Just filled both of my Hitachi refurbished 3 screw SU Carbs with 3 in one  motor oil (Blue and White label). The Temperature here in Panama is 33 degrees Celsius, very hot indeed! The car is running okay, but at first gear sometimes hesitates back and forth. The idle was set to 1000 but does not keep the rpm steady. It lowers to 900 or rises to 1,100 RPM. Sometimes if stuck in traffic it can lower to 500 and could stall.

 

Is this caused by the kind of damper oil? the timing was adjusted to 10 degrees Celsius and the Camshaft is a Schneider 274F (1800 to 6000 RPM)

 

Any recommendations? Both carbs are fully adjusted and fine tuned.

It will be interesting to see if there is difference between the two oils, assuming one is thicker than the other.

 As far as elev. is concerned, When driving up to Timberline Lodge on Mt. Hood, the engine developed a miss. Assuming it was mixture related, I gave the engine some choke to see if the miss went away. It only got worse, so I stopped & screwed both mixture screws in 1/2 turn. Problem solved temporarily. When I got back to a lower elev., I opened up the screws 1/2 turn. You may need to re-tune the carbs for the higher elev. depending on how rich the mixture is set.

Mark

Back and forth hesitation came back when speeding at 1st gear. Damn it! Maybe i need to try ATF as Z therapy says!

 

Car starts shaken when initiating in 1st gear.

Edited April 2, 20159 yr by jalexquijano

If the piston rises too fast (thin oil), the fuel droplets fall out of suspension and the constant velocity drops. This makes a lean bog. Bumps in the road can also cause fuel changes.

The opposite happens if the oil is too thick: the piston rises slower, the air rushes through faster through a smaller area (not CV) and it pulls more fuel. This makes a rich bog.

 

Absolutely correct.  I used 3 in one (black label) and it was obvious that the piston was jumping around way to much.  I tried a straight 30 weight (motor) and while it ran reasonably enough, you didn't have to press too far down on the pedal to realize it was doggy.  The 3 in one (blue label -- SAE 20) has no power or drivability problems.

 

Jetaway

I've gone to a hobby store and bought oil that is used in the shocks for remote control cars, very thin, been using since 94.. They carried 3 or 4 different ones.

From my reading and very limited experience, suggest damper oil, needles (stock or modified), and springs work together; also engine displacement  and driving style have varying requirements.

 

If so, experience and/or experimentation may be required for best performance. Not telling racers anything new, obviously.

I've had good luck with both ATF and 10 wt. motor oil.  In my last race, I used ATF and the car accelerated cleanly with very good AFR readings from mid-corner until the end of the straightaways.