Carb-plugs SFC1000

SkinnyPinny

SkinnyPinny

Full member
Location
Cambridgeshire, United Kingdom
Hi all, I decided to go through my bike to improve the rich running which it has had for a long time,
Never been a major issue as replacing the plugs when it starts to not start cleanly, seemed to keep it going well enough.
sfc1000, with Honda VFR coils, NGK red racing leads & straight caps, I think these are resistor 5k?
It has IIS ignition fitted, .......best improvement I made,
So this time, I rebuilt with new atomisers-AB250, K1needles, 180 main jets, #250 float valves and seats.
Checked float heights at 18mm (black 10gr) it already has #60 pilot, (was 65) air screw is 1.5 out
The result is that I reckon most of the richness is due to the choke seal not sealing properly,
The 3 choke cable adjusters are right up and without the locking nuts, I am only seeing about 44-45mm free length, from base of cable mount to end of plunger, is this usual?
Also, some time ago, I bought some NOS champion N2C. But when fitting I noticed they are actually RN2C,
Will these cause a problem?
Any advice appreciated,
Stuart
 
Unless your running Dope, Methanol 180 mains are crazy big. They sometimes 145 are now to big for modern fuel. Lots are down to 125 or less.
 
Go back to AB265 needle jets, 250 are far too small. You'll soon be running around in circles with them and the K1 needles.

Not sure if the IIS can cope with suppressed caps AND plugs. Usually, aftermarket ignitions call for one OR the other.

If in doubt, replace the choke plungers. The rubber seal can deteriorate to the point that it no longer seals reliably, even with play in the cable.

piet
 
Last edited:
Vince said:
Unless your running Dope, Methanol 180 mains are crazy big. They sometimes 145 are now to big for modern fuel. Lots are down to 125 or less.
Click to expand...
Depends mainly on the cams... no mention of them. But yes, 180 would be far too large for the stock F1s. P1, now that's a different story!

piet
 
ok, I need to learn to type, correction I put in AB265 atomisers, 128 mains, K1 needles, 60 pilot jets, #250 float valves,
but thanks for the pointers,
Champon N2C I believe would be correct, but not that easy to find, they all seem to be RN2C.
that was my question really, what would likely happen with resistor caps and plugs.
I dont know if IIS John is ever on this forum, to confirm.

also, I have replaced the plungers, and made sure I have slack in the cable, ie no lock nut, only way aprt from shortening the outer I could see,
Stuart
 
John pops ver very occasionally, I once ran resistor plugs with resister caps on my Pantah. It ran horribly, flat as a tack.No mistaking how bad, replaced the plugs and back to good.
 
Try going down on the pilots some more and then eventually 2 turns out on the mixture screws.
Sort out chokes of course.

How do you know it's rich?

Paul
 
If it's too rich on idle circuit, it'll start very easily.
Colour of plugs on starting isn't an indication of much. Plug reading is done on full throttle and not much info to be had with lead free petrol.
Are you sure the timing is spot on? And valve clearance? Both can feel like a rich mixture.

Paul
 
Had a similar issue with my SFC1000 - changed to Mikunis. The sooty plug - and the misfire after an hour or so riding which I attributed to the sooty build ups as it took longer to happen on new plugs - went away, plus runs much better throughout. Tried all sorts of Del's jet combinations over a couple years - but just didnt come right - so pretty much gave up in the end. Changing sooty plugs during a ride lost its appeal somewhat after a while.
 
OK - I repeat myselfe again and again on the starting of Laverdas...:

First of all: make sure you synchronize the choke sliders! Best to adjust them while carbs are on the bike, standing right side of the bike, schnorchels removed and looking into the rear of the carbs. Left side you see the hole with the choke slider. Move them up until the first one hides and adjust the others to the same level.
Second: make sure they do close all completely!
third: check float hight accurately and set to factory settings!
fourth: don't just pull open choke when you start the bike!!!! Choke enrichens the starting circuite MASSIVELY! To find the right spot where the bike starts, close choke, turn key on "on", press starter without throttle and slowly engage choke. At one point (somewhere between 1/2 and 2/3 typically), bike starts. Remember this point and only ever open choke to this point from now on. even if its really cold outside, choke setting will be just a bit more then but almost never full!

This has removed starting issues on my bike (and many others) ever since used. ;)
 
Laverdalothar said:
OK - I repeat myselfe again and again on the starting of Laverdas...:

First of all: make sure you synchronize the choke sliders! Best to adjust them while carbs are on the bike, standing right side of the bike, schnorchels removed and looking into the rear of the carbs. Left side you see the hole with the choke slider. Move them up until the first one hides and adjust the others to the same level.
Second: make sure they do close all completely!
third: check float hight accurately and set to factory settings!
fourth: don't just pull open choke when you start the bike!!!! Choke enrichens the starting circuite MASSIVELY! To find the right spot where the bike starts, close choke, turn key on "on", press starter without throttle and slowly engage choke. At one point (somewhere between 1/2 and 2/3 typically), bike starts. Remember this point and only ever open choke to this point from now on. even if its really cold outside, choke setting will be just a bit more then but almost never full!

This has removed starting issues on my bike (and many others) ever since used. ;)
Click to expand...
Check the float heights !!!!!
 
Lothar, thats pretty much how I start thebike anyway, I dont 'pump' the throttle, choke slowly open until it starts then off asap.
re checked float heights, 18mm,
I am more confident that the choke seals are now sealing, I cleaned and rerouted the cable/splitter and made sure its as smooth as possible,
but I will check to see if I can see any mark on the seal after a few miles/weeks
thanks again,
 
SkinnyPinny said:
Lothar, thats pretty much how I start thebike anyway, I dont 'pump' the throttle, choke slowly open until it starts then off asap.
re checked float heights, 18mm,
I am more confident that the choke seals are now sealing, I cleaned and rerouted the cable/splitter and made sure its as smooth as possible,
but I will check to see if I can see any mark on the seal after a few miles/weeks
thanks again,
Click to expand...
OK - in that case, check the sparks. a week spark can cause that, too. Have you painted or coated the frame? Very often when that is done, somewhere on the frame an earthing connection is not working well... Check Battery under load (during starting). should not drop below 12 Volts, at least not below 11V. if it does, there might be something wrong with the battery...
 
sfcpiet said:
If in doubt, replace the choke plungers.
Click to expand...
You don't necessarily have to replace the choke plungers if they're not sealing properly. Have a look at the little rubber seal on the tip. If it has a groove worn into it from the fuel aperture seat, hook the little ribber disk out with a pointed tool, flip it over and push it back in so the unused face is now doing the sealing. If you've already done that and both sides of the rubber seal are worn out, or it has gone hard, you can replace the rubber tip without having to buy a whole new brass plunger. Grab a small piece of 2mm thick viton sheet and a hole punch (6mm I think, but could be 5mm - memory is a bit hazy) and you can punch out as many little sealing disks as you need. Just flip the old ones out of the choke plungers and pop the new ones in. I dunno why Dellorto carb rebuild kits don't come with a new choke rubber. They have a bunch of other rubber O-rings and stuff in them.

Viton sheet is available on ebay: https://www.ebay.com.au/itm/114571495690?hash=item1aacfe490a:g:LX0AAOSwU9xUSMC3
 
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