Dolmar 7910 rebuild. Need some help

[t4driller]

IDK,

Guess I stand alone in thinking more transfer needs to be removed from your jug.

I use acid and sanding. The problem I've found with sanding alone is that you can polish some of the transfer and not see it.

I'd degrease the jug well, apply acid carefully with a Qtip, and see if you've got a lot of bubbling going on there.

Where do you think you see transfer at? And where can I get acid from? I've always just used sanding , and this is the first I've had a problem. I'm willing to try different ways of doing things.

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[drf256]

Every vertical line could be transfer.

Maybe you got an "off" jug if the saw failed a bunch of times.

Get muriatic acid at the hardware store. Wear eye protection.

Mix a bunch of baking soda in a pale of water.

Apply the acid with qtips. Be care anywhere the plate meets aluminum, like the ports and band. You can undermine the plating.

Look for foaming. Rinse with water, then immerse in soda bath. Wash again, dry off, sand and repeat till there's no foaming and a smooth bore with no lines at all.

 

[t4driller]

For the base gasket. There's not enough room to eliminate it. I measured .015 without gasket and then the gasket measured .014. Was gonna use aluminum can for gasket. It measured .004. Should I use any kind of sealer on each side, or will it be good without sealer?



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[t4driller]

Every vertical line could be transfer.

Maybe you got an "off" jug if the saw failed a bunch of times.

Get muriatic acid at the hardware store. Wear eye protection.

Mix a bunch of baking soda in a pale of water.

Apply the acid with qtips. Be care anywhere the plate meets aluminum, like the ports and band. You can undermine the plating.

Look for foaming. Rinse with water, then immerse in soda bath. Wash again, dry off, sand and repeat till there's no foaming and a smooth bore with no lines at all.

From what I was told it only was scorched once. I took some time and tried to sand some of the lines out by hand , and they wouldn't come off. So I assume it's not transfer. And it doesn't look like transfer. So I think I'm gonna give her a try tonight.

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[drf256]

My point is that transfer can polish top and look a lot like plating.

Please report back and let us know how it went.

 

[t4driller]

My point is that transfer can polish top and look a lot like plating.

Please report back and let us know how it went.

I will check again before I try it.
I bolted the jug down with just the aluminum can for a gasket and it did not pass pressure test. So I assume to use a sealer. I use Honda bond. I've never used a can for a gasket, just read it could be done. If not someone please chime in and let me know. [emoji4] [emoji4] [emoji4]

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[Redfin]

I would definately use a good sealer. Did you find where it was leaking?

 

[mdavlee]

I've used beer cans before with sealer

 

[t4driller]

I would definately use a good sealer. Did you find where it was leaking?

Yes. It was leaking all around base gasket.

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[Adirondackstihl]

For the base gasket. There's not enough room to eliminate it. I measured .015 without gasket and then the gasket measured .014. Was gonna use aluminum can for gasket. It measured .004. Should I use any kind of sealer on each side, or will it be good without sealer?



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Sealant both sides

 

[Adirondackstihl]

Yes. It was leaking all around base gasket.

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Old paper gasket or new metal gasket?

 

[paragonbuilder]

Yes. It was leaking all around base gasket.

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If you want to lose the base gasket, glue some sandpaper to your old piston and sand the squish. It doesn't take long for .004. And you gain some more compression!!


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[t4driller]

Old paper gasket or new metal gasket?

That was with the beer can gasket only.

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[t4driller]

If you want to lose the base gasket, glue some sandpaper to your old piston and sand the squish. It doesn't take long for .004. And you gain some more compression!!


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I don't have the old piston. It wasn't in the box o parts I bought. I might have other old pistons laying around that would fit though.

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[t4driller]

If you want to lose the base gasket, glue some sandpaper to your old piston and sand the squish. It doesn't take long for .004. And you gain some more compression!!


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I've been looking into getting something to cut the squish band by hand. There was a thread recently about it. Definitely want to try it.

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[paragonbuilder]

I've been looking into getting something to cut the squish band by hand. There was a thread recently about it. Definitely want to try it.

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I've also made a wooden mandrel with a jig on my table saw. It's pretty easy to do. Then glue the paper to the end. I probably could cut a hss cutter in to it but haven't tried yet.


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[t4driller]

Every vertical line could be transfer.

Maybe you got an "off" jug if the saw failed a bunch of times.

Get muriatic acid at the hardware store. Wear eye protection.

Mix a bunch of baking soda in a pale of water.

Apply the acid with qtips. Be care anywhere the plate meets aluminum, like the ports and band. You can undermine the plating.

Look for foaming. Rinse with water, then immerse in soda bath. Wash again, dry off, sand and repeat till there's no foaming and a smooth bore with no lines at all.

I took a little acid over some of the lines, and nothing happened. No foaming or anything. [emoji2] [emoji2]
I sanded the squish band down to get .019 / .020 clearance without base gasket. Also installed another carb kit just to make sure carb is good. Later today I'll finish getting it back together and hopefully running. Gonna make sure everything is clean and a good coating of oil on piston and cylinder.


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[t4driller]

Success finally. Got it fired up finally and sounds great. Buried a 20 inch bar in some hard maple and it pulled like a freight train. After it cools I'm gonna take a comp reading, and check the piston out. So far so good though. [emoji2] [emoji2] [emoji2] [emoji2]

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[t4driller]

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[t4driller]

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