Topic: cb550 still fouling plugs

[78whiteorbs]

76 with 6 k miles. Recently rebuilt carbs and reset float height to 21mm. Did everything in the 3k mile tune up except adjust valves. My manual says when the number on (far left ) intake goes all the way down and starts to rise line up the timing mark with T and it has to be on the 1/4 mark. Well every time in the stroke when it goes all the way down and starts to rise it's on the 2/3 ?? Why is this . The illustration actually shows the #4 cylinder tappet for reference which further confuses things..

Anyhow aside from that one weird thing is even from a dead cold engine it cannot be started with the choke on. It is suppose to raise the revs but it instantly kills it or will not start with the choke engaged from cold. Somethings not right here. Last night I realized like an idiot I left the retainer clips that but pressure from the carb bowl and hold the (idle?) Jets in. This would cause extra fuel to be sacked up through there thus giving me the symptom I am dealing with which are sooty carbon fouled plugs. It will idle long enough to sync carbs before they start fouling out ...Somehow getting extra fuel in the idle circuit possibly... what to do.
Obviously put spring clips back in and I was thinking to lower all the floats to like 18 mm just in case ....

[calj737]

check your jets. Perhaps a PO drilled them? I found this exact issue on a K1 recently. Looking at the jets, the numbers indicated 38. But when comparing another 40 I had to the 38 in the carb, it was obvious that they had been drilled to about 65s!!!! No wonder I fouled plugs in about 30 seconds every time...

[DaveBarbier]

I also had a PO drill out pilots. They were marked 42s but we're more like 80!

Also, regarding the tappets, when the #1 intake tappet starts to rise that's just when you start peaking through the sight hole on the timing plate. Don't worry that you'll see the 2-3 first, just keep rotating until the 1/4 comes up. You can verify you're good when both the intake and the exhaust tappets are loose. 


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1978 Honda CB550K

[78whiteorbs]

I also had a PO drill out pilots. They were marked 42s but we're more like 80!

Also, regarding the tappets, when the #1 intake tappet starts to rise that's just when you start peaking through the sight hole on the timing plate. Don't worry that you'll see the 2-3 first, just keep rotating until the 1/4 comes up. You can verify you're good when both the intake and the exhaust tappets are loose. 


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1978 Honda CB550K

Thanks will check that out

[78whiteorbs]

Anyone kno en what the correct size pilots are and where they can be bought?

[calj737]

Carb model? And F or K bike?

[78whiteorbs]

Sorry 76 k

Have to check carb model this evening

[Deltarider]

Personally I find it unlikely a PO drilled out the jets of a motor that hardly finished breaking in. Have you checked if the little O-rings around the main jets are in good condition and seal well? If not, the engine will happily suck in the extra fuel. Have you installed the main jets correctly with the spheric hole up? BTW you can do all the checking/removing/installing jets with the carbs in situ. You don't need to remove them let alone to separate them. The spring leafs are needed to keep the main jets in place. Are your airscrews turned out correcty? Any obstruction in the air intake traject? What filter do you use?

[78whiteorbs]

I will certainly check those as well. I may have replaced the o rings as the old ones if I recall were shot...I will look closer here thanks for the ammo

[calj737]

Stock I believe is 100/38

[78whiteorbs]

Thanks

[78whiteorbs]

I did order some extra o rings  from 4-1 when I did my cb350f  carbs....I think they are the same.

All the Viton o rings I had were a little to fat in diameter

[78whiteorbs]

would this excess fuel being sucked in make the choke circuit inoperable as well. all plugs are the same it seems unlikely all those press in main jets aren't sealing

[Duanob]

Yes it would. The choke on gives you a richer condition, with more gas it's even richer probably too rich to run.

You said in the first post you forgot the main jet retainer springs? I would guess that's your problem right there. Maybe one of your main jets fell out? As said before you can check everything except float height with the carbs on the bike. Get a angled ratchet screwdriver with a 1" #2 philip bit to access all the bowl screws. I keep one of these in my tool tray in case I have to do some roadside maintenance.

http://www.harborfreight.com/8-piece-right-angle-screwdriver-92630.html

As far as valve adjustments just put the rotor on the 1/4 T mark, check the #1 cyl (far left) valve tappets to see if they are a bit loose, as in not opening any valves, and adjust by the sequence in the manual, then rotate to the 2/3 T mark and do the rest. Easy Peasy.

