Hello everyone. I've been lurking for a few weeks finding out everything I can about my "new" bike. Its a '72 lightning with a '68 firebird scrambler engine. Now when I got the bike I assumed that since there was a warning light then it must use the pressure switch but now I realize I was dead wrong. Bike didnt run and I thought the bulb was burnt out. So my question is, Is there anywhere on this engine I can fit a pressure gauge to keep an eye on things? I havent had any luck with searches. Thanks for any help
The boss for the pressure switch was a later addition. Somewhere there was a big discussion about it. My way around it and to fix the leak path in the OPRV was to replace the OPRV with a different design that incorporated the switch boss.
Welcome Nate I use google to search this site and works well, just enter what you are looking for with britbike at the end.
Sorry I can't help with your question. I have a 70 A65 that I installed an oil pressure gauge on. I could be wrong but I think they started in 69 with a oil hole and blanking plug in the front of the case.
I approached it similarly to DM. I plugged the return to the sump with an 8-32 Allen set screw which I tapped and removed the existing OPRV. I then installed a tee by taking the cover from an early model OPRV and tapping it for the 1/8th pipe thread. One end of the Tee has in in-line OPRV which I added and returns directly to the tank. The other side feeds the gauge. I will admit that I have not sized the new OPRV correctly. It is a ball spring type that is not big enough for cold oil. Once the engine reaches temp it works fine, however, it is prone to hysteresis (doesn't completely colose off until the the pressure is very low). This was the problem with early OPRV's. I have located a "low hysteresis" valve that is adjustable and will likely solve the problem, but have not got around to finishing my project. I did solve my main objective and have good oil pressure throughout the range, but the system needs some fine tuning. Pic shows cold idle pressure. Obvious OPRV is not bypassing enough oil. Once hot it is fine, idling at 17-20 psi.
Nate...I should have said oil hole and blanking plug in front of the OPRV.The black line in the center is for a crankcase breather system, it is installed in the hole that is used to set the piston position for ignition timing in the fully-advanced position.
Leon...I had the hose and fittings made up from McMaster-Carr, they will make up what ever you want. McMaster-Carr and Gauge Not cheap but well worth the peace of mind that it will stay together and not give me problems.
Hey, I gotta McMaster Carr hose all made up that was a tad short for my changed gauge location. I believe it is 1/8 Male npt on one end and female on the other. I'll donate is for shipping costs but I'll need your measurement to check.
Her "ugly plastic tubing" is about 35 inches long but would look better at 33. It is male and female but can't vouch for the thread size - went right on the O.P. gauge and into the O.P. switch hole. She would love this new addition to her wardrobe if the shoe fits.
I have one like Rogers -liquid filled (0to60psi-I never hope for more)that I got at Graingers for maybe 20 bucks. It got a little yucky looking after about 8 years but I still believe its' reading. Ms. Doolittle will ask me to replace it along with her new fancy hose. I haven't told her yet - she should be glad she's getting an oil and filter change!
To be "in the money" with the thread - what oil gauges do you guys used and how do they last ?
I had a Sunpro auto gauge for a while. That lasted a about six months. Replaced that with one from Accurate Instruments. Again, that lasted about six months. I now have a pretty much generic liquid-filled gauge, still working after over a year. However, I tested the thing using a compressor. It reads about 8psi low, but at least it hasn't self destructed from vibration.....yet.
Originally Posted By: LeonGustus
Does Ms. Doolittle need better breathing? How does one know?
How big of a puddle does the stock breather leave on your garage floor?
Maybe how the gauge is mounted determines its life span? I've not had one fail but I have rubber washers on the bottom where I attach it to a metal tab that's bolted to the instrument plate. The gauge "floats" like sitting at the end of the diving board. I had a cheapy for years and only replaced it cause it looked cheap. Had a metal tab break though. Look at Rogers - I suspect there's a rubber spacer/washer under it.
So I was looking over the bike and had a crazy idea about tapping into the feed line to the head. I'm thinking about using a T fitting but I'm not sure what the thread is going into the head. Tried some npt and didn't quite fit. Any ideas on thread? Already tried the service manual
You will not get any significant reading from the head feed. That is on the return side of the pump and the pressure is only regulated by the oil line to the tank and the chain drip feed screw inside the tank. The only places you have crank feed pressure is the OPRV or one of the blanking screws for the cross drillings. Unless you add another hole somewhere.