'85 & '87 Force 125hp Model Carb Differences and Jett Sizes

[Bubba Blaster]

Greetings! About to order gaskets for my carb rebuild job on my '87 Force 125. I have an '85 that burned up on me and plan on using the top carb from it to replace the '87's top carb - just because the '87 would need more parts to rebuild (long story) than the one off the '85. Three questions for you all:

1. I notice only one difference between the two carbs - the needle and seat are different and not interchangeable due to the seat depth. This makes me wonder if there are any other differences that I can't see that would prevent me from using an '85 carb on this '87. Thoughts?

2. I can't find any definitive answer on the correct jett size for top and bottom carbs. On my '85 they are both .094. On my '87 top is .1015 and bottom is .094. I believe the '87 config is correct and the '85 config is wrong? Can anyone confirm? What should I use if I can use the '85 top carb on the '87 - stick to the .1015 on top and leave .094 on bottom? I'm in Oklahoma City area which is at 1200 ft. sea level, so I think that would be correct.

3. On all 4 carbs between these to motors this welch plug is missing (See pic), so I assume this is correct - all others are plugged with solid plugs except one by the fuel inlet and that one has a small machined hole in it - they are all that way. Just wanting to confirm this is correct.

Thanks All!

 

[jerryjerry05]

Missing plug is the overflow.
Going fishing this AM will answer the rest when I get back.

 

[Bubba Blaster]

Thanks JerryJerry, so that's supposed to be like that then. Thanks for confirming. I look forward to the rest of your reply!

 

[jerryjerry05]

First off sorry I haven't finished.
The next day was a horrible day for fishing.

The carbs are usually made as a set.
I'd use all the ones from the same motor.

The 85 carbs came a couple of different ways????
The body on the 85 carb is too small for the 125
One came with the main jet in the screw that holds the bowl on. 68 70 72 74
​​​​​​​Different size for altitudes
The other came with the jet in the center post in the bowl.Same size as the other.

The 94 size jet I think is used on 125hp. Not positive, but that's what I find in the parts diagrams.

 

[Bubba Blaster]

Man I hate a bad fishing day, sorry to hear!

Thanks! I guess I should have worded my question better - I was wondering if I could take the top carb off my 1985 Force 125 and plop it on my 1987 Force 125 vs rebuilding the top carb on my 87 and be just fine? My 1985 top carb is jetted at .94 but my 1987 top carb is jetted at .105. Other than this and the float needles being different they look identical.

I plan on plopping my 1985 carb on my 1987 motor and putting the .105 jet from the original '87 carb into the '85 carb and calling it good. The severely OCD side of me says to rebuild the '87 carb and put it back on the motor, but the other side is saying it's fine and it's cheaper to swap out. I would still strip and clean it, just not the Welch plugs and main circuit tube, etc.

 

[jerryjerry05]

99% of the time the carb spray will do what you need.
Now if the carb is REALLY crusty then a complete tear down is needed.

Swap the jets on the 125 carb so it matched the original.

Just change the jets from one to the other.

 

[Bubba Blaster]

Perfect that's what I'm planning to do. I've already got the 1985 carb sprayed out and the .105 jet from the 1987 carb pulled and put on this one and am now waiting for a new idle air screw and float needle to come in and I'll slap it all back onto this 1987 motor and see how things go.

I appreciate the clarification as I'm just a little nervous knowing that this 1985 carb came from my burned up 125 Force that I suspect was due to running at max RPM (5500) for 5 min with no load and a really low pitch (13) prop that I only use for pulling tubes. But one always wonders, was it a dirty or mis-adjusted carb that did it. Then I go putting one of those carbs on this '87....it should be fine...lol.

Thanks again.

 

[jerryjerry05]

Some things to check:
where were the air screws set at on the burned up motor??
Check the recirc system for clogged screens? clean/replace
The foam in the cover? loose? remove it.

 

[Bubba Blaster]

Air screws were at 3/4. Not sure about the screens - where are those? Cover had insulation stripped out already so good there. I think it was all due to being a little lean, maxing RPM with zero load, and being jetted with a .94 main when I'm at 1200ft sea level.

