Topic: 1978 CB750F3 rebuild start

[majorzozo]

No cleaning at all just sent him the pipes minus the 3 clamps as is and 5 weeks later he sent back.  They were badly rusted and pitted.  Guys name is Dennis.  The whole reason I posted is because I could not find  anyone who would plate an exhaust so I wanted to share with others who may want some exhaust plating done.

[HondaMan]

Nice job on those pipes! The last ones I had done in PA cost 3x that much.

[grcamna2]

Great work all the way around 'majorzozo'. 

[Ozzybud]

No cleaning at all just sent him the pipes minus the 3 clamps as is and 5 weeks later he sent back.  They were badly rusted and pitted.  Guys name is Dennis.  The whole reason I posted is because I could not find  anyone who would plate an exhaust so I wanted to share with others who may want some exhaust plating done.

I just got off the Phone with Dennis. shipping my double wall CB400f Pipes this morning  $450 + shipping 4-5 week  turn around!

As my new repops are already tuning amber

Thank you majorzozo

[grcamna2]

No cleaning at all just sent him the pipes minus the 3 clamps as is and 5 weeks later he sent back.  They were badly rusted and pitted.  Guys name is Dennis.  The whole reason I posted is because I could not find  anyone who would plate an exhaust so I wanted to share with others who may want some exhaust plating done.

I just got off the Phone with Dennis. shipping my double wall CB400f Pipes this morning  $450 + shipping 4-5 week  turn around!

As my new repops are already tuning amber

Thank you majorzozo

I want to know more ! 

[Ozzybud]

No cleaning at all just sent him the pipes minus the 3 clamps as is and 5 weeks later he sent back.  They were badly rusted and pitted.  Guys name is Dennis.  The whole reason I posted is because I could not find  anyone who would plate an exhaust so I wanted to share with others who may want some exhaust plating done.

I just got off the Phone with Dennis. shipping my double wall CB400f Pipes this morning  $450 + shipping 4-5 week  turn around!

As my new repops are already tuning amber

Thank you majorzozo

I want to know more ! 

Maybe Start a new Post in The General area so more people see it?(inexpensive down pipe re-chroming) After reading about it yesterday when i went to find it this morning it was very difficult to find again. And since The Subject does not mention it the search function couldn't find it.

[SOHC4 Cafe Racer Fan]

Your bike was nominated and seconded for Bike of the Month, but you need to post that you "accept" the nomination in the following thread:  http://forums.sohc4.net/index.php/board,54.0.html

[newday777]

Thanks all for the kind compliments.  I finally found a chrome plater who would do an exhaust.  Pacific plating in Santee Ca did my headers and collars.  Pricey at $450 but they were absolutely wasted and they came out like new.  The muffler was not chromed but I had to have the forward end bottom welded as it was rotted out.  The Delkivic I had was too loud for my old wrinkled --- and this stock set-up is much quieter.

Still fighting to get my carbs perfectly tuned but slowly gaining on it...

How is it running now? And how are the temps while running? What are your ambient temps there now, cooling down yet? I moved back to NH but remember the temps there having taken rides on my goldwings out through Indio on occasion while living in Oceanside.
It's been a while since you replied, are you doing OK?

[majorzozo]

Hi Newday.  When the bike is warm it runs great.  While warming up the throttle hangs a bit.  It drives me crazy as I have tried everything.  Thinking it may be an intake leak I tried the clamps that Hondaman suggested.  I replaced all the felt seals again.  I trimmed the advancer springs.  I installed a new stiffer accellerator pump spring as the stock spring would just not provide enough squirt.  Trimmed the spark plug leads.  Straightened the advancer shaft. Replaced the main and pilot Jets with genuine Keihin from JetsRus (105 mains and 35 pilots).  Completely disassembled and cleaned the carbs at least 3 times.  Timing and vacuum sync are dead nuts.  I guess I just have to live with the fact when cold it just doesn't behave but when warm it runs great.  Takes about 5 miles to warm up.  Maybe it is a symptom of unleaded gas.

Here in Indio it has been too hot to ride.  Today will be the first day below 90 degrees and later in the week it will get down to the 70's.  Perfect for riding.  The bike still seems to be running hot I think but nothing to compare too.  With a heat strip on the valve cover it indicates about 180 degrees or so around town and when idling at a stop light it shoots to around 200 degrees.  No noticeable leaks yet but still only about 400 miles on it as life seems to be getting in the way of more riding.

Thanks for reaching out and yes I constantly peruse this sight.  I read you are restoring an 'F" and would love to see pictures.  All the best...

