Author Topic: F/F1 carb rack ID? (Read 2057 times)

Don R · « **on:** January 08, 2022, 10:18:07 AM »

Does anyone know the correct Keihen 75/76 F carb rack number? I get 16100-392-004 from the parts list but need the 069 or 750A, or whatever number.
My handbook says PD carbs for F's and gives the jets list for most of the other sets. but I need the roundtop number. Thanks in advance.

69cb750 · « **Reply #1 on:** January 08, 2022, 10:24:51 AM »

75F and 76F used K model round top carbs, use K model part number.

seanbarney41 · « **Reply #2 on:** January 08, 2022, 10:41:22 AM »

Don, I have seen a few different casting numbers on 75-76 f. I think 064a and 086a mainly, if i remember correctly.

bryanj · « **Reply #3 on:** January 08, 2022, 10:44:01 AM »

PD's were F2 onwards and 550K3

bustech51 · « **Reply #4 on:** January 08, 2022, 11:07:48 AM »

Here is a chart of what bike takes what carb rack assembly. Hope this helps. If you need a rack I believe I have a couple PD657A racks that have been cleaned and redone. All they need is to have them set up and synced. Send me a note for info and pics.

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Jerry Rxman Griffin aka MuthaF'er · « **Reply #5 on:** January 08, 2022, 11:18:25 AM »

Let me see if I can get a reading back home on my original 75 F carbs...

Request sent. 657 or 69. Don't remember which but my bike is a first month production.

That chart lists the JN (jet needle) as 4 which is NOT correct. Middle position = 3.

Don R · « **Reply #6 on:** January 08, 2022, 11:34:40 AM »

Thanks a bunch, that explains why the handbook seems to list most of the 750 roundtop carbs. This one is a late F0 with a 76 title. I can surely find a set in the carb tote that is correct. I knew I had seen that chart but couldn't find it.

ekpent · « **Reply #7 on:** January 08, 2022, 12:10:58 PM »

One thing I have always noticed on any of the 75/76 F carbs that I have cleaned is that the brass needle jet holder has a cool little extra nylon and mesh fuel filter attached to the bottom of it when its unscrewed from the carb body. Don't see it on earlier K bikes.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #8 on:** January 08, 2022, 12:11:17 PM »

Results coming soon Don

Jerry Rxman Griffin aka MuthaF'er · « **Reply #9 on:** January 08, 2022, 12:43:38 PM »

IF I am able to post a picture I will but I was wrong just as much as that chart is wrong.

064A definite. Not even a 064A listed

Don R · « **Reply #10 on:** January 08, 2022, 02:02:11 PM »

Quote from: ekpent on January 08, 2022, 12:10:58 PM

One thing I have always noticed on any of the 75/76 F carbs that I have cleaned is that the brass needle jet holder has a cool little extra nylon and mesh fuel filter attached to the bottom of it when its unscrewed from the carb body. Don't see it on earlier K bikes.

Good point, I replaced the ones on the previous F1 I had, and those screens were on it. The problem was drilled jets on that bike. It would get 90 miles before reserve and make black smoke.

That's funny Jerry. Like I say, every time you think you've seen a Honda rule it has exceptions.

ekpent · « **Reply #11 on:** January 08, 2022, 03:37:26 PM »

Not sure if its the shape of the tank or the length of the standpipe on the petcock but I seem to notice the F bikes going to reserve quicker then K tanks. Never actually charted the miles per say though.

bustech51 · « **Reply #12 on:** January 09, 2022, 11:35:07 AM »

Went out to my shop today to check my carb numbers on my original '75 750F. Low and behold what did I see but 064A carbs on it all in a row.

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ekpent · « **Reply #13 on:** January 09, 2022, 12:35:58 PM »

As for the chart never believe everything you see on the internet .

The 069a listed might be a mistake or typo and were meaning 064a.

