Tune up - Carb boot advise

[CR125Honda]

Dont think I've ever posted here so hello to all.

1974 stock CB750

I've had a slight hesitation from just off idle to a bit less than half throttle (1/8 to 3/8 ish) for a few years now. It's never been that bad but I'm bound and determined to correct it. Went through this about 8 years ago - replaced intake boots, cleaned & checked all passages, soaked the jets, check float height, adjusted valves, new points, plugs, condensers, etc.. Some of the mercury ran out of my sync tool (in a move) but there was enough to get a good sync up to half throttle. Seems like I couldn't get the engine running perfect in that range way back then.

So..... today I got motivated to pull off the carbs and give it another go.

As I pulled the carb rack, I noticed those new intake boots I put on back then, were relatively loose on the engine side. All would move up and down as I wiggled the rack to remove. Noticed staining on the engine metal lip on #3. Definitely had some leakage there. The clamps were tight but the boots are pretty hard now. Re-tightened the clamps after removing the rack and still have some wiggle.

Also noticed the rear boots (carb to airbox) pull out of the airbox really easy. It's not worn but the rubber lip that hold the boots in place are about the same size as the opening. Shrinkage ?

Plan is to buy all new boots, front and rear, check /clean the carbs & install new carb kits, and probably points, plugs, & condensers.

Anything I'm missing?

Not really on a budget but would like to get the OEM boots at a good price. I noticed a post or two recommending partsnmore in Canada. Checked their site and found they had a great deal on boots for the 78 model but didn't have any listed for a 74. Emailed them this morning, waiting to hear back.

Any other suggestions or links to online sites that have these parts at discount would be appreciated.

Regards, Ken

[CR125Honda]

[Piute]

   Very Nice Honda ! Honda !You meet the the nices people on A Honda Welcome
     O.K. now this "61" Shovel/Pan you have or had These bike I Do know(better the n CB750's)Shovelheads came out in 66 (84 last yr) Had the Annversary FXR(1st yr.5spd.,and rubber mont)Great bike.Tell me you still have it and cleaner the that "74"CB.Great combo,had a "84"CB650 with mine.

[shinyribs]

Vintage has them for $75. I dont know how that price lines up with Partsnmore.
http://www.vintagecb750.com/products/6/fuel-system/54/carb-holders

Welcome,and I think you win for coolest bike pic EVER!!! It looks great setting there!

[CR125Honda]

Thanks for the warm welcome, compliments and web site.  Much appreciated!!



Bought this CB back in 1990. First owner bought it and a CB550 for his son. Put 8K on it and parked it (them) for 10 years or so. Probably owned 10 of these (73 thru 76) in my younger years. Always liked them. This was a good find.  Only issue was when he pulled it out of storage, he put gas in it and tried to get it running without cleaning the carbs.  Blued the pipes a bit..





Built this one about 10 years ago. Again, Had one one these back in 78. Went thru AMI in Daytona in 78. Drove down in a Toyota pickup with a CB750, CB350 and 74 CR125 Elsinore to keep me happy while going thru school.  Traded them while I was there for a 1970 Triumph 650 and a pan shovel. Liked it but didn't really love it back then. Traded it for a 69 Roadrunner. Kicking myself for selling the roadrunner (Factory Dana 410 posi, 4 speed, 383 magnum, Holly & headers). Couldn't take it to college....

Anyway, built this one right. Complete overhaul, installed S&S high flow oil pump, Mallory electronic ignition, cycle electric generator, open primary, foot clutch & hand shift. Took me a little bit to cork up a tranny leak with a Jim's Super seal but since then it usually starts on first kick and doesn't leak ANY oil! I do really like this one and ride this and the Honda about equally.

Since you asked and I'm not to proud or paranoid to share..





Here's my 74 Kaw 750 H2. Almost embarrassed to say I've owned this since the late seventies and haven't done a thing to it (besides collecting the parts need to get it going). What can I say. Kids, family and work, quads and dirt bikes got in the way?  Not really. Took my Triumph down a few years ago  (powder coat, chrome, etc.) and it's been my focus lately. Hope to have it on the road this year.



Pic taken in late 70's



After frame powder coat a couples years ago..  Really sad not to have this one back on the road. Many fond memories on it. It's probably my favorite. Goal is to get it on the road by the end of summer. Just took a bucket full of nuts, bolts, axle, and misc pieces to Burbank plating in CA to have them Cad plated. They did a pretty good job and I'd recommend them but I have been dealing with excess on some of the threads. Bought a 26TPI tap set, still need to purchase a matching die set..

