2F poor acceleration (1 Viewer)

[charliemeyer007]

So how many carbs have you rebuilt? If this was your first one maybe you didn't get it exactly right. Are you the person who was looking for vacuum leaks with propane? I use a can of WD-40 with a pee tube. When it was 35 below zero I used an un lit propane torch as starting fluid and it work great with the nozzle in the carb throat.

 

[1911]

When it was 35 below zero I used an un lit propane torch as starting fluid and it work great with the nozzle in the carb throat.

Hah ha, I have done that also in the past, though not for my 40.

When I was about 12, I discovered by experimentation that my Briggs & Stratton-powered mini bike would run on propane by doing the same. Taped the propane bottle to the frame, removed the burner nozzle, and ran some fuel hose from the burner valve to the carb throat. The exact mixture was not too important, it ran anyway.

 

[Grayscale]

@Ry24000 Does this engine have headers? Is it more when the motor is cold, or is it all the time? Does the engine start easily when it is cold? How long has it been since the ignition system was serviced? Do your spark plugs look normal?

I think that any naturally aspirated engine is a bit challenged working with smog scenarios that are not complete or working well. The intake manifold probably worked better when it was mated to the exhaust manifold, in my case. My 2F-FJ40 is always responsive to throttle, except during the winter or when the block is at ambient temp in spring / fall. The air cleaner assembly doesn't receive hot air like it did when the wax / spring valve functioned and it was attached to the heat shield on the front-side of the exhaust manifold.

 

[Ry24000]

@Ry24000 Does this engine have headers? Is it more when the motor is cold, or is it all the time? Does the engine start easily when it is cold? How long has it been since the ignition system was serviced? Do your spark plugs look normal?

I think that any naturally aspirated engine is a bit challenged working with smog scenarios that are not complete or working well. The intake manifold probably worked better when it was mated to the exhaust manifold, in my case. My 2F-FJ40 is always responsive to throttle, except during the winter or when the block is at ambient temp in spring / fall. The air cleaner assembly doesn't receive hot air like it did when the wax / spring valve functioned and it was attached to the heat shield on the front-side of the exhaust manifold.

Thanks for asking. I was going to start a new thread, but only after I did a few things first. I didn't want to hijack a thread too. I just get frustrated when these threads dead end!!!!

 

[igotta40]

I gotta know. What was the problem?
I have the same issue and I started going through all the steps staring with checking for vacuum leak and then electrical. If that's not it then year down the carb again.

It was 13 years ago so I’m not sure but I probably rebuilt my carburetor.

 

[igotta40]

Thanks for asking. I was going to start a new thread, but only after I did a few things first. I didn't want to hijack a thread too. I just get frustrated when these threads dead end!!!!

I wouldn’t worry too much about hijacking a thread from 2011. More like a resurrection

 

[Ry24000]

I wouldn’t worry too much about hijacking a thread from 2011. More like a resurrection

