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  #1541  
Old 07-28-2016, 12:37 AM
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Try Midol guys!
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  #1542  
Old 07-28-2016, 01:44 AM
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Try Midol guys!
Says every chick I work with!
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  #1543  
Old 07-28-2016, 12:47 PM
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I pressed the TC DriveR unit so that it went back into place. I didn't take it off to see what happened. I'm going to ASSume it is not broken.

I cut a new key for my wheel hub that I almost lost yesterday. Not sure if I forgot it last time??????????????

Time to play.

I probably have about 15 min of firing on this new AR3911 plug. I had it out twice. Each time was similar driving to the last video.

I'll try to get a bit of a longer ride this time and then kill it at WOT after some longer WOT runs.

If I start at one end, I can get up to about 42mph before I hit a decent hill. I have been killing my engine above 40mph, at WOT, just as I start up the hill. So I am already at high RPM, then the hill provides extra load? I have been killing the engine just as RPMs start to drop.

I can coast to the top and roll back to my house.

Let's see if I can get another 15 minutes (30 minutes total) on this plug and kill it at WOT (as described above) for plug chop.

Here we go!
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  #1544  
Old 07-28-2016, 01:07 PM
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Are u still messing with jetting..
Anyhoo.. I will repeat what I said (was that 20 or 40 pages ago?)
IMO. Start with a main jet that is known to be to have a rich mixture. Keep going smaller on the main until your "butt" dyno feels a loss of power or no change. Once you get to that point go back one size larger. Give the engine what it wants to make max power at WOT.
If you have the area you could do timed/distance (time to cover like 200yrds). Tune the main on a average temp day (don't tune it when its 20 when most of the time is spent at 70)
Fuel (even your 100oct) is not like it was 40 years ago, No tetraethyl lead, no ash, reduced amounts of heavy hydrocarbons. Todays fuel is blended to burn cleaner with minimal carbon deposits.
IMO your wasting your time "reading" the plug.
Pilot mix screw set it for the strongest idle, if its only 1/2 turn out you may need a bigger pilot jet. If 3+ turns out it needs a smaller pilot jet.
Now if the pilot jet is sized right, the main is sized right but you have a lean bog before the main picks up then the transition needs tuning. Two ways to tune the transition, Smaller air correction jet on the pilot circuit will richen the transition, or removing the welch plug and opening the size of the transition ports.
99% of all carburetors work on the same principle, Idle circuit, transition, main, emulsion and air correction. Learn the theory of how/why they are designed and tuning becomes much easier.

---------- Post added at 12:07 PM ---------- Previous post was at 12:03 PM ----------

Vm22
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  #1545  
Old 07-28-2016, 02:25 PM
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Originally Posted by rk970 View Post
Are u still messing with jetting..
Anyhoo.. I will repeat what I said (was that 20 or 40 pages ago?)
IMO. Start with a main jet that is known to be to have a rich mixture. Keep going smaller on the main until your "butt" dyno feels a loss of power or no change. Once you get to that point go back one size larger. Give the engine what it wants to make max power at WOT.
If you have the area you could do timed/distance (time to cover like 200yrds). Tune the main on a average temp day (don't tune it when its 20 when most of the time is spent at 70)
Fuel (even your 100oct) is not like it was 40 years ago, No tetraethyl lead, no ash, reduced amounts of heavy hydrocarbons. Todays fuel is blended to burn cleaner with minimal carbon deposits.
IMO your wasting your time "reading" the plug.
Pilot mix screw set it for the strongest idle, if its only 1/2 turn out you may need a bigger pilot jet. If 3+ turns out it needs a smaller pilot jet.
Now if the pilot jet is sized right, the main is sized right but you have a lean bog before the main picks up then the transition needs tuning. Two ways to tune the transition, Smaller air correction jet on the pilot circuit will richen the transition, or removing the welch plug and opening the size of the transition ports.
99% of all carburetors work on the same principle, Idle circuit, transition, main, emulsion and air correction. Learn the theory of how/why they are designed and tuning becomes much easier.

---------- Post added at 12:07 PM ---------- Previous post was at 12:03 PM ----------

Vm22

I remember what you said.
This wasn't too long ago.

"SOME MORE BUTT DYNO AFR TESTING,

BUTT

I don't know what it means.

GIVE ME THE ANSWERS BRO!!!

Whacking the Throttle Wide Open from Idle Stalls the Engine.
The only obvious issue right now is when I punch it.
Didn't notice any backfire or bogging sound?
Still don't know if there is a difference between bog and stall.

I read this may be a problem with this set up.

WHAT DOES IT MEAN?

Not getting enough gas during transition from Low to Main circuit?

My previous "Prep" Research (IIRC) learned me that the air bleed jets "SET" the vacuum level for the transition?

One size jet for the Main circuit to come on quicker?
One size jet to delay the transition to the main circuit ?

(Can be adjusted by drilling and tapping and custom making a set screw air bleeder jet if needed?)


Low RPM, WOT means No manifold vacuum, right?

Decreasing Main Circuit Air Bleed Jet (moves air faster, more vacuum???) will transition to the main circuit faster????

Also something about the pilot jet O-ring (s). Maybe I should add the top one?

