woodworkingboy
TreeHouser
Hondabond or Yamabond are two liquid gaskets that will work. 3M makes a product too.
MS260 port job
- Thread starter sotc
- Start date
- Replies 210
- Views 30K
woodworkingboy
TreeHouser
I rough up the base a tad with some wet and dry paper, before applying the gasket. Surfaces free of contaminent, of course.
Some saws have a slight problem lining up and attaching the muffler after dropping the jug, the cylinder being lower to the case and sometimes the orientation to the housing....same with the carb/air filter arrangement. Probably not a problem though.
Some saws have a slight problem lining up and attaching the muffler after dropping the jug, the cylinder being lower to the case and sometimes the orientation to the housing....same with the carb/air filter arrangement. Probably not a problem though.
woodworkingboy
TreeHouser
Looks good Willie, nice and wide and pretty even. I'd say that is a good texture that you have on the intake walls. I find a small wire brush good for removing small irregularities, and leaving an even texture. One way of thinking is that the texture, as opposed to polishing, causes the intake charge to swirl more in irregular patterns as it enters the cylinder, a good thing for distribution of the charge. Chaotic velocity is what you want.
Are you doing anything with the transfers? I'd at least open them up to the base, so the charge finds it's way up easier from the crankcase. Open just enough to still leave enough base for your gasket seal. I think a rough texture is advisable on the transfer walls as well, though some guys like to polish them. If you do the lower transfers, might as well take the upper ones back up to stock timing, and more angle them in the direction of the intake side. Uppers can be tricky and mess up things if you go too high. Approach with delicacy or leave 'em as is.
Hope you don't mind me offering my opinions on your mod.
Jay
Are you doing anything with the transfers? I'd at least open them up to the base, so the charge finds it's way up easier from the crankcase. Open just enough to still leave enough base for your gasket seal. I think a rough texture is advisable on the transfer walls as well, though some guys like to polish them. If you do the lower transfers, might as well take the upper ones back up to stock timing, and more angle them in the direction of the intake side. Uppers can be tricky and mess up things if you go too high. Approach with delicacy or leave 'em as is.
Hope you don't mind me offering my opinions on your mod.
Jay
squisher
THE CALM ONE!!!!
Mind? I think he's counting on it.
Now I have a question. The one side looks to be alot 'thicker' than the other side. Is it supposed to be like that or is there just more work to be done?
Now I have a question. The one side looks to be alot 'thicker' than the other side. Is it supposed to be like that or is there just more work to be done?
woodworkingboy
TreeHouser
Willie,
Don't know if you've purchased your gasket goop yet, but due to environmental or health concerns, some have been taken off the market. I don't think that Yamabond is currently available, unless it's old stock. I couldn't find it here for that reason, and learned that it was no longer sold. The folks who made Yamabond, now put out their own replacement, called Threebond 1194. You want the 1194 product. It's the same as the Yamabond basically, but without the lead content. I see on the web that it's sold in the states...some Yamaha dealers list it. I've had excellent luck using the Threebond, no leaks on the three saws that have it as the base gasket now. I spoke with the manufacturer about using it for the cylinder gasket, and they said it was designed for such use.
Yes, the transfers are the openings 90 degrees to the intake and exhaust ports. When the piston travels down, it pushes the charge from the intake down into the crankcase, and the pressure forces it up the larger lower transfer, through the channel, and it comes out above the piston rings and then gets compressed as the piston rises before ignition. There are what's called open and closed transfers, depending on whether the whole transfer channel is open to the cylinder, or it has two separate openings. I assume yours is a closed transfer type cylinder. The reason why the upper transfers are angled toward the intake, is because as the charge enters above the piston, the exhaust port is still open, so instead of the intake charge flowing out the exhaust port with the after combustion gases, it actually travels around the upper part of the cylinder and helps push out the exhaust, a very dynamic part of the two cycle process, called scavenging, then the remaining charge gets compressed to explode. Some of the fresh charge gets lost out with the exhaust, one of the efficiency problems of two cycle engines, and a reason why they are considered somewhat environmentally unfriendly. The reason why racers put tuned pipes on their saws, is because a good portion of the unburned fuel that gets lost out the exhaust, actually gets kicked back into the cylinder to be burned. Pipes up the efficiency process. So much for the two stroke primer, I'm far from being an expert.
There is a short section of cylinder wall under the lower transfers, before the base. By shallow grinding that away the whole width of the transfer, the charge can leave the crankcase a bit sooner, and probably with greater velocity to travel up to the upper transfer opening. Grinding away on any material inside the transfer that will allow better flow, is advantageous. There is extra metal in there that can get removed. It can help to picture the flow of charge as how water would respond, flowing better around smooth curves than it would against abrupt angles and obstacles. One of the big aspects of modifying an engine, is improving flow of the gas/air charge, and exhaust. The easier the fresh charge moves at a subsequent greater velocity, a then larger amount of it will get compressed to ignite, which equals more power. A certain percentage of the charge also enters the upper part of the cylinder by traveling through the inside of the piston skirt, the reason why there are openings on the sides of the piston. Removing material on the underside if the piston, enlarging the openings, anything that impedes flow, is also a modifying step, and you can lose a lot of piston weight that way as well....a very positive thing for increased rpms. You just need to consider how much you can take off before strength is compromised, or you leave yourself with an open port situation when the port should be closed.
