Author Topic: Senior project for high school - 78 CB750K (Read 169611 times)

Restoration Fan · « **Reply #950 on:** April 11, 2015, 07:30:04 pm »

A couple of lessons learned over the past few days:
1. A Sylvania H6024 sealed-beam headlight is the same one as used in our Hondas and you can get them at most auto part stores. If you don't remember the exact model number when you're at the store, tell them you need a headlight for a Jeep CJ-7. It's that bulb.

2. Soaking carb boots in Wintergreen oil really does work. I used about this much oil along with 2 cups of water. I put them in a pan and put them on medium/low heat for about 4 minutes and then removed them onto paper towels. They didn't swell but they were (and still are) pliable and you can work with them.

3. When mounting carbs to the bike, use a ratcheting tie-down strap wrapped around the carbs and the front of the frame. It not only helps to pull them into the carb boots properly, it holds them in place afterwards while you tighten the clamps around the boots.

4. Attach the throttle cables and choke cable to the carburetor rack BEFORE you mount the air box.

5. When mounting the air box, push the box in so that the flexible rubber boots in the air box are mostly aligned at the bottom of the 4 carb holes. Then, lift the air box up and then gently but with some force, push it forward to try and get all 4 boots onto the holes at the same time. Once you get all four of them started, gently pull the box back. Remembering that the flexible rubber boots in the air box move in and out, as you pull the box back, make sure to pull each of those boots so that they're staying on the carb and only the air box is moving back into position to be mounted.

Hope these help someone else. Seems like we learned them the very hard way.

Restoration Fan · « **Reply #951 on:** April 11, 2015, 07:33:58 pm »

Quote from: NobleHops on April 11, 2015, 07:16:51 pm

Ron, the first fill of an empty brake system can definitely be a minor PITA. Here are a few things to try:

Awesome explanation! Thank you. We'll give that a shot tomorrow!

madmtnmotors · « **Reply #952 on:** April 11, 2015, 07:53:52 pm »

Quote from: Restoration Fan on April 11, 2015, 06:51:50 pm

I do have a question though: when we twist the throttle, it opens fine but it doesn't spring back. I thought the pull cable was supposed to do that. Is there some type of adjustment that we need to make or something so that it snaps back?

Looking at the picts of your carbs, did you return part number 16036-405-004 to it's rightful place?

Stev-o · « **Reply #953 on:** April 11, 2015, 08:10:37 pm »

Quote from: Restoration Fan on April 11, 2015, 07:30:04 pm

A couple of lessons learned over the past few days:
1. A Sylvania H6024 sealed-beam headlight is the same one as used in our Hondas and you can get them at most auto part stores. If you don't remember the exact model number when you're at the store, tell them you need a headlight for a Jeep CJ-7. It's that bulb.

2. Soaking carb boots in Wintergreen oil really does work. I used about this much oil along with 2 cups of water. I put them in a pan and put them on medium/low heat for about 4 minutes and then removed them onto paper towels. They didn't swell but they were (and still are) pliable and you can work with them.

3. When mounting carbs to the bike, use a ratcheting tie-down strap wrapped around the carbs and the front of the frame. It not only helps to pull them into the carb boots properly, it holds them in place afterwards while you tighten the clamps around the boots.

4. Attach the throttle cables and choke cable to the carburetor rack BEFORE you mount the air box.

5. When mounting the air box, push the box in so that the flexible rubber boots in the air box are mostly aligned at the bottom of the 4 carb holes. Then, lift the air box up and then gently but with some force, push it forward to try and get all 4 boots onto the holes at the same time. Once you get all four of them started, gently pull the box back. Remembering that the flexible rubber boots in the air box move in and out, as you pull the box back, make sure to pull each of those boots so that they're staying on the carb and only the air box is moving back into position to be mounted.

5. A 6" length of tubing attached to the top of the spark plugs makes it much easier to install the plugs in cylinders #2 & 3. The plug holes are slightly angled too.

martin_uk · « **Reply #954 on:** April 12, 2015, 02:31:07 am »

On brake bleeding, I have had good results by using a large medical syringe to suck fluid out of caliper bleed nipple.

