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Reading a degree wheel (pics)

WidowMaker

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Using a torch to determine when a port opens can yield different no's when viewed by eye only. There are different ways that all work, torch, feeler strip, eye etc. Using a torch at the opposite side to your viewing can give the indication that a port is opening earlier than if you were to use a torch from the same side as your viewing. Personally I just eye every port as it opens and use a torch from the side I'm viewing. Sure a port may start to flow a tad before this but it gives baseline no's to work from for future reference. Some use a port map to set no's and I suppose when we quote no's, we should attach our method of measurement.

:cheers:

===

By torch, is it safe to assume you mean light???
 
Kingsley

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Widowmaker,

I was thinking the same thing. "torch" is what the people across the pond call a fashlight. I could just picture some knob reading this and using their oxy/ac on their PC. What a hoot that would be!

The questions we would get.

How do you keep the pc cool with the torch?

Should I shave the other eyebrow off so they grow back evenly?

Does anyone know if I can salvage this PC after I welded them together with my torch?

haha

Marty
 
MattCrowe

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Widowmaker,

I was thinking the same thing. "torch" is what the people across the pond call a fashlight. I could just picture some knob reading this and using their oxy/ac on their PC. What a hoot that would be!

The questions we would get.

How do you keep the pc cool with the torch?

Should I shave the other eyebrow off so they grow back evenly?

Does anyone know if I can salvage this PC after I welded them together with my torch?

haha

Marty

Come'on a torch it a battery powered light, its about time you guys caught up, the oxy/acet you refer to is not a torch, its a gas axe.
 
tdi-rick

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Come'on a torch it a battery powered light, its about time you guys caught up, the oxy/acet you refer to is not a torch, its a gas axe.


:hmm3grin2orange:

What they call an oxy/acetlene torch, we call a blowpipe :D

It's all a bit like;

bonnet = hood
mudguard = fender
boot = trunk
footpath = sidewalk
railway = railroad
railway sleeper = railroad tie
aeroplane = airplane

US citizens can't understand a damned thing we say so our actors have to change their accents to get a gig on US telly etc, etc. :laugh:
 
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roncoinc

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print this out in color on good photo paper at hi res and it's great :)

 
komatsuvarna

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I perfer not to print a degree wheel too. You have to get it centered up perfectly or you could end up a degree or so off. The printed one i had looked perfect, but it contradicted numbers. I check mine 2 ways to be sure its right, and i could never get the same numbers twice with a print out. A drill chuck will run you more than a good degree wheel.
 
steve316

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cheap drill chuck

I just bough a 1/2" chuck from travlers on sale for this month @ 18.00. part # 63-100-004h they also have a 5/8" one for 25.00 part #63-100-005h.
 

046

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also in the change degree to zero camp after finding TDC.
anything to reduce confusion is good.

excellent thread.. thanks for sharing

here's my degree wheel for the Harley
 
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trappermike

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I can suggest also another easy way to find out your port's duration with the degree wheel,which is sometimes less confusing and involves no real math.

-Move your piston so the port in question is just cracking open.Then set your degree wheel to zero. Next rotate the engine in it's corect direction so the port fully opens and then continue until the piston is just at the closing point of the port,then read your degree wheel,there is your total port duration.
 
Terry Syd

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I just spotted this thread. Stumpy, you have measured the strato timing incorrectly. It is measured from when the piston cutaway appears over the bottom of the transfer ports - that's when the strato port starts to flow.

A lot of people have made the same mistake as you and looked through the strato port opening. However, if you think of the strato port is just the other half of the intake system it will quickly make sense. Since when have you ever heard of an intake port with 196 degrees of duration.

The Husky stratos with the removeable transfer port covers are easy to work with. All you have to do is remove the cover and watch for the piston cutaway to appear above the bottom of the transfer port. That 576 looks like it will present some interesting number gymnastics to try and determine the point of opening.

The strato timing is really a critical timing figure when porting the stratos. I found that matching the intake and strato timing gave the best power. Usually the strato timing is longer than the intake timing, maybe by 10 degrees.

When the timing is matched, you get the maximum flow through the intake system, with the maximum base compression.

The way factory stratos are set up with the intake timing being shorter, the strato port is setting the 'intake' duration and the intake port is being shortchanged from flowing all it could during that duration. That may work for the EPA, but not for me.
 
Terry Syd

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I also note the 11 degrees of blowdown. The Husky stratos have very low blowdown figures. The 450 I worked on had 12 degrees and another fellow measured a 455 at 12.5 degrees.

I sacrificed a piston and found that only another 2 degrees (taking the blowdown to 14 degrees) was enough to get the cutting speed up. I also did a little trick with the top of the piston crown to shape it to the top of the exhaust port. This greatly increased the area during the blowdown period and felt like I had added another 2 degress to get 16 degrees of blowdown. Shaping the crown kept the timing figures down and the increase in flow more than made up for any loss in compression.

