Author Topic: 1975 CB750 Build! "Kona" - Sold and gone. (Read 69541 times)

edwardmorris · « **Reply #450 on:** March 20, 2016, 08:28:03 PM »

Out makes it rich, in makes it lean, but the air screws' working range is only between 11/4 and 3/4 turns, no effect after that when controlling the mix. Type up ALL the carb info here, lets get you sorted out

Carb body numbers (later EPA crud carbs work differently than the early ones)
Air screw type (solid/holed)
Air filter kind (choked up stock/EMGO or free flowing K&N)
Needle position
Baffled/Open/Semi-baffled exhaust
Stock coils?
Standard or hotter plugs?
Anything I missed?

Ravie · « **Reply #451 on:** March 20, 2016, 08:36:08 PM »

657B
Holed
Emgo
2nd from bottom
Semi-baffled. I've drilled it much bigger than it was. I can get a pic up if necessary.
Dyna 5 ohm coils with their standard copper wires and brand new NGK resistor Caps
D8EA plugs
110 Mains
40 Slows

Davez134 · « **Reply #452 on:** March 20, 2016, 08:41:18 PM »

I'm sure that turning mine out leaned out the idle circuit. Both by symptoms and plug color

edwardmorris · « **Reply #453 on:** March 20, 2016, 08:44:07 PM »

Needle clip needs to go up a notch (to the middle one) to lean it out some more. That's what I'd start with, you may not even have to drop to #38 idles after that, but lets see.

@Davez, mine did/do the opposite, but mine are the early 7As, before all the EPA crap got in there...I'll have to dig up the post about that setting again, maybe tomorrow

edwardmorris · « **Reply #454 on:** March 20, 2016, 08:49:28 PM »

My convo with our well known legend

The description of idle shift with temperature matches a too-rich scenario. Remember this: despite the posts you read in the forums, these carbs are LEANER when the screw is turned inward, RICHER when out. The trouble with most people's "diagnosis" comes when the hoses are leaking vacuum: then they get past the 7/8 to 1-1/8 range of the screws. Once that happens, all bets are off: the whole range of these air screws is 3/4 to 1-1/4, after which the whole system goes dead rich for lack of vacuum control (beyond 1-1/4) or air availability (pinched off below 3/4 turn). This has always seemed to confuse everyone. So remember: 7/8 to 1-1/8 turn, and if you are outside that range, you need a different idle JET to get you back into that narrow range. (This is the foible of simple carbs like these, with no moving parts!)

Ravie · « **Reply #455 on:** March 21, 2016, 08:02:19 PM »

I have to admit, I'm a bit tired of working on it at this point.

I will get the carb rack off sometime in the next week or two. I got the new front forks together and installed and got the front end back together this evening. Decided to start the bike and waddaya know, number 1 isn't firing. *huge eyeroll*

Pardon my stupid question but - if my issues seem to be idle and off idle, why do you think I should bring the needle up to the middle position? Doesn't that mainly just affect the higher ranges? I will do so, I'm just curious.

As a side note - I've noticed a lot of pressure building up in the oil tank. Like, so much that I can hear air seeping past the cap seal when I turn the bike off and if I open the cap I get a similar sound to opening a pop bottle...so there's a decent amount of pressure there. Why is this happening? I can guarantee you I made sure all of the passages in the tank were free and clear when I cleaned it.

Ravie · « **Reply #456 on:** April 02, 2016, 02:57:33 PM »

Okay. A fellow Corvair guy got me motivated to get out and get on the bike stuff. I pulled the rack off, raised the clip to the middle position (was 2nd from bottom), rechecked the float heights (Because....I realized after RTFM that I've been setting them incorrectly and they were all several millimeters off), pulled the plugs and cleaned them all (saving the new ones for plug chops). I also installed two small clear fuel filters with bronze filtering stones in them in each line from the petcock to the carbs (I was getting sediment in the bowls and I think that was key in my floats not always closing the needles). I also used some good band clamps for the carb side of the inlet rubbers because the CruisinImage ones were stripping with any amount of force..

While I was at it I drained out the 10W40 I've been using for tuning and break in (not much breaking in as the cylinders/rings were about all that got brand new parts) and switched over to some 20W50 Honda 4 stroke moto oil (just conventional for now)

Got it all back together and started her up and BOOM! HUGE (or as Trump would say YUGE) difference. It'll now rev up to 7k without any problem. It struggled to do that before. It was still a bit rich at idle so I did end up going to about 7/8's of a turn out (had them at 1 full turn) on the idle screw.

I'm about to do a test drive. Will report back.

Ry

Ravie · « **Reply #457 on:** April 02, 2016, 07:36:33 PM »

Dear god, yes. Yes. Yes. Yes.

Took her for two short drives this evening. I was GIDDY. Ran so great! Rafi, I owe you a cool beverage.

Washed and waxed her, too. :-D

edwardmorris · « **Reply #458 on:** April 02, 2016, 08:28:36 PM »

Ride it some more and check a couple times, but really glad to hear its doing better. Check after a lousy stop and go city trip, and a fun freeway trip to make sure its all good.

Ravie · « **Reply #459 on:** April 02, 2016, 08:36:05 PM »

Cool. Will do. Tomorrow I think I'll pull the plugs and see what they look like after todays couple of rides. it's still rich enough at idle that I can smell it but I'm not as worried about that. It smokes much less now.

