Choke set up 180

T

TOMMY666BIKES

New member
Location
derbyshire
Hope this isn’t a daft question 🤷‍♂️ When I start my 180 jota using full choke it revs it’s t-ts off , my question is it possible to adjust the choke so that it doesn’t rev quite as high please
Ian
 
It isn't a "choke", Tommy, and shouldn't be used as one.
It's a set of start enrichment jets which are opened by the lever pulling the seals off them.
Technique is: on for cold starts, some require a touch when warm. As soon as possible, shut the lever and ride off.
 
The Sock said:
It isn't a "choke", Tommy, and shouldn't be used as one.
It's a set of start enrichment jets which are opened by the lever pulling the seals off them.
Technique is: on for cold starts, some require a touch when warm. As soon as possible, shut the lever and ride off.
Click to expand...
Ok thanks 🙏🏻 I did wonder as I can’t see anyway to make adjustments, as soon as it fires I back the lever off anyway but I just wondered if I could stop it reving so high on initial start up on a cold engine
 
have one hand on your choke lever, not easy for the under tank models, and press the starter, almost immediately back off the choke to half way, ride off, close choke.

If your carbs are set up correctly it should not need any choke at all to get it (re) started, stinking hot or mildly warm, if you cannot start it like this the low end of your carbs (pilot jet, slide cutaway) are out, or somethimng else perhaps, which is very common, I even know of one dealer that gives (or did in the past) a printed page stating how to start hot or cold, it includes "use half choke when bike is warm" after he has serviced your bike.

CLEM
whose TS has been on Slipstreams dyno so many times that it wore the thing out
 
Last edited:
Ignition on, hand on bar lever choke while still in off position. Press starter button and at the same time slowly open choke lever till she fires. Usually about a third to half travel of the lever. From there adjust choke for a settling tickover. I don't like starting on an instant scream when the oil hasn't had time to make it's way round things.
 
Alan said:
Ignition on, hand on bar lever choke while still in off position. Press starter button and at the same time slowly open choke lever till she fires. Usually about a third to half travel of the lever. From there adjust choke for a settling tickover. I don't like starting on an instant scream when the oil hasn't had time to make it's way round things.
Click to expand...
Thanks Alan, I’ll try your suggestion and see how I get on with that , like you I don’t like the motor reving high on cold start
 
CLEMTOG said:
have one hand on your choke lever, not easy for the under tamk models, and press the starter, almost immediately back off the choke to half way, ride off, close choke.

If your carbs are set up correctly it should not need any choke at all to get it (re) started, stinking hot or mildly warm, if you cannot start it like this the low end of your carbs (pilot jet slide cutaway) are out, or somethimng else perhaps, which is very common, I even know of one dealer that gives (or did in the past) a printed page stating how to start hot or cold, it includes "use half choke when bike is warm" after he has serviced your bike.

CLEM
whose TS has been on Slipstreams dyno so many times that it wore the thing out
Click to expand...
Thanks Clem , I’ll have to practise my yoga 😊
 
TOMMY666BIKES said:
Thanks Paddy , I’m not sure what size jets are fitted at the moment
Click to expand...
easy enough to find out. Take one float bowl off. Main jet is the biggish on in the center. Starter jet is the slightly smaller one right beside it. Removes easily with a short straight blade screwdriver. Number will be on the face of it. May as well also heck main jet size while you have the float bowl off.

starter jets will typically be anywhere from a 50 (smallish) to a 70 (bigish). Not sure which year/displacement/compression/cam 180 you have, typically a 55 or 60 starter jet works well. You crder a size smaller than what you have and try that. People put larger starter jets in to compensate for other hard starting issues.

Other thing to check is the adjustment of each choke plunger to be sure each is actually fully closing when off, and that the rubber tip on each has not perished. If someone has not already done it, you can cheap out on choke plungers by just prying out the rubber tips and flipping the tips over to get another several years out of them....

as Clem alluded to above, could be incorrect slide cutaway fitted, worn slides, worn slide bores, on and on.... if you are anywhere near Ducati Paddy, take the carbs/bike to him.
 
