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Considering port work on Stihl 362

Started by dsroten, December 21, 2018, 09:30:23 AM

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ehp

ya that pipe could use a lot of help on the 090, first real racesaw I ever built was a 090 , the faster I made it the more money it cost in parts LOL, got to the point I think a top fuel dragster was more dependable . first real problem is the crank with the flywheel sitting out so far away from the crank bearings and case is sure a weak link, it would break a crank as fast as it came out of the wood , took new crank and machined it to take a 064 flywheel in close to case and bearing , put new 064 coil in saw. crank breaking was fixed so switch to methanol with 20% nitro . Got saw to handle that but then the clutch would not handle the power and once I got that fixed I could not get clutch to stop slipping on the crank . Sure was a learning curve but helped me figure out how to solve problems . It was pretty fast but just never knew when trouble would show up so parked it and went with 3120

HolmenTree

Madsens admitted the pipe was built for a Jonsereds 111 so didn't charge me for it. Still worked ok for size of wood I was running it in.
I had more plans for the 090 like a cut off head and epoxied transfer covers.
I did run it without the flywheel fan plate and got rid of the clutch. Made it direct drive with a 11 T spur sprocket and machined hub screwed onto the crank. Saved quite a but of weight and better spoolup off a cold start into the wood.

My next project was my last with the Yamaha YZ bike engine. Had alot of fun building and running  it over the last 30 plus years. Still a tough little little engine.

Making a living with a saw since age 16.

ehp

i was running a 13 tooth at the end at a rpm the 090 was never meant to see LOL

HolmenTree

Ed did you ever see anyone put a full circle crank in a 090?
It seemed everyone in the upper level of competition back in the 1980's was running a stock appearing saw with those crankshafts.
Making a living with a saw since age 16.

ehp

ran I seen lots of full circle cranks , not really a fan of them . They tighten the crankcase up but you end up not being able to move much air inside engine compared to full race porting with a stroked crank . But the full circle crank sure makes building a carb a lot easier to run on methanol/nitro  , mainly cause it doesnot move as much air so no need for lots of fuel , The limiting factor is the amount of fuel a carb can move and how much torque/power can stuff like the crank take before it breaks , On gas you donot have this problem but on methanol/nitro you do have this problem

ehp

On crankcase volume , there is a lot of things that go into this area and a lot more than a lot of people think goes into this , crankcase volume is very important on how much power a motor can produce . A stroked 3120 that is 60 mm bore by 46mm stroke has a ratio on 1.47 to 1 , the perfect ratio is 1.20 to 1 but to have that you would need to build a new crankcase with larger volume . Now on gas you could supply enough fuel to feed the motor at that ratio but on methanol/nitro that would most likely never be done , If motor was ported and piped to any kind of a race saw you just could not get enough fuel to it with a single carb which rules state we must use . The difference in hp is about double using a 1.20 ratio crankcase over the 1.47 . Main reason for double hp is cause the 1.20 crankcase  can move double the air volume and to make power you got to move air . You cannot compare a chainsaw engine to say a snowmobile engine. Most chainsaw motors are built with the bore/stroke ratio being totally backwards to a snowmobile engine so if you do the crankcase volume ratio on a snowmobile engine its a lot closer to the 1.20 ratio .

EZTundra77

Quote from: HolmenTree on January 11, 2019, 08:42:42 AM
Yep my 395XP came from the factory with a 7 pin 3/8" rim sprocket for good reason.

Work saw with a round filed chisel chain no matter what cc 7 pin is the best.
Race chisel bit chain thinned out, cutter square filed half ways back, .015 lowered depth gauges you can get by with a 8 pin fine in smaller logs with a work saw.
But round filed chisel chain sucks the power out of todays high revving work saws.

Race saws....I once had a Stihl 090 I raced that was ported etc on a tune pipe. Madsens from the PNW saw pictures of my small logs we cut in our contests. They said you need a 11 pin sprocket on the 090, I believed them and got beat by the Mac 101's race after race.
Then I found out they were running 7 and 8 pin sprockets on the Macs, I put a 7 on the 090 and was then beating them or keeping up to them.

My 40 horse YZ125 bike saw I run a 11 pin sprocket. Works good for big and smaller wood.
My buddy gave me a bunch of spare parts including 8 pin sprockets for my smaller 036 pro, my 362 CM, my 462 CM , and my 661.  I could swap them easily.  But everything Ive seen shows a loss or torque.  If I was running a 20" bar on the 661 or a 16" bar on the 462 -having massive torque to spare- I might run an 8 tooth.  But in my real world, those 8 pin sprockets will stay in the tool chest.  
241 CM - 036 PRO - 362 CM- 462 CM - 661 CM
16" ES Light
16" Hard Nose Duro Bar/RD3 Chain 
20" Tsumura Light .063
20" Tsu Lt .050
28" ES .063
28" Tsu Lt .050
28" ES Lt .050
36" ES .063
36" ES .050
41" Cannon .063
All run Stihl Chain (PS, RS, RD3, RSF, RSLF, RMX)
48" Granberg Alaskan w/ 10' EZ rail

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