Chainsaw Repair

Here is the big crack in the bottom of the auto decomp line. 

I was able to replace the fuel line easily without removing the tank.  Once the carb was off, the carb support plate came off easily which allowed me to access where the line exits the tank.

Here's what i did:
Put on manual decomp valve
Replaced intake partition
Replaced impulse line
Replaced fuel line + filter
Replaced fuel cap
Cleaned it up the best i could

I re-assembled and tried running the saw.  The same problems persist.  The saw will kick over in a few pulls with the choke out. Once the choke is disengaged, the saw starts in high idle, runs for a few seconds then dies.

I believe the saw is getting plenty of fuel.  The plug is very wet with fuel, and when i crank it over, it puffs out fuel vapor from the exhaust. 

I tried removing the limiter cap.  I removed the plastic piece surrounding the adjustment screws, thinking this would take away the limiters.  It didn't.  The adjustment screws are still limited.  Do i need to cut the moulded high spots off the sides of the adjustment screws so they can turn beyond the factory range?

I bought a pressure/vacuum fitting for the saw, so i am going to try my first vacuum test to see if i can find any other air leaks. 

I have to go out and look again, but i'm fairly sure the carb is a Walbro.  It looks like the carbs are pretty expensive.  So, i'd like to make sure it's the problem before i buy one. 

Anything else i should look for?

Thanks.

Ok, i just performed my first ever vacuum/pressure test on a saw. 

I used a piece of rubber to block off the exhaust port
I also managed to block off the intake boot, where the carb connects successfully (this part wasn't easy).

The saw held 10psi pressure for over a minute.  Similar for vacuum.  Does this successfully eliminate the possibility of air leaks?

So, does that leave only the carburetor?  What is my next step?

Should i first cut off the limiters off the carb needle screws and try that? 

I verified that this is a Walbro carb.

If that fails, should i try rebuilding this carb, or spring for a Zama?  If so, where should i get the Zama? 

Thanks,

Well, the saw runs! 

I cut the limiters off the carb needle screws, and decided that, while i had it out, i would disasemble and clean the carb.  It didnt take too long, and went back together easily.  The diaphragm was in good shape, as were the reed valves. There was a bit of junk built up in a few spots, that came off easily with carb cleaner.

Put it all back together and it fired right up.

However, when adjusting the carb, i noticed a pretty nasty rattle.  Sounds to me like a bearing.

Here is a video, if i can get it to work.

http://youtu.be/0VYjpqRd2XA

What does this sound like to you guys?

Is there a gasket under the cylinder?  Was the squish checked?  Sounds like the piston is tapping the cylinder but hard to tell from vid.

Ok, i have a plan.

First i'm going to run the saw without the clutch to verify that the clutch isn't making the noise.  I have read that a weak clutch spring can do this.  I also noticed that while tuning, it was difficult to make the engine idle without the chain surging forward a little.  Any reason i should not do this?

If this doesn't work, im going to order up some more parts and tools. 

Questions:
- The service manual says "press out the gudgeon pin".  Does this require any special tools, or will it just slide out by hand?

I'll probably get another base gasket and wrist pin bearing. 

Anything else i should get while i'm at it?