Don R · « **Reply #14 on:** January 12, 2022, 09:56:10 AM »

Thank you all for taking time to help me out. I'll especially be on the lookout for 64A's. I'll check for screens above the float valves.

seanbarney41 · « **Reply #15 on:** January 12, 2022, 12:01:38 PM »

tbh Don, no idea why it would make any difference to use any 71-76 roundtops, just possibly have to adjust needle position and/or main jet.

Don R · « **Reply #16 on:** January 12, 2022, 05:01:37 PM »

I agree, I will use any set here, I thought I'd look for correctness. The wrecked F0 that I parted out was missing its motor but I might still have gotten the original carbs. I won't know until I go through the tote of carbs.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #17 on:** January 13, 2022, 07:16:36 AM »

The one difference is the needle jets/jet needles have a distinct -392 part number for the F0 parts catalogue

HondaMan · « **Reply #18 on:** January 16, 2022, 07:03:59 PM »

The 064a and (when found on the "F") the 086a use needles #271307. These are leaner below 1/4 throttle than the ones found on the 1970-1976 750K models with the 657a/b or 086a carbs (#27201).

StockRider · « **Reply #19 on:** January 17, 2022, 04:28:33 PM »

Quote from: ekpent on January 09, 2022, 12:35:58 PM

As for the chart never believe everything you see on the internet . The 069a listed might be a mistake or typo and were meaning 064a.

I just pulled up Mike Nixon's Carb Chart for another thread. Might as well reference it here as well. His footnote makes it very clear that inaccuracies abound.

He does show:
75 CB750F 064A

https://motorcycleproject.com/text/specs.html

seanbarney41 · « **Reply #20 on:** January 17, 2022, 07:39:50 PM »

Yeah, the inaccuracies thing?...Well, a quick anecdote from my F0, F1 experiences...I have ridden my F0 tens of thousands of miles with a number of different intake set-ups and it always runs great with just a mainjet change, cheap pods, HA breadbox, no filter whatsoever when the breadbox falls off, stock airbox, absolutely no problems with part throttle with any of these changes, and really, only mainjet problems at the very top of the range, well above legal speeds. I also had a similar experience with an F1 that I owned for much shorter amount of time. So I got to thinking maybe these F's have something special of a needle profile compared with other K roundtops? Nope...after checking every rack of carbs I own(lots), 064, 086, 657a, 657b, 7a...they ALL had the same number on the needle.

After perusing Mike Nixon's chart, it does not jive with my experiences at all except in respect to basic pilot and main and clip position for year of bike. The 064 does not even appear there. And he does not include the needle number, or the needle jet number, which iirc, are all the same among roundtops as well. But you have to wonder, if Keihin gave it an id number, where are the other sizes?

Jerry Rxman Griffin aka MuthaF'er · « **Reply #21 on:** January 18, 2022, 06:49:30 AM »

The 75F Honda part book, which I have and am not able to access, does give the 75F a different -392 part number for the jet/needle set. I managed to collect 4 over a period of time.

Don R · « **Reply #22 on:** January 19, 2022, 03:28:06 PM »

I had 657A and B, a set of 77 keyhole carbs, a set of 7a with broken posts on the end carbs. The good ones are 7A and 086A. The 7a were on an 836 motor and have 43/145 jets, the 86A have 105 and 40. My 76F liked 110/40 jets with a stock air filter and glass pack baffle.
I'll check the jet needles on both sets of 7A. I also found a #1 carb body from a 4-cable carb. Alas, it has a short choke lever.
Thanks for the help.

Don R · « **Reply #23 on:** January 23, 2022, 12:14:50 PM »

I found them, thanks for the help.

seanbarney41 · « **Reply #24 on:** January 23, 2022, 12:24:19 PM »

Yeah Don...that's what I do too. Sharpie labels on the float bowl.

Don R · « **Reply #25 on:** January 23, 2022, 12:33:31 PM »

They need a good cleaning, I'll get the ultrasonic cleaner out for the small parts and try the new parts washer on the outside of the rack.

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Author Topic: F/F1 carb rack ID? (Read 2057 times)