3CL carby settings

G

ghwallice

Hero member
Location
Ipswich
Currently moving house and all reference material is packed away.  My bog stock 3CL refurb project has been running on the bench, but was/is poorly set up. It's only about a klm from one house to the next, so thought I might ride the bike and risk the cops. It will be the first time the bike has been ridden since 1985, and I'm curious as to how it feels.

So, I decided to balance the slides with a 5mm drill first, and using a sniffer and a heat gun on the pipes, get the idle screws/stochiometric about right. Catch is, it now won't start.

The idle screws were on about 1 1/4 turns. What should I set them at to fire it up?

Using a drill as a feeler guage, about where should I set the slides for idle?

Does the Ignitec ignition shut down spark if it doesn't fire in X amount of turns?

I guess if I don't get to give it a run after 35 years of sitting around, I can put it on a trailer.....

Regards, Greg
 
yeh, done all that. carbs went through the ultrasonic cleaner, float levels are spot on. new rubbers ect ect. I think its just a combination of idle air mixture and throttle opening, and now its probably flooded...
 
ghwallice said:
oh well, there's always spray cans of ethanol?or is it methanol..... "Start you Bastard"
Click to expand...

The active ingredient ether (dimethyl ether or diethyl ether). The can actually contains a mixture of ether and petrol. Somewhere between 30% and 60% ether. Ether used to be used as an anaesthetic gas, so don't use it in confined spaces and avoid breathing it in, unless you feel like a quick snooze on the floor. Rarely used as an anaesthetic these days because of its propensity to explode, which is an undesirable side-effect during surgery.
 
Ether is never used as an anaesthetic nowadays.
In fact, I believe it's not allowed in hospitals at all over here and can only be obtained strictly on prescription because of its addictive properties.

Can also be poured directly into the tank, transforms your triple into a V6.
For a short period of time.

Paul
 
Hope you did warm the bike up properly before you adjusted anything. If not, start all over again... How much are the idle screws out from fully in? should be 1,5 turns.

Are the choke sliders are all moving equally, too, and are closing and opening completely? Check them on the lower position when they juuuust open and the same when they start hiding at the top (you can see them on the left side of the carb (assuming we are talking about PHF).

I have seen bikes where choke sliders were totally uneven and people adjusted the idle screws to compensate the richer running on one or the other cylinder. The bike stalled after only some seconds of relatively smooth running. I took the rubber connectors to the airbox off, saw the sliders were moving on different positions and adjusted them to the same hight. then I simple turned the idle screws completely in and 1,5 turns out et voila - the bike kept running smootely. ;)

Also, if you start the bike, leave the choke closed first and gentle pull it open until the bike starts. With weak sparks, I have seen many bikes having an issue with full choke: the spark plugs get wet and they do not start anymore. If that happens, All you can do is take out the spark plugs, let the bike sit for a while and clean the spark plugs or take new ones and try again, with the choke only gently pulled from fully closed to open while you start the bike.

If all that does not help, check electrics. What voltage does the battery show under starting? If f.e. you have a DMC, below 9 Volt the DMC simply does not produce a spark...
 
I think that is what has happened. Full choke and overwet the plugs. I chucked a new set in and away it went. Got it warmed

up and did my best on the air screws, which finished up about 1 1/4 turns out. Header temp was pretty even.

Im thinking there is a choke seating issue as the afr would stabilise for 20/30 seconds, and then go super rich and settle back down.

Anyhow, met my goal, rode the bike for it's first time in 35 years, and rode it around to the other property.

Thanks for the comments!
 
dave48 said:
Can somebody explain the carb balancing with a 5mm drill bit?
Click to expand...

Put a 5 or 6mm drill bit in each carb mouth so that they're held by the slides.
Observe drill bits when you twist the throttle. They should all lift together.

I use my finger as well to be certain that the slide disappears at the top of the carb bore in each carb at the same time.

Vacuum is more precise but you can start again after 3 hours running of the engine.

Paul
 
Paul Marx said:
Vacuum is more precise but you can start again after 3 hours running of the engine.
Click to expand...

Where does that leave the drill bit method?  At most, it can be considered as a starting point, no more.

piet
 
maurice turner said:
100% and you dont have to use a 5mm drill bit !!!!!!
Click to expand...

Agreed. In the absence of vacuum gauges, I'd say a better method is to achieve a smooth idle between the cylinders and then use the simultaneous slide lift off the idle stop screws. You need a good ear and have fine tuned the idle mixture screws though.
 
To me that might work on a twin but the carcofany made by my bike especially the 180s would defeat my ear to balance it. That reminds me of when John Wilson fitted his EI to my bike and it suddenly made a very odd sound at idle. It was suddenly a different sound than it made for the first 10 years I owned it. It had a really nice rumble like a V8 with a miss. I can tune my Pantah by ear but it takes Vacum Gauges for my 3c.
 
Vince said:
To me that might work on a twin but the carcofany made by my bike especially the 180s would defeat my ear to balance it.
Click to expand...

You don't do it with the engine running Vince. Just open and close the throttle and listen for the simultaneous "click" as the slides bottom on their stops.
Anyway, it's not an option on a triple because they don't have individual throttle stops. Idle is controlled by the single stop on the linkage at the top of the carbs.

My Guzzi LM1 seems to need carb synchronising quite often. I do it by listening for the noise as the throttle closes. Not sure why it goes out of whack all the time. Could be something to do with the long cables for each carb (twin pull throttle). Actually, I replaced the cables a while back but haven't ridden it since then. Hopefully it'll stay synched better with nice new cables.
 
Piranha Brother 2 said:
Agreed. In the absence of vacuum gauges, I'd say a better method is to achieve a smooth idle between the cylinders and then use the simultaneous slide lift off the idle stop screws. You need a good ear and have fine tuned the idle mixture screws though.
Click to expand...

Your idle stop screws are not at the same level.
If you use simultaneous lift off the stop screws as your starting point, you're reproducing that level difference all through the slide's travel.

Paul
 
Where does that leave the drill bit method?  At most, it can be considered as a starting point, no more.

Agreed Piet! I do have vacuum gauges, and they are more accurate. Drill bits as a starting point though. Vacuum gauges don't work so well on a motor that is stopped...

I'm still working out this process, given that I have a shit "ear" for tuning..I have never been able to tune a bike...

Use drill bits, 1 1/2 on idle screws, start the bike and warm it up, set with vacuum gauges, heat gun the headers, adjust air screws for even temp, check afr and adjust air screws for about stochiometric, check header temps, and the cycle goes on....

What do I struggle with is does an air screw adjustment on a cylinder impact on the efficiency of that cylinder and cause an imbalance in vacuum????

ive noticed a couple of times that after setup the drill test fails... 
 
You must log in or register to reply here.
Back
Top