OK Then

First I brought my Pig back from the dead. When I bought it, it barley ran with the choke pulled. back fired sometimes.
One of the previous owners replaced the original '76 2F with an '86, but kept all the '76 auxiliaries,brackets, and covers.
The engine is equipped with what I believe is a Downey header with an EGR outlet on cylinder 6 pipe.
The smog equipment was on when I got it and is now removed.
First thing I did was empty the gas tank and check for corrosion and debris in the system. Didn't see anything unusual. ran it with a clear filter to see if it would catch anything.
Next was the carb. Pulled it and tore down and started a rebuild.
While rebuilding the carb I replaced the points with Petronix electric ignition and a vac. advance from @4Cruisers. I noticed the intake had been welded to fix a crack!(need to revisit this).
Basically a total tune up at this point with plugs, wires, pcv valve, vacuum hoses, oil, and filters.
The Carb rebuild...to answer @charliemeyer007 ...No I am not very experienced here! I actually pulled it twice to make sure I got it right. I did a great job of keeping track of parts and got them in the correct spot but I didn't get the jet on the new power valve and the accelerator pump was sticky, the first time.(I still suspect this). When I tore it down the choke butterfly was buggered up like someone had pried it open or something. Also the secondary was sticking. When I opened the air horn I could not belive how much debris was in some of those passages! I could not believe this could run at all. Cleaned her up and put it all back together. I adjusted the linkages according to the FSM and actually made a tool to set angles. YES Made sure the fuel cut solenoid works! Got it running and tunned albiet with that hessitation! A friend who helpped me with the Petronix, dizzy, lean drop noticed the sticky Power valve and put a nut on top of the spring to help it out. He also asked me how I felt about the carb rebuild and specifically the power valve jet. Power valve jet? what Power valve jet? yup! I forgot that.
Second tear down and a better kit with a leather seal on the Accelrator pump. still a hessitation upon acceleration. Didn't know to oil that leather when installing!(there is no replacement for experience!)
Basically that is where I am at now. It has excellent vacuum, starts right up, and idles well. If i accelerate slow or normal it runs fine. If i floor it is when I get the hesitation. I have been driving it and now it is time to figure this out!
I plan on removing the intake/header to remove that EGR pipe and weld up the hole from the header. This will be after I do some other tests.
I have checked for vacuum leaks everywhere with spraying carb cleaner. I have excellent vaccum. The vac lines are routed properly for the desmog.
I have excellent fuel level in the bowl. The stream in the primary looks good. The fuel level in there dropps just a bit when I hand accelerate the linkage. I have pushed the pump with my thumb while giving it gas and this the hessitation helps a bit.

Ignition...I need to check this! I hear from this forum that I need to recurve the dizzy. I desmogged a '79 FJ40 I had years ago and never had this issue! My current dizzy seems to be working and rotor moves freely and snaps back. My friend went through it when he put in the Petronix. As mentioned I have a vac advance with a hose running to the base of the carb near the fuel adustment. I do have a new 19100-61180 dizzy I picked up for a song that I want to try. Don't want to go back to points and am waiting on the Petronix stuff to arrive.
I recently have been checking a voltage drop from the battery through the ignition sw and back to the coil(yes a proper low ohm coil for the Petronix). 1 volt! been going through and cleaned up stome stuff and recovered .4 volts. Voltage needs a replace and I am waiting for that to arrive. Massive fluxuation from Idle to acceleration!
Hopefully this weekend I can try that Non usa dizzy and regulator and see what happens? I need to pull the plugs and check them too and maybe do a compression test.
This is a long winded one! Thanks guys!

​

 

[Grayscale]

Can't say. Are the plugs black or brown?

With a warm motor, have you done a valve-lash check?

 

[Ry24000]

gonna check the plugs this weekend and yes a full valve adjustment on a warm engine.
That's a funny thing too. I have recently done the infamous timing cover seal leak reseal and read a ton on that! So I did a pre and post warm up adjustment. With that being said I adjusted the valves twice when doing my post purchase baseline tune up. Like it burned off some stuff off the valves and came out slightly out of adjustment? or I just didn't get it right? wierd!

 

[Ry24000]

Reference pics

 

[Grayscale]

Have you checked manifold vacuum at (warm) idle?

 

[Ry24000]

Have you checked manifold vacuum at (warm) idle?

Yes. 20 in. Hg.vac.

 

[Ry24000]

#2 & #5?
Should I gap these for USA 1.0mm or world .8mm since it is desmogged?

 

[Grayscale]

It seems to not be lean (plug reading) or a vac leak (plugs and manifold-vac.).

I thinking that oil is making it into the combustion chamber on cylinders 2 and 5. Either thru the valve stem seals, or the piston rings. I don't know that this is the problem, but, maybe you're engine will perform better with clean plugs. I clean my plugs about three or four times a year - this certainly helps the idle remain smooth as silk, and I know when I'm due for a cleaning by the rough idle. However, I only have hesitation on a cold motor, and there was more of it when I first fired up the engine, post scrap-yarding.

 

[Grayscale]

Set the plug gap according to the Pertronix coil.