Topic: Slowly - CB650 Custom 1980

[Azzarius]

Hi Everyone,

Here is a quick update following the new jet installation.  It starts but as explained above, the #2 and #3 Cyl exhaust stays cool (they warm up over time but likely through convection from the engine warming up).

cheers

[Azzarius]

Hi Everyone,
So I did swap the spark unit in the hope that the problem would follow the.  So Originally it seems that the bike only ran on cyl#1 and cyl#4 as these were the only hot exhaust.  Now after the swap I was hoping for cyl#2 and cyl#3 to work.  .... No.  It seems that Cyl#1 and cyl#2 are the one working and 3 and 4 stays cool.  So what's next ?  may be bad connection to the spark unit. else ?  I'm a bit confuse now. 

cheers

[CBJoe]

What do the plugs look like? Are they wet with gas or dry? 

[Azzarius]

Hi CBJoe,
I've connected the spark unit the way they ware originally connected.  So cyl#1 and cyl#4 were getting hot and #2 and #3 were cold.  Then I removed the plug and took pictures.  It seems that #1 and #4 were dry(as they burned the fuel) and #2 and #3 were wet(so fuel does get to it).  I still suspect a problem with the spark unit.  Your thoughts guys ?

cheers

[CBJoe]

Hi Everyone,
So I did swap the spark unit in the hope that the problem would follow the.  So Originally it seems that the bike only ran on cyl#1 and cyl#4 as these were the only hot exhaust.  Now after the swap I was hoping for cyl#2 and cyl#3 to work.  .... No.  It seems that Cyl#1 and cyl#2 are the one working and 3 and 4 stays cool.  So what's next ?  may be bad connection to the spark unit. else ?  I'm a bit confuse now. 

cheers

So you've ruled out the coil by swapping.  Can you confirm what you stated here after you swapped the igniters (spark Units)?  When you swapped them, did the situation really change to 1&2 working and 3&4 Cool or did it stay the same? 

Have you inspected the wiring between the Pulse Generator and the igniters?  It may be that you have a bad pulse generator where one of the pulsers isn't working.

Joe

[CBJoe]

My money is on either an issue with wiring between the pulser unit and the igniters or a bad pulser.  If you have a multi-meter I would ohm out the wiring to be sure you don't have an obvious issue with corrosion or a connector.

[Azzarius]

Hi Everyone,
So I did swap the spark unit in the hope that the problem would follow the.  So Originally it seems that the bike only ran on cyl#1 and cyl#4 as these were the only hot exhaust.  Now after the swap I was hoping for cyl#2 and cyl#3 to work.  .... No.  It seems that Cyl#1 and cyl#2 are the one working and 3 and 4 stays cool.  So what's next ?  may be bad connection to the spark unit. else ?  I'm a bit confuse now. 

cheers

So you've ruled out the coil by swapping.  Can you confirm what you stated here after you swapped the igniters (spark Units)?  When you swapped them, did the situation really change to 1&2 working and 3&4 Cool or did it stay the same? 

Have you inspected the wiring between the Pulse Generator and the igniters?  It may be that you have a bad pulse generator where one of the pulsers isn't working.

Joe

Hi CBJoe,

Here were the facts with original connections:
 - Cyl 1 and 4 exhaust were getting hot
 - Cyl 2 and 3 exhaust were staying cool.

So my assumption on the possible culprit:

• Or one of the coil was bad.  I do have one that is slightl crack, so that could be it
• I thought that the spark unit could have been the issue.  These two unit had their black goo melted.  I've replaced it with epoxy but still these, that would just fix the goo coming out not necessaily it functioning or not.
  

#1
In swapping the coil, if the coil was to be problematic, the problem should follow the faulty coil.  In My case swapping the coil didn't do anything.  The issue remained on the cyl 2 and 3.  cyl 1 and 4 were still becoming hot and the other staying cool.  Thus eliminating the possible faulty coil.

#2
In swapping the spark unit, same reasoning, the problem should follow the faulty spark unit.  Swapping them gave me a different result, but not the expected one.  It seems that cyl 1 and 2 are the one working and cyl 3 and 4 stayed cool.  Which is very confusing as you would expect either 1-4 or 2-3 not to work.  But now there was one working on each spark unit.

So to answer your question after swaping the spark unit, with the coild in their original position, 1 and 2 were working(getting hot) and 3 and 4(staying cool) weren't.

Check the wiring and all seems ok.  I also did a follow the test from the Claymer and from another place on the web to test the coil.  All of them seems ok beside the strobe test(I don't have a strobe light).

I've checked the pulse generator.  It was a bit rusty but almost moving freely(some grinding feeling). With some wd40 it was moving free and nice.

Now there are surely a problem since it seemed to move the issue when I swapped the spark unit.  When I put back the carb and all I haven't sync the carb with a vaccuum gauge nor check the compression on cylinders.  Would any of these could pojnt to a better diagnostic?

thnx
Cheers

[Azzarius]

My money is on either an issue with wiring between the pulser unit and the igniters or a bad pulser.  If you have a multi-meter I would ohm out the wiring to be sure you don't have an obvious issue with corrosion or a connector.