The solution to measuring the strato timing may be to drill a small hole in the side of the transfer port and look through that. Shine a bright light down the strato intake and look through the hole to see when the light appears. You can then patch and fill the hole with GB Weld later.
 
trappermike

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I'm not sure about your blowdown times,they don't jive with any I've ever seen on performance or racing engines,or any other. Long ago I compiled a list of port timing figures from various famous and successful racing engines of various types(Yamaha,Kawasaki,Suzuki,McCulloch,others),the blowdown times range from the lowest of 20 degrees to a high of 37 degrees for very high rpm high output full race ported engines.
I'm not sure how you are measuring them(Different from me somehow),I calculate them just as the factories do and some of my data is actually published by them so I know it's right.
Also I've been building racing engines for almost 40 years.
I don't know why they are so different...
If there was only 10 degrees blowdown time in your engine,your transfer ports would be almost as tall as your exhaust port. Racers shoot for more blowdown time,so the exaust pressure in the cylinder is much lower before the relatively low pressure transfer fuel charge tries to get up into the cylinder for better filling.
A relatively normal blowdown time for a standard to medium performance 2-stroke is 26-30 degrees.
The minimum figure that I gave above of 20 degrees blowdown time was unusually low from an engine that was altered a little incorrectly,and it did not run very stable or well.
 
Terry Syd

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Mike, I know exactly how you feel about those blowdown times, I come from a racing background myself. When I first looked at the 450 blowdown times I had to measure it three times to believe it!

First off, there is no expansion chamber on these can muffler saws to pack the charge back in. The second point on the Husky stratos is the long transfer tunnels.

I tried to get my head around how such short blowdown times could work. I figure it is the long transfer tunnels that do it. On the 450 I noticed I was getting blowback into the tunnels halfway down to the crankcase.

What I figure is happening is that the tunnels trap the exhaust gas in a column above the air of the strato charge. When reverse flow finally occurs so that the charge can move into the cylinder, the exhaust gases trapped in the tunnels are the first to enter. They move in, collide and then start moving up the back of the cylinder. Normally, if it was the fuel mixture charge, there would be considerable mixing of the fuel mixture and exhaust gases. That doesn't happen with the Huskys as it is exhaust mixing with exhaust to establish the flow.

After the exhaust gases establish the flow, the strato air charge comes in and then followed by the fuel mixture. The relatively long transfer times allows the transfer flow to keep going to make up for the lag caused by the blowback into the transfers. The result is better trapping efficiency with the lower exhaust port. All in all, there is less mixing and better trapping efficiency in the Husky design.

That's why I sacrificed the piston (trimmed the exhaust side to alter the timing). I didn't want to scrap a jug by assuming that the blowdown was too short and end up raising the exhaust port too high.

What works, is just that - what works.

That is also why I put the curvature on the piston crown to follow the curve of the top of the exhaust port. I had tried that mod on other engines with good blowdown and there was nothing in it. However, on the 450 it made a big difference. The increase in the area of blowdown is actually more than if the roof of the exhaust port was completely flat. Since the opening follows a curve that is longer than a straight line across the port, the area upon opening (when the exhaust gas pressure differential is the highest) is greater than the flat port.

Only the edge of the piston is nipped to create the sudden opening. The mod allows the engine to retain an extra 2 degrees of the power stroke and an extra 2 degrees of cylinder trapping. I picked up the lost compression by changing to a colder plug that took up more space (and removed the gasket).
 
trappermike

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OK,I think I understand you better now,you are talking about just one peculiar engine,right?
I read about an old design tried many decades ago where Suzuki experimented with a transfer port almost as high as the exhaust,I don't think it worked for them though.
So I think I understand what you're thinking and what you did,you made a "trough" down into the piston crown in front of the exaust port,so the piston opens the port sooner,same effect as raising the ex. port without grinding the port,to get more ex. duration and blowdown time,am I correct so far?
If I'm right what you did is an old 2-stroke mod trick,you can make a trough in the piston crown in front of the ex. port or transfer port to increase port duration,I've done that trick many times in the past fot various reasons and it works fine. In your case you got the same effect as raising the ex. port without actually raising the ex. port and losing comp. ratio much,that was good thinking.I don't know how deep you made the trough,but from my experiments you can make it pretty deep depending on how thick the piston crown is above the ring,I wouldn't be afraid to go 2-3mm deep....I try to leave 1.5 to 2mm meat above the piston after digging the troughs...
Did increasing the blowdown time this way help the engine,I would think it helped a lot,with only 10-12 degrees blowdown time,holy crap!! With so little blowdown time,under normal circumstances a motor would experience exhaust pressure trying to go back down the transfers into the crankcase,and blow back out the carb,a miserable condition.
So did it help this bizarre design? I hope so. I'm really curious about this.
 
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