Head Gasket Gap On New Engine?

[RPM]

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

 

[NunyaBidness]

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.

 

[MelMartinez]

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 !!!

 

[Junster]

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.

 

[RPM]

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

 

[Rockenstein]

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

 

[RPM]

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

 

[Pablo]

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!!)

 

[Junster]

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

 

[RPM]

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

 

[Junster]

Cool maybe you can get them to just ship you a new jug. Many times they don't want the old parts back. You can also up the ante by telling them how you hope to brag up their fine customer service here. heh heh
BTW: The sealing surface is well inside the headbolts. Look at a headgasket on SBP's site.

 

[RPM]

Well guys I heard from the company today that I bought the engine from and they are more than willing to work with me on this. They will either send another engine (which I will have to send this one back plus shipping) or they will ship me a jug. I'll have them ship me a jug and any gaskets that will be needed instead of shipping it back.

Pablo, you said you lapped your head, I don't know if you took the jug off but if you did was a base gasket needed or did you use the old one?

Maybe you had a jug off Junster, if so was a base gasket needed? What about replacing the head gaskets? The engine hasn't been fired up yet its still new. I suppose I could smear a very thin thin coat of copper seal on the gaskets and use the ones on there now. I've torn down and had jugs off of at least eight or ten chainsaws over the years when I use to work in the woods for on site repairs and never replaced any of these gaskets with no problems what so ever afterwards.

I think I read somewhere the head bolts are to be tightened 15-20 lbs torque, is this right?

RPM

 

[Junster]

Most say 12lb torque on the head. If you lap in the head and the jug that will be fine. Needed gaskets will depend on if you break them when you dissasemble it. Ask them to send a base and a head gasket with the jug. You can reuse headgaskets but new is better. When you get the new base gasket just use it for a pattern to cut a new one out of 1/16" high temp gasket mat. from a auto parts store. The china gaskets aren't very good and as long as you have the jug off you might as well do it right. I also used lok-tite 501 for alum flanges on both sides of the gasket. Pull the headbolts out of the case then put them back in with blue lok-tite. Also while your waiting have you replaced the engine mounting studs? If not please do so. The china ones are very soft. Sick Bike Parts has a kit for doing that on their site for 9.95 I also always replace the stock tank petcock and the clutch cable with the ones from SBP too. It's an extra $28 bucks but it will save you alot of greif. You'll find dealing with SBP a very good experience.

(28 includes shipping) If you do goto their site look at the expansion chambers the difference in power from these engines with one is night and day.

 

[MelMartinez]

9 - 10 lb of torque on the head bolts are more than plenty. It´s not safe for some bolts to go higher than that.

That´s according with personal experience. I just hope this helps you on anything.

See You in the Road !!!

 

[Pablo]

If the jug is taken off you should replace the bottom gasket.

9-10 lb - ft of torque is not adequate for a well built 67cc engine with 8mm studs.

 

[RPM]

Well I'm gonna pull the head tomorrow. Seeing how they will work with me I'm curious as to how far the casting flaw extends into the jug. We'll know soon enough.

When I untorque the head I'll take a reading on the graph as to how much torque it took to break the head bolts.

I'll post some pics and put them up here so you can see what I found.

RPM

 

[reg454]

RPM where at in michigan are you i am in the southgate area

 

[RPM]

Well the jurys out and the verdict is in. I took the head off today and the pictures speak for themselves.

Pic# 1_ clearly shows the no "contact area", Pic# 2_ is an x_ray of that area which shows it as a 'Hot Spot', Pic# 3_ is a blow up which gives a better detail of whats going on, Pic# 4_ is the head (the bottom left where the arrow is pointing) this is the area that makes contact with the area of the cylinder in question, Pic#_5 is an X-ray of the head and there is no 'Hot Spots' anywhere. Pic# 6_ is the cylinder and if you look close to where the tip of the pencil is pointing you can match the gasket with the slight foot print in the area.

It looks like there is roughly a 2mm distance from the outside edge taper of the bore to the head bolt in Pic# 7_. I also see no decay here as well as Pic# 6.

So the good news is the decay of the cylinder (right rear intake side) does not extend into the critical seal area as in Pic# 6 & 7.

I was right when I said I could see the stud. But that was the extent of it. The area affected only consumes about a quarter of the cylinder bolt area. I believe the area not affected will be sufficient enough to make a good seal with the head now after examination. If I have problems with it I'll take Rockenstein's advice and lap the cylinder head. So for now I'll put it back together and see what happens.

I checked the torque as I took the nuts off the head and they were all over the place. The bolt where the area affected was maybe 10 lbs. One was 15 lbs. and the other two were over 20lbs.
I retorqued the head bolts and now I don't see any gap at all in the affected area.

I did notice something unusual inside the cylinder wall when I pushed the piston down and that was there were two "dimples" as if hit by a BB from a BB gun. I was a little bummed out at first but kept looking at it from every angle and I could see that the slight indentations were annealed to the wall as the cylinder is. If they would have been open "pits" I would have sent the cylinder back.

Seeing how I had the top end of this thing apart, I took the carb intake tube off and noticed all kinds of "Slag" from the casting process inside of it. As you can see in Pic# 8 & 9 its certainly restricting. I can only imagine what kind of performance I would have gotten if I hadn't noticed this. So now I'll take the dremel tool and buzz away until I have a smooth non-restricting surface within the tube.

Boy, I don't know, the more I look the more I find stuff. I really don't want to take the rest of the engine apart but I'm gonna have to pull the covers before I fire it up. Hopefully I won't find anything scarry inside.

Looks like I'll have to put another post up to get all the pics in here.

RPM

Hey Reg, how's it go'in. If thats your recent pic I swear I'm look'in at Jimmy Jake from Port Huron Mi.
You got a double walk'in around bro.

My sis use to live in Southgate many years ago, and what down stater hasn't heard of the famous words "UP NORTH" West Branch! (smile)

 

[Pablo]

Where are the rest of the pictures? X-ray???

Did you check the head for flatness? I didn't know we are talking about a slant hand (I missed that).

Interesting - but I'm not exactly following you on the x-ray thing and hot spots. Those don't look like x-ray shots to me.

 

[reg454]

Rpm yes that is a recent pic from like winter, their are a few people that kind of look like me and most of them are younger.