Another chainsaw dyno...

[Bigmac]

The 2000 Honda curve is close in concept of what the KTM was doing. After peak the timing increased, then fell off when it was hitting red-line.

EDIT: You can see the development of the engine with those ignition curves. The '98 model had a hard hit as it came on the pipe and had to back the ignition down quickly. Then had to stabilize, then drop off again. When you look at the ignition curve of the 2001 model, it looks like the engineers had worked out the 'music' of the pipe and ports and had a nice even steady decrease as the engine revved to full power. - Gotta love dynos.

The 01 curve is considered the best ignition by all! lol I have butt dynoed the 97,98,99,01, 03 and 04 ignitions on several different trx application, I really like the 99 and 04, but i can’t fine those timing curves

 

[BonScott46]

Awesome thread, big thanks to Joe and all the guys sending saws.

 

[huskyboy]

Hd17 with no choke, thinned shaft, & massaged Venturi

Stock .66 jet and transition jetting? The HD11 jetting is better than the HD17 stock as mentioned.

 

[Deets066]

Stock .66 jet and transition jetting? The HD11 jetting is better than the HD17 stock as mentioned.

Never touched the jetting, never really had a need to

 

[huskyboy]

Never touched the jetting, never really had a need to

Would be interesting to test your theory on the dyno. Unless of course a guy can’t handle the results .

 

[CR888]

i concur. Not beating up on OP for how he does it, not one bit. It “would” be ideal if the load was computer controlled and applied the exact same on every saw. Not saying he doesn’t, from the videos i have seen it looks pretty consistent, but to remove any and all doubt it needs to be -00% the same every time. No, I do not know how to make the load the same. Just speaking for sake of scientific method. Please don’t beat me with dull chains

When you get out the measuring stick and lay it up against man's prized possessions there will always be doubt. Hand controlled/computer controlled wont deter a keyboard fact checker. Complicated saw dyno's have been tried before with limited success, this one appears simple and good. So far over 100pages in a couple of weeks is a good measure of a threads worth.

 

[Deets066]

It's a question that may lead to an interesting answer. The other alternative I see is that Deets may have used a bit more time/area on the transfers.

My upper trans are untouched, lowers were not ground on either. Little JB in there actually

 

[Deets066]

Would be interesting to test your theory on the dyno. Unless of course a guy can’t handle the results .

If I wanted to upgrade the carb in anyway, it would be fitting a modified WJ69.

 

[Terry Syd]

Stock .66 jet and transition jetting?

The transition jetting affects the LOW SPEED CIRCUIT JETTING. For example, if the transition jetting is a tad lean, then you bump it up. That will make the low speed circuit run richer - that's what all of us have done.

HERE'S THE IMPORTANT PART -
It is the combination of the low speed circuit flow and the high speed circuit flow working together that determines the total fuel mixture curve for the carb as the revs build.

Many times as you have increased the low speed flow, you have had to lean out the high speed flow to keep the peak power the same.

There are TWO CURVES, one is the fixed jet low speed circuit in the straight section of the carb and the other is the high speed circuit in the VENTURI. The venturi in the high speed circuit makes the low pressure continue to rise much faster as the revs increase. - You have to make the two curves blend together in the best total fuel mixture you can achieve.

I wish I had an easy formula for computing the total fuel flow, but at this point I just have to wing it, that is, feel what's happening and then go to another step.

 

[Moparmyway]

Would be interesting to test your theory on the dyno. Unless of course a guy can’t handle the results .

Mason, lets see you mess with a few things and send in your stuff

Deets has already said a bunch of times that Joe can post anything he wants off of his saws.

Are you willing to pay Joe the extra time that you're typing about that must be taken to do these things ?

It saddens me to see you trodding down this path of "keyboard warriordom" ...........

 

[huskyboy]

Mason, lets see you mess with a few things and send in your stuff

Deets has already said a bunch of times that Joe can post anything he wants off of his saws.

Are you willing to pay Joe the extra time that you're typing about that must be taken to do these things ?

It saddens me to see you trodding down this path of "keyboard warriordom" ...........

You read into my post too far Kev, no need to get riled up. Wasn’t my intention. Merely friendly ribbing. I am curious what carb mods do on the dyno as are other people. Unfortunately tensions seem to get the better of people in these kinds of threads, which is why I stick to the sidelines and read for the most part.

 

[Terry Syd]

Stock .66 jet and transition jetting? The HD11 jetting is better than the HD17 stock as mentioned.

We don't know that yet.

 

[huskyboy]

We don't know that yet.

.66 vs .70 for the main jet I believe if I remember right

 

[Terry Syd]

The main jet runs in parallel with the high speed needle. It does NOT influence the low speed circuit.

A bigger main jet is used to keep the needle in a reasonable range of movement (say two turns out).

When modding a carb to run more low speed circuit (Zama, Walbro) it often occurs that you have to block off the extra high speed jet.

Sometimes that jet is on the back of the main discharge nozzle, sometimes it is a separate jet. On some carbs I have had to block off the hole (jet) on the back of the main discharge nozzle, however on a couple of Walbros that I've done I've had to block off the separate main jets.

It was because I increased the low speed circuit flow enough that it became difficult to tune the high speed needle. Once the extra main jet was blocked, I could easily tune the carb.

 

[Terry Syd]

My upper trans are untouched, lowers were not ground on either. Little JB in there actually

Great, that eliminates an increase in time/area of the transfers. So, I figure it may be a timing or carb jetting issue between the two curves. (don't you love dynos?)

Crikey, imagine a carb swap where Deets saw is now King of the Mountain!

 

[XP_Slinger]

Great thing about both of those Hi-Breeds is they’re work saws. Take them in the woods and pound the piss out of them all day and they’ll ask for more.

 

[Moparmyway]

You read into my post too far Kev, no need to get riled up. Wasn’t my intention. Merely friendly ribbing.

Not riled up in the slightest Mason.
You've not seen me riled up yet
I was merely friendly ribbing you with a few questions
You've read too far into MY post

 

[dustinwilt68]

Looking forward to seeing more results, let's keep it fun.

 

[BonScott46]

Interested to see if there is any difference advance vs. no advance on something like a hybrid.

 

[dall]

Mason, lets see you mess with a few things and send in your stuff

Deets has already said a bunch of times that Joe can post anything he wants off of his saws.

Are you willing to pay Joe the extra time that you're typing about that must be taken to do these things ?

It saddens me to see you trodding down this path of "keyboard warriordom" ...........

best answer