Where to Start-1979 750f Super Sport? Carb/Compression or both?

[Connella08]

you're welcome! if you have any uncertainty, post some pictures of the plugs or anything you find. pictures are worth 1,000 words.

 

[Hastings]

A somewhat unrealted question:
I was able to ride this bike 5-6 miles for the first time since I got it.
Overall ran well not great but well.
Never ridden a Honda CB anything before let alone a 750F (wasn't running when I bought it)
Definitely not a Road King
Seemed very torquey in every gear, I assume thats normal?

 

[Hastings]

Ok here are the pictures of the plugs.
Its starting and idling great.
But bogs down when I get on the throttle
I can hold it 80% open and eventually it seems it comes to life but by then I have run out of road in my subdivision so not sure
anyway I did check the boots on the airbox side and they were not sealed very good and did fix that, not sure it had anything to do with it.
Also confirmed the jetting is 68 and 88

 

[Loose Chain]

That is probably a 98 instead of 88. You could try upping that number to at least100-105. Here is a chart showing what carbs got which jets.

http://www.hondachopper.com/garage/carb_specs/carb_specs.html

 

[Hastings]

I also just did a compression test and all 4 cylinders are setting at 150 psi
I was able a couple of times to add choke when revving it and got it to go to 7K but it soon bogged back down.

 

[brettp]

Jets. I couldn't tell from your spark plug pics, but you're likely running lean.

 

[Loose Chain]

I also just did a compression test and all 4 cylinders are setting at 150 psi
I was able a couple of times to add choke when revving it and got it to go to 7K but it soon bogged back down.

Yes as Brett says, it sounds like it is running lean. Also have you got the floats adjusted properly?

 

[Hastings]

I did adjust the floats to spec and bench tested them
Here is a better shot of the plugs

 

[brettp]

Wow. Those don't look lean, with the obvious exception of the one that looks like it isn't getting fuel at all. Which you need to address.
Those are fairly dark; I wonder if those are actually rich! I would fix the fuel problem on that one carb first. Then see how she does.

 

[Hastings]

Yeah #3 needs attention. You think the 150 compression on all cylinders should be ok?

 

[Loose Chain]

The compression is good. That one plug tells the story.

 

[Hastings]

Thanks to you both, looks like I will pull the carbs again hopeully its the last time.

 

[Hastings]

I have pulled the carbs again and extracted the slow jet, I thought it would be clogged but it seemed to be clean.
That was the only jet left to clean.
Bought new slow jets, any tip to pressing it back in without dammaging them?

So I get fuel to the bowl, and all jets are clean, I can also tell the accelerator pump is spraying into each carb.
What is left to check with #3?

 

[brettp]

I have pulled the carbs again and extracted the slow jet, I thought it would be clogged but it seemed to be clean.
That was the only jet left to clean.
Bought new slow jets, any tip to pressing it back in without dammaging them?

So I get fuel to the bowl, and all jets are clean, I can also tell the accelerator pump is spraying into each carb.
What is left to check with #3?

Air Cutoff Valve (ACV). I think when they go bad, it will cause a rich condition.
Note, I didn't read back through this thread to see if that's been done.

 

[Hastings]

Ended up changing all slow jets and there was some improvements
What I have found is that both the coils are cracked I have ordered new coils and wires.
Would the bad calls have an effect on it reving smothly?
I did notice that some days it would rev well then the next just terrble

 

[brettp]

Yes, cracked coils could definitely cause problems. And throughout the rev range.

 

[kirky]

mine had a badly cracked coil and melted cdi's and was bogging out so i replaced them , nothing changed, the problem stayed the same, found out the main jets were far too big than the ones it came out of the factory with and that was the problem.

 

[brettp]

It does amaze me when people increase jet sizes thinking it will magically produce more power. But who knows, maybe they changed the air intake and made an adjustment. Then later put the stock air box back on. Who knows.

 

[Hastings]

Main jets are stock so hope these coils fix my issues.

 

[Hastings]

Replaced the coils and it runs a whole lot better, reving up nice.
So its my first real ride on the bike, and didnt really know what to expect.
Not very much torque ( I usually ride a Harely Dyna) and revs 4K at 60mph I assume all this is normal?