Love the classics! Got my eye on a 73 Norton Commando!

[shinyribs]

That is quite a collection you have! I love those old Triumphs. They have an awesome exhaust note to them. My dad started out on Triumphs like yours,but when he got his first CB750 he stuck with them. He still brags about the Triumphs,though. ''So much torque it would climb a tree if you could get it to stick to it''. Seriously ,I have been hearing that exact sentence for years now.

One time he went to the beach with some friends who all rode Harleys. One fellow was very proud of his Harley and also very irritated at my Dads filthy Triumph. He refused to ride with them until my Dad washed his bike and cleaned all the grease off the back tire!Dad refused to clean it and they all took off anyway. Long story short,the Harley died in the very early morning hours a few hundred miles from home on the way back in. It got towed by rope behind my Dad's Limey allll the way back home!Greasy wheel and all!

[CR125Honda]

YES! love the note this one put out!

It's had open MCM megaphones on it since I've owned it. Quite a bit louder than stock but I love it.
They've been out out business since the 70's I think but I did find a new set to put on it when I get it rolling.
Also found a new header pipe set and a new Corbin Gentry seat, exact replacements!

Two wires running up the frame, zenier diode, points, original Lucas headlight, Hepolite pistons, Manley stainless valves, etc.. Took good care of it and it never let me down. Only time I had to push it is when I ran out of gas..

[Jeremy]

Nice bike.

Sounds like your on the right track with your carbs.

[robs750]

I just bought some carb isolators on ebay for my sons '82.
They were Genuine Honda parts.Dont know if the early ones are the same.

[CR125Honda]

Update ---

Got the carb boot issue corrected. After removing everything. I found the intake boots to be good. They were hard but still pliable with a squeeze, no cracks, etc. Weird thing was, when I held the boots in hand and mounted one of the original 1974 clamps, I could pinch the clamp by hand and make the ends meet.. All those clamps "looked" fine (tangs not bent over from over tightening, etc.). Did they stretch with age or? The boots were not grooved where the clamps mount. Still has me a bit puzzled. Anyway, ordered a set of the superseded type. They tightened the boots with room to spare.
Carbs are now cleaned, mounted, ready to go..

 

While changing the plugs, decided to check the resistance of the plug lead resistor caps. Two came in spec (4.9 K ohms), one read somewhere in the 27 M ohm range and the last one was open.
So of course now I had to check the coils. Primary check, good. Secondary, not so much. With my trusty Fluke 77 connected, I'd watch the reading change from open to a constantly varying reading on all the plug leads. I can assume I had a weak spark at best. Really don't know how it was running as well as it did. Debated changing to a Dyna set up but it's just not in me to change my 37 year old friend from stock.

Searching now for a new coil set (30500-300-013). Spendy little guys. Retail around $225. Found them on Ron Ayers for $160. Will probably go with them.

Ken

[CR125Honda]

While I'm in repair mode...  



Can anyone tell me what these two wires are for?
Neither has been connected for 20+ years.

The solid red wire is connected in the hot lead from battery to starter solenoid.
The green comes out of the wiring loom running along the frame rail.

Both are original. No splices, etc..
Reviewing the Clymer wiring diagram didn't do me any good..



Pic showing location of green wire in loom and red on hot lead.





Ken

[CR125Honda]

Digging around, I found a pic of the wiring diagram for a K4 posted by Re-run on this site.
I've never seen this wiring diagram in any manuals I have or elsewhere before.

Look at the "winker relay" and "starter magnetic switch" in the pic below (Right side - top & bottom).

Clearly shows the green and red wires I had in question, not connected to anything..  Amazing!!

Link to the pic if the one below is too small. K4 wiring diagram



***************************************************************
Update..

After seeing that wiring diagram pic and wondering where it came from...  I got to thinking.

Popped open the lid under the seat on my bike and took a look at the little owners manual.
Tucked inside was a fold out of the same wiring diagram..  Been sittin on it for 20 years!  

[CR125Honda]

Ok.... I caved.. Change can be difficult for me sometimes.

Ordered a Dyna S kit from World ATV (seller on eBay). ph. 1-[phone]
Spoke with him on the phone a few times before making the purchase.
He didn't have a specific kit listed for the CB750 but put one together (Dyna S, 5 Ohm coils, and Dyna 8mm wires).
Best price, authorized dealer, very knowledgeable /personable, and has been in the game for a long time (draggin CB750's since 1972).

I usually don't post business plug's but after our talk's, I have no problem recommending him.

[shinyribs]

I appreciate the plug. It lets us know who is good to deal with,and who to shy away from.