Topic: Can I clean my carbs without having to re sync?

[mathbishop]

Checked timing and it looked good, on 1-4 atleast. I had the plugs changed not too long ago last time I took it into the shop. 3-4 months ago maybe.

It does in fact have a aftermarket Kerker exhaust on it

[mathbishop]

bump

[Geeto67]

ok, so timing is good at idle. did you check the advance? I have a timing light that lets me advance or retard the strobe so I usually check the advance by revving the bike to  5-6K and seeing how far the advance kicks in, but if you don't have such a light you can check the advance manually with the bike off.

 carbs aren't that dirty or missing pieces. where does that leave us? jet size.....

[flybox1]

Pull the main jet and leaf spring off.  Then pull out your emulsion tubes.   Post a picture of all 4....

[flybox1]

Before you throw your carbs back together, just verify your float height is set properly on each, as well as your air/fuel mixture screws...

[mathbishop]

Do I need a dial caliper to check float height? Not sure how to check the air/fuel mixture screw to see if they are right

[mathbishop]

some guts

[seanbarney41]

float height?...nope, just a small ruler...but you have to be very exact about what and where you measure from.  The clear tube check might be more useful...mount your carbs in a vice or something so that they are level as they would be on your bike, rig a clear tube out of the drain in your float bowl, add gas, hold the clear tube alongside the float bowl, the level of the gas in tube shows you where the level of the gas in your bowls is, 3 or 4 mm below gasket should be ideal

this pic is on a cb350 twin though...idle screws? turn them in until they are gently seated counting the number of turns, now screw them all the way out, watch out for tiny spring, and possibly a tiny washer and/or o-ring(I can't remember what all is in those carbs), blow carb cleaner and air through the hole, replace all correct parts, screw them in until gently seated and then back them out the same/ correct number of turns, should be tweaked and adjusted when the bike is running via a plug reading

[crazypj]

Do I need a dial caliper to check float height? Not sure how to check the air/fuel mixture screw to see if they are right

I use a 6"x 1" wide engineers stainless steel rule and a loupe tocheck float level.
You can make a gauge from an old credit card though. The float height gauges don't have very accurate markings, I set with a vernier when I use them (haven't used one for years though)

[mathbishop]

float height?...nope, just a small ruler...but you have to be very exact about what and where you measure from.  The clear tube check might be more useful...mount your carbs in a vice or something so that they are level as they would be on your bike, rig a clear tube out of the drain in your float bowl, add gas, hold the clear tube alongside the float bowl, the level of the gas in tube shows you where the level of the gas in your bowls is, 3 or 4 mm below gasket should be ideal

this pic is on a cb350 twin though...idle screws? turn them in until they are gently seated counting the number of turns, now screw them all the way out, watch out for tiny spring, and possibly a tiny washer and/or o-ring(I can't remember what all is in those carbs), blow carb cleaner and air through the hole, replace all correct parts, screw them in until gently seated and then back them out the same/ correct number of turns, should be tweaked and adjusted when the bike is running via a plug reading

And am I right in thinking that I have to bend the little metal tab on each float to adjust the height of it? how do I know how much gas to put in each float bowl?

[seanbarney41]

you got it on the tab...pour it in til it stops, that is really what you are adjusting, where the float stops the flow of fuel at...if your carbs are off the bike, just use a piece of fuel line connected to the carbs with a funnel on the open end...pour the gas until the funnel has a "fuel supply" built up...don't catch yourself on fire please

[flybox1]

Yes. The 'tang' is adjusted to set the float height. It's the little square tab in the middle of the float.
The emulsion tubes look pretty clean.  Set the height and put them back together.  You can rig an aux fuel tank and allow it to fill the bowls to see with the clear tube method if the float heights are correct before wrestling the carbs back on Tue bike......Air mix screws set, and you're golden.

[mathbishop]

In the picture it looks like the carb is fully assembled. How do I adjust the tang accordingly?

Are there any "less messy" ways to said the float height?

