Progress report on 88 70 VRO and questions

[sssports]

Hello all,

Today I went to Auto Zone, and purchased both a vacumn guage and a compression guage.

Here is what I have done testing wise to date. First I installed the vacumn guage on a "T" placed a vacumn cap on one leg of the "T" and then connected a length of 5/16" fuel line with a OMC fuel fitting on the end. I then removed all spark plugs and spark/coil wires. I then hooked this vacumn setup up to the fuel inlet on the engine and turned it over. The vacumn guage immediately went up to 7 Hg of vacumn and I stopped turning it over, the vacumn guage went down to 6 Hg of vacumn and held for at least 5 minutes untill I disconnected it.

I then proceeded to the compression test. Each cylinder measured 120 psig of pressure and all the same within 1 psig.

Is 120 psig an acceptable compression level for this engine ?

After reading the FAC on vacumn levels for a good pump, I believe I have eliminated the VRO2 fuel pump as being bad, and also have elminated the possibility of any vacumn leaks at least from the fuel hookup at the engine cowling to the VRO2 fuel pump.

I then removed all three carbs, I have at this point only dissassembled one of the three. Overall the carb was pretty clean inside (no varnish) with the exception of what looked to be possibly sloghing off of some rubber from the old line. This had collected at the bottom of the float bowl in the small recess between the plug and the jet. It was not hard or stuck to the float bowl, but loose in the bottom.

Can someone tell me which is the high speed and low speed jets? And possibly a picture if you have one.

I plan on getting rebuild kits for the carbs, since I have taken them off, but I did blast carb cleaner through all the tubes and holes and they were all clear.

My plans are to install all new alcohol resistant fuel line inside the motor cowling during re-assembly. Since I have it all apart it only makes sence to do so. All the small lines supplying each carb had zip ties on them which I cut off to remove the lines, are zip ties acceptable ?

I also have a technical question on the carbs. the carbs were marked with the following numbers.

#1 AN 431983 (stamped) The aluminum tag on this carb was marked 432909 then MX in the middle then 16 CM at the bottom (three rows of numbers)

Both #2 and #3 carb were marked N431983 (stamped) and the aluminum tags were both marked 432909 then MX then 14 CM.

Is this right or is one of the carbs (#1) mismatched?

Any and all help appreciated! Thanks!

Marty

 

[R.Johnson]

Re: Progress report on 88 70 VRO and questions

Your compression is fine. Use your vacuam guage with the engine running. 7hg would really be to high, indicating a restriction. Do not use the primer bulb with the guage hooked up, the pressure could damage the guage. You can buy a combination vacuam, pressure guage, but i always felt they were not sensitive enough for our work. My favorite guage is an old Allen that only read's to 24hg. It has a 2-34" face, making it easy to read. With the engine running, your pump should pull about 4hg, with about 4lb. of pressure. This guage was taken from and old Allen automotive distributor testing machine. If anyone should have the notion, these machines can be found in many of the older auto repair shop's, and are seldom used anymore. Beside's the vacuam guage of high quality, This machine has a all brass vacuam pump that is perfect for checking gearcase's. It makes the Stevens tool in the OMC manual look cheap. This machine was made for checking distributor's with breaker point ignition. I got mine for the asking as it was setting on a shelf with an inch of dust. If nothing else, it has a minature 3 jaw Buck lathe chuck that would probably bring $50.00 on ebay

 

[sssports]

Re: Progress report on 88 70 VRO and questions

Thanks R. Johnson,

The test was just to see if the fuel side of the VRO2 pump was working. I found a rebuild kit for it on another site, with instructions for taking it apart and putting it back together, while looking at the tutorial it was obvious that this particular fuel pump is a diaphram pump driven by an air motor that drives both the fuel and oil side of the VRO2 pump. The test I did was simply to see if the diaphrams were good and pulling a vacumn and if the lines inside the cowling were holding vacumn. Diaphram Pumps are fairly simple, if they pull a vacumn and hold it, then the diaphrams and seals in the pump are sound. If a diaphram is split or has a hole in it it will simply pull a low vacumn or none at all. My fuel line from the tank and the tank itself are brand new lines and fittings, and the fuel is new as of two days ago.

While taking apart my carbs, I found enough crap in the bowls to have caused my high speed fuel feed to be considerably less than necessary. I also found one of the three carbs had the low speed fuel tube to the low speed jet clogged, which I am sure is the reason for my less than stellar idle.

However I had no problem cleaning out the carbs completely, I did find another problem in that some previous owner had used a faucet washer to seal the high speed jet cover screw and it was cracked badly. The 70 vro carbs are really very simple, much simpler than even a briggs lawn mower carb. other than the dirt and the rigged washer and a few clogged passages, everything in the carbs looked just fine.

Because of all the crud I will replace my carb feed lines, the solenoid primer lines looked just fine. Here in St. Louis they have to put ahcohol in the gas for EPA reasons, so I will replace all remaining lines with ahcohol resistant.

Sitting for three years and only being run at idle in a barrel was no doubt the source of the crud and subsequent high speed bogging. I had planned on getting and installing new carb kits, but after going through them I could see no reason to. I may regret that decision, but only testing on the water under power will tell. I did the blow test and all held just fine on the float needles, and opened just fine right side up.

Thanks!