Head Gasket Gap On New Engine?

Hi everyone, I'm recently new to the forum and have already picked up some really helpful tips. This is a great site!

I put my first build together last December (49cc) and a few problems came along and was able to resolve them but I just received my second engine today (68.5 cc) and have a major concern with something I have observed while inspecting it.

On the rear right side (intake) there is a gap between the head gasket and the (jug) cylinder of .006 or 0.015 mm. I noticed this as I held the motor in my hand and could see the light shinning between these surfaces. I don't think this is suppose to be this way or maybe it is.
I don't know? On my 49cc engine it isn't like this.

My concern is should I contact the company I purchased it from and inform them of the condition or should I mount the engine and set the bike up and then try it to see how it runs or, should I take the head off and apply some "LOCTITE GASKET ELIMINATOR 515 SEALANT" ?

From what I can see the problem isn't in the head. It looks to me that it wasn't a completely perfect cast on the jug on the right rear corner.

I'm sure I can probably fix this problem with sealant and or even J & B Weld depending on how severe the problem but I will have to take the head off to inspect the jug for a closer look.

I've included a couple pics. The white arrows point to the gap and the feeler gauge stuck in the corner of the head and gasket speaks for itself.

I'm not that experienced on these engines only from what I've experienced and have read here.
Anyone with any insite on this condition I would greatly appreciate.

Thanks Guys

RPM

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For something that thin you might even be able to use a thicker gasket and simply squish it down a little bit.
I don't really know but I'm sure someone who does know will be along soon enough to help.

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"I would rather be exposed to the inconveniences attending too much liberty than to those attending too small a degree of it." - Thomas Jefferson

The question in here is if your engine HAS a gasket between the head and the cylinder.

If the engine has a gasket and good compression, there is nothing to worry about; the engine will run normally, even if the gasket is smaller than the heath´s surface.

Try to turn the engine and double check if it has compression. I´m almost sure it does and will have no problem.

Good luck and welcome to the boards.

Please do not hesitate to request any further information regarding this matter.

See You in the Road !!!

I used 515 on both sides of my base gasket when I had to replace it. It gave me a killer seal but I don't think it will hold up to the top end pressure. (it failed as a seal on the base with no gasket) If it were me, I'd just pull the head and jug off the motor and lap both in with some 220 wet sandpaper and water on a piece of thick glass. It's easy to do just get the paper wet on both sides and lay it on the glass. Hold the paper still and use a circular motion and light pressure on the part. Rinse the part and the paper every couple minutes. As you check the mating surface you can easily see how far you have to go till it's flat. Since I did that I don't have to overtorque my head to get a perfect seal. You might have to make or buy a new base gasket if you pull the jug. It's bit of a pain but you'll save yourself alot of trouble in the end. Maybe Pablo will chime in with how many headgaskets he went thru till he lapped in his new slanthead.

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Put something FUN between your legs..

Thanks for the insite.

You bring up a good point Mel. The engine is brand new. I was holding it in my hand when I took the pictures and it's not mounted. It's never been fired up. It's in the box as I write this.

Yes, it has 'TWO' head gaskets. I don't know if these engines (68.5cc's) come with two or one head gasket. If only one then what they did was try to make up for the discrepancy by putting two in there.

As far as lapping these two surfaces Junster, Boy I really don't want to get into that if I don't have to. I use to work in a machine shop some years back and it wouldn't have been no big deal to put her on the bridgeport then, but now by hand, I'd have to take down at least .006 or 0.015mm before the jug was true. Then probably another couple to mate the two surfaces. And whatever I take off I'll have to make up for with a shim.


I'm not sure but it almost looks like I can actually see the head bolt. I would have to tear it down but this may void the warranty.

I'm kinda caught between a rock and a hard place for time. I think I read somewhere I've got only forty-eight hours to try it out to see if this thing works properly before the warranty is off.

Boy, that don't sound right, I'm gonna have to take another look at that warranty again.

RPM

If the casting flaw is bad enough that it's allowing you to see the stud then your faced with the possibility that the head may eventually warp and at that point both jug and head are paper weights. If the casting flaw is in from the outer edge by only a few thou it would likely be ok since support in and around the stud area would not be adversely affected.

I'd send the pics to the seller and ask for some direction or another jug without a serious flaw in such a critical area. I wouldn't even loosen a nut or whatever until the seller is contacted though, most will void the warranty if you spit on the thing and leave a stain

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I refuse to be taken apart...

Hey Rockenstein,

That sounds like a better option at this point and time and good advice. I'll contact the seller today and send the pics.

The last motor I bought from them I had a problem and they were pretty good about it.
It seems the rubber O-ring in the pit cock that is the seal, has a series of O-rings within it. One of those had a small chunk of rubber out of it and as a result was leaking at the petcock. All they wanted was a pic to confirm this and rather send just a new O-ring they sent the whole pit cock. I'll see if they will work with me on this.

If there was just a few thousands on the other edge I'd probably go for it. But there is alot of material missing and there is no way of knowing what the inside looks like unless I remove the head. Dilemma..

RPM

If the seller balks, the lapping is so easy a caveman could do it. Fun and rewarding. Just make sure it's ultra clean when done. Chances are it's mainly the head as was the case with my slant head (very severe!!)

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I have bought 2 slanthead motors from zoom. Both has 2 head gaskets. I think it's to slightly reduce the compression so they start easier when new. I removed one of them after my motor was broken in. The clearance was fine but it seemed like the motor was pinging a little so I put the second one back in. It may also be to try to make up for non flat surfaces. If you do lap it in you would have to remove alot of material before any shiming was needed. I was just trying to help you avoid the shipping turn around delay. Esp. since even if it looks good you may have to do it anyway. GL

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Put something FUN between your legs..

Well I hear ya Junster and that was exactly what I was thinking when I started this post. I really don't want to send it back unless absolutely necessary.

It looks like the manufacturer of these motors have been listening to the people buying them and have made improvements as I can see. The motor looks to be clean, I'm rather impressed.

Rockenstein made a good point. Yeah, these people wouldn't touch it if they knew you tore it apart. My hands are tied for the moment. As far as your case Pablo being the head, I'm sure its a tasks I could perform if it was just the head but its not from what I can tell. With this motor its specific to the area that I have described as being the jug. I know its not the best picture but it's definately the jug area. I don't know if the inner immediate area around the stud is decayed or not. Examination would only tell the story.

But I did email these guys today with pics and I will be curious as to what they will recommend I do. I don't believe this motor will perform as it should with what I see here. I think it will either do poorly from the beginning or within three to five miles when it warms up its gonna fail.

I'm blessed with where I live in a rural area where there is looong country roads, gravel and pavement and my rides are a minimum of twelve to fifteen miles each outing.
I just don't have faith while looking at this motor that I would make the trip the way it is.

I'll keep you posted on what their reply is.

RPM