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6Hp carburetor for Tohatsu MFS5C engine.

J

Jarda

Member
Hello, I want to replace the GR3 carburetor on the Tohatsu MFS5C 2014 engine. To increase the power to 6 Hp. The 5Hp and 6Hp engines are the same including the camshaft? If so, would a new one suffice: main nozzle 3JE032520, main jet (70) 3GR044700 and adjustment of mixture richness at starting and low speed? Alternatively, a new carburetor 3JE 03200, is this type suitable?
 
The throat sizes are different, so you need a new carb.
3R4032001MCARBURETOR ASSY, MFS/NSF6A2

The earlier carb is made for the earlier EPA spec, so it idles better.
 
pvanv said:
The throat sizes are different, so you need a new carb.
3R4032001MCARBURETOR ASSY, MFS/NSF6A2

The earlier carb is made for the earlier EPA spec, so it idles better.
Click to expand...

Okay, I'll buy the recommended carburetor. Another question, what will be a suitable propeller, the current one is marked 78x8?
Thanks for the anwers. Jarda.
 
All carbs will interchange; The 6A2 version will have better lower end performance.
Props must be selected by trial and error. What is the WOT RPM? If near 6000, you have the best prop. Sounds like you have an 8 pitch now. There is also a HT prop available.
Of course, you will need to swap carbs before testing.
 
Hello, I tested the recommended carburetor with this result: (I adjusted the richness of the mixture), the engine in reducing the full gas in half has an irregular operation, tarocess, and loses performance. The ignition candle has a light brick color. This defect is only reflected in half of the gas and only when it is collected from the Max. Where can be a fault?
 
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The question is : the flap in the carburettor is fully open, the engine is running normally, I close the flap in half and with this flap position there is irregular operation of the engine and fluctuating power, I close the flap further and the engine speed is again regular.
 
This situation only occurs when the throttle is open to one half, the engine is running erratically and losing power. This situation does not occur in other throttle opening positions.
 
The pilot screw is in the position that the engine speed decreases when loosening or tightening. The pilot screw is 3 1/4 loosened from full tightening, it seems a lot to me, isn't the mixture poor in this position? When I tighten the bolt by 1/2 turn, I enrich the mixture, will it affect the engine operation with the throttle open to 1/2?
 
No. CW on the screw leans the mix. You should have left it where it was; it's set by instrument at the factory. Pilot has the most effect near idle, but does affect the mix somewhat at all throttle settings. Does the plug seem wet after that midrange issue of poor running?
 
The plug looks fine. Can you return the pilot screw to the Factory setting? Did you drill out the plug that covers that screw? What dealer sold you the carb? It could have a defect.
 
Ok, first of all I appreciate and thank you for your patience, which you also give me about your free time on Saturday and Sunday. I bought the carburetor with the same type number from a non-branded supplier, which was a mistake. The mixture richness screw did not have a stopper and was almost unscrewed, the mixture richness could not be adjusted, a small hole on the side in the diffuser was blocked, after cleaning I could adjust the mixture richness. Where do you think there could be another mistake? Of course, after this experience, I do not recommend such purchases and I should have bought this carburetor from a branded dealer!
 
Hmm. You may have gotten a buggered used carb. I always do OEM, so I can't be sure. If so, it may be varnished in the low speed circuit. You could try a complete carb disassembly, then soak all non rubber bits in real carb dip overnight, then liberally blow out all passages with generic carb spray. Then carefully reassemble, noting float height. If it was dirty, that might fix it. If not, maybe get a real 6A2 carb from a legitimate dealer.
 
Ok, the carburetor was new, I'll leave it soaked and then try to clean it by ultrasound, the size of the main jet is 75 and the pilot jet 38 or 45 ?, the diameter of the air intake inlet 27, venturi / trottle diameter 15/19 (throttle diameter 19), oil level, (from flange surface to float bottom) 9-10mm?
 
It is stated in the service manual for the 5A2S 13 / 19mm engine, for the 6A2S 15 / 21mm engine. The size of my carburetor is 15 / 19mm. So I don't know what is right, if it could be measured on orig.carb. and tell me, I'll be glad. Is this the last option where there may be a mistake?
 
Hello, sorry for the late reply, the dimensions of ventury tube 15/21 for 6hp are given in the service manual of the tohatsu engine 4,5,6hp.
 
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Okay, there's nothing stamped on the carburetor, it was purchased on alliexpr. with the type 3R4032000-0 and size of the venturi tube 15/19, therefore I would like to communicate the dimensions of the venturi tube on the original carburetor of this type for the 6Hp engine, if it should be 15/19 or 15/21?
 
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