It's crazy how fast this thing is. What's crazier still is I haven't even had it past 3rd gear. 40mph is about 4k rpm which is the speed limit near my house. I'm not looking for any road stops...lol

Ravie · « **Reply #460 on:** April 04, 2016, 07:58:31 PM »

I'm not sure why I continue to update this thread. Certainly not because it's a popular build. Meh.

Rode the bike to work today. I couldn't NOT. It was beautiful sunny blue sky and already in the 50's when I left for work. It ran GREAT! I'm hitting about 4k at 40mph. I don't even go past 3rd gear in town...lol

It still doesn't seem perfectly smooth just cruising there, really I could be nitpicking. It is still breaking in a bit afterall, too. I pulled a plug this morning before I left and it was a beautiful tan color...so I've got to be damn close.

Next door to me is the world famous Wolfe's Camera where a buddy of mine works. I alerted him I'd finally driven the bike to work so he snuck out and snapped some photos. Here's one:

calj737 · « **Reply #461 on:** April 04, 2016, 08:59:10 PM »

She looks fantastic sitting there, Ryan! Big thumbs up!!!!

SOHC4 Cafe Racer Fan · « **Reply #462 on:** April 04, 2016, 09:26:23 PM »

Quote from: Ravie on April 04, 2016, 07:58:31 PM

I'm not sure why I continue to update this thread. Certainly not because it's a popular build. Meh.

Rode the bike to work today. I couldn't NOT. It was beautiful sunny blue sky and already in the 50's when I left for work. It ran GREAT! I'm hitting about 4k at 40mph. I don't even go past 3rd gear in town...lol

It still doesn't seem perfectly smooth just cruising there, really I could be nitpicking. It is still breaking in a bit afterall, too. I pulled a plug this morning before I left and it was a beautiful tan color...so I've got to be damn close.

Next door to me is the world famous Wolfe's Camera where a buddy of mine works. I alerted him I'd finally driven the bike to work so he snuck out and snapped some photos. Here's one:

Good looking bike, Ryan. Way to get out there even if it was a frigid 50s!

70CB750 · « **Reply #463 on:** April 05, 2016, 04:11:39 AM »

Sweet!

seanbarney41 · « **Reply #464 on:** April 05, 2016, 01:53:52 PM »

Keep updating...even when you think no one is reading, we are reading. It is great to hear that you are sorted, or close to it. Many others only come back with more problems and questions. You have done well at a task that many are unsuccessful with. Excellent job.

SKTP · « **Reply #465 on:** April 05, 2016, 03:25:11 PM »

I feel my thread has also become unpopular...Your bike looks great

SOHC4 Cafe Racer Fan · « **Reply #466 on:** April 05, 2016, 08:07:24 PM »

Quote from: SKTP on April 05, 2016, 03:25:11 PM

I feel my thread has also become unpopular...Your bike looks great

Nonsense, Chris. You have a bunch of members waiting to see your bike as it makes its way through the shakedown process.

Retro Rocket · « **Reply #467 on:** April 05, 2016, 09:40:42 PM »

Quote from: CB750 Cafe Racer Fan on April 05, 2016, 08:07:24 PM

Quote from: SKTP on April 05, 2016, 03:25:11 PM
I feel my thread has also become unpopular...Your bike looks great

Nonsense, Chris. You have a bunch of members waiting to see your bike as it makes its way through the shakedown process.

Yep, fifteen and a half thousand views, stop whinging and get on with it....

Tews19 · « **Reply #468 on:** April 06, 2016, 06:26:34 PM »

Glad to see it on the road! I remember when you first came to the site and posted pics. You have come a far way!

Buckskin Bandit · « **Reply #469 on:** April 09, 2016, 04:09:17 PM »

Enjoyed reading through this build thread! Subscribed so I can watch the future progress.

Ravie · « **Reply #470 on:** April 23, 2016, 10:46:30 AM »

The bike is running great, when I get the time to ride it. Unfortunately That isn't often and I don't foresee that changing.

She's for sale. http://forums.sohc4.net/index.php/topic,157042.0.html

calj737 · « **Reply #471 on:** April 23, 2016, 11:09:56 AM »

Ravie · « **Reply #472 on:** April 23, 2016, 11:16:43 AM »

Is that confusion and anger?

It sits in my garage a lot. Riding through town traffic isn't much fun and I really don't like telling my girls "Hey guess what I'm leaving to have fun and you can't come with." So...yeah. There are other things happening in life (We're buying a house soon and I'm getting tired of driving a 64 Corvair every day) that are motivating me to sell it as well. Honestly I think I had more fun building it than I do riding it.

Ravie · « **Reply #473 on:** May 10, 2016, 06:58:43 AM »

Sold. Last night a badass rocker chick named Jill drove up from Wichita and handed me some money and we loaded the bike up in her man's truck and they drove off into the...thunderstorm. haha

We are buying a house this week and there are a million things going on in our lives and the bike just needed a new home. The girl who bought it is going to have a lot of fun with it and honestly...probably more than I was having. In some weird way it's almost like I built the bike for her.

There will be more later in life!

Thanks to everyone who helped!

evanphi · « **Reply #474 on:** May 10, 2016, 07:35:07 AM »

Glad someone will love it too!

Good luck on the house... another money pit

News:

Author Topic: 1975 CB750 Build! "Kona" - Sold and gone. (Read 69541 times)