Something along those lines
Jay
Don't know if you've purchased your gasket goop yet, but due to environmental or health concerns, some have been taken off the market. I don't think that Yamabond is currently available, unless it's old stock. I couldn't find it here for that reason, and learned that it was no longer sold. The folks who made Yamabond, now put out their own replacement, called Threebond 1194. You want the 1194 product. It's the same as the Yamabond basically, but without the lead content. I see on the web that it's sold in the states...some Yamaha dealers list it. I've had excellent luck using the Threebond, no leaks on the three saws that have it as the base gasket now. I spoke with the manufacturer about using it for the cylinder gasket, and they said it was designed for such use.
Yes, the transfers are the openings 90 degrees to the intake and exhaust ports. When the piston travels down, it pushes the charge from the intake down into the crankcase, and the pressure forces it up the larger lower transfer, through the channel, and it comes out above the piston rings and then gets compressed as the piston rises before ignition. There are what's called open and closed transfers, depending on whether the whole transfer channel is open to the cylinder, or it has two separate openings. I assume yours is a closed transfer type cylinder. The reason why the upper transfers are angled toward the intake, is because as the charge enters above the piston, the exhaust port is still open, so instead of the intake charge flowing out the exhaust port with the after combustion gases, it actually travels around the upper part of the cylinder and helps push out the exhaust, a very dynamic part of the two cycle process, called scavenging, then the remaining charge gets compressed to explode. Some of the fresh charge gets lost out with the exhaust, one of the efficiency problems of two cycle engines, and a reason why they are considered somewhat environmentally unfriendly. The reason why racers put tuned pipes on their saws, is because a good portion of the unburned fuel that gets lost out the exhaust, actually gets kicked back into the cylinder to be burned. Pipes up the efficiency process. So much for the two stroke primer, I'm far from being an expert.
There is a short section of cylinder wall under the lower transfers, before the base. By shallow grinding that away the whole width of the transfer, the charge can leave the crankcase a bit sooner, and probably with greater velocity to travel up to the upper transfer opening. Grinding away on any material inside the transfer that will allow better flow, is advantageous. There is extra metal in there that can get removed. It can help to picture the flow of charge as how water would respond, flowing better around smooth curves than it would against abrupt angles and obstacles. One of the big aspects of modifying an engine, is improving flow of the gas/air charge, and exhaust. The easier the fresh charge moves at a subsequent greater velocity, a then larger amount of it will get compressed to ignite, which equals more power. A certain percentage of the charge also enters the upper part of the cylinder by traveling through the inside of the piston skirt, the reason why there are openings on the sides of the piston. Removing material on the underside if the piston, enlarging the openings, anything that impedes flow, is also a modifying step, and you can lose a lot of piston weight that way as well....a very positive thing for increased rpms. You just need to consider how much you can take off before strength is compromised, or you leave yourself with an open port situation when the port should be closed.
Something along those lines
Jay
woodworkingboy
TreeHouser
Good score, the 1104 is actually the predecessor to the 1194, but with lead content. It's been phased out over here.
Are you checking the piston clearance at the top of the cylinder after eliminating the base gasket? You'll need one of these, or one with a digital read-out, that measures down to .001". I can explain the procedure if you need, easy enough to do.
Are you checking the piston clearance at the top of the cylinder after eliminating the base gasket? You'll need one of these, or one with a digital read-out, that measures down to .001". I can explain the procedure if you need, easy enough to do.
Attachments
squisher
THE CALM ONE!!!!
Please do Jay.
woodworkingboy
TreeHouser
Just heading off to work, will try to 'splain this evening.
squisher
THE CALM ONE!!!!
Cool, have a safe day.
N
Newfie
Guest
This thread is making my head hurt. I may have to go slow and re-read some of these posts. It would be nice to better understand the inner workings of my saws.
just kidding
woodworkingboy
TreeHouser
Squish measuring method:
First thing I do is take off the starter cover, if it's still on. Then you can move the piston up and down by turning the flywheel. Taking the ring(s) off makes for easier putting the cylinder on, especially if you are going to be making a number of clearance checks. No rings doesn't effect the squish measurement, if you measure on at least two sides. I usually measure on all four sides of the crown. I put a little dab of grease on the four points of the crown to hold the solder, then cut four half inch long pieces of solder and set them in the grease, just a tad in from the outside edge, and pointing towards the crown center. I use 1/16" diameter electrical solder. I think the plumbing type solder is harder, and you want the soft type.