Used a female bullet connector insulator to connect to nipple.

May need a few squeezes on master cylinder lever to dislodge air trapped around piston.

You can see it coming out of return hole, but be careful of fluid squirting back as it will remove paint.

Restoration Fan · « **Reply #955 on:** April 16, 2015, 04:57:28 pm »

Our starter turns but it sounds as if it's stripping the gears when you hit the starter button, rather than engaging and turning the engine over. Is there a bendix inside this starter that might have gone bad and that's the sound we're hearing? Because we took the stator cover off and the teeth on the gear that goes between the fly wheel and the starter motor gear seems fine. The end of a few teeth on the starter gear look a bit sketchy but not enough that it should make the sound it's making.

evanphi · « **Reply #956 on:** April 16, 2015, 05:07:29 pm »

Quote from: Restoration Fan on April 16, 2015, 04:57:28 pm

Our starter turns but it sounds as if it's stripping the gears when you hit the starter button, rather than engaging and turning the engine over. Is there a bendix inside this starter that might have gone bad and that's the sound we're hearing? Because we took the stator cover off and the teeth on the gear that goes between the fly wheel and the starter motor gear seems fine. The end of a few teeth on the starter gear look a bit sketchy but not enough that it should make the sound it's making.

Is the washer there? (Part #3)

mystic_1 · « **Reply #957 on:** April 16, 2015, 05:14:38 pm »

You can also consider pulling the starter part way out or all the way out, and running it briefly to see if the sound is coming from the starter itself, or from the rest of the system.

mystic_1

AintNoEasyWay · « **Reply #958 on:** April 16, 2015, 06:18:08 pm »

Ron, any chance you could post a video of the sound?

edwardmorris · « **Reply #959 on:** April 16, 2015, 06:36:43 pm »

Long shot but could it be the starter clutch?

Restoration Fan · « **Reply #960 on:** April 16, 2015, 07:16:43 pm »

This first one was from last Saturday.

This one is as of a few minutes ago.

It does have the washer in there. I removed the connecting gear and the washer and pin and replaced them back in yesterday but it's still doing it.

madmtnmotors · « **Reply #961 on:** April 16, 2015, 08:13:18 pm »

My money is on the starter clutch. Mine will do it intermittently (60,000 miles) but will usually "catch" on the next try. Bad part is you have to pull the alternator rotor off the crank to get to it. I don't recall, have you pulled the alternator rotor on this build?

Stev-o · « **Reply #962 on:** April 16, 2015, 08:22:38 pm »

Quote from: madmtnmotors on April 16, 2015, 08:13:18 pm

My money is on the starter clutch.

I'm betting with Wilbur. I too had a K7 that did it, but only after 4-5 seconds of cranking.

mystic_1 · « **Reply #963 on:** April 16, 2015, 09:06:13 pm »

Yeah that's the roller clutch in the behind the alternator rotor slipping. You can hear from the sound that the starter is just freewheeling and the crank is not turning. You can confirm that by pulling the points cover and watching there while you crank.

You SHOULD totally be able to kick start it, but with the clunking sound I suspect you may have a missing or damaged roller or even possibly some parts gone walkabout inside the alternator cover.

You'll need a rotor puller to get the alternator rotor off the end of the crank in order to access this.

Items 3 and 6, plus three sets of (4, 5, 15) and three of 21 from the first diagram. All mounted to the back of the rotor and with the rollers running against a machined part of the starter gear, item 4 from the second diagram. These parts constitute a one-way clutch. When crank speed exceeds starter gear speed, the rollers ride up into ramps on part #6 (I think of this as "the cage") which allows the gear to freewheel on the crank. During starting, the springs and plungers push the rollers forward on the ramps which cause them to clamp down on the starter gear and spin the crank.

edwardmorris · « **Reply #964 on:** April 16, 2015, 11:12:43 pm »

I fully tore mine down checked them all and put it back together along with a new seal, there are some pix in my K2 thread if you want to see what they look like. Gordon/ilbikes makes a great rotor puller (very high strength material) that makes quick work of removing it (just did that on my K3 thread). Bill might have the factory puller too, but I doubt the rotor will come off just twisting by hand. While on the bike, you'll probably want to get it into the fifth gear, fully tighten the rear brake adjuster, have someone fully engage the rear brake, then use a cheater bar to remove the bolt.