Quick question, I had a shop do the tune-up on that '85, but doing myself on this '87 w/ the '85 top carb I'm putting on it. Do you tune each carb separate or in sync? Also do you tune to run just a tad rich to where it runs slightly rough? I'm used to tuning small 2-cycle engines and you want them tuned a little rich to where they run a little rough so that they get the lube they need.

Thanks.

 

[jerryjerry05]

If you follow the 50-1 recommendation you shouldn't need extra lube.
The factory suggested 1 turn out and leave it there.
The screens: under the dogbone shaped cover next to the fuel pump,
the screens are behind the cover and reeds.

 

[Bubba Blaster]

Thanks sir. So I'll tune for the best running and highest RPM idle when adjusting the screws (maybe erring on the rich side every so slightly...).

Three clarifying questions:

1. The screens - are they something to check as regular maintenance? I have'n't checked them on this '87 motor, assuming they are fine but should I?

2. Are you saying there are screens under the reeds? I'm assuming you are still just referring to the screens under the dog bone shaped cover next to the fuel pump.

3. About tuning the carbs - do you tune one carb at a time, or together in sync as one?

Thanks.

 

[jerryjerry05]

#2 the screens are under the dog bone.
#3 you can set them running but the motor needs to be running, in gear
and in the water.
There's an equalizer tube running between the carbs, you'll need a way.
to pinch off this tube
Pinch it off.
Start at 1 1/2 turn out.
Then top carb, turn the screw in 1/8th a turn, wait 10 seconds
for the fuel to burn at the old setting.
Repeat until the motor bogs, stutters, misses.
Then turn thee screw out 1/2 turn.
Repeat on the other carb.

In some cases(mostly the 85hp) the screws won't set right unless they're 2-3 turns out.

 

[Bubba Blaster]

OK cool, I never thought to tune them under load. I don't have an equalizer tube between carbs. Is that a concern? Same on my 1985 motor.

So to clarify, those screens, is that a maintenance item to check before I get her going or only if I find out she doesn't run right? First I've heard about checking those screens.

Also, my new float needle is too long! I'd have to bend the float tang a lot to compensate so I guess I'll just keep the old one. It doesn't look particularly warn, I just like replacing them when I'm in there.

 

[jerryjerry05]

I'm pretty sure you do have the tube.
EVERY 120/125 I've ever seen has the tube.
About 8" long 1/2 in tube on the intake manifold.

Most don't know about the screens until the motor takes a dump and they
tear it down and find the screens clogged. That can kill the motor.
Low hrs. not to worry.
It's some thing they did away with in the later years.

 

[Redbarron%%]

Again I have an opinion with little or no real experience with these engines, but with the 1995 90 Sport Jet.
The later engines have the balance tube built into the intake manifold and in this case they suggest tuning from the nominal 1 1/2 turns out and making small adjustments to each carb with clearing burps and waiting for the engine to settle.
I assume that that this is due to the lack of the external tube between the carbs.
I have had a problem myself in understanding the adjustment I am looking for here. Any guidance would be appreciated.

 

[Bubba Blaster]

Jerry I think you're right, I didn't notice since it sits up against the intake manifold.

Now I'm concerned about what to do with my 1985 carb vs repairing and putting more money into the 1987 one that actually goes with this motor. As mentioned previously, the two carbs look identical other than the needle and seat. The '85 has a shallow seat and it's brass, whereas the '87 has a deeper seat with a SS seat (both pressed). I did order the correct parts for the replacement needle and it's the same part for both years, but on this '85 I'm trying to use the needle is clearly shorter but matches up fine with the '87. I can bend the tang on the float by quite a bit to make it work, otherwise it won't fit. Now I'm wondering should I:

a) just reuse the old needle (looks fine)
b) try to hunt down the correct needle
c) switch back to the '87 and rebuild it (more money)

I found this needle that looks like it may work but can't tell what motor this is for: F10265

Thoughts?

 

[Bubba Blaster]

I called a shop that used to do Force motors and they knew what I was talking about with the short vs long needles between the '87 and '85 models but did not know what part that would be for the shorter one since they used to service them 20 years ago. I'm going to order the part number previously mentioned and see what that looks like. jerryjerry05, I would like your thoughts on my previous post. I don't think I'm going to rebuild the '87 carb, just run with the used needle on the '85 or try to find a shorter needle.