dolmar PS-421 mods

[fordf150]

Had a 421 on the bench making a few minor adjustments.

 

[fordf150]

Most popular mod is removing the cat. Which is pretty simple to do. The muffler is 3 pieces with the cat spot welded into the center piece. Drill the 2 spot welds and the cat comes out. [/ATTACH]

 

[fordf150]

And no more cat

 

[fordf150]

After the cat is gone I use the embossed area as my outline for the opening.

 

[fordf150]

They do require tuning after this and require a DD screwdriver for high side adjustments. Some of the older ones had epoxy covering the adjustment screws.

 

[fordf150]

The only real problem we have had with these saws is the fuel line coming off the nipple inside the tank. That issue is solved by adding an O ring to the fuel line for that little bit of extra clamping power.

 

[RedFir Down]

Looks good Nate! How much gain do you see out of a muffler mod like this? Not to mention the other benefits of getting rid of the CAT.
Where would you recommend a guy to look for a DD tool? Thats about the only one I dont have.

 

[fordf150]

I don't know about the true gains. Never took the time to video and time cuts on one before and after. Even without any performance gains the reduction in heat is well worth it. This saw took an extra 1/4 turn on the high side to get 13000 for break in. Don't know how it was tuned before hand though. DD tool is find a willing dealer to supply you one or ebay. There is spline, D and DD plus the pac man screw driver.

 

[MS460WOODCHUCK]

I don't know about the true gains. Never took the time to video and time cuts on one before and after. Even without any performance gains the reduction in heat is well worth it. This saw took an extra 1/4 turn on the high side to get 13000 for break in. Don't know how it was tuned before hand though. DD tool is find a willing dealer to supply you one or ebay. There is spline, D and DD plus the pac man screw driver.

Do you have any pics of these screw drivers or is there other names for them? I just looked on ebay and could not find any d or dd screw drivers.

 

[RedFir Down]

I don't know about the true gains. Never took the time to video and time cuts on one before and after. Even without any performance gains the reduction in heat is well worth it. This saw took an extra 1/4 turn on the high side to get 13000 for break in. Don't know how it was tuned before hand though. DD tool is find a willing dealer to supply you one or ebay. There is spline, D and DD plus the pac man screw driver.

Good to know. I bet the saw does run a lot cooler. Plus im sure the improved throttle response is nice for a saw that size.
Also thanks for the heads up about the occasional issue with the fuel line coming loose.

 

[RedFir Down]

Do you have any pics of these screw drivers or is there other names for them? I just looked on ebay and could not find any d or dd screw drivers.

http://www.ebay.com/itm/ZAMA-CARBUR...703?pt=LH_DefaultDomain_0&hash=item5d4bf13db7

 

[fordf150]

http://www.ebay.com/itm/ZAMA-CARBUR...703?pt=LH_DefaultDomain_0&hash=item5d4bf13db7

That's the one.
I have only had a few with the line come loose but this saw isn't going to be close to me so I wanted to fix it before it was an issue

 

[MS460WOODCHUCK]

http://www.ebay.com/itm/ZAMA-CARBUR...703?pt=LH_DefaultDomain_0&hash=item5d4bf13db7

Wow them sure are not cheap! I am glad I bought two splined ones when they were six bucks each.

 

[fordf150]

This saw didn't get it but I took a couple pictures just to show what is needed for installing a .325 bar and chain on these saws. A clutch drum and bar from a 5105 plus a 10x16x.2 mm shim is needed. This is probably a worthwhile modification just to have rim sprockets instead of spur. The bar needs slight modification to allow it to oil. We drill 2 holes in the groove down through into the adjuster holes. Black lines show where to drill. That is how I run mine and have set a few up to run it. Haven't ran anything but a 16" .325 on these but sticking with 3/8LP an 18" bar is pretty common.

 

[wildroamer]

After the cat is gone I use the embossed area as my outline for the opening. View attachment 358456

Just had a chance to use it this past weekend. Cut and ran great, but definitely got HOT.
Can you be more specific regarding this step for a newb?
Thanks

 

[KenJax Tree]

Just had a chance to use it this past weekend. Cut and ran great, but definitely got HOT.
Can you be more specific regarding this step for a newb?
Thanks

I Ieft the gills in mine but the CAT is gone. It runs much cooler with the CAT out.

 

[fordf150]

I use that almost oval shaped edge that surrounds the gills as my guide to cut the opening larger. just removing the cat is a good start. I will take mine apart and snap a picture of the finished opening. I forgot to take a picture of the finished product when I did this thread.

 

[KenJax Tree]

I saw it in a thread you did a while ago

 

[wildroamer]

Hey thanks, I appreciate it! That said, I may just go ahead and order the catless muffler, as it is only around $35 or so I think. That might allow me to do this mod sooner, and replace stock muffler for any warranty work...

 

[SawTroll]

..... Haven't ran anything but a 16" .325 on these but sticking with 3/8LP an 18" bar is pretty common. ....

The 3/8 lo-pro bars that are called 18" actually are (slightly long) 16" bars.