461 with a bit of modding

[Deets066]

I found this on a Asian fb page, it could be tosh, but three maybe troof in it ?
It’s a 2stroke bike thing.....


MPH with the best MPG.

Blowdown of 18 to 22: Low RPM powerband timing.Good for low & mid rang torque power, up to 8K-9.5K RPM rang.

Blowdown of 20 to 24: Very usable timing. Works best with weaker hitting pipes. Good mid rang torque & power up to 9K-10.5K RPM range.

Blowdown of 23 to 26: very good all around Wide power band timing. Will work with most pipes. Strong upper mid rang torque with hi RPM power up to a 9.5K-11K RPM range.

Blowdown of 25 to 27: A good pipe is a must. Best all around power band timing. Riper upper mid rang torque with hi RPM power Wide power band with a big power hit. Best power for everyday use up to 10K-11.5 RPM

Blowdown of 26 to 28: Low power under 5K, Good mid range. works best with pipes that peak hard in the 8K to 11.5K range fading/topping out at 12K This the max for most street set ups.

Blowdown of 28 to 30: Works best with a tuned variomatic or shifter engine, Very low power under 6K. Weak mid rang under 7.5K. The power band starts to get narrower and more peaky. needs a HIGH RPM pipe. gives the best power in the 9k to 12+K rang, will pull past 13K with some set ups.

Blowdown of 30: At this point 99.% of you will just have a door stop. Very narrow power band. No power at RPM's under 8K, higher power at high high revs. You will fry most one speed well tuned clutch's to be able to ride with a blowdown as high as this, You need a well tuned variomatic or shifter engine that can spin over 14K.

Blowdown of 32+: Way too high for any 1 speed or 2 speed automatic. This is only ride able at the race track on the very very best tuned variomatic shifter engine.


What does peeps say, does it hold water?

Cheers

No

 

[Wonkydonkey]

In my limited experience bike motors and chainsaws are way different. Bikes have insane port duration compared to saws because of pipes and reeds. So in my opinion it doesn’t really translate to saws. Raising peak power up in rpm has a lot to do with exhaust port height, but as you know it’s all working together.

I hope I didn’t come off as a jerk when I commented on your chain. Didn’t mean to take anything away from your saw. That wood must be harder than woodpecker lips!

I take things as they come, I try to read how some one else reads what I’ve said, in ther reply,
So no offence taken regarding chain and yes the wood is hard.

I was thinking of re trying the oem gasket, which would raise the exhaust etc I smidge, as I seem to recall it seemed better.

I will retest and time what’s on there now and what a 50/80 thou gasket does. Prolly not even twiddle with the carb..

 

[Wonkydonkey]

No ? deetsy... I’ve calculated a few timing numbers that peeps have posted of saws and less than 30 but more like lower 20's is more the norm ? ...18's- 19 is good too..

But size ,duration, and other stuff matters.

How do I say it, ,,,,,,!, I,m not jumping in with both feet, that’s why I’ve not just gone with the 100-120-80.
Just a ickel bit, at a time till I’m more happy. And it don’t take a lot to make me more happy

 

[XP_Slinger]

I take things as they come, I try to read how some one else reads what I’ve said, in ther reply,
So no offence taken regarding chain and yes the wood is hard.

I was thinking of re trying the oem gasket, which would raise the exhaust etc I smidge, as I seem to recall it seemed better.

I will retest and time what’s on there now and what a 50/80 thou gasket does. Prolly not even twiddle with the carb..

Just remember when using a thicker base gasket you’re not doing much except reducing compression and losing intake timing and duration. You most likely won’t like the result if it’s noticeable.

 

[Wonkydonkey]

Yeh is see what your saying, xpslinger.
I just wanted to ping it back a step. Aa little like tree monkey with that 461. That reminds me I must have another read of that thread.. see if. I can add and subtract those gains to Calc the end timing numbers.
Also by. Stepping back, I can check all my numbers again, I’m sure there’s some erreroius readings somewhere in there..

 

[XP_Slinger]

One step at a time is the way to do it. That tree monkey thread is a good one. I’m still fairly new at all this too, interested to see where you find gains.

