3.6 hp question

[edmo]

I'm tinkering with an old (about 1980) 3.6 merc that my son bought. It's a direct drive with tank under the cowling. Gas delivery, I believe is gravity(no fuel pump or diaphram in Mikuni carb). Motor will run all day at 1/2 to 3/4 throttle, but runs out of fuel after a few seconds when at full throttle. Am going to clean card and replace needle and seat, but am wondering how much compression is a factor in fuel delivery, if any, in these small engines. It has about 85-90 # cold. Thanks for any information

 

[mr 88]

Re: 3.6 hp question

It sounds like the float is not set correctly or a jet has a small obstruction.Compression/worn rings can be a issue when starting a two stroke as it does not draw the gas in like it is designed too.It will not affect the gas delivery when warmed up and you keep it pinned.

 

[jerryjerry05]

Re: 3.6 hp question

Test the comp after you spray some WD-40 or another spray.
If it goes up signifinatly then the rings need work.
Pull start motors are harder to test.
Like 88 said clean the carb.
Any junk in the tank??
Maybe a small particle filter between the tank and carb.

 

[edmo]

Re: 3.6 hp question

Thanks for the info. I've soaked the carb overnight washed and blown out all the jets, replaced fuel lines and filter and am having the same full throttle issues. Going to the float next . Anybody happen to know the float specs before I start trial and error method? The carb is a mikuni with a slide choke, looks like a motor cycle carb and 3.6 merc is about an 1980 model, serial 5574652. I don't have a manual

 

[jask]

Re: 3.6 hp question SETUP CARBURETOR MERCURY 3.6 2 stroke.

Re: 3.6 hp question SETUP CARBURETOR MERCURY 3.6 2 stroke.

Thanks for the info. I've soaked the carb overnight washed and blown out all the jets, replaced fuel lines and filter and am having the same full throttle issues. Going to the float next . Anybody happen to know the float specs before I start trial and error method? The carb is a mikuni with a slide choke, looks like a motor cycle carb and 3.6 merc is about an 1980 model, serial 5574652. I don't have a manual

Hi, I had the same problem of you, and now i finally solved. So, you have to : Clean the carburator properly in all parts, and setup the carburator with the two spring... (If you look the carburator..there are 2 springs... one is responsable to give petrol..and one spring is responsable to open gain of air...).. I remind you that carburator has the duty to mix part of air and part of fuel. When there is too much air or to much fuel in the mix.. the engine doesn't work properly.

The spring of air is close the main gain of carburator which take air.... if you look carburator is placed on left side (booth are in left side). The spring of fuel which help you even in low speed is placed in left side but after the previuos.. (closer to the block of engine). You have to setup them. How? close definetly the spring .. rotate like clock-time direction. and after open... approximally turn 2 times. (for both springs do the same.. ) .. maybe for the spring which is close to the main gain of air.. turn..for 1 or 1,5 times..max 2,5.. those springs are very important and the work of carburator is very sensible when you turn them. maybe you have to try more times... before you find the perfect combination.

Another part wich i dont suggest to tuch if you dont know how, ,, is to setup the PIN of carburator (called JET NEEDLE). When you open or close the fuel.. this pin is moved up and down...it is also responsable to give more or less petrol in the mix. First try with spring... after try to setup it. My experience is that i setup it and i placed the ring in 2th position. My configuration is: Ring of JET NEEDLE in 2nd place (i consider the 1st place where the body of PIN is smaller,... ).. SPRING of fuel which is closer to main part of engine..open 1/1,5 turns Spring Of air open 1 turn + 1/8.
Bye.