Carb re-build / 87' 48 johnny spl

[navrivr]

After 20 yrs of no problems with original carbs on this motor ,
I had rough idling and problem holding prime at the end of last season.
Motor strong when under load and compression high and in spec.
upper carb intermitting spitting fuel / compression upper cyl 145
lower carb not spitting and compression lwr cyl 130.
Today I removed carbs as per manual and remove float bowls
the upper carb bowl was clean as well as the lwr bowl, the upper float was
dry and has a dirty tinge on it , as the lower float has a clean black appearance.
What does this indicate ???
The rest of the carb is clean and mechanically sound.
I dont know about the jets and orrifices.
I will be buying the rebuild kits and replace all parts and gaskets
Any suggestions , heads-ups , and help here will be greatly appreciated.
This forum is a great way of learning and sharing experience with these older motors, the post on maintenance and repair are very interesting and helpful.

Thanks,
Navrivr

 

[HighTrim]

Re: Carb re-build / 87' 48 johnny spl

A thorough cleaning and rebuild is probably in order. Pay attention to those jets and orifices as mentioned. This video may help. Good luck.

"http://www.meegsonline.com/tmd/TMDsVideoChronicle2.wmv"

 

[tashasdaddy]

Re: Carb re-build / 87' 48 johnny spl

if you find out why, i want to know, i have an 88 48spl, that is spitting out the carb also, i've had the reeds out, replaced gasket, still doing it.

 

[rolmops]

Re: Carb re-build / 87' 48 johnny spl

I had a similar problem on my 1986 50 horse (exact same carbs) It turned out that one of the floats had sprung a leak on a seam, filled up with fuel and stayed down,thereby causing the carb reservoir to overflow and start spitting through the air intake.
It took me a while to figure it out because it is not where I would normally look for a problem.

 

[Silvertip]

Re: Carb re-build / 87' 48 johnny spl

You said the engine will not hold prime. There are two reasons for that. First, when you initially squeeze the primer and it firms up, it should stay that way until you start the engine. Once the engine starts, fuel is being drawn through the bulb, not forced through it so it will not stay firm. Next, if the bulb initially firms up and then without starting the engine, it goes soft, you have a sticky, non-functional, incorrectly installed, or incorrect inlet needle and seat, or as was mentioned the float is no longer bouyant and therefore cannot shut off the flow of fuel when the float bowl is full. After 20 years, replace the floats whether they need it or not.

 

[navrivr]

Re: Carb re-build / 87' 48 johnny spl

I will replace the floats they are quite old looking.

they are black and dirty.

thanks for the input.

 

[navrivr]

Re: Carb re-build / 87' 48 johnny spl

I will let you know the reeds on this motor : visual exam through intake manifold are unbeliveably clean and they all seem sealed at rest and operate (open) when I manually turn the flywheel.
I dont think I should touch them, I'll do carb. re-build then update.
Thanks so much for your input!

 

[jwilkey84]

Re: Carb re-build / 87' 48 johnny spl

if you need any parts, I have a similar 50hp motor lying around. What was the difference again between the 48spl and the 50?

 

[tashasdaddy]

Re: Carb re-build / 87' 48 johnny spl

the basic difference, is the 48 is premixed fuel, the 50 is VRO.