dustyxbla

Well? Any progress?

1979 CB750 Limited Edition

I followed it start to finish and everywhere in between. I really feel like the wire is good and the sensor is bad, despite many people saying its the wire. I've exhausted my patience with the wiring as I found nothing wrong. Its so confusing and it bothers me. I put a test light clipped on the wire and poked at the battery positive and it lit up.. I'll report when I get the switch and replace it. Thanks guys. I don't know what else I can do till then

1979 CB750 Limited Edition

Round quick disconnect. Also called banana connector. Honda loved using them back in the day.

Okay, I know exactly what you mean. Thanks!

1979 CB750 Limited Edition

Derp. Skipped over this somehow. Chase wiring back from the light. Pull the headlight out, download a wiring schematic from Google images and chase it back. Wire from the light should go into a connector and back out of the headlight bucket and eventually down to the sending unit. If this only started happening after you did the oil change I would walk yourself back though everything you did while changing the oil. Did you lift the bike up somehow? Chances are you pinched the wire and split the insulation enough to ground it out. To isolate the wire as the problem run a jumper from the sending unit to the hot dog connecter in the headlight bucket and see if that fixes it.

I like this idea. I have the clymer, so I have a wiring diagram. I'll bridge the wire. But what is a Hot dog connector?

1979 CB750 Limited Edition

I did this earlier, this is between ground and switch, with the switch wire lead attached.

Bike off:

Frame ground to switch: 1.5 Ω

Bike switched on (not running):

131.6 Ω

1979 CB750 Limited Edition

It stays lit.

1979 CB750 Limited Edition

Different things happen in the electrical system when a bike has the key on vs when it is running. For example most bikes the headlight won't come on. I have re-read your posts and I see you have not checked it with the wire off and the bike running.

I understand you don't want to run it, I would not be too keen on doing that either.

Well I took it for a 2-3 mile ride with a passenger with the stop light on ( I know, I know) and she survived. Engine sounds healthy and I know the pump is working. That doesn't mean I have pressure, but I feel confident I can run the motor long enough for tests. You want me to give you the resistance between the unplugged sensor wire and ground with the bike running?

1979 CB750 Limited Edition

https://vimeo.com/125804836

This is how the light responds when the lead to the sensor/switch is unattached from the switch. As you can see it is delayed for a second. When attached it comes on immediately. I'm not sure that I think that the wire is grounded. If it was grounded wouldn't it just come on immediately?

1979 CB750 Limited Edition

Is this not the oil pressure sensor? The wiring for this sensor never goes through the stator/alternator cover.

1979 CB750 Limited Edition

You da man, crazyskullcrusher. The switch is going to be a super PITA to pull due to location and size. I'll report back once I get some time put into it

1979 CB750 Limited Edition

Check the wire from the sending unit to the light. You're looking for that wire touching ground somewhere.

When the bike is off, the sending unit grounds the wire, when the bike is running oil pressure pushes up the thing in the sending unit and you no longer have a ground and it turns the light off.

Don't use Teflon tape to put the sender back in.

Thanks, Gump. I'll check as much of the wire as I can tomorrow. the timing of this issue is what perplexes me. Especially because the oil system appears functional.

1979 CB750 Limited Edition

Sensor interrupts a normally closed circuit iirc.

Well I double checked my fuses, they're intact. I guess I'll beat on the sensor tomorrow and wait for a replacement.

1979 CB750 Limited Edition

I'm not sure how to test the sensor because i dont know how it works. Does the sensor kill a circuit to ground when activated, or what?

1979 CB750 Limited Edition

I pulled the wire off, didn't start the motor, but turned the key to on and the light was still on, but it was delayed to turn on by a second or two. Grounded the wire to the sensor to the main ground and it still stayed light.

1979 CB750 Limited Edition

Was there oil in the filter/housing when you opened it up?

1979 CB750 Limited Edition

Update: I tapped on the sensor, maybe not hard enough? I tried "burping" the filter and lost about a quart of oil lol it's DEFINITELY pumping oil to the filter. Also, because I'm an idiot, I rode it for like 2-3 miles yesterday after the change. Would I not have blown or seized my motor in that amount of time if my oil wasn't under pressure? I bought a new sensor on eBay today, should be here next Wednesday.

1979 CB750 Limited Edition

I haven't noticed any odd sounds. I took the filter and cover BACK off today and inspected them and put them back on. I haven't heard of burping though.

1979 CB750 Limited Edition

. Okay, so I own a DOHC 79 Cb750 K/limited edition. I spent the past 2 months replacing the entire charging system because it was all bad. Last night I received my regulator and wahla!/it was fixed. So I got 4 quarts of Pennzoil 10w-40 and did and oil and filter change, excited to take it for a ride. After the boil change my Oil/Stop light came in and won't shut off. I'm demoralized. I have no idea what went wrong but the light stays on even when the motor is running (5-10 second tests). What could possibly have happened and how do I fix it? This is the last straw

1979 CB750 Limited Edition

I use this for chrome and anything I have polished. I was told it was designed for flat bumpers on Semis. No need to tell me if I'm using the wrong stuff, I like it.

http://www.amazon.com/Zephyr-Pro-40-Metal-Polish-16/dp/B002SS5ZCU/ref=sr_1_1?ie=UTF8&qid=1429522414&sr=8-1&keywords=zephyr+pro+40

Never even heard of this stuff! Nice!

