1957 35HP Big Twin (hitting hard Knocking)

[HighTrim]

Re: 1957 35HP Big Twin (hitting hard Knocking)

Your idle is likely set too low to start. Screw it in a couple turns.

Now alot of these OMCS like to be on the rich side for starting purposes. Not all my motors exhibit this, but some definately do. I richen the needles, start the motor, then readjust. Yours is not the only one, but upping the idle will make it less extreme. They do back out over time due to vibrations.

 

[bigballerg]

Re: 1957 35HP Big Twin (hitting hard Knocking)

Ok, I will find that happy medium... Thank you!

 

[bigballerg]

Re: 1957 35HP Big Twin (hitting hard Knocking)

One last thing I just remembered When adjusting the high speed, I read posts where it starts reeving up then back out 1/4 turn or so. Mine when it hits the point of reeving, it goes from say (using as just numbers and not actual) 100rpms to 10000rpms Real significant jump and within a 1/32 of a turn. Real tight window of increase, SO turning 1/4 turn from that spot seems a lot. When I gun it WOT it is sluggish...

 

[HighTrim]

Re: 1957 35HP Big Twin (hitting hard Knocking)

1/4 turn back out from the point where it wants to die or sneeze is just a guideline. It is WITHIN that 1/4 turn somewhere.

Im wondering, what was the condition of your needles?

 

[bigballerg]

Re: 1957 35HP Big Twin (hitting hard Knocking)

My ss needle is not a perfect point... a tad rounded. My HS needle seems blunt not needle point at all. On the rpms.. Do you want me to stay at the higher rpm level?

 

[boobie]

Re: 1957 35HP Big Twin (hitting hard Knocking)

Is the choke plate in the carb closing all the way when starting ??

 

[bigballerg]

Re: 1957 35HP Big Twin (hitting hard Knocking)

I will check.... will advise..

 

[bigballerg]

Re: 1957 35HP Big Twin (hitting hard Knocking)

Update, choke plate closing... Here is the motor at idling. It seems like everything is good but it does rev up a tad then down then rev then down then eventually will cut out....

 

[bigballerg]

Re: 1957 35HP Big Twin (hitting hard Knocking)

What causes this fluctuation? Is it incorrect knob settings?

 

[nwcove]

Re: 1957 35HP Big Twin (hitting hard Knocking)

sounds like you could up the idle a bit and maybe do a bit of fine tuning on the ss needle. you're very close now earl!!

 

[bigballerg]

Re: 1957 35HP Big Twin (hitting hard Knocking)

I just dont want to run to LEAN? How can you tell if you are running to lean vs increasing idle?

 

[nwcove]

Re: 1957 35HP Big Twin (hitting hard Knocking)

they will usually sneeze quite violently if running lean at idle. as mentioned, i would adjust the idle screw to raise the rpms, then try working with the ss needle in small increments, giving the motor time to react to the changes. go to the rich side first and see if it smooths out, if not go back to the original setting, wait for the motor to respond, then go to the lean side.

 

[bigballerg]

Re: 1957 35HP Big Twin (hitting hard Knocking)

OK, will follow that... thank you!

 

[nwcove]

Re: 1957 35HP Big Twin (hitting hard Knocking)

and also......if you have a fan, set it in a safe spot away from splashing water, and blow the exhaust smoke away from the carb area. they dont like breathing in exhaust.

 

[HighTrim]

Re: 1957 35HP Big Twin (hitting hard Knocking)

It will sneeze when it is too lean. Increasing the idle has nothing to do with the low speed needle, nor the air/fuel mixture. It is accomplished at the base of the throttle tower. There SHOULD be a bolt which threads in, increasing the idle.

Almost sounds like you have an air leak from the video. Have all the fuel lines been replaced, connections all tight?

Here is a '57 Johnson I tuned at idle. Notice the water flow as well. Yours looks weak. The flow on the non t stat motors should gush pretty good.

 

[bigballerg]

Re: 1957 35HP Big Twin (hitting hard Knocking)

I think mine comes with stat? 1957 Lark 35hp with my old Big Twin components now.. cover etc.. Good video to hear how yours sounds/works.... New fuel hoses when I did tank conversion to fuel pump.

 

[HighTrim]

Re: 1957 35HP Big Twin (hitting hard Knocking)

Nope, no t stat on your motor. That was the '58 Lark. The 57s had the single water line waterpumps.

 

[bigballerg]

Re: 1957 35HP Big Twin (hitting hard Knocking)

Question, motor starts at cold using choke and runs for as long as I want..... when i turn off, I have a hard time restarting... wait an hour or two then starts. I squeeze the bulb and gas comes out of the muffler (or whatever that part is that attaches in front of the carb. has like two intakes on it (Intake manifold possibly?)) Anyway, bulb doesnt get hard, just squeeze, squeeze and gas pours out of a hole on the intake manifold? What causes this and is this why it doesn't start after warm?

 

[nwcove]

Re: 1957 35HP Big Twin (hitting hard Knocking)

Sounds like your float needle isnt seating for some reason. Could be trash in it, or if you are still using the cork float, it may not be floating anymore.
If you are using choke to stop the motor it probably gets flooded with fuel and hard to restart. Waiting a period of time allows that extra fuel to evaporate.

 

[bigballerg]

Re: 1957 35HP Big Twin (hitting hard Knocking)

I noticed im at the bottom of fuel and has a lot of oil in the mix right now. Im thinking float full of oil and yes it is cork.