Wrong size orifices in carburetors...is this bad?

[bayprowler]

I have a 1987 Johnson 140hp V4. It has been recently stalling so I have begun cleaning the carburetors. I noticed that the idle, intermediate, and high speed orifices have size IDs stamped on them that are different than what my parts catalog says I should have on this model engine. The engine has run great for a long time despite the incorrect orifice sizes, but should I change them to the size listed in the catalog to try to improve performance and hopefully stop the stalling problem? The size differences are listed below:

Parts Catalog calls for:
Idle air bleed- #28, intermediate- #20 port, #16 stbd; high speed- #61D

In carburetors now:
Idle- #45, intermediate- #32, high speed- #59D

 

[Big flop]

Re: Wrong size orifices in carburetors...is this bad?

Make sure your looking at the right
model #, that's so far off unless
your at 7000ft then still is way off
Can you post model number ?
If it ran good I would put them
back where they were?

 

[Joe Reeves]

Re: Wrong size orifices in carburetors...is this bad?

If that engine has run satisfactory in the past, DO NOT change the orifices. There are three different size orifices for the various models and what you have in those carburetors now are one of the sets. Changing them will result in many problems.

 

[bayprowler]

Re: Wrong size orifices in carburetors...is this bad?

Info above correct
my model #: J140TXCUA
what do these big size differences do to engine?

 

[bayprowler]

Re: Wrong size orifices in carburetors...is this bad?

Thanks Joe. You may have saved me from catastrophe...so I shouldn't bother sourcing the "correct" size orifices that the parts catalog calls for and install them?

 

[Joe Reeves]

Re: Wrong size orifices in carburetors...is this bad?

Correct.... Leave them alone!

 

[daselbee]

Re: Wrong size orifices in carburetors...is this bad?

Someone has changed the carbs at some time in the past.

 

[edfishing2]

Re: Wrong size orifices in carburetors...is this bad?

Does someone know how much the jets could wear over time? It is very possible someone could have drilled them. Some of my 1984 100hp jets check at least .004 over with wire pin gages. Elevation 800 feet. I have heard you can use one set of jets for summer and another set for winter.

 

[Dhadley]

Re: Wrong size orifices in carburetors...is this bad?

Most likely the carbs and throttle bodies have been changed at some point. I'd leave the jets alone, they're probably the right ones for those carbs. If you really need to have a better idea of where the carbs came from take note of the jet sizes and number of screws in the side cover. Then start going thru the parts catalogs until you find a match. Keep in mind most jet sizes in the catalog will be "sea level" sizes that were from the factory.

As for measuring jets, that's hard to do. Jets are rated by their flow, not necessairly by the hole size alone. The are several things that affect the flow - hole size, ramp angles, rifeling and flow direction. Drilling a jet usually does more harm than good.

Yes, todays fuel will eat at brass jets over a long period of time. Any jet that's sitting in fuel can be affected. If you are concerned just pull the jet and look thru it. If the hole is still round it's probably OK. If fuel has eaten away at it it'll no longer have a round hole but rather odd shaped or oblong.