Honda "l'arancio dolce" CB 750 Resto-Mod Project

2_DONE_THE_TON

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Re: Honda "l'arancio dolce" CB 750 Resto-Mod Project

pidjones said:
And, if you have a leak on one of the cross-over tubes, you get to pull the rack and separate the carbs to fix it. Might be best to do all of that now.
Was thinking about that too....But since pulling these carbs was so easy (in comparison to my XS 750) I will risk that.Normally I would go all the way, but a good friend advised NOT and NEVER to split these carbs ;D

I have a question converning changing the oil on that bike:
SInce this is a dry sump is it possible to drain the oil fully without running the engine?...I read that there is a valve that shuts the oil supply when the engine is not running.
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irk miller

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This is a guide to totally rebuilding these carbs and separating the rack, but I wouldn't do it unless absolutely necessary. The throttle shaft requires a set of felt O rings that you'll need to get or replace with viton to do it.

http://forums.sohc4.net/index.php?topic=146893.0
 

chicagobob

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I got so fed up with the carbs on my '78 (and I did separate them during the rebuild) that I replaced them with a set of round-tops from a '72 (eBay and a rebuild kit). Very simple carbs to work on. I needed new boots, airbox and cables, but now, no more choke cable and easy bowl access without removing the entire rack. Bike runs like a champ.


 

2_DONE_THE_TON

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chicagobob said:
I got so fed up with the carbs on my '78 (and I did separate them during the rebuild) that I replaced them with a set of round-tops from a '72 (eBay and a rebuild kit). Very simple carbs to work on. I needed new boots, airbox and cables, but now, no more choke cable and easy bowl access without removing the entire rack. Bike runs like a champ.


Thank you!
That might be the way to go when everything goes wrong.The guy that owns the bike has a second doppelgänger bike with the same carbs so I guess that doesnt help.For now we´ll be cleaning them and then see how it goes.
 

2_DONE_THE_TON

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So guys-----
SUCCESS!!!!

We have spark!
I cleaned the points with some fine grit paper, puilled the clutch and off we go!!
Needs a new battery since the battery I used is the old battery of off my XS 750 produces not enough power to make a good spark.

So now I face a different problem.The carbs are stripped down, not split and theres this jet that is just stuck into the carb body (see picture).These jets are blocked on all 4 cylinders...theres no way to get these free.Where do these jets/orifices go?I would like to blow trough from the other side and see if it will work..Even a guitar string was useless.Should I remove these?

Thanks in advance!
 

irk miller

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Grip with with vice grips, twist and rock to get out. They'll come out. I would ultrasonic clean the carbs first, but if that doesn't work then they have to come out.
 

2_DONE_THE_TON

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Re: Honda "l'arancio dolce" CB 750 Resto-Mod Project

irk miller said:
Grip with with vice grips, twist and rock to get out. They'll come out. I would ultrasonic clean the carbs first, but if that doesn't work then they have to come out.
OK thank you.... Little anxious with these carbs :)

The electrical system seems to have hibernated in good condition. Just a few very rusted connections under the tank.
Had to weld a bolt onto one of the screws holding the coils in place :)

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2_DONE_THE_TON

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Ok so there is NO WAY getting these jets free whatsoever?They are seriously gummed up.Ultrasonical, carb cleaner, air no way, even getting them out was impossible.

For starters: Where do these jets go to?And what are they for?I cannot find any info on the net about these .
Maybe if I can find the "rear" part of this circuit I can blow or poke trough there....

I also cannot find these in the aprts diagram...can anyone point me out where I can find them in the diagram?

The other circuits and passageways are clean and show a good stream of carb cleaner when blown trough.Keyster kits are installed.

Thanks in advance for your help!
 

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irk miller

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Those are your pilot jets, so unfortunately they are hugely important. You can spend a few cans of carb cleaner and keep spraying them out and digging at the crap with an E string. They should come out, albeit very resistantly.
 

2_DONE_THE_TON

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More progress on the Cb....
We finally got the carbs cleaned and nearly ready for putting them back on the bike.
The pilot jets came out and all orifices and jets are clean and free.
We made sure that the pumper circuit was also free and clean.
We are missing a few little pieces and hoses but all in all we are good to go.
Next up is draining the old oil and changing the old oil filter before the first start.
Before we can start the bike we need to 'find a spark'.
It currently has no spark on all 4 cylinders.


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irk miller

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Awesome you got the carbs sorted. That is the biggest piece of hell working on these things. What have you checked for spark? If it still has stock ignition, don't overlook testing the resistor caps. I've gotten these after sitting for years, and all the plug caps were bad.
 

