Interesting Post about Force carbs

[SkiDad]

Hi Guys, i stumbled across this a few months ago - it makes a lot of sense when you read it....

(scroll to bottom and look at very last post in the thread)
http://my.justanswer.com/question/guest/d2057ff6ae40478f90226dc3357ca070

The idea of only force using 2 carbs for 4 cylinders instead of 4 like other makers and jetting was eye opening to me at least. I think my force always has 2 much gas in it for the restarts.

 

[Jiggz]

I'm not sure I am in agreement with the last post. I have the 125 and is basically the same configuration as the 120 with two carbs on 4 cylinders. But if I have any starting problem it will be when the engine is cold. In fact, when it is warm or hot it starts almost instantaneously on the first crank everytime. I'm not sure about fuel consumption for I have not seen a side by side comparison with other 120~125 HP 2 stroke engines of different carb configuration or different brand.The only thing I came across is the rule of thumb for fuel consumption which is like approximately 10 gals/hr at WOT speed.

The customer's problem seems to be around hard re-starting the motor when hot or warm. But does not have the same problem if throttle is placed in fast idle. From these two symptoms I can surmise the problem is with the idle speed setting. It is obvious the throttle's butterflies need to be opened up a little bit more to get the motor started and idle accordingly. The owner did mention that the motor starts fine when cold but failed to mention it does so either because it's choked and at the same time in fast idle position. The mechanic's suggestion of ensuring the butterflies are fully closed at idle is contrary to general knowledge. Unless, he is referring to mechanically zero'ing the carb and timing linkages.

As for the strong smell of fuel, there are two reasons for this: With 2 stroke engines using feather valves called reed valves, there will always be blowback of fuel from the carbs when running. One of the main function of the carb air covers is to collect this blowback. Second, if you tilt the motor high, yes there will be fuel overflow from the carbs. Hence strong smell of fuel.

 

[racerone]

Not sure I agree with that last post either !!

 

[jerryjerry05]

I agree to disagree.
​Sounds like BS to me.
I didn't read the whole thread: did they ever figure it out?

 

[GA_Boater]

From the last post - "Every other inline 4 cylinder outboard out there has 1 carb per cylinder."

I better look for the two missing carbs in my 4 cylinder inline 50 and I'm sure all the other Merc inline owners didn't know they are missing half their carbs,

Jerry - I think the OP got tired of throwing money at it.

 

[fmt2bx]

if it idles fine, if it works well at WOT then it's all good right? If one has to add a bit of throttle to start when warm then consider this the "start when warm" procedure.

Also curious to know if a broken reed would allow more gas to back flow in carb?

 

[tommarvin]

We had an air leak on our 125hp that we didn't know about until we changed every single fuel and fuel drain hose and vent on the motor to the tank with USCG A1-15 fuel line two and a half min burn time.
Our 125hp now starts idles, hot starts , like a Yamaha 4 stroke with fuel injectors really.
I'm curious also, does a broken or bent reed, let gas back into the carbs?

 

[Jiggz]

I agree to disagree.
​Sounds like BS to me.
I didn't read the whole thread: did they ever figure it out?

Mind you the OP has to pay for all these BS! Lol. NO, they did not figure it out instead the OP was given a full list of BS while taking his money!

 

[jerryjerry05]

Shoulda came here.
​Tom, Yes it can.
A broken reed manifests itself with: mist out the front of the carb, splatter out the front. fuel draining out the front, a miss, poor idle, poor high speed, poor acceleration and MORE!! And NO you can't use any of the above unless you experience it personally.

 

[SkiDad]

i guess I created a passionate thread Love my Force, it runs like a top except for the warm start quirk - that link i posted was meaningless to me except for the last guy.

I thought it made sense that you have to make the jets bigger to support 2 cylinders and wondered if that is why my boat usually starts 2nd try when warm but starts 1st try when cold. I thought maybe it's dumping the excess fuel from the ski run i just did. I've linked and synced, tried different forward gear RPMs, 700, 750, 800 - not much change. It's just a quirk i have to live with b/c I don't think there is anything else I can try. But like the poster my boat will always start 1st try in fast idle.

and yes, the guy should've came here !

EDIT - what about the Force 150's - i wonder how they handle 5 cylinders with 3 carbs - guessing 1 cylinder has it's own ?

