SOHC.co.uk Forums > CB350/400
Progress - She runs at last! (75 CB400F)
Chris400F:
I had a rummage in my garage and found the tool I made when I did my float heights.
I can't remember whether I read about it on this forum or elsewhere, not that it matters - maybe it will be of help to others.
The tool was made from the lid of a tub of soft cheese (Philadelphia in this case; other brands are available).
Outer cutouts are 21mm deep (float height), inner cutout is as deep as it needs to be to clear the tube holding the main jet.
Working with the bank of carbs on end eliminates the effects of gravity - the height needs to be set with the float arm just touching the needle jet.
If the pivot pin is loose in the holes use masking tape or similar to hold it in place.
I have noticed that the text in the Haynes manual says set to 22mm. This is the 500/550 setting, 400 is 21mm according to the specifications.
I had never set float heights before but found this method worked well for me.
Laverda Dave:
All very interesting info and unavailable in the Haynes manual. I found the piece of card I used, it's 22mm, not 26mm as I stated in my earlier reply, two of the four carbs still leak though so I'm going with your idea Chris to make a proper 21mm gauge followed by the bench sync as recommended by Bryan.
Laverda Dave:
Well, I made the gauge from some ali sheet to 21mm. All floats carefully reset and checked over and over just to be sure. I set the carbs using Bryan's recommended technique and all was good. I thought I'd bench test the carbs before putting back on the bike and placed them very gently in the vice, connected the bottle of fuel and waited. Everything as great for 5 minutes and then petrol poured from 2 of the overflows and also the central overflow pipes between carbs 3&4 >:(. Am I doing something fundementaly wrong?
To cap a bad afternoon, I got that horrible feeling when one of the float bowl screws just kept turning, undoing the screw pulled out the tread with it! I need to get a 4mm helicoil kit now although opinion is timeserts are a better option (I've never used one). At least it's winter and I'm not missing out on any sunshine ::).
Bryanj:
Not enough meat for a timesert as they are a lot thicker in the wall, Do the float needle seats have an O ring on them? Are the float bowls very full or could the internal standpipes be cracked
K2-K6:
The float height would not usually alter how it shuts fuel off within reasonable range, just the mixture when running.
If the valve seats are brass you can use something like a cotton bud with brasso or T-cut to spin slowly with a drill and get them smooth / polished. Needs thorough clean afterwards.
If the needles are plastic or rubber tipped, they can be hard to get to seal properly with just the float pressure on them. I know it's a slim hope, but the heat and engine vibrations do seem to assist this process when installed and running. I can see why you'd want to reassure yourself prior to install though.
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