Doms CB550F1 project

[DomP]

All standard Keihin jetting for 069a carbs Bryan, the air filtervis a standard F type but missing the rubber snorkel so I covered the hole in mesh but quite coarse.  I'll post a photo

[DomP]

Could this be too free flowing?

[Bryanj]

Doubt it, from what you describe its too rich.

That would give similar airfow to 500 which does have larger jets than 550

[DomP]

Its better at 2⅛ to 2¼ turns out so do I just keep going until I get a good amount of rideability?  Its better but still has a significant flat spot at low revs then fly.

[Bryanj]

Cant answer that one sorry

[Oddjob]

Dom do all the jets bear the Keihin K logo?

I’m thinking someone has used a carb kit on your carbs in the past and the problem is the float needle valves and seat. A lot out there wouldn’t stop petrol flowing past if you held them against each other with your fingers. Lot of reports of the tip of the float needle being made off centre so fuel just leaks past, which would make the engine run rich as hell.

The only way to test is to remove a float bowl, turn on the petrol and use a float height setting tool set to 22mm and use that to lift the float, if the fuel stops when it reaches 22mm then it’s ok, if not then you have a problem. Container under the carb of course. I seem to recall genuine Honda float needles has rubber tips whereas copies just had steel tips. If it doesn’t stop at 22mm see if it stops at a higher setting, if it doesn’t stop at all then you need to replace that entire setup.

[DomP]

All genuine jets Ken, I've stripped and replaced all orings etc in the carbs.

The float needles are fully metal, ie no viton tips so maybe worth replacing them, where can I get them as replacements?

[DomP]

Nothing i can find suggests they were rubber tipped Ken, everything seems to be metal.

[McCabe-Thiele (Ted)]

I'm a tad confused Dom, all this talk about the float valves?
Are the carbs flooding?
If not certainly worth ensuring the levels are correct.

[DomP]

No flooding Ted, I think Ken was wondering if they were letting fuel through causing rich running as at 2¼ to 2½ turns think i might be a bit rich on some cylinders. No2 and 3 run quite a bit hotter on the exhaust headers

[McCabe-Thiele (Ted)]

Are the carbs synched Dom, if 2 & 3 are a tad on the rich side or could it be float heights?
Do you suffer some hanging throttle issues?

[DomP]

Id like to think the float heights are correct now, I spent ages fettling them with vernier calipers, I do need to tweak the carb balance a bit so that might settle the 2/3 issue.  Hanging idle seems to be a thing of the past thankfully.

[DomP]

I'm struggling to get some decent uninterrupted time on this at the moment, as it's a straightforward job and not time sensitive I thought I'd check my float heights on level ground, number 3 carb seems a little low but all others I believe to be good.  What is the effect of a slightly low float height?

What do you all think?  My carbs have a definite slope down towards the engine on the centre stand is this of significance?

[DomP]

I've been out on a 15 mile run having balanced the carbs with a Carbtune about as close as I could get them.  Things I've noticed are the following-

Just a recap on the set up, 550f with genuine keihin jets and carbs set to factory.

•Still bogging down below 3k to the point I have to drop a get away
• top end seems to hit a bit of a wall at 5.5-6k but I am being careful due to the rebuild .
•the front suspension bounces like tigger at about 30-40 mph, I wonder olive ive used too light an oil so may replace with something a bit thicker.

Other than that at cruising speeds on main roads its very smooth

[Bryanj]

There is no power below 3,000 would be my comment, top end could be timing