Carbs

[captaindonutbikes]

yes you know its that cb550 k3 lean burn carb time!

so she will start but only on full choke, if i reduce to 2/3rds choke she will die. no idle.

so my thoughts are to richen first ? running far too lean or does this sound more like an air leak ? carbs were fully rebuilt with new needles and floats.

floats were set as per book -
running k & N filters.

want to to carb sync but i am right in thinking this will be irrelevant until i can get a solid idle?

all help as always warmly appreciated.

so close but yet so far

[captaindonutbikes]

oh and have been reading the MOT stall thread.
 

[Bryanj]

pull out the pressed in pilot jets and clean them in a solvent solution, always cured that problem for me

[K2-K6]

Bryan seems to no more about which jets to clean than me, so I guess that's where to go first if not done already.

Pilots are mainly there to give fuel supply when throttle closed / near closed so try revving it a bit and take choke off to see if it'll run at higher throttle as this will confirn pilots without dismatling if that makes any sense!

Friend had a new 550F2 in the 70's and that alway's seemed to need a lot of warming on choke before it would run clean, we were always waiting for him on cold starts.

What number plugs has it got they should be something like NGK 8's any higher and you may struggle.

Balancing can be something and nothing. I've always set the slides up visually first and if you are fairly particular / accurate then that is normally good enough to get running so can't see that causing the  problem you describe. Final balance when you get it running reasonably, it mainly gives a smoother idle when done.

[captaindonutbikes]

brand new press in jets infact everything is brand new and cleaned meticulously.

i shall try the high throttle to see if its the push in jets but it seems a bit lean to me.

[captaindonutbikes]

o.k so a ran it up to temp with full choke, got it to idle but the idle screw was quite far in.

When reving up the engine it seems to pull quite nicely but when you engage first to pull away it dies after a few seconds motion.

does this fit with your suggestion Brian ? going to remove the carbs but just checking in first.

(oh and my fork seals have gone south) ! fun, fun, fun.
 

[Bryanj]

The K3 chop i built had to have the pilots out if it stood for more than 4 weeks, got quite adept at it in the end. Was like that till i got some solvent from my brother in law that the printing industry used to use to disolve plastic out from under the ink they wanted to recycle!!!dont know what it was but it sure cleared the sinuses

[totty]

It sounds like an air leak to me. Spray any old flamible spray on each join listening for an idle change.

[K2-K6]

That sounds a bit lean as you thought, won't hurt to make it richer to see if it improves, it's a no cost option.

That's a good trick of spraying flamms on possible leaks to see if it changes totty.

Have they got an accelerator pump on those carbs / if so, is it working. Unsure how much knowledge you have in this area but acc pumped carbs run too lean to accelerate the motor under load and so require additional fuel to make it go, this is provided by the pump as you open the throttles quickly and then leave to run lean at steady revs.

That solvent sounds like MEK if so this is also used on plastic plumbing fittings to clean joints prior to glueing and will melt plastic, it may be harder to get hold of as it is quite "aromatic" if you know what I mean.

[captaindonutbikes]

So after being hit but an unobservant cab driver on friday night pulling across two lines of traffic then into the bus lane and getting away with nasty bruise ,a slight limp and a bent engine guard on the BMW100 runnaround i could do with some luck! (luck although seemed to be on my side as although it pushed one of the carbs off its rubbers via my leg, the damage was minimal and the front of his car was a total write off, which i am still not entirely sure how it got so damaged and my leg did not break!)

any how just richened the mixture by a half turn and she started easier but was hunting revs on 1/3rd choke tick over so i think we have ourselves a nice juicy air leak, will investigate this further tomorrow with carb cleaner.

and realized the replacement rev counter is completely off after i hooked up the original. ordered it as a honda ratio but says 6000 when its infact 9000! glad i found this out now! what would cause this ?

apart from that she pulls quite nicely up just got to sort this air leak out!

[Yoshi823]

Did you read this thread about air leaks that I wrote..?

http://www.sohc.co.uk/index.php?topic=2849.0

Glad that you're ok after your Friday night escapade...

[captaindonutbikes]

yep, they are sealed tight. think its it the felt dust washers causing grief.

[captaindonutbikes]

its all the felt dust seals. leaking at 8 points think think i must have not removed these when i soaked and cleaned them. 

any one got an idea of part numbers ? can't seem to find it on the fiche.

anyone running the new version cr29mm's ? worth the cash ?

cheers

[Bryanj]

They aint available seperate I'm afraid you will have to get a sheet of felt and some hole punches--Hint:- cut the centre hole first