Topic: New to cb750k 1978 need help

[Can550]

Hi
I have owned and worked on couple of cb550k s but this is my first cb750k 1978 which was sitting for several years before I got it couple of weeks ago.

I removed the left crank cover thinking I'll clean behind it (sprocket) and polish the cover (like I did on my 550).

Unlike 550, it was not dry so a lots of oil came out (from red circled area) and made mess.

I then removed the rear half cover to expose sprocket. Sprayed some degreaser and washed/ hosed it.

I think I sprayed some water probably on bearing (orange circle) or some other opening that water has entered inside.

I have drained all oil from tank and lower drain point. Also did some air blow (blower through oil tank so that water should dry or come out.

Have I done something terribly wrong/ bad?

Oh by the since there's a gasket, is it crucial to replace it as it's not available at Honda.

Thanks





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[BPellerine]

you do have to replace the gasket,it holds the oil in,I would not think you got too much water in there,but change the oil to be safe and check for foaming in the tank,

[Can550]

Oh ok thanks for saying what I wanted to hear
Oil was drained day before and it was sitting to drain even the last drop.

Is it normal for oil to come out of this passage (unlike cb550k)

I'm waiting for oil to arrive tomorrow and I shall put fresh oil and filter. Should I see foaming in tank, simply drain the oil or do I need to be concerned for anything ?


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[Can550]

Did I install front fender correct ?
Wasn't sure if fender bracket goes on top of brake bracket or between brake bracket and fork?

Is it normal that while removing front wheel, tyre (stock size) is hard to pull out or I have done some wrong installation




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[Stev-o]

Did I install front fender correct ?

Appears to be correct, my K4 is same.

What size tire is it?  Can be snug to get off, let some air out next time.

[BPellerine]

when water mixes with oil it will foam,no foaming and you are good.the shifter cover you took off holds oil,unlike the 550,so it needs to be sealed.when you take this cover off oil will come out,it rests in there when not running.bill

[Can550]

when water mixes with oil it will foam,no foaming and you are good.the shifter cover you took off holds oil,unlike the 550,so it needs to be sealed.when you take this cover off oil will come out,it rests in there when not running.bill

Thanks Bill
Now in the unwanted/ unfortunate event that I do see foam in the tank, what is the remedy and if there's a way to avoid it since bike is not in use and oil has been drained. Leaving it out in the sun, would it help to dry the water inside?

I don't even know how many openings are there that hose water could get in. I know bearing is one, are there anymore?


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[Can550]

Filled up new oil, ran it for few minutes, added more oil to bring it up to mark on dipstick. No foaming in oil box (checked more than ten times. Relieving to see that!

Ran ok, hooked up carb tuner and synced carbs, sounded amazing then adjusted mixture screws and idle knob.

Ran good. Couldn’t go for ride as battery is yet to arrive. Left it in garage and happily started to wait for battery to ride.

Next day tried to fire her up but would not start

While investigating, noticed accelerator nozzles weren’t spraying. Took carbs off again. Cleaned nozzles, passage and diaphragm plus Check valves. Put it back attempted priming and yet no fuel out of jets.

Removed again. Tested on bench with carb cleaner. It squirts out of float bowl check valve with good pressure, sprayed through tiny hole on carb 2 body, spray out of all four jets. Yet cleaned everything and put it back on. Still no spraying jets.

Doesn’t even start. Plugs were wet all four.

Not sure what did I do wrong. It started fine. I know acc pump is not going to prevent from firing up.

Started ignition trouble shoot. No spark on 1 and 2. Clipped wire 1/4” but tiny bit of spark. Measured caps on meter and NO READING. Went and bought 2 new caps and spark is back on but not firing up though makes attempts.

It’s all stock (jets, air filter, pipes) would appreciate help on troubleshooting
a- acc pump
b- hesitation to fire up



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[Can550]

Did I install front fender correct ?

Appears to be correct, my K4 is same.

What size tire is it?  Can be snug to get off, let some air out next time.

It’s stock tyre from factory
Good idea to deflate a bit for easy access thanks


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[calj737]

Is it possible after swapping caps, you have mixed up the plug wires/cylinders? If the plugs are wet, you’re getting fuel. Measure the voltage at the coils on the BLK/WHT wire with key ON, and bike set to RUN.

