MS360 build

[Chainsaw Jim]

Well I made some more progress on this thing this evening. I came to the conclusion yesterday that I went way overboard with the carbs metering seat for a stock cylinder and had to punch it out and replace it with another. Normally that's a good size after port work but not before.
Only thing is not all carbs are capable of this replacement and I found out the hard way! The same size replacement just falls back through. After several hours of searching through bad carbs I found a seat that is .0015 larger in diameter and drove it home to save the day. Now I have it at the right size and it will get another run tomorrow before pulling the top end.

 

[paragonbuilder]

Well I made some more progress on this thing this evening. I came to the conclusion yesterday that I went way overboard with the carbs metering seat for a stock cylinder and had to punch it out and replace it with another. Normally that's a good size after port work but not before.
Only thing is not all carbs are capable of this replacement and I found out the hard way! The same size replacement just falls back through. After several hours of searching through bad carbs I found a seat that is .0015 larger in diameter and drove it home to save the day. Now I have it at the right size and it will get another run tomorrow before pulling the top end.

Just so I'm clear Jim, by metering seat you mean the needle seat?

I'm not sure of the proper names for carb parts...

 

[drf256]

I haven't had any issues with the stock Zama Jim, as long as it's new.

It seem any restrictions in the carb won't manifest until the Saw gets ported. Then suddenly it runs out of gas with a carb that ran fine before. Had it happen to me on 3-4 builds. On one, the fuel line got soft and would suck closed at high rpm. The line/filter/carb supplied fuel in stock configuration just fine. But after porting, it would hold high tune for 1-2 seconds and then start to scream.

 

[Chainsaw Jim]

Just so I'm clear Jim, by metering seat you mean the needle seat?

I'm not sure of the proper names for carb parts...

Yes that would be correct.

 

[Chainsaw Jim]

I haven't had any issues with the stock Zama Jim, as long as it's new.

It seem any restrictions in the carb won't manifest until the Saw gets ported. Then suddenly it runs out of gas with a carb that ran fine before. Had it happen to me on 3-4 builds. On one, the fuel line got soft and would suck closed at high rpm. The line/filter/carb supplied fuel in stock configuration just fine. But after porting, it would hold high tune for 1-2 seconds and then start to scream.

I've noticed it in a few different epa models when the ignition is advanced and muffler modded so I figured it was worth checking into, just not like I did. When I say I took it too far I mean I was even concerned it was too much for a good work saw port job. I've seen 076 carbs smaller than the size I drilled it. Lol

 

[paragonbuilder]

I've also noticed it in a few different epa models when the ignition is advanced and muffler modded. When I say I took it too far I mean I was even concerned it was too much for a good work saw port job. I've seen 076 carbs smaller than the size I drilled it. Lol

So does this change the running characteristics of the saw, or just allow the carb to be fed fuel faster to keep up with demand?

 

[Chainsaw Jim]

So does this change the running characteristics of the saw, or just allow the carb to be fed fuel faster to keep up with demand?

Once in a while a lack of fuel will leave the saw a little weak under load. I don't see any tuning problems or running problems, only a little shyness of full load grunt.

 

[Chainsaw Jim]

I don't recommend drilling on carbs unless you have plenty of good working spares to practice on. The metering pin seat hole needs beveled and polished perfectly or it will just drain the gas tank from leaking. The hole can be enlarged far enough where the pin sits too low and you'll need to start grinding material away to make room for the fork in the metering lever to shut all the way down...more leaking. Then there's the added force of pressure from the fuel when the hole is larger making it necessary for the spring to be stronger. When I oversized the hole too far I needed to use a spring from a WB carb to make it strong enough hold the fuel back and tune correctly.

 

[paragonbuilder]

Once in a while a lack of fuel will leave the saw a little weak under load. I don't see any tuning problems or running problems, only a little shyness of full load grunt.

So when a saw runs great normally, but after a big long cut, it comes up thirsty, this mod could help?

 

[Chainsaw Jim]

So when a saw runs great normally, but after a big long cut, it comes up thirsty, this mod could help?

There's only one way to find out. Track down a spare carb to play with and step it up a size. To me that would be worth checking out.

 

[Chainsaw Jim]

So when a saw runs great normally, but after a big long cut, it comes up thirsty, this mod could help?

I would also look into the tank vent on that. I've modified a few to still function while allowing an easier flow.

 

[junkman]

Wonder if a ms440 tank carb and filter would fit in the 360 case ? To get an hd filter system.

 

[Chainsaw Jim]

I gave it hell today but the log won. It was nice and fast for the first four steps but now it's just knots. It cleaned up decently but still not like it was at first.

 

[bikemike]

just through a 088 carb on it and be done!

Yeah and he can send me the original carb and intake boot for a 026

 

[bikemike]

View attachment 45625
I'm going to start off by video recording this thing while still bone stock for a before and after. It'll wear a 25" full comp/chisel set up. But it's not exactly going to just be a before and after video of the build. I'm going to record a few cuts after each step during the progress of the build.
My question for starters is which of these three mods that will be performed do you all want to see for the first step?
My first three options are timing bump, muffler mod, or carb mod.
I'll cast my vote for muffler mod since it's already noticeably restricted there.
View attachment 45630

When you say carb mod is that a bore job, or bigger carb or limiters taken off. I vote mm single port

 

[bikemike]

I'm not shure if I'm correct on this. Just an observation I noticed I have a 0h34s bone stock, the screen fell out. I use a oh36 at work and seems like the oh34 has more wide range of of a power band vs a 036 360. Was there much difference I the way they are ported or baffled out?

 

[Chainsaw Jim]

I'm not shure if I'm correct on this. Just an observation I noticed I have a 0h34s bone stock, the screen fell out. I use a oh36 at work and seems like the oh34 has more wide range of of a power band vs a 036 360. Was there much difference I the way they are ported or baffled out?

Does your 034 have an open port cylinder?

 

[bikemike]

Here's a few videos. I didn't retune or touch the carb after any of the mods.

Stock:

Advanced ignition only:

Muffler modded only:

Muffler mod and advanced ignition:

That's it so far. I'll do the carb up this evening so I can check that out tomorrow.

Mm seamed to be the strongest 1 only mod. Timing and muffler mod together no tune almost sounds like the saw was a bit richer now that it can fart out more exhaust

 

[bikemike]

Does your 034 have an open port cylinder?

Not shure I have never had the jug off it. . Thing has been a good runner slash work saw since the day I got it. It's the big bro to the oh26

 

[Chainsaw Jim]

Not shure I have never had the jug off it. . Thing has been a good runner slash work saw since the day I got it. It's the big bro to the oh26

You don't need to pull the jug to tell. You may need to pull the carb. I'm thinking the intake has the little uvula thing hanging.