is dry. It's like the area below the bottom two studs just will not seal. I sealed up the decomps by tapping for an m5 and then using a little jb weld around the threads, I screwed in an m5 set screw and let it setup for 24 hours.

Re: MK65 Head and Cylinder Sadness

I was gonna suggest tap and thread if you didn't already... and it's double tapped haha

I don't think you can find a copper head gasket, you'd have to make one. It could be out of fine gauge though. It just sounds crazy that you have a leak anywhere still based on what you've done.

Maybe something to try is get some prussian blue dye from the craft store and stick the head on there with no gasket - it'd help you see if there's a gap/crack/divot some where you didn't see. Seems kinda odd that it's don them on two.

Try different head orientations as well... idk... just thinkin' out loud.

One other thing you might try is a stock puch hi torque head - the ones that are supposed to seal without a gasket. If you've got a clean one of those, the fine aluminum rings in the sealing surface should at least get it sealed up.

Are you using new spark plugs? I heard one time crush gaskets on plugs are a one time deal (though, I don't really believe that). Still something else to try though.

I'm just brain storming out loud... no pro advice or anything. Just what I'd try (edited)

Re: MK65 Head and Cylinder Sadness

Actually.... this advice sounds pro to me!! I have tried the different head placements. I'm going to try the blue dye. That sounds like a great idea. You know what's funny is that I had the same thought about the plugs. I am going to buy some new plugs on the way home today and try it out. Can't hurt! Also, I think I have a stock hi torque laying around somewhere. Thanks for the ideas.

Re: MK65 Head and Cylinder Sadness

One more thing... if it turns out to be something with the plug, I'm going to shoot myself right after quitting mopeds.

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Haha... thanks

Also, you know how it is... it's usually the stupidest easiest thing that ends up being the matter.

I ended up honing a top end and doing rings on a sachs d cylinder because I forgot about the decomp... hurpdaderp....

Let us know when ya get this bitch sealed up! ya gotta be gettin close

Re: MK65 Head and Cylinder Sadness

At this point, the o-ring 70cc high comp head from treats has really seemed to help. I've been checking for leaks this morning and so far, so good!!! Yes! I went out for a ride and things feel good and my plug looks nice. For the moment, I'm considering this sealed! (fingers are massively crossed). Thanks for the input, dudes.

Re: MK65 Head and Cylinder Sadness

Josh Leigh /

Just a heads up I had serious issues running a hi comp head on my Metra and came to the conclusion that these kits do not benefit from a heightened compression (as it already is through the roof with a stock head). My Metra was ping-ing and pressure combusting before the spark. I put on a stock head and no more worries...I might try the hi comp head with a gasket in a few hundred miles but..... Just saying

Re: MK65 Head and Cylinder Sadness

How much compression were you seeing? I've got a mopedfactory head I'm anxious to run... not too stoked about it though if it's giong to push comp over 200psi

Re: MK65 Head and Cylinder Sadness

I ran my other Metra with a high comp head at 190psi for about four years. No issues. 240 seems really high though. What kinds of issues can arise with crazy high compression. I rose for about 30 mins this morning and all seemed fine.

Re: MK65 Head and Cylinder Sadness

I made this last night:

I hope it helps. I'm also back to using the Moped Factory head. My comp is at 185, which seems totally fine to me.

Re: MK65 Head and Cylinder Sadness

sookia sookia /

Did u ever figure this out? I'm having the exact same problem. No amount of head gaskets, rtv, and I've blown out two of those vitton rings.... I'm probably just going to sell it and throw on the treats reed kit that I've had kicking around

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