Hi CBJoe,
For this one I've buzz the cable it seems that I have continuity everywhere.

Cheers

[CBJoe]

I'm as well baffled a bit by the results of switching the igniters.  Hopefully someone else will chime in with some thoughts.

I know you said that you started this project off with a charging issue...do you know if it was running on all 4 cylinders then? 

[Azzarius]

I'm as well baffled a bit by the results of switching the igniters.  Hopefully someone else will chime in with some thoughts.

I know you said that you started this project off with a charging issue...do you know if it was running on all 4 cylinders then?

Hi CBJoe,
I cannot tell for sure, but I ride that bike for almost 1.5 year and it did run smoother than it runs now.  I'm assuming the roughness comes from it running on only two cyl.

cheers

[Azzarius]

Hi Everyone,

Flasher

Here was the next issue encountered.  The flashers.  Once I plugged everything back I've tested that the flasher/brake light, etc ... were still working.  I realised that the flasher would light up but stayed lit instead of blinking.  I've worked back to the little can that makes the flasher blink.  I've opened it see it was working with little help so I assume that the capacitor was likely dead.  Anyway, when I've plugged my new LED flasher, they weren't working at all so I would have had to change something.  Digging in my school memory, I've remembered that LED work on current and not on voltage.  So I got my electronic kit box and started trying different resistance.  With about 100 ohm I have able to get the LED flashed to properly light up.  Still I had to changed the flashing unit so I bought(haven't received it yet) and 2 pin Motorcycle Electronic LED flasher relay.  They says that it would work with LED flasher.  So once I receive it, I will be able to complete the flasher installation.

Needless to say that got rid of the ginormous original flasher and tail light and replaced it with smaller bullet like flasher.  I will post some pics once I finalise the location for these.

Cheers

Flasher Part2


So here it is.  Since I'm a bit stuck with the engine, I've move the other area along as I've received my part for flasher and rear light.  I've bought a new flasher unit from the ebay, you can see in the pic the model(5-10$).  I also bought a LED rear brake light with embedded flasher.  I might plug the flasher part of the LED strip but I will stiull install my bullet flasher.  I was very sad (exactly 4.74$ sad) to find out that some of the LED don't work (I will have to order a new one and wait another 2 months ).

Anyway, I will still put it on in the mean time. So that should allow me to put the bike on the road.  For the flasher, I had to make some bracket to install them where I wanted them to be.  You can see the two bracket I made.  For the rear one, I've used the braket to hold the license plate as well.  Now it might not be the final version as I find the rear flasher to be too far away back and looks funny(ugly) to me.  I will try to build separate bracket that will attach just behind the rear shock on the fender.  I already have filleted holes there.

Cheers

[purplechickenweasel]

Have you tried unplugging all the connectors involved with the ignition system and cleaning them?
My last electrical problem was before i sanded all the connector plugs, and filled the connectors with dielectric grease. Also sold as bulb grease.
Water was getting into a connector and it would run on 1 , 2 , or 3 clyinders. Depended on how  long the puddle was.

Your cylinder coldness pattern seems odd.
If you have a air compressor take your pods off, and blow air down the small air tubes in the Intake bell of each carb.
You do not have any diaphragms in your carbs so you shouldn't damage anything.


What colors are you going to paint it?
Looking like a good project so far.



Pcw

[Azzarius]

Hi Pcw,
Indeed the pattern did threw me off as well.  I was betting so much on the problem being one of the spark unit, that when the supposedly dead one worked on 1 cyl, I started doubting what I did.  I will still redo the whole testing as even now it doesn't make sense to me. 

I will ensure thought to sand(remove any rust/verdigris) on all connector, hope that will fix the problem.  If it doesn't I will try to use parallel wire to ensure that it is not a bad wire somewhere.  I did already buzzed all of them and they all came out ok, but still, these are ~35-40 y/o wires.

As for the color, I want the tank to be beige or green.  I found the color I want, it going to be either the Fiat 500 beige or the Subaru green.  But so far the beige seems to be winning for me.





Cheers

[SOHC4 Cafe Racer Fan]

I think Subaru calls that color khaki.

[GV1390]

I really dig that Subaru color! Although I rather rock an "Italian" manufacturers color if I had the choice!

[Azzarius]

Hi Everyone,
Engine compression

I have, what appears to be a bad news(actually 4 of them).  I bought a compression gauge and read the compression on all cylinders.  This is what I got for reading.
C1 - 95psi
C2 - 90psi
C3 - 90psi
C4 - 90psi
As per the bike's manual, I should have 170 +- 28psi, so I am about 50psi short of where it should be.  What's next ?  Really what's next ?  How do I fix that ?  Where that low compression comes from.  Valves that are not seating properly ? bad head gasket ? bad piston rings ?  From you experts out there, what would be your approach to address the issue ?  What are the most likely cause so I can try to fix the usual suspect first before going into the dark, twisted one of issue.