 

[Jiggz]

To say the jets are larger on a dual served carb (one carb for two cylinders) than a single served carb is a myth. This is almost the same as saying the two cylinders suck air-fuel mix at the same time! NO, it doesn't! Each of the two cylinders served still suck air one at a time almost identical to a single serve carb where one cylinder sucks air-fuel mix one at a time. So why would a dual served carb needs to have a larger jets?

It's obvious the last post on the said link is a fine example of the following, "Ignorance maybe an obstacle to progress but even worse is the illusion of knowledge!"

 

[Jiggz]

For the force 150, yes one of the cylinders has a single served carb. And yes there are different stock numbers for each and that is because of the fuel connections. There are also different sizes of jets but based solely on operating elevation.

 

[Jiggz]

As for your hard start on a hot or warm engine, check the following:
1. Carb vent hole is not covered or blocked.
2. Float setting should not be too high
3. Inlet needle valve seats and seals properly

The reason for the above is after a WOT run and then suddenly stopping the engine, there is this so called boil over. What it means is that as soon as the engine is stopped after a WOT run, cooling water also stops. Hence, the remaining heat from the engine block is released through the engine itself and not carried off by the coolant anymore. This also heats up the carb and just about everything inside the cowling. Heating the carb causes fuel expansion in the fuel lines and bowls. If the carb vent hole is blocked the excess fuel will rise to the main jets semi-flooding the carb. And if the needle valve is not sealing properly, excess fuel from the fuel lines will also dump into the bowls.

This is all theoretical but you can experiment if it applies in your case. After running at WOT try cooling down the engine by running it at low speeds ~2000 RPM or idling it for about a minute or two before turning it off. Leave it off for about 3 mins and start again. Is it the same hard starting?

 

[flyingscott]

There was nothing wrong with the guys motor I read the whole thing. He didn't know how to start it when it was warm he never moved the throttle lever to give it gas. He just sat there and choked it expecting it to start he figured it out by the 5th post to move the lever and they kept him going with BS. They never told him thats how carbed 2 strks are. He had excess gas because he just kept choking it expecting it to start. That tech whoever he was, the explanation he gave on 1 carb per cylinder making it better running is a joke. I want to stick that guy on my 1986 evinrude 70 hp watch his head explode trying to get a smooth idle out of that thing. The fewer carbs on the force motors effect the HP more than anything they are down on hp compared to other manufacturers motors. I am not ripping force motors they are as good as anybodies as far as reliability goes just down on power.

 

[SkiDad]

As for your hard start on a hot or warm engine, check the following:
1. Carb vent hole is not covered or blocked.
2. Float setting should not be too high
3. Inlet needle valve seats and seals properly

The reason for the above is after a WOT run and then suddenly stopping the engine, there is this so called boil over. What it means is that as soon as the engine is stopped after a WOT run, cooling water also stops. Hence, the remaining heat from the engine block is released through the engine itself and not carried off by the coolant anymore. This also heats up the carb and just about everything inside the cowling. Heating the carb causes fuel expansion in the fuel lines and bowls. If the carb vent hole is blocked the excess fuel will rise to the main jets semi-flooding the carb. And if the needle valve is not sealing properly, excess fuel from the fuel lines will also dump into the bowls.

This is all theoretical but you can experiment if it applies in your case. After running at WOT try cooling down the engine by running it at low speeds ~2000 RPM or idling it for about a minute or two before turning it off. Leave it off for about 3 mins and start again. Is it the same hard starting?

I will definitely try that test out next time - i think you are on to something I'm learning some new stuff here.

where is the vent hole ?

what is the procedure to check floats - can i do it with carbs on engine ?

thanks Sir.

 

[Nordin]

The wenthole is located at the side of the carb. Can be starside or port depend on typ and brand of the carb.
But it is higher then the bowl surface to the carb body.

The level of the float should be parallel to the carb surface where the bowl seal to the body, when you invert the carb upside down.
You adjust it by bending the stoptab at the float. Be careful so you do not break it.

 

[SkiDad]

I had never heard of heat soak before - thanks for that info - i think you might be right as that makes sense - waiting for a good day to take the boat out and test it.

anyhow here is a pic of my carb - this appears to be the vent ? Safe to run a pipe cleaner in it or just spray with carb cleaner ?

 

[Jiggz]

No I do not believe that is the vent hole. That is way too high. It is actually on the other side just to the right of the fuel line connector. It does have a brass liner with a tiny hole in it.

 

[SkiDad]

OK - so it's this one ?

 

[Jiggz]

That is correct. That vent hole should be open to the atmosphere.