Author Topic: 750F Running Rough When Giving Gas (Read 2960 times)

YoungBlood · « **Reply #25 on:** May 25, 2021, 10:57:58 AM »

I took copper wire and wrapped it the teetering plate to the non started position. Thus eliminating the constant draw to start the starter motor with the key on, kill switch off.

I’m about to open up the box, and send a pic. My new idea is to use some rubber sheathing and then electrical tape over the rubber sheathing, trying to eliminate the open circuit likely grounding in handle bar assembly.

YoungBlood · « **Reply #26 on:** May 25, 2021, 11:00:21 AM »

Cleaned up the solenoid and the fuse box with some CRC qd electrical cleaner, Emory paper, and brushes

YoungBlood · « **Reply #27 on:** May 25, 2021, 11:31:49 AM »

This is what I originally did, about to re do this with rubber sheathing and electrical tape and eliminate the copper wire wrapping keeping the black/red contacted

YoungBlood · « **Reply #28 on:** May 25, 2021, 11:35:41 AM »

Any ideas until the replacement box arrives?

YoungBlood · « **Reply #29 on:** May 25, 2021, 04:59:10 PM »

I realized after splitting open the starter button box, where I wired the circuit to the closed position (black to black/red) that this is NOT the culprit to the blown 15A fuse. It runs to the front headlight 7A fuse, which never blew on me. In the process of taking it apart a second time, because without the copper wire I used to jump the black and black/red on the switch board, I lost the precious rectangular piece with two saudered posts that teeters.
After using copper wire a second time, I first started the bike, ran around the block and noticed the hesitation. I then came back, took some volt readings, everything I tested got power... coming from the starter switch assembly. I took the bike out again, drove about 8 miles, no hesitation.
So I have a phantom hesitation problem that I believe is electrically related. But it cannot be related to wiring the red/black and black together in the starter button console (7A circuit not 15A). So the only last thing I can think is the problem is my gunked up oil pressure switch which is on the 15A line. I cleaned it up a bit, noticed some electrical tape which is never good.
Also, I have not blown the 15A fuse yet... I'm at a lost on what to do.

Lastly: How do I tell if a wheel bearing is shot/going bad? I have a terrible squeek/squeel when wheel rotates, or I'm parked and turn the handles left to right. Not a grinding, a squeel.

scottly · « **Reply #30 on:** May 25, 2021, 07:49:55 PM »

Quote from: YoungBlood on May 25, 2021, 04:59:10 PM

I realized after splitting open the starter button box, where I wired the circuit to the closed position (black to black/red) that this is NOT the culprit to the blown 15A fuse. It runs to the front headlight 7A fuse, which never blew on me.

The BLACK wire is fed directly from the 15 amp main fuse; if it touches the handle bar or switch housing, the fuse will blow........

Alan F. · « **Reply #31 on:** May 25, 2021, 07:53:47 PM »

I'm thinking the cleanup you did on the starter solenoid and fuse panel is what made the difference. Keep looking around for old electrical tape and dirty connections and cleaning things up, after a little while you'll have gotten to everything. Don't forget to clean up the battery ground wire where it connects to the frame.
Good work, sorry that part went missing.

YoungBlood · « **Reply #32 on:** May 25, 2021, 08:02:08 PM »

Scottly, well I'll be damned. It is not blowing yet, hopefully the new jerry-rig I have for the time being will keep the black from grounding in the housing. Thank you! I'll be sure to study up that diagram some more, I thought it was only the 7A.

Thanks Alan, I ordered a new main harness, I don't want to deal with problems like this happening anymore. It's sad and funny that I lost that contact plate, it's in the alley next to my apartment. I was on my hands and knees for 30 minutes looking for the #$%*er. Does anyone know if the 77' Honda CB750F uses the same starter button housing components? Someone has one for sale $20 on ebay: https://www.ebay.com/itm/274670359876?hash=item3ff3a11544:g:VpgAAOSwyf9gGsXY

Also ordered wheel bearing kit for front and rear. I figured it's never been done on this bike. Got the creepers thinking about it riding the bike.

scottly · « **Reply #33 on:** May 25, 2021, 08:11:13 PM »

What makes you think you need a whole new harness??? ALL of your problems so far have been related to the failed start switch and your attempts to by-pass it.

