McCulloch Algebra

[cpr]

Solved the high side hunt riddle. The grommet wasn't holding the setting and the vibes were making the needle screw all the way onto the seat. I replaced it. It's not GTG ready. That big bar has me leaning on a fat fuel setting. 1 and 1/2 out on the low (makes it load up pretty quick at idle) and 1 and 1/4 on the high. WFO briefly shows 11200 at this setup. When I still had the 20" bar on I dialed in an easy 12500, but thought it too lean to start with. Out of time for today, but I'm close. Now it's the fun stuff.

<iframe width="420" height="315" src="http://www.youtube.com/embed/OtBrGeCGYxs" frameborder="0" allowfullscreen></iframe>

You're going to laugh your ass off at the next video. Fist of air start :jester::msp_tongue:. Despite that, once it's warmed up, it's pretty easy to light off .

 

[cpr]

Cuttin' hard ash.

Little tuning and then it's time for a race against the Super 797.

<iframe width="420" height="315" src="http://www.youtube.com/embed/wwKFXJi3FKo" frameborder="0" allowfullscreen></iframe>

 

[Brian13]

Looking good!!! I love the sound of the kart saws.

 

[leeha]

Sounding pretty good there cpr.
Can't wait to see the race between
this and the 797.



Lee

 

[rwoods]

Yes, Lee. 2nd of 3 cars to go airborne and the most violent. It went cockpit first into the catchfence and it appeared as though the carbon-fiber roll-hoop was damaged. Details aren't known right now, but some sort of neck fracture or basular skull fracture (what killed my hero, Earnhardt) is highly likely.

Talking it out makes me feel better. No one here "gets" how it hurts. We've come so far, but...Dammit! Any other angle of impact, he lives. How do we stop it? Closed cockpits from now on? They're debuting a totally new car for 2012. While the rear bumper may help stop the wheel-over-wheel launch it doesn't address the impact that killed him. :msp_sad:.

cpr, when I was your age my sister-in-law's husband and I spent many hours dreaming of big adventures together flying and hunting in Alaska and Canada. Besides marrying into the same family, we had a lot of the same interests and obligations - he had a three year old daughter and I had a five year old daughter and a three year old daughter Tragically, he was killed when the plane he was piloting crashed in a freak late April snow because he was flying by the letter of the book so as to not jeopardize his license. He kept his license and lost his life. His wife was eight months pregnant (also a daughter) and my wife had just given birth to our third daughter the week before. It took three days to find the crash site. I had to break the news to his wife, her family and his family. A lot of dreams died that day for many good folks. I believe I can understand why your hurting. But GOD is merciful. In my situation, I have had the priviledge of watching his daughters grow up to be beautiful young ladies for whom he would have been very proud. I don't think the FAA rules have changed but maybe you'll see some positive change in Indy Cars. I feel for you, man. Ron

BTW your saw is sounding pretty good.

 

[cpr]

Beautiful sunny morning with temps in the 40s, which my McCullochs seem to like. Sounds like a good day for RACING!

Yes, this was not a "scientific" test. The log changes quite a lot for these saws and I didn't run the same B&C for all, but SO WHAT? I had fun.

Let's meet the players.
[video=youtube_share;1gZDkci-ncc]http://youtu.be/1gZDkci-ncc[/video]

First out (okay actually last, but whatever), the 1-72. My watch says 43.85s. Not bad, start could've maybe gained a couple tenths.
[video=youtube_share;ytuQoo1CUVY]http://youtu.be/ytuQoo1CUVY[/video]

Next, the Super 797. I am surprised. I expected more speed. 41.75s.
[video=youtube_share;d64jujm77sk]http://youtu.be/d64jujm77sk[/video]

Lastly, the 791R. A little tuning this morning before the run. It had been really fat last time I had it out. 29.55s :hmm3grin2orange:. Not even close to empirical, but it sure howls.
[video=youtube_share;qQLaGmbcJ14]http://youtu.be/qQLaGmbcJ14[/video]

 

[leeha]

Nice vid's, But i'm rather disapointed in the 797.
Only 2 seconds faster than a 1-72, Just doesn't
seem right.





Lee

 

[blsnelling]

It was sure holding more RPMs. I'm guessing chain or gearing.

 

[cpr]

I could make excuses for the 797 that, at 130psi, it'd be faster with new rings, but the 1-72 is in the same boat. You're right, doesn't seem right. May have to play some more this weekend.

I'll maybe recreate with the same b&c. 1-72 has stock 7t and the governor hooked up. 797 has an 8t, standard for the 125, not sure on the 797. 791 has an 8, too.

 

[leeha]

That could be why, 130 psi is way low for a 797.




Lee

 

[Eccentric]

The S-797 did sound sick to me. Hard to tell from the video, but it sounded like it was leaning out in the cut and falling on its face. The 791R sounded a tad lean to me too, but the S-797 sounded much worse...

 

[cpr]

You may be right Aaron. I had to force myself to "listen" to the video rather than "hear" it as I recorded it if that makes sense.

S797 does need rings, this wasn't a fair fight. Carb, I haven't verified the tune since last year. 791R could go fatter on the high side, low is close if not still fat. I took nearly a 1/2 turn out of the low for today (which leaves about 1 1/4 out) and left the high at 1 1/2 out. Can't go any richer on the low or it won't idle. It'll load up and stall after 30 seconds the way it was. Refire and it smokes off the excess, repeat.

Kart motors are thirsty pigs ...

 

[Jacob J.]

What are your points set at in the 791R? It sounds like when you get way down in the cut you're either getting a little point float or the timing is retarding a little.

 

[cpr]

What are your points set at in the 791R? It sounds like when you get way down in the cut you're either getting a little point float or the timing is retarding a little.

Points gapped .019, module .010, plug .020.

They could've moved. As far into this saw as I was, I ought to check everything. The bottom bracket came loose after the first checkdown start and I've tightened the muffler twice now. It's possible something has shifted.

Good advice guys, keep it coming...

 

[Jacob J.]

Which carburetor are you feeding the 791R with? If it's a flatback, keep in mind they have that huge metering diaphragm and it takes a split second longer to react than the Tillotson HLs or the SDC. RPM in the cut is what you're concerned with on these saws, not R's they're turning out of the wood.

If it were me I'd check the points again and also check the contact surface of the points. There was a long discussion on one of the kart forums years ago about NOS Mac points deteriorating in the package over time and not working correctly new out of the package. Some of the guys were trying acetone to clean the points and didn't have any luck with it.

 

[cpr]

48890b flatback and thanks, I'll check it out.

 

[blsnelling]

It's always good to see sound advice being shared like this. That's what it's all about.

 

[Brian13]

Definitely check your points. When I was working on the 890 I was sure I was having carb problems, and just for kicks I pulled the flywheel and checked the points and they had just about closed. It was sounding like is was flooding real bad to the point where it would only pop and not even fire. I reset them, it was idling good for a few minutes and sounded like it flooded out and stalled and would only pop again. Sure enough the points closed on me. Had to put some locktight to get them to stay.

 

[cpr]

Update. Flywheel had loosened to just finger tight and points closed up to about .014. Reset to .019 and retightened everything. Ought to be good to go.

I tore down the SP125 tonight. If I had all the parts I need here, the 101 would be built tonight! On the hunt for parts :angry2:.

 

[cpr]

So, when putting a 101 in a SP125, what do you do at the rear av mount?
View attachment 206530

No boss to drill into. Mount the isobracket to tank and let it float against the shroud? Seems like asking the oiler tank to shoulder a lot of force.