An electrical impact driver will make things a lot easier.

Restoration Fan · « **Reply #965 on:** April 17, 2015, 12:38:28 am »

We didn't pull the rotor on this build but I did go ahead and buy a puller, just in case we needed to do so. And I have an air impact wrench. So, we'll get to this this weekend and I'll be contacting my buddy Bill to see if he has some replacement parts for me. Maybe then, we can get this thing to fire up.

mark52 · « **Reply #966 on:** April 17, 2015, 05:35:46 am »

Stella's fighting you and Logan at every turn, she's a real diva!!! I'm sure Bill can help out but I guess he is moving a little slow right now. Keep on keeping on time is getting short. Trying to get up there in a couple of week so maybe I can help in the finally push, I will give you a call.

Mark

knottedknickers · « **Reply #967 on:** April 17, 2015, 06:53:42 am »

Quote from: mystic_1 on April 16, 2015, 09:06:13 pm

<snip>
Items 3 and 6, plus three sets of (4, 5, 15) and three of 21 from the first diagram. <snip>

mystic_1 wins for clearest ever parts diagrams! Could you share your source?

Restoration Fan · « **Reply #968 on:** April 17, 2015, 07:03:59 am »

Quote from: knottedknickers on April 17, 2015, 06:53:42 am

Quote from: mystic_1 on April 16, 2015, 09:06:13 pm
<snip>
Items 3 and 6, plus three sets of (4, 5, 15) and three of 21 from the first diagram. <snip>
mystic_1 wins for clearest ever parts diagrams! Could you share your source?

I agree. They appear to have come from CMSNL.
http://www.cmsnl.com/honda-cb750k8-four-usa_model14397/partslist/E10.html#results

Stev-o · « **Reply #969 on:** April 17, 2015, 07:17:03 am »

Quote from: knottedknickers on April 17, 2015, 06:53:42 am

Quote from: mystic_1 on April 16, 2015, 09:06:13 pm
Items 3 and 6, plus three sets of (4, 5, 15) and three of 21 from the first diagram.

mystic_1 wins for clearest ever parts diagrams!

Was thinking that too! Glad he's back...

mystic_1 · « **Reply #970 on:** April 17, 2015, 07:47:27 am »

Thanks guys, source is a Clymer manual from the 1971-1972 era. This came with my bike when I bought it in the early 90's, I've since taken high resolution scans of every page in order to preserve it.

mystic_1

mystic_1 · « **Reply #971 on:** April 17, 2015, 08:31:45 am »

Quote from: mystic_1 on April 16, 2015, 09:06:13 pm

During starting, the springs and plungers push the rollers forward on the ramps which cause them to clamp down on the starter gear and spin the crank.

I guess it's the other way around, really, it's when the clutch is releasing than the plungers come into action, helping the rollers to ride up into the ramps so that the retract positively.

sorry, my bad.

mystic_1

Restoration Fan · « **Reply #972 on:** April 17, 2015, 07:30:11 pm »

When you're right, you're right! You guys were spot on. It was the starter clutch.

Despite the fact that the rotor itself looked really good

there were some hidden problems on the back side.

Turns out that 2 of the 3 screws were actually broken and one of the springs was missing.
Got the old one off tonight and we'll put the new one on tomorrow and see what happens from there.

edwardmorris · « **Reply #973 on:** April 17, 2015, 07:58:37 pm »

I guess I shouldn't have prefixed the call with "long shot"

Grab a rebuild kit here

http://www.cb750supply.com/products/5/electrical/49/batteries-and-starter-system-parts

Restoration Fan · « **Reply #974 on:** April 18, 2015, 03:53:56 am »

Rafi,
I just went over to Bill's yesterday and bought a whole new rotor with the starter clutch assembly still on it.

News:

Author Topic: Senior project for high school - 78 CB750K (Read 169611 times)