Alan F. · « **Reply #34 on:** May 25, 2021, 08:13:56 PM »

Changing wheel bearings is a good idea if you don't know how old they are or if you hear something you don't like. Steering bearings too. Easy check is to put the bike up on the centerstand if you have one and spin the wheel, check for side play or wobble too. Same for the front, have someone sit on the rear of the seat so the front wheel comes up, check your steering bearings with front wheel off the ground too, if there's a notch you can feel while slowly turning the bars side to side, your steering bearings may need a change too.

I dunno if that switch will have the same guts or not.

YoungBlood · « **Reply #35 on:** May 25, 2021, 08:20:04 PM »

I dunno Scottly, I think it's the beer talking to me after cleaning all those connections... might make a return lol.

Thanks Alan, I'm going to be sure to do this with someone soon. Can a high pitched squeel noise be due to bearings? I'm have a suspicion it might be the front rotor is partially warped pushing the pad against the caliper housing. Making that brake squeek noise even when not braking at certain rotations of the wheel.

scottly · « **Reply #36 on:** May 25, 2021, 08:25:59 PM »

The squeal is caused by the brake, and has nothing to do with the wheel bearings. At this point in your education, I would leave the bearings alone until you've learned how to determine their condition; you can do a lot of damage if you don't know what you're doing. Don't fix it until it's broken!

Alan F. · « **Reply #37 on:** May 25, 2021, 08:27:23 PM »

Word.

YoungBlood · « **Reply #38 on:** May 25, 2021, 08:28:39 PM »

Scottly you're on the money. When I originally looked at the diagram running from the 15A fuse, I saw the black wire as a brown wire. An error on my part. I now see and understand why it was my bypass that was causing a short, thus drawing power away from also the coils! Thus, that was why I was having hesitation issues and then blowing the fuse! The coils weren't getting enough amps/voltage?

I'd like to understand why the fuse blows,, electrically/theoretically, when previously supplying intermittent power to the coils.

YoungBlood · « **Reply #39 on:** May 25, 2021, 08:33:33 PM »

The wheel squeals without applying the brakes when at very low speeds, or turning the handle bars when backing up the bike.

I'm more than confident I can do a wheel bearing change. I thought something like this would be recommended due to the age of the bike? I've done fork oil and seals, as well as rebuilt the rear caliper.

seanbarney41 · « **Reply #40 on:** May 25, 2021, 09:50:52 PM »

I have been messing with sohc4 honda's for about 15 years now (not even close to Scottly!)and have ridden them over 100 thousand miles. I have had to replace exactly 1 set of rear wheel bearings and they were cheap aftermarket junk, not Honda oem. Your squeak/ squeal is not from the bearings. It is the brakes, possibly caused by a slight mis-assembly or maladjustment of the axle assembly, caliper, or caliper bracket. That is not to say that your bearings will never go bad, but I will bet you they are not.

jonda500 · « **Reply #41 on:** May 26, 2021, 04:06:24 AM »

My brakes often squeal at very low speeds (despite the caliper having a new piston & seal), but as I don't really travel anywhere at very low speeds, I don't let it bother me.
I have never had to replace a wheel bearing on any of my bikes (eight honda's over forty years)!
John

74CB750K4 · « **Reply #42 on:** May 26, 2021, 07:25:24 AM »

Can you push the bike easily or is it really hard to push? When I dug my bike out of my dad's garage the caliper and all that was seized and gunked up. Replaced master cylinder, brake hoses and pipe, caliper with new piston with rebuild kit, and pads. Initially was still a little hard to push and then when riding it was making a squeal until I applied the brake and then squeal stopped. The new pads were not releasing the whole way and rubbing on the rotor. Fixed that, easy to push, but still squealed while just applying the brake. When I got new tires a few weeks ago they tore it apart, greased the back of the pads, and sanded them down properly and it's all good to go now, super quiet.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #43 on:** May 26, 2021, 01:52:00 PM »

Does anyone know if the 77' Honda CB750F uses the same starter button housing components?

Learning how to cross reference parts will save you a LOT of hassle. I believe, without looking, that the switch is NOT a -392 part but rather a -341 part? Since I'm not sure you should cross reference the part number. OK, I looked. NOPE! it is a -377 part number but could have also been superceded. 35130-377-670

YoungBlood · « **Reply #44 on:** May 26, 2021, 02:37:41 PM »

So I have eliminated the possibility that the starter button switch was causing a short in the housing. I disconnected the black and black and red male bullet connector. I then make shifted my own wire with two males on it. I plugged one into the black/red female running from the frame, and plugged the other end into one of the black females on a four way connector (two black, two brown).