[78whiteorbs]

I did but was fouling plugs before that as well.
I am looking forward to the pulling the carbs again llol. The more I do it the easier quicker it gets. Ha!

[Duanob]

I did but was fouling plugs before that as well.
I am looking forward to the pulling the carbs again llol. The more I do it the easier quicker it gets. Ha!

Correctamundo! I can do it my sleep. 

Have you checked the carb tops/slides? I had a rich condition that was from crud build up on the top of the needle whereit sits in the emulsion tube. It wouldn't sit down far enough on it's own. Once I cleaned the needles with 0000 brass wool and set the needles to there stock position, it ran like a dream and the plugs were a nice brownish tan color after that. Before that no matter how many times I cleaned the jets and bottoms of the carbs it still sooted and fouled plugs. Remember any time you mess with the slides you will have to vac sync again.

[Deltarider]

My method would be first to leave the carbs where they are, remove the needle jets (aka emulsion tubes) as I have described before and then spray solvent (carb cleaner, WD-40 or something similar) upwards to attempt to clean the needles. It's no guarantee but it can work. It did for me.

[scottly]

Check the fuel levels in the float bowls with the clear tube method.

[HondaMan]

You haven't mentioned something very important here: if there are vacuum leaks around the hoses or the castings where the hoses bolt to the head, you will be very rich on all cylinders where the leaks are. It's backward from a car's intake system.

The #1 item I find on the Mid-Fours is: leaking O-rings at the castings against the head. They are hard as plastic from the heat and years, and leak as if they are not there. The O-ring is the same size as in the valve caps, on that bike.

[78whiteorbs]

You haven't mentioned something very important here: if there are vacuum leaks around the hoses or the castings where the hoses bolt to the head, you will be very rich on all cylinders where the leaks are. It's backward from a car's intake system.

The #1 item I find on the Mid-Fours is: leaking O-rings at the castings against the head. They are hard as plastic from the heat and years, and leak as if they are not there. The O-ring is the same size as in the valve caps, on that bike.

Wow, yes I never would have thought of that I was under the impression that intake leaks like those that hole pistons and fry top ends in two stroke cause a serious lean condition. That's. Easy enough to check for with a can of carb cleaner , thanks for the tip!  When I first got the bike oddly enough two nuts were missing on the intakes...I replaced them but thought it odd.

[DH]

Check the fuel levels in the float bowls with the clear tube method.

x2..If the level is too high, the carb throats will instantly flood whenever the throttle is opened the slightest amount.
i witnessed that very thing with the air cleaner element removed, but the rest of the system still attached, while watching thru a remote inspection camera snaked in thru the plenum and engine running. . Corrected, clear tube/verified fuel levels fixed things. (In my case anyway)


edit: There's more to my scenario, if it helps....maybe read the entire thread. Thought I posted it, couldn't remember



http://forums.sohc4.net/index.php/topic,141012.msg1600876.html#msg1600876

[scottly]

76 with 6 k miles. Recently rebuilt carbs and reset float height to 21mm.
 I was thinking to lower all the floats to like 18 mm just in case ....

Changing the measured float height from 21mm to 18mm would be even richer. Clear tube will tell what's actually happening in the float bowls.

[78whiteorbs]

76 with 6 k miles. Recently rebuilt carbs and reset float height to 21mm.
 I was thinking to lower all the floats to like 18 mm just in case ....

Changing the measured float height from 21mm to 18mm would be even richer. Clear tube will tell what's actually happening in the float bowls.

Yes my minds eye has seen this backward.
Thanks for all the ammo. Wish I had the day off to put it all into effect.
For now the plan is to pull the carbs replace the spring clips . Check the o rings in the manifolds, check and replace the main jet orings, inspect the idle jets, hook up the auxiliary tank and clear tube the carb float bowl levels via the clear tub method. Also double check all four needles are spotless. Then, gulp, reinstall and see what happens..

[scottly]

Do the clear tube test FIRST, before pulling the carbs...

[78whiteorbs]

Clear tube method says....drumroll........

Fuel was at gasket level :-(  even though floats set exactly at 22mm.

From what I read it should be 3-4 mmm below gasket surface.
Sooooo- guess I am gonna drop the float height to 26mm. And then clear tube it
Fuel level is even with gasket surface.