2_DONE_THE_TON

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Yes irk.... Thank you again for your help... The carbs were a piece of work and took awhile I'm happy that for now they are sorted.
We had weak spark a few days ago with a half good Battery... Tried with a new good battery no spark.
How do you test the resistor caps you wrote about?
If you mean the spark plug caps we will be replacing these and the ignition cables... Tried cutting away a piece but it didn't really help.

One interesting thing I found too today when I drained the oil... There is no other part in there than the oil filter. No spring, no washer like in my Yamahas...is this normal? Will be checking in the diagram later.



Thanks


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pidjones

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Re: Honda "l'arancio dolce" CB 750 Resto-Mod Project

Yes, the filter needs both the spring and washer they go over the bolt first with washer against the filter. The spark plug wires on these use a solid conducter wire with 5k ohm resistors inside each plug cap, and non-resistor plugs. The wires screw onto threaded (like course wood screw threads) posts on both the coils and caps to give good contact. The screw in the cap can be gripped with pliers and pulled out to permit cleaning the resistor ends and contacts, but the caps are still available (NGK) and fairly inexpensive. There are good step-by-step ignition troubleshooting instructions in the Honda FSM.
 

irk miller

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There should be an O ring and spring for sure. If this isn't a pure resto, you may want to consider getting the oil filter adapter so you can run a standard car type filter. It makes life way easier. You can get them with ports for adding and oil cooler too.

https://www.randakks.com/standard-oil-filter-conversion-kit-version-a-see-fitment-chart.html
 

2_DONE_THE_TON

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Looks like theres something wrong...maybe the police changed out the oil before it was hibernated wrongly....No spring no washer like in the diagram.And no copper washer under the drain plug...I ll talk to the owner about the spin on conversion! Do you have pics of the converted part on your engine irk?


Sounds very reasonable!Irk do I find the one with the adapters for the oil cooler also on this website?

thank you!
 

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irk miller

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TranceMachineVienna said:
Sounds very reasonable!Irk do I find the one with the adapters for the oil cooler also on this website?


You can see it in this pic of the whole bike.



I use the Wix filters because they're high quality and come with a check valve.
 

2_DONE_THE_TON

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For now we are keeping the stock oil filter system as it is...maybe a mod we´ll do later because the whole oil change is messy as hell!

Next up since the carbs look clean and ready is the spark.
This weekend I´ll be cleaning all plugs and contacts of the ingntion coils and cleaning the breaker points with some fine grit paper.
New spark plugs, spark cables and resistor caps will be mounted.

I also ordered new condensers and breaker points since the owner wants to keep the stock ignition and we will be having these as surplus.

Is there a method to measure the ignition coils and see if they are up to par?

thanks!
 

irk miller

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TranceMachineVienna said:
Is there a method to measure the ignition coils and see if they are up to par?
Set your multimeter to the lowest ohm setting (probably 200), touch leads against both wires to the coil. It can be at the bullet connectors, or at the coil itself. You should get 3 - 5 ohms. Stock is 5 ohms. Leave one wire in the connector, change the multimeter to 20k ohms, then put the other wire into the plug cap where the spark plug goes. You should see more than 10k, and preferably around 14k. If you get no reading, take the plug cap off and stick the lead into the plug wire and see if you get a number. No number with the cap probably means the cap is bad. You can test the caps for resistance by themselves, also. They should be around 5k ohms, iirc. When the go bad, they typically don't give a reading at all.
 

2_DONE_THE_TON

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irk miller said:
Set your multimeter to the lowest ohm setting (probably 200), touch leads against both wires to the coil. It can be at the bullet connectors, or at the coil itself. You should get 3 - 5 ohms. Stock is 5 ohms. Leave one wire in the connector, change the multimeter to 20k ohms, then put the other wire into the plug cap where the spark plug goes. You should see more than 10k, and preferably around 14k. If you get no reading, take the plug cap off and stick the lead into the plug wire and see if you get a number. No number with the cap probably means the cap is bad. You can test the caps for resistance by themselves, also. They should be around 5k ohms, iirc. When the go bad, they typically don't give a reading at all.
Thank you Irk for your insight!
I´ll be doing these tests tomorrow evening!

The oil sump got me on the wrong foot.
When I took of the oil sump there were bits of gasket and some hard pieces which I first identified as a circlip.I stored the pieces on a baggy and wemt to bed (I admit I had a few beers).
The next day I took the pieces put them into alcohol to clean them and suddenly I found out that the circlip come out to be a Oring... :D :D :D
The bike now gets an oil refill with a fresh filter (waiting for the missing parts that I wrote about earlier).
Hope to have here starting soon!
 
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