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Removing base gasket on a pulse port cylinder

NorthcentralYooper

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Hi I'm working on a husky 51 Epa 49cc this has a pulse port and pulls air in from a notch in the gasket .
I read someone deleted the gasket on one of these and never mentioned any details other then it ran good.

I'm removing the H limiter on the carb I checked squish and without the gasket I'm at .030" has anyone ever worked on a solution to running without a base gasket.

The current one is .009 " so I could use brown paper at .004" but would that even be adequate for a air gap to draw air?

My solutions would require machining but maybe I'm missing something.

Thanks !
 

Stihlbro

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You can remove the gasket, but you need to check the clearance between the top of piston and the combustion chamber. Most use a gas/oil resistant sealer for the base. I am alittle confuse d on what your asking but if you are referring to the impulse passage, the factory gasket has a spot cut out for the impulse signal. You need to make sure the passage is open for which ever method you choose to use.
 

CrufflerJJ

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If you decide to use sealer instead of gasket I normally give a little shot of air into the impulse hole on the jug to make sure its clear.

Good idea! When I rebuilt my first saw a little while ago (a Husky 51 EPA), I used Permatex 51813 sealer. I was concerned that it might gunk into the impulse hole, so I inserted a small piece of insulated copper wire into the jug (so it was just flush with the base) before I bolted it down. Once it was bolted down, I removed the piece of wire.

Compressed air sounds much easier!
 

NorthcentralYooper

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You can remove the gasket, but you need to check the clearance between the top of piston and the combustion chamber. Most use a gas/oil resistant sealer for the base. I am alittle confuse d on what your asking but if you are referring to the impulse passage, the factory gasket has a spot cut out for the impulse signal. You need to make sure the passage is open for which ever method you choose to use.
I appreciate your help but your not understanding what type of cylinder I'm dealing with. I'm hoping someone else has husqvarna experience in this cylinder type. And like stated the squish is .030" with no gasket
 

NorthcentralYooper

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I like the wire idea , if I use air what's to say it won't blow the permatex gasket out to the outside?
 

CrufflerJJ

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I like the wire idea , if I use air what's to say it won't blow the permatex gasket out to the outside?

If you just use a quick shot of air, with the spark plug removed, you'd just clear out the impulse passage. Even with the sparkplug installed, I've read about folks running saws immediately after being assembled with the 51813 or Loctite 518. This would be before the sealer has had a chance to cure. 51813 is fairly thick stuff, and there's no real chance that a quick shot of air would blow it out from between the jug & crankcase once you've got the bolts grunted down.
 

Stihlbro

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If you use a sealer, once you have the jug installed and tightened. A quick little shot of air will verify the impulse passage is open. It the cylinder is tightened it will not blow the permatex sealer.

If you want to use a gasket then you will need to machine the base to achieve the desired clearance. Hope this helps.
 

CrufflerJJ

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If you use a sealer, once you have the jug installed and tightened. A quick little shot of air will verify the impulse passage is open. It the cylinder is tightened it will not blow the permatex sealer.

If you want to use a gasket then you will need to machine the base to achieve the desired clearance. Hope this helps.

Do you still (Stihl?) use the compressed air approach if using a drying type gasket sealer like Yamabond or 1194? I guess I'd worry about shooting some of that stuff down into the crankcase where it would harden At least the 518 / 51813 stays liquid & washes out if it gets "down below".
 

NorthcentralYooper

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Ok I'll try that out , I'm just thinking the with no gasket the hole at the base of the cylinder is flush to the crankcase so even if you blow into the cylinder are you just relying on the closeness of the hole to the crankcase to open up.? Sorry maybe I'm nuking it out but I was thinking I'd have to machine a actual passage in the cylinder base or the crankcase mating surface BTW I'm using permatex motoseal
 

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It is nothing more than verifying the passage is open. Just a quick check. It only takes a tiny smear of sealant.
 

NorthcentralYooper

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Yea I understand the concept but imagine placing a hole on top of a flat surface with basically no clearence . The whole method this impulse passage works is by having clearence or a air gap
 

hoskvarna

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I use anaerobic sealer like yamabond on my 55 with out gasket. It doesn't take much a thin smear. Never had a problem.


From the Hills
 

NorthcentralYooper

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I use anaerobic sealer like yamabond on my 55 with out gasket. It doesn't take much a thin smear. Never had a problem.


From the Hills

How is the cylinder setup does the pulse port sit on top of the flat mating surface of the crankcase. Basically without a air gap I see no way the port is open to the case .
 

NorthcentralYooper

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Just to update , I put a real small notch on the crankcase mating surface to ensure the pulse port wasn't blocked. I put a small wire in the hole just for good measure . I used motoseal and torqued cyl bolts. After it set up a bit I pulled th e wire out and shot a burst of air through to make sure it was still clear .
I'm now reading 182 psi with no base gasket and .030" squish.
I believe the higher psi is from the assembly oil sealing better.
 

ft. churchill

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I'm using Hondabond and most of the ones I build do not have base gaskets. I have never had a leak with Hondabond nor have clogged up the impulse hole. I do not employ any of the tricks here (I do like the quick shot of air) and have good success. I have had leaks with hylomar and no gasket.
 

NorthcentralYooper

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I'm using Hondabond and most of the ones I build do not have base gaskets. I have never had a leak with Hondabond nor have clogged up the impulse hole. I do not employ any of the tricks here (I do like the quick shot of air) and have good success. I have had leaks with hylomar and no gasket.

I haven't had issues with the motoseal to date. This was a different design that I'm not quite sure everyone on here was understanding. I had to physically Dremel a 1/8" notch on the crankcase sealing surface because on this saw the pulse port of the cylinder is closed off to the case with out a gasket to create a air space gap.
 

ft. churchill

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Now I understand what your stepping in. I dont believe I seen one with that design. I have heard of folks who drill and tap a hole and run an external hose/line for the carb impulse. Usually done with a carb swap that has a different style of carb.
 
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