Lastly was modding the transition holes in the pilot circuit next to the Fuel Mix screw behind the "WELCH PLUG".
Something like increasing the diameter by 0.002"?

See I Remember some of the stuff I read. AND some times it is relevant.



WHAT YA THINK????


Also heard engaging the clutch / TC above 3000 RPM helps. I got the springs for that.
The higher engine speed (at 3000 RPM) may increase the vacuum (faster air across the main circuit air bleed jet) and get to the main circuit quicker during quick transition from idle to WOT?"


Just trying to learn hands on. I REALLY DO APPRECIATE ALL YOUR HELP!!!

---------- Post added at 02:44 PM ---------- Previous post was at 02:19 PM ----------

I am going to prepare today and organize all my jets and bits.
I'll see what I have and what I can make.

I should be able to get a decent range. Like 0.040, 0.041, 0.042, 0.0433, 0.0453"

I'm fairly confident that covers me.

---------- Post added at 03:25 PM ---------- Previous post was at 02:44 PM ----------

Pedal are here. More HD than I expected for 50 cents a pop.
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  #1546  
Old 07-28-2016, 03:27 PM
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Part of the problem is the carb you are using is from a utility engine with almost twice the displacement ment to run at 3600rpm.. I assume when you wack the throttle open it goes lean because velocity through the carb drops to much. It would take an accelerator pump to cover the lean "hole"..
example.. remove the accelerator pump linkage from an automotive carb. Now try to rejet/tune that carb to remove the lean stumble. It will not happen.. Now take the Solex carb from a VW bug and bolt it on a standard 350 chevy. Remove the accel pump from the Solex and it will (proper jetting) run that 350 chevy just fine, well it would make possibly a whopping 80hp

---------- Post added at 02:27 PM ---------- Previous post was at 02:18 PM ----------

I usually don't mess with transition holes.(last resort effort). then again I don't mess with utility carbs.
Mikuni, Keihin and Walbro are what I mostly mess with now days.
Why don't you try the stock carb..
  #1547  
Old 07-28-2016, 03:42 PM
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Are you ready for this Bob?

This is actually a quite common problem with beginning port and polishers. The VOLUME is increased...while the VELOCITY is decreased. At idle...not a problem...as air velocity is not a problem. (Seperate circuit...so...jetting is the solution.)

Now...not as big a problem at top rpms...because NOW the air IS moving at high velocity. (And again...controlled by jet size.)

Sooooo....it's INBETWEEN that the problem exists. Small "fixed" carbs don't have an accelerator pump...but an emulsion tube, which curiously, works BACKWARDS....leaning out the mixture.

Welcome to the world of GAB modification!

Refresh my memory on everything on your carb mods.
  #1548  
Old 07-28-2016, 05:25 PM
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I think the big can be fixed by restricting the low speed air bleed. You can get automotive electrical wire and strip it slipping one strand at a time into the air bleed until it's right. Make sure to make it long enough so that the air filter can hold it in place. I can straight "whomp" my minibike throttle as hard as I want from a dead idle and it has no hesitation at all, also just put a carb from a 17hp lawnmower on a go kart with an 8hp briggs and tuned the air bleeds this way and it runs great as well.
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  #1549  
Old 07-29-2016, 02:00 AM
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My brain is still hurting
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  #1550  
Old 07-29-2016, 02:13 PM
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So Every time I kill my engine the TC driver is stuck. I can press it back in (It is hot and it takes some force!).

When I take it apart to inspect, I will change to the white garter springs (if nothing else is broken).
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  #1551  
Old 07-31-2016, 02:43 PM
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So I just got my call back from Tim Iskenderian at Small Engine Cams.

We discussed where peak torque might be for my engine.

Told him mild port and polish with gx390 carb and Black Mamba Jr.

He said peak torque might be in upper 4000's and should spin to 6500.

I should have asked more questions but he caught me off guard on a Sunday afternoon.
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  #1552  
Old 08-01-2016, 04:01 PM
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Originally Posted by bob58o View Post
So Every time I kill my engine the TC driver is stuck. I can press it back in (It is hot and it takes some force!).

When I take it apart to inspect, I will change to the white garter springs (if nothing else is broken).
Have you cleaned and made sure it moved freely before you put it on?
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  #1553  
Old 08-01-2016, 09:41 PM
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Have you cleaned and made sure it moved freely before you put it on?
It was cleaned and lubricated and working when I worked on the tie rods. The bushing was new. The belt was new.
I'm avoiding removing the DriveR unit for the moment.
It is not easy without the impact wrench. Since the last scare with the threads, I'm trying not to mess with it too much. I know I HAVE to, but want to try another jet size first.

I haven't taken the weights and spring assembly out since I bought it.
There was lots of belt material. I scraped out what I could between the outer drum and moveable surface, but didn't get inside.

I'm sure it needs cleaning.


6000 + RPM and 16 Ft lbs torque may be too much for the stock garter springs?

As it cools down it gets easier to push back in.
Not easy when hot.

I started bringing my spark plug socket and a pry bar and towel on my runs. Lol
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  #1554  
Old 08-06-2016, 12:46 AM
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0.026"
0.048"

Lock it! I'm done!
Find this engine soon in my mini bike thread
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  #1555  
Old 08-06-2016, 12:49 AM
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No way. The end of the Original GAB!

IBTL
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