 

[Deets066]

No ? deetsy... I’ve calculated a few timing numbers that peeps have posted of saws and less than 30 but more like lower 20's is more the norm ? ...18's- 19 is good too..

But size ,duration, and other stuff matters.

How do I say it, ,,,,,,!, I,m not jumping in with both feet, that’s why I’ve not just gone with the 100-120-80.
Just a ickel bit, at a time till I’m more happy. And it don’t take a lot to make me more happy

It was refering to blow down in a larger piped engine. Most of those rules don't apply to these little saws. I've heard of people runnin 40 BD with a pipe saw and it made a lot of power. Take the pipe off and go back to a muffler and you cut BD in half. With that being said, I think case compression plays a big role in BD also

 

[blsnelling]

After , squishy 0.0200 102/3 - 74/5 - 120/1

Give it some more intake. Trim the intake skirt if you like.

Have you advanced the ignition?

 

[MustangMike]

I agree with Brad. Based on my limited knowledge, an intake of about 78 would likely be good.

It would also be interesting to see how an exhaust of 100 would compare.

Just my thoughts, for what ever they are worth, which may not be much!

 

[Wonkydonkey]

I had it out again today as a mate want to come round, I wished he'd brought his 46.

Anyhow I changed the gasket from a coke can to a beer can. The aluminium is thicker in a beer can.
So we ran it and gave the rakers a file down. And ran it a bit more. It turned 14k out of the wood and ran 10k in the cut.

Can anyone tell me why the saw blips in the cut, it’s the revs rise a bit then settle then rise. A bit like it’s lean/ing then gets more fuel which equates the the Rev blip. It mot the operator blipping the trigger

I will give it some more intake time, but I think I will get another piston for this job and trim the skirt off. Piston is cheaper than a cylinder.
Interestingly the skirt is shaped at the front, guessing it’s to do with flow to the trans.

Yes I have taken 16/18 thou off the key brad, I could take a tad more but wanted to get a feel,,, not go to far.

 

[Wonkydonkey]

The retest, chain sharpened by my mate as well as the rakers.

Btw, he said the beech wood is hard

 

[Deets066]

It's doing that in the cut because it's still a little fat, lean it out a touch

 

[huskihl]

Rakers are still high or the chain isn't sharp, or not enough hook in the cutters. Or maybe it's a safety chain? You shouldn't need to push down to get it to cut.

Here's a ported 461 with a round ground chain in frozen beech.

 

[MustangMike]

His saw seems to be cutting well, but the chain is not self feeding. I know how to fix it on square, but not on round file.

Perhaps the horizontal needs a dip of 10*???

 

[Deets066]

i agree Kev, this is red elm and very hard wood around here

 

[huskihl]

His saw seems to be cutting well, but the chain is not self feeding. I know hoe to fix it on square, but not on round file.

Perhaps the horizontal needs a dip of 10*???

If his rakers are between .025 and .030", and it's not a safety chain, it's either not quite sharp or not enough hook. The 10° down angle leaves a stronger working corner and sharper opposite corner, which helps it feed, but not as much as what he needs.

 

[huskihl]

i agree Kev, this is red elm and very hard wood around here

Haven't seen red elm like that since I was a kid. We used to burn oodles of it

 

[blsnelling]

The retest, chain sharpened by my mate as well as the rakers.

Btw, he said the beech wood is hard

It's doing that in the cut because it's still a little fat, lean it out a touch

Considerably rich. A ported 461 will turn closer to 15K.

 

[Wonkydonkey]

Cheers for the replies,
I’ve ordered a am piston, so when that comes along with the exhaust, I,ll fit them both, re time those port numbers, give it a bit more intake duration , check everything again, and again then find some softer wood, . But still keep that hard beech to compare it’s cutting

 

[Deets066]

Cheers for the replies,
I’ve ordered a am piston, so when that comes along with the exhaust, I,ll fit them both, re time those port numbers, give it a bit more intake duration , check everything again, and again then find some softer wood, . But still keep that hard beech to compare it’s cutting

Change your tune before you change anything else. Get her dialed in first