First build 365 special to 372 XPW

[morbius18]

https://www.arboristsite.com/commun...terested-in-seeing-how-i-port-a-372xp.240686/

A good one to go off of

 

[vienster]

Just match the jug you pulled off on the new jug on the lowers. The 75cc jug was designed for a chop saw originally and is restricted on the transfers

I spent some time comparing the old 48mm jug to the 51.4 and I could see a major restriction on the transfer port on the exhaust side.

I want to spend the time with a degree wheel to modify the engine timing, but I don't want to risk it. I'd have to do a lot more research before I felt comfortable. I also don't want to wait.

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Thank you for posting the pictures it helps a lot. There is so much information on the subject that i'm sure there's a lot of bad info. I didn't want to follow bad advice.

I was initially planning on using one of my air powered die grinders but that would've been a bad idea. I could've turned down the air pressure to regulate the speed, but there's no way to be as precise as needed with such large tools. I bought a cheap foot pedal flex shaft 1/8" grinder. Within the past year I bought a straight and an angle die grinder, and I have to say i'm impressed with norton's tools. They are more powerful than my ingersoll rand 3101G.

 

[morbius18]

I've been using a dremel with a flex shaft.

Here's what I did to the restriction in the transfer on the 48mm.

 

[mdavlee]

I used the harbor freight flex shaft with good hand pieces for years. The one that comes with the kit will get hot quick. A foredom brand can be had off eBay for $50 roughly. The motor and foot pedal is probably $50 on sale for Christmas

 

[morbius18]

I used the harbor freight flex shaft with good hand pieces for years. The one that comes with the kit will get hot quick. A foredom brand can be had off eBay for $50 roughly. The motor and foot pedal is probably $50 on sale for Christmas

This one?
https://m.harborfreight.com/flexible-shaft-grinder-and-carver-40432.html

 

[Yotaismygame]

I use the HF dremel with a flex shaft i got off amazon for $10. Or amazon sells a knock off dremel and a flex shaft for around $30. Used my HF one quite a bit. The flex shaft makes grind cylinders much easier. Careful on the transfers, too little restriction and it'll slow the charge down too much.

 

[mdavlee]

This one?
https://m.harborfreight.com/flexible-shaft-grinder-and-carver-40432.html

Yes. Any Foredom brand hand pieces and most of the no name on eBay fit. Buy at least one good hand piece to go along with it if you plan to do a lot of grinding.

 

[vienster]

I ended up ordering a foredom hand piece as well based on your suggestion. Apparently it will also accept 1/4" shank carbides. Nearly all my carbides are 1/4" but they are too large to use on this. If anyone is interested in good carbides blackstone makes great carbides. I never knew how good carbides can be until I used a good brand. They throw steel everywhere, it's something you'd have to see to believe.

Harbor freight does stock some decent cheap tools. I recently bought a powder coating kit along with $500 worth of other tools.

 

[mdavlee]

Probably 3/32 or the metric 3mm

 

[vienster]

I'm an idiot the 1/4" was inside the tool. At least I admit it when I screw up. The smaller was 3/32.

I brazed a port on a test muffler today and it came out decent for my first try. I tried to weld one at work, but the speed control on the welder malfunctioned and I ruined it. Theres a youtube video I watched and the guy said don't weld them braze them. If you get a piece of slag inside that breaks free it can get sucked into the engine.

There can be pretty big differences in quality of certain $10 mufflers. The first one from xuanxuan was better than the haishine. It was thicker and better built. I'm amazed I was able to braze this thin one without melting through it.

 

[Yotaismygame]

I’ve bought probably ten mufflers from a few eBay vendors. All have been the same quality. I’ve also welded 1” pipes in them with no problems. Takes a little practice to weld that thin of metal.

 

[mdavlee]

I tig weld all of mine. The hyway brand with top outlet are the thickest I’ve seen. The rest were pipe outlet and I add 1” pipe. Grind it all out as they leave the piece where they punch the hole attached on the inside some times. I feel better about getting it out of there before someone gets it mounted on their saw.

 

[vienster]

I've never seen a 1" port. That's not a bad idea. We have a tig welder at work and no one knows how to use it. I'd like to spend some time watching videos and practicing.

The only real differece in those two mufflers was the thickness. You could feel the weight difference and it sounded so tinny when you tapped on it. The thicker one had flat paint vs gloss paint.

 

[Ketchup]

If you don't want to mess with brazing or welding, the original deflector can be pryed open on these mufflers and the hole opened with a carbide burr. The port can be opened almost 4 times the original size. If you're carfule the screen will even slide back in. Watch the clearance to the plastics. If you pry too much you end up melting the top cover or brake flag. It keeps the stock appearance but may not be quite as open as a welded port. It's a little quieter too. Just another option.

 

[Yotaismygame]

If I had a tig I would use that too. If you’re not a professional I personally find the piped mufflers best too mod. I got the 1” idea off of here. I start with a step down drill bit until I drill out the entire original pipe and then take a dremel with carbid burr to open it up to 1”. I can do the whole process in about 30 mins now. I’ve also used 3/4” pipe and for a completely stock saw I think that’s best.

 

[Yotaismygame]

Here’s a sound clip of that saw with 1” pipe

 

[huskyboy]

Make sure the caber rings are 51.4mm like the oem rings. 52mm rings won’t work.

 

[vienster]

If you don't want to mess with brazing or welding, the original deflector can be pryed open on these mufflers and the hole opened with a carbide burr. The port can be opened almost 4 times the original size. If you're carfule the screen will even slide back in. Watch the clearance to the plastics. If you pry too much you end up melting the top cover or brake flag. It keeps the stock appearance but may not be quite as open as a welded port. It's a little quieter too. Just another option.

I had to cut the old muffler off with a cutoff tool otherwise i'd have used it.

Make sure the caber rings are 51.4mm like the oem rings. 52mm rings won’t work.

I realized i'd ordered the wrong rings before they got here. The listing said big bore and so did the p&c listing.


I spent some more time looking at the cylinder and i'm not going to do any porting right now. I'm going to run it stock so then I know what to expect and I can mod it in the future. I also see no point in removing the restriction on the transfer ports if I don't open up the area where the transfers go into the cylinder. I thought it looked like a large restriction compared to the 48mm cylinder but every port on the 51.4 is larger. I have to do a lot more reading before I port the entire cylinder.

 

[vienster]

Is the hd12b carburetor adequate or should I upgrade to the rwj4b? The seller never ended up shipping me the new hd12b so I just used an ultrasonic cleaner and carb kit for the old one.

After I run the saw i'm going to either spend the money and have someone port it or buy a right angle japanese hand piece and do the work myself. Neither is cheap. I have never paid anyone in my life to do engine work for me so it's a tough decision.

 

[huskihl]

There's more to it than upgrading carbs. You'd need to re-clock the boot or use one from a 390, different filter elbow, and bolts.
I'd use the one you have for now. Once it's ported, it may be worth upgrading