Topic: What a Day! ... and Question on Carbs

[Imago]

On this unseasonably warm day in Saskatchewan I just had to start work on my new (to me) 1978 CB750F.

I got it out of the garage and running great on all 4 cylinders (each exhaust header hot to touch), but it won't idle without stalling unless the choke is pulled pretty much all the way out.

I need to replace the choke cable (which I have - new OEM Honda), change the oil and get a new battery as I was boosting it... off to Canadian tire for the battery... any recomendations on oil?

What first re: the crappy idle... carbs?

I'm thinking the slow jets are plugged... do my symptoms describe this condition, or is there something else I should look for?

If so, is there a link to a carb cleaning thread for bikes with accelerator pumps? I searched, but haven't found anything definitive.

What a day!!!   

[Stev-o]

That is my first thought, clogged jets. If you haven't done so, you really should give it the full 3000 mile tune up (plugs, points, condensers, time and valve adj). And change the plug caps too.

[Imago]

...and another question... is the 3000 mile tuneup information in the shop manual (which I have but for this year jumps from 600 to 3600 miles) or in a dedicated link here somewhere? I've searched, and seen many references to it, but...

[harisuluv]

I see the stock airbox on the 78 in the picture, is that still the case?  If you went to pods or have the airbox off it could do the same thing.

[Imago]

Yes, it's stock. I took the photo this morning right after I got the '78 started.

Unfortunately the yellow '76's engine is stuck. That's my next project starting with the ATF/Acetone de/un/sticker.

[Greggo]

Those Henry Abe wheels on the yellow bike?

[Imago]

Those Henry Abe wheels on the yellow bike?

Yup, a 19" front and 18" rear. I was happy to find this bike recently in Saskatoon. The PO over-rev'd the engine passing a truck and a valve hit a piston... so I've got a bit of work to do on this one! He said he drove it home and it froze sometime thereafter, but I have yet to open it up to see how bad it really is.

[Greggo]

Nice.  Of the sets I've seen go for sale on ebay, most went for nearly $1K, and were sold to buyers in Japan.  Great find!

[kap384@telus.net]

On this unseasonably warm day in Saskatchewan I just had to start work on my new (to me) 1978 CB750F.

I got it out of the garage and running great on all 4 cylinders (each exhaust header hot to touch), but it won't idle without stalling unless the choke is pulled pretty much all the way out.

I need to replace the choke cable (which I have - new OEM Honda), change the oil and get a new battery as I was boosting it... off to Canadian tire for the battery... any recomendations on oil?

What first re: the crappy idle... carbs?

I'm thinking the slow jets are plugged... do my symptoms describe this condition, or is there something else I should look for?

If so, is there a link to a carb cleaning thread for bikes with accelerator pumps? I searched, but haven't found anything definitive.

What a day!!!

Sounds exactly like mine.  Make sure slow jets and pilots are clean.  Check out the video and write-up on this page:


http://forums.sohc4.net/index.php?topic=66779.50

[kap384@telus.net]

On this unseasonably warm day in Saskatchewan I just had to start work on my new (to me) 1978 CB750F.

I got it out of the garage and running great on all 4 cylinders (each exhaust header hot to touch), but it won't idle without stalling unless the choke is pulled pretty much all the way out.

I need to replace the choke cable (which I have - new OEM Honda), change the oil and get a new battery as I was boosting it... off to Canadian tire for the battery... any recomendations on oil?

What first re: the crappy idle... carbs?

I'm thinking the slow jets are plugged... do my symptoms describe this condition, or is there something else I should look for?

If so, is there a link to a carb cleaning thread for bikes with accelerator pumps? I searched, but haven't found anything definitive.

What a day!!!

Sounds exactly like mine.  Make sure slow jets and pilots are clean.  Check out the video and write-up on this page as I think it's what you're describing:


http://forums.sohc4.net/index.php?topic=66779.50

[Bootlegger56]

My K5 had been sitting for an extended period of time when I rescued it.  I had the same problem with idle.  Even though I disassembled and cleaned the carbs, tank and low speed jets (e-string) it continued to die on idle.  I must have pulled the bowls and cleaned them and the jets about half a dozen times before they stayed clean.  In retrospect; I believe that my continued problem was the result of sediment that was trapped in the fuel lines from the petcock to the carbs which I failed to clean initially.  I learned on that one....next time I will make sure of the lines as well.