[Geeto67]

were your carbs leaking out the drains before? no? then don't worry that much about it. Just check it with a ruler (against the gasket surface) and bench test to make sure they aren't leaking.

Don't try to do the clear fuel tube trick, it is too confusing and if you are new to this what is written above will only confuse you further.

I would check to make sure the overflow tubes are not blocked. If they were and the float heights out of whack then you would be flooding your engine with fuel.

[Geeto67]

here is the clear tube method:
How to check motorcycle float heights

here is the ruler method:
Checking the Float Level on a Mikuni VM38 Carb

warning: neither of these are for the 400F so you need to look up float height in your manual.

[mathbishop]

Very helpful indeed. Thanks for that geeto. On my carbs my floats are attached to my where my ting is im unsure what exactly I need to measure to. I start at the gasket and end where...

Here is how my carbs look. You can see the ting in there. Am I measure to the ting or the floats themselves? Since the floats are square if I were to measure furthest to the right of the float it would be vastly different if I were to measure furthest to the left.

Sorry for the 90 degree rotation on the stupid picture

[mathbishop]

I have stumbled upon a new question. The valve springs on my carbs seem to react differently to the weight of the floats. When the floats tang just touches the valve spring they line up accordingly and thankfully just at 21mm. But when I set them down (upside down) on my work bench they dont line up at all. Should the valve springs be replaced? or is it not that big of a deal???

[Deltarider]

Unless you have serious indications a PO has tampered with the floattangs (members of this forum are suspect), I would leave them as they are. If the little tang is perfectly parallel, it's an indication it's all right and not messed with. I have yet to see the first float that needs to be adjusted.

I wouldn't even consider doing a carb clean without re-sync

I, on the contrary, would and have done so several times. All maintenance done from the bowlside - which I strongly recommend - does NOT require a sync.
In principal all jets and even the emulsion tubes can be removed, inspected, cleaned and put back with the carbs on the bike. I can do it blindfolded. The relative position of slides and needles will not be affected. If you go in from the top, it's another story. 

[dave500]

theyve probably never been synced in years?,,youd be mad if they wernt as youve gone this far,,its only half a job otherwise,go the extra mile,itll run that little better.

[trueblue]

If you haven't changed your condensors yet, I would do them before worrying about your carbs too much.  Most of the time people go through the carbs a dozen times and find out later it was another problem.  I had a similar issue, my bike was topping out at 120kph.  I went through the carbs 3 times and was certain they were clean, then I found the ignition advancer was stuck.  Once it was cleaned and lubed I got 130kph out of it.  Then I found this, a 113 link cam chain, someone replaced the cam chain without releasing the tensioner and added an extra link to make up the difference.  I was just lucky that it didn't cause more damage.  Once this was replaced, the idle smoothed out, and the power increase was incredible.

[mathbishop]

Thanks blue, I am definitely going to change my condensers out. Im still trying to learn all this vocabulary. What exactly is the ignition advancer and where is it? I have checked the timing and it seemed to be okay.

[Scott S]

 I wouldn't even consider putting the carbs back on without at least checking the synch and bench synching them. Like Deltarider said, that will get you really, really close. Probably good enough.

 Did you pull the jets and spray cleaner through the passages? The hard part is getting the carbs on and off the bike. Take a few minutes to clean them while they're off.

[Geeto67]

The spark advancer sits behind the points plate. As the bike revs up the spark needs to happen earlier and earlier so the explosion happens when it is supposed to. Your service manual should tell you all about how to find and check it. Do the condenser first because checking it may require you to retime your bike.

[mathbishop]

Cleaned out all the jets as much as I could. Re-set the Float heights. Are there any good bench sync guides I can use before I put them back on my bike? Im also waiting on some new gaskets for my float bowls. My other ones were all shot minus one. The new set of 4 should be here next week, so my carbs will be off probably until next weekend to do any more adjustments to it.

[crazypj]

Back in the 70's a common method was to use four 12" pieces of welding rod under slides.
They should be level when slides are closed and all droop the same amount when slides open