I Just May Have it This Time?

[rideevol]

Four idle circuits all need to be just right. The secondaries need to be set first. The two idle ports within the secondaries need to be uncovered by adjusting their bottom of the carb adjustment screw, just 1/4 to 1/2 turn, which barely opens the secondary throttle plates. As stated earlier, the floats, especially the secondary floats also need to be set just right as they of course determine the fuel depth which has a direct effect on the secondary delivered (richness) idle fuel supply. Dripping secondary venturies within the secondary bores during idle indicate too high a float setting, which affects both idle and higher throttle performance. After sorting out the secondaries these carbs usually run much better.

[csuggs]

Michael- glad you finally got your Comp bud!

I had some similar issues with mine last year (2012 season) after having the carb rebuilt by an old school gear head like yourself. He wanted me to install an angled spacer, but I refused to believe that the 15* angle of the motor was an issue since it (and so many others like it) ran great for the last 25 years. What is different is today's gas. The ethanol causes the fuel to vaporize at a lower temp. Here's what I did to resolve the problem:
First I removed the cast iron carb spacer and replaced it with a phenolic spacer of the same thickness (flat). I had to drill and tap the spacer for the pcv hose fitting, and cut a channel through the spacer to the primary side of the carb. The purpose of this was to try and isolated some of the heat from the carburetor.
Second I installed an insulation wrap over the fuel line between the fuel pump and carb.
Ever since this modification, I've had no trouble starting the motor when hot. No fuss, no muss.








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[michael hunter]

Thanks guys the boat actuality runs very good it keeps getting better . I think I'm being a little anal looking for perfection. Ill look into your suggestions.

[mapleleaf]

The bar has been set pretty high Mr. Hunter...

[Supra_Comp]

Michael- glad you finally got your Comp bud!

I had some similar issues with mine last year (2012 season) after having the carb rebuilt by an old school gear head like yourself. He wanted me to install an angled spacer, but I refused to believe that the 15* angle of the motor was an issue since it (and so many others like it) ran great for the last 25 years. What is different is today's gas. The ethanol causes the fuel to vaporize at a lower temp. Here's what I did to resolve the problem:
First I removed the cast iron carb spacer and replaced it with a phenolic spacer of the same thickness (flat). I had to drill and tap the spacer for the pcv hose fitting, and cut a channel through the spacer to the primary side of the carb. The purpose of this was to try and isolated some of the heat from the carburetor.
Second I installed an insulation wrap over the fuel line between the fuel pump and carb.
Ever since this modification, I've had no trouble starting the motor when hot. No fuss, no muss.






Sent from my iPad

I like what you did with the insulation liner. I haven't had my fresh motor on the lake yet but my old motor (very tired) would get the same problem after running for some time and would get vapour lock causing the hard starts, even to the point when it would bog down after doing lots of stops/starts with skiing. I think I will try the insulation as a second line of defence. Where did you get the phenolic spacer from ?

I like your point about today's fuel vs old fuel. From what I have heard from friends in the industry, the pumps up here say 15% ethonal contect but could actually contain upwards of 20-25%.