fuel leaking from carb@cylinder head

hi, i have a 1980 batavus m-48. i would like to know if i should tighten the 10mm bolts, as tight as can be, or leave them snug(as they are right). i have fuel coming out after traveling about 1 mile, it not much but this is probably why it stalls out after operating for about a mile.( (starts right up w/ the choke) this is a dicontinued carb, and i want to find out if the bolts are snug , not over-tightened should i locate something for the gasket. thanks, -tim

Re: fuel leaking from carb@cylinder head

Flange-mounted carburetors and maifolds tend to warp over time, from overtightening and gasket compression.

If a flange is leaking due to warpage, you can true it up.

Lay a piece of wetted wet-o-dry sandpaper on a surface plate (you can use a plate of glass) and lap the flange flat, using a figure-8 motion. Reverse the motion, and give an even number of strokes in each direction. You'll know when it's flat, when the whole surface of the flange is getting marked by the paper.

Re: fuel leaking from carb@cylinder head

hi, where do you buy the wet o dry sandpaper? should i put anything on the gasket, how tight do you drive in the bolts thanks alot -tim

Re: fuel leaking from carb@cylinder head

Don Pflueger /

the cylinder head bolts need to be torqued to 10 ft/lbs.

Re: fuel leaking from carb@cylinder head

Don Pflueger /

sorry, i reread this. i thought you meant cylinder head bolts. there is a torque spec for 10mm bolts. i think you can find it in the back of the batavus service manual, if not, i can look it up in my dealers service manuals. you dont want to use anything like form a gasket on an intake. do like legendre said and make sure the mating surfaces are flush. then you can use a brush on atv sealant. put it on very thin tho. you dont want it to squish out into the intake when you tighten the bolts.

Re: fuel leaking from carb@cylinder head

You can get 3M wet-o-dry just about anyplace - hardware store, home depot, menards etc. I'd suggest a medium grit, like 180-200 grit, and use it wet.

If it's way out of true, start with a coarser grit, and finish up with medium or fine.

You can use a little of the orange permatex on an intake gasket, but just the thinnest smear. If you need more, then the parts need truing.

I would not torque a manifold flange that uses a thick gasket more than 4-6 ft/lbs, assuming 6mm bolts. This is one of those places where the "mechanics feel" is very helpful..

Re: fuel leaking from carb@cylinder head

hi, i just googled atv sealant and i'm not sure..is it a tire air sealant product? thanks, -tim

Re: fuel leaking from carb@cylinder head

would i make one figure 8 going forward,then one backward, then repeat several times? thanks again -tim

Re: fuel leaking from carb@cylinder head

Yes, just try to make an even number of cycles in each direction., and change your grip on the part once in a while. You just want to lap it evenly, not wear a flat spot on one edge, etc.

Re: fuel leaking from carb@cylinder head

Don Pflueger /

no. it looks similar tho. what i use says aviation sealer or something like that. its made by permatex and i buy it from auto zone.

Re: fuel leaking from carb@cylinder head

Matthew Scholtens /

Another tip to help see if you sanded the entire surface is to use a sharpie marker. Color the entire surface to be sanded. If some black marker is still left, then sand a little more. It's a quick visual that I learned at work.

Matthew

Re: fuel leaking from carb@cylinder head

I know the stuff you're talking about don, it's a brown material similar to the Gasgacinch product, and comes in a little brush-cap bottle.

It can work really well if the surfaces are true, but IIRC it can make things really difficult to take apart - and usually destroys the gasket when you do.

Have you ever used Hylomar? Just curious what you thought of it.

Re: fuel leaking from carb@cylinder head

That's a really good suggestion Matt.

In the trade, there is a product called DyKem, which comes in red or blue, and is used for just this purpose. A bottle will last for just about ever, and it applies much quicker than a sharpie.

Used for everything from checking valve seating, to setting mesh on gears.

Re: fuel leaking from carb@cylinder head

Don Pflueger /

yep sounds like the same stuff. ive never had a problem getting things back apart, even years later. it will destroy the gasket, but in my shop nothing goes back together with an old gasket anyway. so its never been a problem. no i've never used hylomar. is it anything like hi-tack?

Re: fuel leaking from carb@cylinder head

Hylomar is a non-drying gasket dressing, that can be used with our without a gasket. The base "gasket" on a BMW R-series motor was just Hylomar, no actual gasket. The nice part, is that hylomar doesn't really dry, so disassembly is much easier. Maybe try it sometime.

Re: fuel leaking from carb@cylinder head

If you remove the carb you'll see a small pin hole at the bottom bolt area....it goes thru the bolt area and into the intake of the carb. It's there as a safety valve,in case the float doesn't work properly....sometimes the pressure from the gas tank will force gas by the float , so you should shut off the gas vavle when stopped. I just went thru this with mine and had to install another shut off cause mine doesn't work. It solved the problem! Also pin point up on the float... Mine was the other way.

Re: fuel leaking from carb@cylinder head

John Joedicke /

Used Hylomar on a Lotus 907 engine rebuild. Worked great and as you say it stays workable but seals. Stuff I had was a redish orange color.

Re: fuel leaking from carb@cylinder head

I use Permatex 2 (non-hardening gasket sealant) (#2BR) on intakes .. it's a soft dark brown/black goo .. smear or brush some around an old dried gasket and on flanges.. Recommended for sealing oil pans and valve covers where removal without destroying the gasket is always a nice thing..

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