[Can550]

Is it possible after swapping caps, you have mixed up the plug wires/cylinders? If the plugs are wet, you’re getting fuel. Measure the voltage at the coils on the BLK/WHT wire with key ON, and bike set to RUN.

No I did not because I replaced one by one (what comes off gets replaced) plus there are numbers on each wire

I’ll look at the manual for measuring the coil
Thanks


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[Can550]

Points are gapped right @ .013”. Connections seem fine unless someone can see and spot anything wrong as spark is weak.



There’s an other point of concern. What is this (blue) splitter/ connector doing on coil primary black wire



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[calj737]

And the black electrical tape beyond it!!! Unwrap that tape and I bet you find a dodgy splice just twisted together 

[Can550]

And the black electrical tape beyond it!!! Unwrap that tape and I bet you find a dodgy splice just twisted together 

Thanks for replying
I shall unwrap tape and see what is hidden there. How do I clean it up and what is original set up ?


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[Can550]

At last Acc pump is fixed, please to see gas shooting out through the carbs (decent pressure). Just a question, cylinder 1,3,4 shoot gas towards the centre (whole in choke valve) #2 somehow shoots a bit towards right side wall of carb body but still within the carb slider area. Saw some plier marks on the jet ??

O ring between bowl and body had fallen out at some point in time which I didn’t realize, couldn’t find it after 2 hours of flashlight search so got few different sizes from local bolt store and one seemed just right. Prep for only about 4-5 times and there it shot very pleased
Now since carbs are off, will go over once again with carb cleaner.

Slow jets were pulled out and cleaned but when tapped back in, (1,2,3) they sit just a hair higher than the older marking whereas 4 got in all the way. Would it influence idle ?


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[Can550]

And the black electrical tape beyond it!!! Unwrap that tape and I bet you find a dodgy splice just twisted together 

Removed the electrical tape and factory bullet connector is there but no insulation sleeve therefore tape was used. I slid a shrink tube and shrank it to seal. One of the double female connector is broken (as seen in photo below thus PO opted for this splicer/ splitter.

After shrink tubing



Rust seen on ground post where coils are bolted, is it a concern and should I clean it off ?


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[BPellerine]

your acc pump should be ok now,wont matter if it is a little off to the side,if you are just starting the bike then shutting it down,you can foul your plugs,try cleaning them or have new ones on hand when you try to start it again.bill

[Can550]

Removed condensers and checked them with voltmeter. No reading at all. I tried to connect it with battery to see if will store any voltage but none. Both condensers show no reading. Meter setting I checked on all settings of resistance. Are these bad ?

There are 12volts on Black/white and yellow wires blue is ground ?

HT wires 1-4 and 2-3 show resistance/ continuity, guess that’s good thing


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[Stev-o]

Look here concerning your condensers...

http://forums.sohc4.net/index.php?topic=7850.0

[Can550]

Thanks Stev
I have a brand new Honda set (condensers and points on plate) somewhere and looking for that. Might as well put it on


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[Can550]

Is it ok to put cb550k (1976) plate+condensers and points, in cb750k 1978?
I got this one, recall had bought it for my 1976 550k and never used not sure if it will work on 750k ? As whole set or should I replace only condensers.



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[Can550]

your acc pump should be ok now,wont matter if it is a little off to the side,if you are just starting the bike then shutting it down,you can foul your plugs,try cleaning them or have new ones on hand when you try to start it again.bill

ACC pump/carbs were sitting out of bike for last few days. Had time to put them on bike earlier today. Got them up started bike ran very smooth and strong but acc pump jets were not squirting gas. Took them off and sprayed through, came out fine. Damn, realised had sprayed through brake cleaner instead of carb cleaner. Sprayed some wd40 thinking it may neutralise brake cleaner then sprayed carb cleaner but no pumping gas. Opened it up and plunger/ diaphragm was swollen and cracked in few places.



Now will have to order new diaphragm. Is there one standard size as I have read on forums stem being long and short.



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[Desert-SOHC]

Make sure the orings are centered, they can keep the squirt from happening too.

[Can550]

Thanks for reminding though I have been keeping an eye on this tiny o ring so that it is there when put back


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[Can550]

Got the diaphragm with new boot, spring and O ring. Put it back on and it sprays through all jets perfect.

Will sync carbs once again tomorrow


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