Carb Rebuild Advice

[ebne0018]

I'm going to tackle rebuilding the carb on my aq125A. I ordered a rebuild kit and yesterday I tore down the carb to inspect it. From the looks of it, it has either never been rebuilt or it was rebuilt when you could still get volvo parts (or NOS parts were used).

Anyway, I am rebuilding it because the engine idles fine in and out of the water. Will smoothly rev up in neutral, but when I am in gear and under load if I slowly try to increase speed the engine will start to bog down and die once I hit 1500-2000 rpms. I can almost always stop the engine from dying if I pull back on the throttle. If I am very careful I can get the boat to slowly increase speed, but usually it is easier to just punch it and go straight past the 2000RPM mark. Once I get underway and past 2000 RPM the engine performs great. WOT is around 4500-4800 RPMs and it is very strong. Once at plane I can back off to around 2500-3500RPM.


So, anything I should pay particular attention to when cleaning the carb parts?

Any recommended cleaner?

Should I soak any of the parts first? Especailly the small tubes where it is going to be very hard getting cleaner into them?

It looks like the starting place of the idle screw is 1.5-2 turns out. Any other default adjustments I should make?

Finally, there is a black rubber hose running from the engine to the flame sheild. It doesn't really clip in securely. Should I be concerned?

Thanks

 

[kenny nunez]

There are some small holes in the butterfly area of the throttle body, be sure they are not plugged. That carburetor is pretty simple just be sure to remove everything that screws in to it and thoroughly clean the small orifices.
The black hose just directs crankcase vapors to the flame arrestor, just be sure it stays close to the arrestor.
1.5 is usually the “sweet spot” on the idle mixture. Be sure the engine is idling as slow as you can keep it from stopping to set the timing, if it is too fast the centrifugal advance will give you a wrong base setting.

 

[ebne0018]

The manual says to back out the "venting screw" one turn. Where is the venting screw? Is that the screw that can hold the butterfly open?

If not, what should the screw that holds the butterfly be open be set to?

 

[Scott Danforth]

chase every passage with a piece of fishing line to make sure its not plugged. I soak in berrymans and i spray with what ever cheap spray I get. I also use compressed air.

your post leads me to believe you may also have an accelerator pump issue

 

[ebne0018]

The accelerator pump is the little hook looking pipe that pumps has in when you move the throttle, right?

Before I took the carb off the pump would push plenty of gas when I would active it manually. Is there an adjustment that I should look at it just clean it really well?

 

[kenny nunez]

On the idle stop screw I used to back the screw away from throttle lever then slowly turn the screw in until it contacts the lever then 1 turn. You may have to play with it after the engine warms up. Just be sure the accelerator pump squirts when you reinstall the carburetor.

 

[ebne0018]

I finished the carb rebuild last night and re-installed it on the boat. After only a few minutes of adjusting the motor was idling around 900RPMS.

I think I may have an issue with the accelerator pump still. With the throttle cable disconnected I could re-produce the issue I have on the water where if I punch it the engine rev's high and strong. If I go really slow the motor wants to die.

When I was manually opening the butterfly it looked like the accelerator pump was lagging behind when I would slowly open the throttle. Any way to adjust the pump? It doesn't seem to have anything that can be changed.

One thing to note, the new pump diaphragm does appear to be pumping more gas than the old one.

Thanks

 

[ebne0018]

Adding a photo of the Accelerator Pump spring. Looking online people mention washers being needed. Does is look like parts are missing?

 

[kenny nunez]

When you open the throttle does fuel start to flow from the jet in the center top of the carburetor. ?

 

[ebne0018]

When I open the throttle fuel flows from the "candy cane" that is connected to the accelerator pump, however it looks like it lags behind the opening of the butterfly.

 

[kenny nunez]

Try to tighten the the nut on the rod with the spring to compress it, just a little at a time. As I asked before does fuel discharge out of the center jet as you open the throttle? That is the main jet .

 

[ebne0018]

Hi Kenny-

The nut doesn't want to spin in either direction. I don't want to use too much force and damage it. It looks like it is screwed down as far as it will go. Should I try to get it off and maybe add a washer or two to increase the compression of the spring?

As for the fuel, do you mean from number 1 in the attached photo? If so, I can't say for sure. I was only watching number 2 when I was last working on the boat. It must work though as the engine has no problems running at 4500RPM, right?

I did notice the throttle cable assembly was different than the repair manual. If you look at the repair manual the spring is below the throttle lever, where mine is above. I don't know if this could be causing any issues.

thanks for the help.

 

[kenny nunez]

As the throttle opens you should see fuel to start coming of the #1 center jet. One other thing I just remembered, is the small metal plate that goes under the carburetor with a slight bend still on the manifold ? If there is none that could be the problem, it is designed to increase the air velocity to draw the fuel from the Venturi.
The spring on the throttle lever should be opposite of what it is. The purpose was that the spring should compress when the throttle is at idle in neutral. As the drive is shifted into forward or reverse it allows the drive to be fully engaged before the throttle starts to open. In other words you do not want throttle movement until fully in gear.
I have never had to move the nut on the accelerator rod, so maybe you can try adding a split washer to tighten the spring .

 

[ebne0018]

Hi Kenny-

I'll try to look more closely at the main jet next time I have a chance.. There is a small metal plate between the carb and the manifold. It is the same external size as the gastket but the center hole is slightly blocked. does that sound like the plate you are describing?

I managed to get the nut on the accelerator rod to move so I removed it and cleaned the threads on the rod and nut. The nut on my accelerator rod was flush with the rod. Most of the photos I have seen online show the nut in about 1/8 inch so I moved the nut to that position.

Unfortunately it has done nothing but rain here in Minnesota this year so I didn't get a chance to give it a try over the 4th. Hopefully this weekend is nice.


Thanks

 

[kenny nunez]

That is good the plate is still in place. Gotta keep those 10,000 lakes full.

 

[ebne0018]

Hi Kenny-

I got the boat out last night and there is some good news and some bad news.

The good news is the carb rebuild definitely helped overall. The engine runs quieter and idles smoother. The engine is so quite now at idle I thought it died while idling at a dock. I can also back off the throttle more once the boat is at plane and run slower across the water.

The bad news is the hesitation hasn't gone away. I paid closer attention to the RPMs this time. The hesitation starts at 1400 and ends around 2000. So as long as the engine is below 1400 and above 2000 it runs great. So right now to get underway I basically have to put the boat in gear, get underway with the engine between 1200-1400 rpms and then punch the throttle slightly to get over the 2000 rpm mark and then I can get up to speed at any rate I want.

I didn't get a chance to look at the main jet. I had my kids with me and the boat is already tight on space. Moving the dog house wasn't going to be an option.

Should I keep moving the accelerator pump screw inward to tighten the spring? Could it be a fuel pump issue? I don't really know what else to do. There are not many screws I can adjust on the Solex carb.


Thanks
Dylan