Also, I starts sometime, but not all the time, and it is very hard, it takes a whole full battery and sometime a boost from another bike.  Would it run with a lower compression ?  Is that a reason for it being super hard(near impossible to start ?)

cheers

[SOHC4 Cafe Racer Fan]

Hi Everyone,
Engine compression

I have, what appears to be a bad news(actually 4 of them).  I bought a compression gauge and read the compression on all cylinders.  This is what I got for reading.
C1 - 95psi
C2 - 90psi
C3 - 90psi
C4 - 90psi
As per the bike's manual, I should have 170 +- 28psi, so I am about 50psi short of where it should be.  What's next ?  Really what's next ?  How do I fix that ?  Where that low compression comes from.  Valves that are not seating properly ? bad head gasket ? bad piston rings ?  From you experts out there, what would be your approach to address the issue ?  What are the most likely cause so I can try to fix the usual suspect first before going into the dark, twisted one of issue.

Also, I starts sometime, but not all the time, and it is very hard, it takes a whole full battery and sometime a boost from another bike.  Would it run with a lower compression ?  Is that a reason for it being super hard(near impossible to start ?)

cheers

I'll let more experienced engine builders chime in, but this may have been avoided by lapping valves, installing new valve seals, piston rings and light honing as previously suggested. 

[rb550four]

Bummer.
CB750 Cafe Racer Fan speaks the truth.
 That's what I was getting at on post 19 of this thread.
You have come a long way,learned much ,Grasshopper , but there is more to learn.
This is the part where you do it twice and you will  learn the valuable lesson about letting the unknown parts slide( like new rings ,honing, valve seals and lapping , That kind of stuff)
  Aaaaand as an added bonus. once you rebuild this engine again, it will be imprinted in your mind. There will be only a  few things about the 650, that you may need the manual for after that.
  It's all fun. Nothing wrong with a do over, so long as you get it right .So when you gonna start?

[Azzarius]

Hi Everyone,
Now that I am there, I think I will just roll into a ball on the floor a weep away... I think to only thing I really dread is getting the engine off and on again.  That is the most painful thing I have to deal with on this bike(that's not counting all the scratch that I did on the new paint in doing so).  So much so that I will see if it is even possible to do it(change the gasket and get the head off) without getting the engine out.  Worst come to worst I will have to take it out.  If I'm lucky, I might get away with the engine still on(but I have some doubt, the room between the frame and the top of the engine is very minimal).

I've read a bit on compression, an one was suggesting to put a spoon full of oil and to redo the compression test.  If the compression is better, then focus on changing the ring, if not, focus on the valves.  So before anything I will do that simple test.

Cheers

[scunny]

head and cylinders can be removed and replaced in the frame on the 650.

[SOHC4 Cafe Racer Fan]

head and cylinders can be removed and replaced in the frame on the 650.

Yes, you can do a complete top-end rebuild with the bottom of the engine remaining in the frame.

[scottly]

Hi Everyone,
Engine compression

I have, what appears to be a bad news(actually 4 of them).  I bought a compression gauge and read the compression on all cylinders.  This is what I got for reading.
C1 - 95psi
C2 - 90psi
C3 - 90psi
C4 - 90psi
As per the bike's manual, I should have 170 +- 28psi, so I am about 50psi short of where it should be. 

Some compression gauges will read much lower on these small motors. Since your readings are very close across all four cylinders, and it is running on two of them, the top end is most likely not the problem.
You need to verify if you have spark on 2&3. Pull the spark plugs and lay them on the head while cranking the motor. Also, note the condition of those two plugs: are they black and sooty, or clean and wet?   

[Azzarius]

Hi Everyone,

Engine compression

So I did one test that I've read somewhere.  i.e. to as a spoon full of oil in the cyl.  and redo the compression test.  So on Cyl #1 i got 100psi instead of 95psi.  So I assume that based on the result that the loss of compression at the piston/rings level is minimal and that the rest is lost at the gasket or valve level.  So I will remove the head, change the gasket and lap the valve. 

Cheers

[rb550four]

What? Why would you assume that it 's the head gasket or just the valves?
Do you have blow by at the gasket level?
Did the valves look like they wouldn't seat properly when you had it apart last time?
And why would this 5 psi upgrade result cancel the need for a hone and rings?  You are still  70 lbs light on all cylinders.
  I know $ is always an issue for everyone, but, if this is still a failure , you will still be into $100 worth of new gaskets( throw the old ones out) .... and all your time.
  Please, you've done so much work, it's coming out great, don't cheap out on this, you'll only be doing it again.
 Go the extra  this time, take nothing for granted, get it right  and ride the hell out of it next season.

[Azzarius]

Hi rb550four,
 
Not sure I understand what you say.  Are you saying that new gasket and lapping the valve will be enough or not?  If not, what else can I do?  I could change the piston ring too, but they were nice and even, no wave in them, not sticky nor closed(they were still springy to open).

As for the first question, yes, it looks like I have a bit of oil coming out from the right side between the cylinder block and the block that contains the valve.  When I started the engine one day I gave it a good go.  I saw some exhaust fumes coming out of there, these is definitively a too old gasket there.

I never, took the valve out.  I clean the part with the valve as good as I could, but didn't removed the valve.

cheers