     

[denward17]

major,
My '78K is cold natured as well.  I have to use the choke set at about ~3/4 closed for the first mile or so.

Bike is looking great!

[majorzozo]

Hi Denward.  What drives me crazy is not the cold blooded nature but the hanging idle during the warm up.  When cold, two throttle twists, full choke then it starts right up and idles around 1800.  When I advance the throttle when cold it sticks at around 3000.  The fast idle cam has no affect when cold and it is adjusted correctly. I play with the choke until warm then drive off.  After about 4 or 5 miles I completely remove the choke and it runs great most of the time although some times the throttle continues to hang.  When it is warmed up the fast idle cam works perfect.  What i cannot figure out is why when cold does the idle hang and when warm it does not.  Just doesn't seem right to me.  The PO had jacked up the #1 carb slide so I had to file quite a bit to get it to operate smoothly so maybe that may have something to do with it.

By the way your 550 and 750 are beautiful.  Great job...       

[newday777]

I woke up early again this morning...had to pee....the brain wouldn't shut down to get back to sleep so I reread this whole thread again as I just bought a 78F on Saturday, so I have another project..... I drove the minivan over to Schenectady NY to get it, the round trip was @ 7 hrs. That was the furthest I have driven to get a 750(and paid more to get). It sounds good, albeit needs carbs cleaning and leaks a bit.
Again , you have done a fine job with your bike! And set the bar high for me. I noticed that you didn't post(or I missed them??) before pictures of your bike in the beginning of the thread. Do you have any?
Sorry that you have the running problems still. When cleaning the carbs, did you clean the accelerator pump circuit? There are some great threads on cleaning the PD carbs. I haven't completed a set yet, jut the roundtop carbs of the early 750s.
This thread is on cleaning the 78F PD carbs in detail, did see this and use it when cleaning your carbs?
http://forums.sohc4.net/index.php/topic,48858.msg515204.html#msg515204

[majorzozo]

Unfortunately I do not have many before pictures.  A few below.  I picked up the bike in Santa Barbara that was being stored outside under a tarp.  Everything was rusted bad as you can imagine.  Yes I have read the post on PD carbs many times and found it very useful when reassembling.  I have done it so many times that I am embarrassed to say that I can now hook up the choke shafts  springs without viewing (LOL).  Madmtnmotors description and pictures helped tremendously as well.  Note the very soft metal of the carbs has required several heli-coils.     

The accelerator pump has been replaced twice and I have spent a lot of time on the spring associated with the pump at the top of the carbs.  My stock spring does not provide enough squirt in other words when the throttle is rotated the pump linkage lags as it doesn't immediately follow the throttle to the stop.  I replaced the spring with a stiffer one obtained from Ace hardware and now it immediately follows the throttle and a good squirt is evident when viewing with the airbox off.  When you get your tank off you will see what I mean when operating the throttle. 

Yesterday I adjusted the air / fuel screws to 2 1/8 and the bike runs better.  While warming up the throttle still hangs a little but when warm all is well.  Strange to me but at this point I think I can live with it as once warm all is well.  If you need any specific pictures or videos while you are working your project, please reach out and good luck.  Will be following.         

[HondaMan]

You've done a beautiful job with this bike!

About the carbs:
since you've described that the needles in the slides need 3 shim washers to even get close to correct performance, this indicates the brass inside (at least those needles) are Keyster parts, not Keihin parts. The OEM Keihin idle jets for the PD42B series carbs was/is #35, and the mainjets were #105 if the bike was sold in California or New York/New Jersey or #110 if outside there.

If the jets are Keyster jets, they would require the numbers be #38 idle and #115/#120 respectively. This would help to drop the choke sooner while warming up.

Also: today's gasolines burn MUCH too slowly when compared with the 1978 fuels the bike was designed to drink. Our modern Regular grade burns at about the same speed as the 1970s era Premiums did, so try using Regular gas to see if it settles down sooner after cold start, and it should also run cooler. When the fuel is still burning as it exits the head (i.e. too much octane in today's numbers) it puts a lot more heat into the front of the engine, which slowly transfers throughout.

Also: if the idle jets are Keyster jets, then the adjustment range of 1.5 to 2.5 turns of the low-speed mix screw will end up being turned further out to get enough fuel to let it run well at idle when hot.

[majorzozo]

Thanks Hondaman,

Sure enough i didn't change my slide needles, only my pilots and mains.  I will try the gas and order some needles from JETSRUS and give it a go without the shims.  Getting close, hahahaha.  Thanks agian,