I turn the flywheel until the piston is low in it's stoke, sitting close to the crankcase, then carefully slip the cylinder over, not disturbing the solder. With the rings still on, you will likely mess up the solder positioning while fiddling to get the cylinder started. Bolt down the cylinder and re-apply the starter cover. Give the starter a good strong pull and smash the solder against the top edges of the combustion chamber. Solder won't damage anything. With a good pull, the piston will probably go up and down in it's stroke a few times. Pull the cylinder off and the solder should still be in place, or may have greased itself to the top of the cylinder.
Combustion chamber edges, the squish band, are not always flat, often taper up at an angle towards the spark plug hole. If so, with a flat top piston crown, the closest tolerance will be tightest towards the edge of the crown, and the smashed solder should be thinner at the outside point. The thickness of the smashed solder is the squish measurement that will tell the clearance. .020" is generally recommended as the minimum for a woods mod. You are probably ok at .018, but any less is likely potential for damage. My 036 runs at .018", figure maybe .017" with some carbon buildup on the crown...and is one bad azz saw. I usually aim for .020" squish.
What to do if your squish is too close? You need to either make a thin base gasket, remove material off the combustion chamber edge, or shave down the top of the piston. I have always shaved down the piston crown, using my metal lathe. A "pop up" piston works great, where only the outer edge of the piston crown is lowered. This will add a bit more to compression. Whatever you do to the top of the piston, leave at least .10" of material above the top ring groove for strength.
What to do if your squish is still too large? I turn the cylinder base down on my lathe. It can be ground down by hand as well, making a jig to keep the base square to the bore.
Hope that is all reasonably clear.
Jay
Some pics:
1. Turning cylinder base down on lathe.
2. "pop-up" piston.
3. Lower transfers opened to the base - Husky 359 cylinder.
First thing I do is take off the starter cover, if it's still on. Then you can move the piston up and down by turning the flywheel. Taking the ring(s) off makes for easier putting the cylinder on, especially if you are going to be making a number of clearance checks. No rings doesn't effect the squish measurement, if you measure on at least two sides. I usually measure on all four sides of the crown. I put a little dab of grease on the four points of the crown to hold the solder, then cut four half inch long pieces of solder and set them in the grease, just a tad in from the outside edge, and pointing towards the crown center. I use 1/16" diameter electrical solder. I think the plumbing type solder is harder, and you want the soft type.
I turn the flywheel until the piston is low in it's stoke, sitting close to the crankcase, then carefully slip the cylinder over, not disturbing the solder. With the rings still on, you will likely mess up the solder positioning while fiddling to get the cylinder started. Bolt down the cylinder and re-apply the starter cover. Give the starter a good strong pull and smash the solder against the top edges of the combustion chamber. Solder won't damage anything. With a good pull, the piston will probably go up and down in it's stroke a few times. Pull the cylinder off and the solder should still be in place, or may have greased itself to the top of the cylinder.
Combustion chamber edges, the squish band, are not always flat, often taper up at an angle towards the spark plug hole. If so, with a flat top piston crown, the closest tolerance will be tightest towards the edge of the crown, and the smashed solder should be thinner at the outside point. The thickness of the smashed solder is the squish measurement that will tell the clearance. .020" is generally recommended as the minimum for a woods mod. You are probably ok at .018, but any less is likely potential for damage. My 036 runs at .018", figure maybe .017" with some carbon buildup on the crown...and is one bad azz saw. I usually aim for .020" squish.
What to do if your squish is too close? You need to either make a thin base gasket, remove material off the combustion chamber edge, or shave down the top of the piston. I have always shaved down the piston crown, using my metal lathe. A "pop up" piston works great, where only the outer edge of the piston crown is lowered. This will add a bit more to compression. Whatever you do to the top of the piston, leave at least .10" of material above the top ring groove for strength.
What to do if your squish is still too large? I turn the cylinder base down on my lathe. It can be ground down by hand as well, making a jig to keep the base square to the bore.
Hope that is all reasonably clear.
Jay
Some pics:
1. Turning cylinder base down on lathe.
2. "pop-up" piston.
3. Lower transfers opened to the base - Husky 359 cylinder.
Attachments
Al Smith
Mac Daddy
woodworkingboy
TreeHouser
That's a good method to chuck up the cylinder, Al. The wood block I use soon warps.
woodworkingboy
TreeHouser
Yes, without. With all respect, I know that Al mentioned thinking some difference would occur with the liquid gasket, but I haven't seen any measurement change with the gasket applied. I don't think it could be more than .001, if that at all.
Could use a venison steak
Could use a venison steak
Al Smith
Mac Daddy
If you use some type sealant ,whatever slight diff it makes on the squish won't amount to two shakes of a lambs tail . Go for it .
Al Smith
Mac Daddy
You kinda have to use what you've got .Many methods but they all work .
