I acquired what was supposed to be a running and ready 359 a few weeks ago on a trade for a couple parts saws. To make a long story short it went to the hunting camp Saturday to clean up fallen trees. It started out running and cutting fantastic but as the day went on I found myself having to keep screwing with the carb to keep it running and ended up smoking the piston. I was enjoying cutting with it too much to do the smart thing and grab another saw out of the truck. I tore it down this morning and ordered a new piston and a catless muffler. Loose intake clamp was the problem. So now I’m thinking i want to make it even more enjoyable. I’m leaning real hard to trying out light porting. I know to widen the exhaust and intake ports and not raise or lower them. Should I do anything with the transfers? I popped the transfer covers off and the gaskets tore. Can gasket maker be used or do I need to track down the gaskets? Also on the carb it has the walbro 199a is there a better option? In my research the general conclusion seems to be the 199a is a problem but I cannot find a straight forward answer on what to replace it with.
Porting and building 359
- Thread starter rw05
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The zama carb the later ones came with is the preferred option. The Walbro's have a few issues although the main one is the compensation & that's fairly easily fixed.
Measure your squish & decide if you can reduce or delete your gasket to gain some compression. If you can & decide to then you can take the same few thou off the top of the ports without significantly affecting timing.
You can make new gaskets using the old ones as templates or seal them with a good petrol rated sealant (not silicone/rtv).
Be sure to vac/pressure test it afterwards or you may find this time to be a practice run
Measure your squish & decide if you can reduce or delete your gasket to gain some compression. If you can & decide to then you can take the same few thou off the top of the ports without significantly affecting timing.
You can make new gaskets using the old ones as templates or seal them with a good petrol rated sealant (not silicone/rtv).
Be sure to vac/pressure test it afterwards or you may find this time to be a practice run
link
Gone fishing
What I did, I got my document writer on my PC and I copied every paragraph I found interesting in these threads in to my own "porting" document;
https://www.arboristsite.com/threads/best-porting-instructions.358732/Your brain just process the information better if you actually put some work in to it.
https://martysgarage.info/reference/two-stroke-port-duration/"The exhaust port shape is important too. The more squarish the top is, the better the top rpm power is.
Too square though is dangerous because there is more possibility that the ring will snag on the top middle of the port, especially if there isn’t a sufficient bevel there. Take note of how...
https://www.arboristsite.com/threads/best-porting-instructions.358732/Your brain just process the information better if you actually put some work in to it.
https://martysgarage.info/reference/two-stroke-port-duration/"The exhaust port shape is important too. The more squarish the top is, the better the top rpm power is.
Too square though is dangerous because there is more possibility that the ring will snag on the top middle of the port, especially if there isn’t a sufficient bevel there. Take note of how...