1979 CB750 Limited Edition

From experience with old bike electrical gremlins... make sure the fuse box has clean contacts. Once they get light brown corroded, the heat generated there will cause fuses to blow out. Everyone looks everywhere except that.

I've had three CL350, I liked them a lot. Don't set the exhaust valve lash at the minimum dimension. It doesn't like that when the engine gets hot. Ease up a bit. One of the valve rocker shafts is bored a bit off in the head on all of them that I've seen. With some engine wear, it will never quite adjust. Don't worry about that, just get it as close as possible.

Some of the coils have spark plug wires that will unscrew. Replace those with generic from NAPA, cut to fit.

I cut gaskets from an inner tube to put under the tail light bracket. Run a ground wire if needed. The tail light/brake light vibrates and blows bulbs out easy.

Thanks for the advice! I'll be sure to keep all that in mind as I run forward with this

1979 CB750 Limited Edition

Oh, and two mix matched ignition coils. With questionable reliability lol motor seems healthy from what I can tell though. And I'm glad the electronics are so basic.

1979 CB750 Limited Edition

The fenders are rusty, as as some of the frame. The engine, is rust free though. There's so much dirt/debris/rust on the frame that I don't even know where to start. I really want to hose this pig down, but its Ina pretty delicate state. Carb boots have no clamps, gas lines have pipe clamps etc etc. I'd agree with your battery comment. The box is full of powdered rust. The rear fender was held up by a wedged short handle screw driver. Not even kidding. It had a gigantic homemade sissy bar on it as well as a steel beer cooler rack on the back. The throttle cables are frayed and some of the electrical connections are soldered on, or were and came loose. Front brake is non responsive. I told him I'd help because I want the experience on a points ignition bike, but there's a lot to learn. It only had one owner who passed away. $300 and a clean title.

1979 CB750 Limited Edition

This is the bike I'm really asking this question for. 72 CB350k3 it's my buddies barn find and as you can see its quite the piece. I'm waiting on an ignition switch which has all forward progress on hold. Wanted to clean her up since I can't work on her. No rust, though! Just gunk.

1979 CB750 Limited Edition

That's a very nice 79 CB750. Looks like it was well cared for and stayed stock.

There are some "don'ts" also:

Do not use steel wool on aluminum. (Most of the aluminum is clear coated anyway, not a good idea.)

Do not use ArmorAll or similar on tires or seat. Way too slippery.

Avoid most automotive wheel cleaners. Too aggressive and can blemish surfaces. Use something like Simple Green.

Avoid pressure washing. It gets past seals and gaskets too often.

If the bike is dirty or dusty, wash it first. And yes, the Bike Spirits and Mother's Chrome Polish are quick and easy good stuff.

Kerosene and/or mineral spirits are good solvents for really tough gunk. (Chain and stuff around it.)

Lube the chain after cleaning or washing or rain.

There are special cleaners and polishes for engines. Sometimes I use them, sometimes I don't. Haven't tried them all, expensive and unnecessary. I have my doubts about all "special" cleaners and polishes.

Get some cheap microfiber towels from Harbor Freight or similar.

Given the age of the bike, stay aware of electrical gremlins, and check connectors for corrosion when you can. Some can be cleaned, some will have to be replaced. Also check the front brake hydraulic line (and fluid), and replace it if necessary.

Thank you, I've got all the original parts minus the 4-4 exhaust and front turn signals. The front brake was seized when I got it so I rebuild the cylinder with all new parts and cleaned the hose as well. That's for the advice, I've got a slight oil leak, left side. Haven't located it yet, which is why pressurized water is scaring me. I'll have to keep the simply green in mind. Also, currently dealing with an electrical gremlin. I'm replacing the regulator/rectifier. Its the only part of the charging system I HAVEN'T replaced. I'm not guessing, all the parts tested bad. Hope this is the last piece of the puzzle. Also, since armor all is obviously bad news on a seat, so you use anything to keep your leather nice? My old lady is nearing 40 and has a flawless seat, I'd like to keep it that way.

I have used a pressure washer almost every time I have washed my bikes over the last 40 years it has never caused a problem. Isn't riding in the rain at 60 plus mph almost the same thing?

For cleaning burnt on road film on engine blocks and fins I get the engine warm (not hot) and spray it down with WD40 then let it stay on all night then the next day I spray it down with engine degreaser and power wash it off it comes out looking like new every time.

I've never had a bad experience with pressure washers, I've just never used one on a bike, seems like it could be trouble. Good to know I can use it though. Also I really like that wd-40 tip. I'll have to try that. I really want to have my engine "shine" I haven't cleaned it up at all yet, so I'm not sure of elbow grease and a spit shine will do it, or if I'll need something to help. Thanks for the tips all.

1979 CB750 Limited Edition

Hey guys, I've been making custom leather gloves here as of late. I've only been selling to friends, but figured I'd put my skills out there for those of you who might be interested. If nothing else let me know what you think! Thanks

1979 CB750 Limited Edition