The bike still hesitates. I'm starting to get off my rocker on this issue. I am pulling the new plugs to look. All cylinders are hot, all must be firing. I am going to check my contact points gapping and check the timing again. Could it be that I somehow threw off the timing in all of these blown fuses and the starter motor cranking until the battery was dead a few days ago?

Need help! Also, a few weeks ago I installed new coils and caps. Could a coil be bad or had gone bad? Way to test would be appreciated.
PS: I greased and emory filed the front brake shoes. No more squeek, you guys were right about it not being bearings. Thanks...I returned all those items.

Alan F. · « **Reply #45 on:** May 26, 2021, 05:41:42 PM »

Have you downloaded a manual for your bike yet?
If you have a Haynes manual it likely has a bit on testing your coils as well, the Honda manual will have coil specs.

The 2 little wires on each coil are the primary winding, measure resistance here and write it down, measure both coils.

The two plug leads from each coil are the secondary windings, measure resistance and write it down, measure both coils.

Plug caps should measure 5,000 ohms or 5k, take them off your wires, stick a probe at each contact, write it down.

Your readings should be very similar if you have a healthy set of coils and caps.

Good on ya for taking the guidance that it was your brake squeeking. How are your steering bearings? Check them so that you have a good opinion on them either way.

YoungBlood · « **Reply #46 on:** May 26, 2021, 06:43:22 PM »

Thanks Alan, always appreciate your feedback. Yes, I normally download the Honda Manual to check things. The Haynes doesn’t have anything on testing coils, it refers to a Honda Technician. I figured out what the problem was, I opened the timing case and found sparking on 2/3 contact points a lot of sparking on the points. 1/4 had no noticeable sparks in the gap when running. Also the contact arm for 2/3 was rubbing against the crank case causing sparking/grinding. I push it away, swapped the condenser with another I had. I replaced both previous condensers with the coils a few weeks ago. I’m not sure why swapping that condenser solved the problem. No more hesitation or blown 15A.

Before the condenser fix I pulled all the caps and got approx 5k ohm reading. All were very close. For the moment I’m going to leave it as is until the new starter switch assembly can be arranged.

Thanks again everyone. Also, Alan, I noticed the rear wheel needs truing, it has a wobble. I know the Honda manual has stuff on that, you ever done truing?

Alan F. · « **Reply #47 on:** May 27, 2021, 09:30:27 AM »

I have built a few wheels and will be building a few more soon. Is it your rim that has a wobble or is it the tire? Sometimes the tire bead isn't completely seated and the tire has a wobble.

I'd say the first thing you want to check for are loose spokes. Put the bike up on the centerstand and turn the rear wheel to locate the valve stem, this is the best start/stop/reference point on the wheel. Tap the first spoke with a screwdriver or a small wrench and notice the sound it makes. High pitch = tight, low pitch = less tight, thud = loose. You might even find broken spokes, it can happen. Tap and make your way around the rim listening and after a few rotations you'll notice that they're all the same or they're not. Mark the low tone/loose spokes with some painters tape on the tire sidewall where it won't get in the way, then spin the wheel and look for your wobble, is it in the same area?

Don't tighten any spokes, just scope it out for now.

YoungBlood · « **Reply #48 on:** May 27, 2021, 01:01:21 PM »

Awesome, thanks Alan! I’ll take a look soon, it’s only in one spot from when I eye balled it. It appeared the tire was bulging at a spot. I’m not sure yet about the spokes. I went around feeling them all, pretty much all were the same tightness. No broke spokes. I’ll try out the chime and tap method, then report back. If it’s the tire, does that call for a tire professional to reseat the tire granted the tire is still in good shape? No corrosion or cracking on the tire, threads still seem deep.

Alan F. · « **Reply #49 on:** May 27, 2021, 01:39:21 PM »

I'm not experienced with tire changes and dealing with tubes, I'll be taking mine to a tire pro. You will want to find the date codes on your tires though, 4 digits tell the week and year they are made.

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Author Topic: 750F Running Rough When Giving Gas (Read 2960 times)