"FrankenCarb" J10RCDB 1986 9.9hpJohnson

[cprodave]

This is a continuation of a Topic I started on 8/4/2019 with most recent posting on 8/19/2019 (moderators please tell me if I should have continued or linked to original thread ). Sorry to leave Joe Reeves and any other folks in suspense about what dimensions this Carburetor has. After an 8 month hiatus I got back to this project...

I got the motor running in water tank, although it doesn't start easily (usually needs starter fluid) and it still doesn't seem to achieve full RPM's . Plus the pee stream is weak. I am currently awaiting Water Pump Kit (to arrive this week). Meanwhile I replaced the Starter Rope and removed the Carburetor. Metal bowl of carburetor had some debris in it but not very bad compared to many others I have seen. There were several drops of water (I run only non-ethanol fuel), possibly enough to make engine run rough. To recap "vital signs" compression is OK but not great 80psi each cylinder, spark jumps 5/16 inch, fuel pump and crankcase vacuum are good. However Carburetor Throat dimension seems weird. Using thin but stiff cardboard templates, throat is definitely greater than the 0.625 inches that LeeRoy's Ramblings indicate for 9.9hp but definitely less than 0.875 for 15hp--seems to be around 0.700. In the throat there is visible a machined "flat" that is not the "as cast" metal . This flat measures 0.700 inches. A couple questions: 1) is this 0.700 "flat" normal (i.e. LeeRoy's 0.625 is wrong/different?) , or does this indicate a Previous Owner modified from an "as cast" 0.625 inches? 2) to do a thorough Carb Cleaning, do I need to remove Welch Plug(s)? If so, should I remove/clean the larger Welch Plug on top of Carb, or the smaller Plug Partway down the side of Carb (on Starboard side, near Choke Lever). If I remove the Plug(s) is it OK to reinstall with JB Weld to avoid buying a Carb Rebuild Kit? 3)I am unable to remove the brass insert that the Float Needle ride in--but air blows freely through this--so OK to not remove/clean?

BTW I haven't yet done the Kill Switch Bypass test for 2 reasons : 1) there doesn't recently seem to be a problem with intermittent fire and 2) I am unsure how to do the test!

Thanks for any input.

 

[cprodave]

I forgot 1 other question: how do i determine if correct 9.9 hp 0.040 inch Main Jet is present vs. 15hp Jet 0.054? With my micrometer set at .040 i can see the tip of existing Jet is much less than .040 diameter.

 

[racerone]

What do you mean by ---" tip of existing jet " ?--Picture of it ?------Jets are a calibrated hole in a brass piece.----On most motors the high speed jet has a number stamped on it.-----Magnifying glass may be required.

 

[Bluestream]

I forgot 1 other question: how do i determine if correct 9.9 hp 0.040 inch Main Jet is present vs. 15hp Jet 0.054? With my micrometer set at .040 i can see the tip of existing Jet is much less than .040 diameter.

Jets usually have their size stamped somewhere

 

[cprodave]

Racerone and Bluestream, thanks for your inputs. To clarify my question about "tip of existing Jet" I should have said "tip of Slow Speed Needle Valve". Overall I am looking for any evidence of modification from factory standard.

It looks like for Slow Speed Needle Valve p/n 330884 was initially specified for both 9.9 and 15hp although on 15hp only (I.e. not the 9.9) the p/n was changed to 432781. Is there any way to tell if (incorrect?) p/n 432781 is installed instead of 330884? That is what I meant above.

I understand that in order to examine for non-standard MainJet/Oriface Plug Number 45 ( number 23 in diagram, p/n 323151 or per LeeRoy 321742) first I would need to remove Nozzle Well Expansion Plug (#25 in diagram, p/n 316991). I'm not anxious to remove this Plug if I can't replace the Plug with overseal of JB Weld (I placed a big parts order just yesterday, didn't include a Carb Kit for this and I'm not anxious to place another order soon).

So...does JB Weld hold up OK when used to hold the Nozzle Well Expansion Plug in place (despite being constantly submerged in fuel)?

Also (still foremost question in my mind) what are your thoughts on the Throat Diameter 0.700 inch ( vs. 0.625 or 0.875) that I am finding?

I will try to post a photo using my cellphone camera set on lower resolution (Hi res exceeded forum size limits).

Thanks

 

[cprodave]

Sorry I still can't upload photo from either cellphone or standalone camera. I am trying to show that the inside diameter of throat is machined smooth (vs. as-cast,).