bluerm166
Well-Known Member
Anybody please suggest correct start point to adjust pilot screw .No. of complete turns from fully in ?
Thanks
Thanks
Tohatsu 3.5 4stroke Pilot screw turns setting
- Thread starter bluerm166
- Start date
Heckler
Well-Known Member
Ever since Noah was a lad a good starting point is 1.5 turns out. So, lightly screwed all the way in to start, 1.5 turns out and then adjust from there.
Stu
Muddy Boat
Well-Known Member
Just did mine and it was between 2.5 and 3. Not sure of factory setting as I rejetted from 2.5 to 3.5hp.
RichardS
N/A
Interesting Stu. If in doubt, I've always worked on the basis of 2.5 turns out .... but either way should be enough to get the engine started so you can tune by ear.
Possibly a bit less on a 2T air screw.
Richard
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bluerm166
Well-Known Member
Many thanks.I'm probably in the right area then at 2 full turns.
Trouble is that this screw faces into the engine (apparently in the US you're not supposed to have access on environmental grounds) meaning that it's inaccessible with the tank in it's proper place.Although the tank lies there pretty easily so the odd bolt is sufficient in between tweaks.
Thanks.
Trouble is that this screw faces into the engine (apparently in the US you're not supposed to have access on environmental grounds) meaning that it's inaccessible with the tank in it's proper place.Although the tank lies there pretty easily so the odd bolt is sufficient in between tweaks.
Thanks.
Heckler
Well-Known Member
Richard you are right, Amal carbs back in the day, recommended setting, then Honda came along to kill off the Brit bikes but still the same. Sorry folks 2.5 turns it is.Interesting Stu. If in doubt, I've always worked on the basis of 2.5 turns out .... but either way should be enough to get the engine started so you can tune by ear.
Possibly a bit less on a 2T air screw.
Richard
Stu
Muddy Boat
Well-Known Member
Agreed, a bit of a pain. It is possible to hold the tank (level!) while tweaking, just be careful of the twirly bits ;-)
RichardS
N/A
I bet you'd enjoy the PC software we run on my Son's LPG Rangie, Stu. The laptop monitors O2 exhaust content, throttle position, gas volume intake and engine revs on a live graphical display. When you adjust the idle or main LPG jets you can see the effect on combustion in real time.
It's the first time in 50 years that I can actually see from live engine data whether my judgements about whether I have set the carburation correctly by ear can be backed up by the actual facts .... and although my ear is pretty good, the science is even better because you can check combustion throughout the rev range whilst actually underway.
Richard
macd
Well-Known Member
Oddly enough, Mikuni, Japan's major carb manufacturer during that period, obtained licence to make Amal carbs early in it's history and went on to refine them into far better instruments than the originals. That the Brit bike industry was killed is one point of view; that it committed hari-kiri is another. But, one way or another, turns of the screw were definitely involved...
Heckler
Well-Known Member
Was in a bike shop in Spain the other day, saw a modern Amal on the shelf. They manufactured them there for a while. My mate who I used to spanner for back in the early 70s, Gary Bryan, was racing his Weslake converted 8 valve Triumph, powered sidecar at Oulton Park. It ended in disaster, Pat Sheridan and passenger copped it, Garys' passenger as well, Gary ended up paraplegic but then started making very successful Weslake powered, developed by him, solos. He won the Battle of the Twins series with it, whupping the works Ducati!Oddly enough, Mikuni, Japan's major carb manufacturer during that period, obtained licence to make Amal carbs early in it's history and went on to refine them into far better instruments than the originals. That the Brit bike industry was killed is one point of view; that it committed hari-kiri is another. But, one way or another, turns of the screw were definitely involved...
Anyway was talking to him last year, he has stretched the engine to over 900cc and the Spanish Amal carbs, which is where I started, he has bored out the biggest ones (38mm) to over 40 mm.
He is getting over 100bhp from the engine but is at the limit now, the crankcases of the unit Triumph, even though they are beefed up are cracking.
Stu
PS http://www.rgb-racing.com
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Heckler
Well-Known Member
I would! Was thinking about getting involved again with RGB but not enough time! His ignition system still uses a Boyer electronic type ignition system trigger running off the camshaft. I put a strobe on it, it was jittering all over the place, still using the Triumph base plate and crappy screw adjustment. I reckon something like your system using a crank trigger and software control, then adjusting it in real time would be good for a few more hp!I bet you'd enjoy the PC software we run on my Son's LPG Rangie, Stu. The laptop monitors O2 exhaust content, throttle position, gas volume intake and engine revs on a live graphical display. When you adjust the idle or main LPG jets you can see the effect on combustion in real time.
It's the first time in 50 years that I can actually see from live engine data whether my judgements about whether I have set the carburation correctly by ear can be backed up by the actual facts .... and although my ear is pretty good, the science is even better because you can check combustion throughout the rev range whilst actually underway.
Richard
Stu
steve66
Well-Known Member
I bet you'd enjoy the PC software we run on my Son's LPG Rangie, Stu. The laptop monitors O2 exhaust content, throttle position, gas volume intake and engine revs on a live graphical display. When you adjust the idle or main LPG jets you can see the effect on combustion in real time.
It's the first time in 50 years that I can actually see from live engine data whether my judgements about whether I have set the carburation correctly by ear can be backed up by the actual facts .... and although my ear is pretty good, the science is even better because you can check combustion throughout the rev range whilst actually underway.
Richard
You can also do that with a colourtune
RichardS
N/A
I last used one of those about 40 years ago. Do they still make it?
Definitely better than nothing but you can't use it under load conditions, of course.
Richard
steve66
Well-Known Member
Why cant you use it under load?. I have many times
RichardS
N/A
OK. It's must be something different to the gadget I'm thinking about from way back. That was a sort of clear plastic spark plug and short solid tube which allowed you to see the actual combustion process, which meant that you had to have your head under the bonnet with the engine running whilst you looked down the tube. No way that could be done as the car was motoring under load of course, unless you were sitting on top of the engine with the bonnet resting on your head at 50 MPH.
Richard
PaulRainbow
Well-Known Member
Can't beat setting carbs up with a piece of hose in your ear
steve66
Well-Known Member
OK. It's must be something different to the gadget I'm thinking about from way back. That was a sort of clear plastic spark plug and short solid tube which allowed you to see the actual combustion process, which meant that you had to have your head under the bonnet with the engine running whilst you looked down the tube. No way that could be done as the car was motoring under load of course, unless you were sitting on top of the engine with the bonnet resting on your head at 50 MPH.
Richard
Nope they havent changed. Admittedly difficult using in a car but dead easy running a 3.5hp outboard flat out in a test tank
RichardS
N/A
LOL. I'm not sure that your quoting of my post #8 was quite the ticket as "that" is something you definitely can't do with a Colourtune.
Richard
steve66
Well-Known Member
I have no idea what you mean Richard. All i know is you can, and I have set outboard carburettors up under load in my test tank using a colourtune
Heckler
Well-Known Member
SUs?Can't beat setting carbs up with a piece of hose in your ear
