70 VRO idle orifice and VRO questions

[rwiens]

I have been having the (seemling common) problem of throttle bog going to WOT and was doing some trouble shooting on the weekend. I took out the idle orifice plugs and unfortunately lost one. In looking up the part online, it calls for a #28 plug, but I'm sure the ones that were in there had 30C stamped on them. Do these numbers relate to the diameter of the orifice and will it make a difference which one I put in? Also, is it possible to run the motor with one of the plugs missing?

An unrelated issue is that a section of clear (?) hose supplying oil to the VRO has totally disintegrated. I assume this was there so that you can see if there is oil flowing. It looks like it went from an elbow on the end of the supply line from the tank to the intake on the VRO pump. I'm thinking that now may be the time to ditch the VRO...can I simply plug up that intake (does it need to be airtight) and disconnect the harness?

 

[Biggieb400]

Re: 70 VRO idle orifice and VRO questions

You will definitely need the orifice jet in place to get the proper vacuum and Air/Fuel mixture for your engine to idle properly. The throttle bog typically indicates you are lean at idle and the engine isn't getting enough fuel to transition off idle to higher engine speeds. Once you get the idle orifice jet back in place, you may need to richen up the idle settings to improve the transient response.

I recently rebuilt my 60hp 3cyl engine and disabled the VRO. Assuming your fuel pump works correctly, you block off the oil inlet with a hose and a bolt, remove the VRO tank and disconnect the plug to the VRO pump, which disables the alarms. There is a sticky in the Top Secret files section highlighting the process with pictures.

Out of curiousity, what is your main jet size for a 70hp? My 60 has '46D' stamped in the main jets.

 

[rwiens]

Re: 70 VRO idle orifice and VRO questions

I don't know what the main jet size is, just that all the jets are fixed. If you look at a parts list it says 57D. I can verify the next time I have access to the motor.

When you say "richen up the idle settings" how exactly do you do that? I have seen all kinds of suggestions regarding increasing the amount of fuel flow, from replacing bad hoses to adjusting the carb floats a little to even installing bigger orifice plugs. I rebuilt the carbs a couple of winters ago but it seemed to make absolutely no difference.