motor kills under load

[portedmetal]

Hello I am new to the forums and figured this would be a good place to ask my question.

I have a brand new HF 6.5. I broke the motor in following manufacturing specifications. After the break in I modified the motor. The following is what I have done.

Hi-flow air filter
Header/Muffler
Governor removed
18lb springs
Billet aluminum flywheel
gx140 emulsion tube
.036 jet
Walbro fuel pump
Running 93 octane

The motor runs beautifully throughout the entire throttle range. Once a load is put on the motor in runs for a few seconds then dies. I am using a clutch from an older motor that I will be replacing anyway.

My question is this. Is it the clutch making the motor die? Or is it something else?

 

[Russ2251]

Not the clutch. Check for a lean condition.
Why 93 octane??? Waste of much needed dinero.

 

[firekiller52]

try some old fahsoned regular gas, even tho you have heavier valve springs you dont have higher compression to NEED the highte octane, which might be causing your issue

also what oil are you running? and how old is the motor(like a couple rides or a season on it?) you might be experincing valve float even with heavier springs, also could be your jet is too small for higher Revs, you may need a bigger jet yet, which is a pain, too much fuel to idle yet not enough to scream

 

[portedmetal]

I'm running 93 octane because I had about a gallon left over from a racing ATV I recently got rid of. I will run regular, just didn't want to waste good fuel. I'm using 10W-30 synthetic oil. The motor is actually less than a month old. I also forgot to mention that I am still using the stock spark plug. If I would need a bigger jet, what size would be a good starting point?

 

[anderkart]

.036 jet


My question is this. Is it the clutch making the motor die? Or is it something else?

I see you already have a larger than stock main jet.
You might try a .038 but I'm not sure if this is your only problem here.

Here's a bit of clone jetting info you can trust} http://arcracing.blogspot.com/search?q=clone+jetting

I think maybe you've either had a bit of dirt in your fuel that's partially plugged your main jet, or needle and seat valve, and/or your carbs mounting gasket might have been mistakenly installed upside down where it cant make a good seal.

Does your clutch seem to be locking up at way too low of an rpm? (will the kart Idle without taking off?)

How old is your 93 octane fuel?

 

[portedmetal]

The fuel is maybe 2 weeks old since I just recently go rid of my ATV. The kart does idle without moving. I can get the kart to move about 100 feet at full throttle before it dies, maybe 200 feet at half throttle.

 

[fowler]

there isnt a block in the fuel line
or a clogged filter

 

[portedmetal]

No clog anywhere. Fuel flows freely and its got a good pulse. Reading the blog anderkart had posted, maybe I need to change my low speed jet also?

 

[anderkart]

I can get the kart to move about 100 feet at full throttle before it dies, maybe 200 feet at half throttle.

Does leaving the choke partially or full-on help keep it running?

As an easy test:
Next time as soon as it it dies, reach over and quickly turn the fuel petcock off. (or clamp the line with vice grips if you dont have a petcock) Now simply remove your float-bowls drain plug to confirm if you had any gas in that carb when It died or not...

 

[anderkart]

No clog anywhere. Fuel flows freely and its got a good pulse. Reading the blog anderkart had posted, maybe I need to change my low speed jet also?

That info is to squeak out max performance, I think you're dealing with some type of basic fundamental problem here.

Carefully spray your entire carb to intake mating surface with carb cleaner (w/straw) while the engine is idling. If you sense the rpm changes at all your not making a good seal there for some reason... (gasket on backwards and/or loose nuts/defectively-machined mating surfaces)

 

[portedmetal]

I appreciate all the help so far but i wont be able to try anything until I get home from work. I'll update later with my results from testing.

 

[portedmetal]

I was just pondering while on my lunch break, you mention that I may not be getting a good seal at the Carb to intake surface. The black insulator that goes between the carb and head, if this piece were to be on backwards, would that be a possible cause?

 

[Doc Sprocket]

I would think so- why? Is there a chance you've got it the wrong way 'round?

 

[portedmetal]

Well here are the results of my testing. The black insulator that i was worried about was on the correct way, but the gasket behind it was on backwards. I fixed this and still the problem persist. I started running regular gas, still the problem. Everytime the motor would kill, i would shut fuel off and check carburetor bowl, it had fuel. After removing the spark plug i noticed the gap was way small and the tip was black. I reinstalled the stock emulsion tube and main jet. After i did that i did notice an improvement but the problem still persist.

Now everytime i am full throttle the kart runs excellent, but as soon as i let off the throttle the motor instantly dies.

Also at open choke the motor would idle for a few minutes then die. Restart and it would idle for about 10 minutes then die. Restart and it would idle for a few seconds then die. Restart and it would just repeat this pattern running for different intervals every time.

Now i have 3 new questions.

1: Can i revert back to stock valve springs with governor removed? If so would this help in any way?
2: I still have the low oil sensor hooked up. Would this may be the cause of all my woes?
3: Is it wise to run it with stock "E" tube and stock main jet with the hi-flow air filter and header?

 

[Doc Sprocket]

1) Yes- In fact, having the stock springs with gov removed will create a sort of "failsafe" to prevent overrevving. The concept is that the valves will float and cause power loss at an RPM that is lower than what is required for s**t to start grenading. Please note that there are never any guarantees.

2)Yes, it's possible. Unplug sensor lead and retest.

3)Give it a shot, and do some plug reads to see if it's running particularly lean in that state, and adjust jetting as necessary.

 

[portedmetal]

thanks for the info. I wont be able to mess with it much until the weekend. I'll disconnect the oil sensor first, then move onto the valve springs.

I was also thinking of putting everything back to stock except for the governor/flywheel to see if the problem persists.