Paul LeClair said:
easy enough to find out. Take one float bowl off. Main jet is the biggish on in the center. Starter jet is the slightly smaller one right beside it. Removes easily with a short straight blade screwdriver. Number will be on the face of it. May as well also heck main jet size while you have the float bowl off.

starter jets will typically be anywhere from a 50 (smallish) to a 70 (bigish). Not sure which year/displacement/compression/cam 180 you have, typically a 55 or 60 starter jet works well. You crder a size smaller than what you have and try that. People put larger starter jets in to compensate for other hard starting issues.

Other thing to check is the adjustment of each choke plunger to be sure each is actually fully closing when off, and that the rubber tip on each has not perished. If someone has not already done it, you can cheap out on choke plungers by just prying out the rubber tips and flipping the tips over to get another several years out of them....

as Clem alluded to above, could be incorrect slide cutaway fitted, worn slides, worn slide bores, on and on.... if you are anywhere near Ducati Paddy, take the carbs/bike to him.
Click to expand...
Thanks for the advice Paul , when it warms up a little I’ll nip in the garage and whip the float bowls off
 
Hi Tommy

Think of the 'choke' as a tiny carb, stuck onto the side of the main carb. It allows fuel AND air into the flow, for the starting mixture.

As others have mentioned, you should not be using your full 'choke' for anything other than maybe getting the bike initially started. Immediately half close it, once the motor has caught and then close asap thereafter. I close after a hundred yards or so (having not started the bike before I'm seated and ready to get on my way). I use the same method as Alan above, spin the starter, then introduce choke until she fires.

If your bike is revving too hard when on full 'choke' then that is kinda normal. And in the other direction, if it starts but will then bog down when on higher choke openings, the your startr jet is too rich. Bikes that just about start, but then rev too high at half-choke usually have a starter jet that is a bit too lean.

On the subject of rich/lean, the starter jet is long and has some v-small emulsifier horizontal holes around the shank. If a DPO has been very ham-fisted when tightening the jet, then the jet can twist, around the weak section created by these holes and close th holes up a bit - check for that.

HTH

Paul H
 
Last edited:
lets not get confused here, and the American terminolodgy (or Canadian) may have created some variables,
take one float bowl off and dead centre you will see the main jet (it is screwed into the bottom of the emulsion tube) which will not have (much) effect until the throttle is 3/4's open, off centre is what we call in the UK the "pilot" jet this takes care of the fuel coming in on tickover or at teeny weeny (very weeny) throttle openings, not usually refered to as a starter jet in UK, because in PHF carbs THERE IS a starter jet. Both pilot and main jets can be changed from the outside, by removing the float bowls, (it is fiddly, you will lose something under the starter, so dont do it) but since you need to get a good look at the slides (are they all the same? are they scored?) take the bank of carbs off the bike and have a more thorough delv, you will also be able to see what needles you have (are they all the same? is the clip in the correct and same groove on all?) and have good general clean out, replace the float valves and their seats with ethanol proof type, this usually only get done when you have a sump full of petrol (eek).

the starter jet, well its not realy that, more like a "starter orifice" is external, but again fiddly to look at, where the choke cable enters the carb body (top) there is a pear shaped plate with a countersunk screw, remove this and the cable and it adjuster will be in free air, the plunger which seals the orifice at times when the choke is "off" wil be hanging on the cable at the end, the bottom of this brass plunger has a rubber insert, it should be hardly marked, it can be removed from the brass plunger and turned around, but they are cheap enough to buy and replace with new, so that is what I would do, with a magnifyer look down its bore hole and you will see the brass seat with raised edges, this is very unlikely to ever get blocked due to its size, but the "rim" needs to be in reasonable condition.

All of this prompts me to suggest that you remove the bank of carbs, put them in a box and send them to paddy, Be carefull when removing the bank if you have the type where they fit onto a male alloy spigot and are isolated by a plastic sleeve in the throat of the carbs, DO NOT WIGGLE, pry them of in a very straight/square fashion, dont thump the bodies with anything, a squirt of WD40 wont hurt, and when you re-install post Paddy, be sure to add some lube to the male spigots to aid the removal the next time. I use 3 in 1. this does not apply if your carbs are the rubber mounted type, that is to say there are two jubillee clips to fix them to the manifolds, or (like Dave Silver) have a 45DCOE carb and a half
CLEM
 
Last edited:
Haggis said:
Hi Tommy

Think of the 'choke' as a tiny carb, stuck onto the side of the main carb. It allows fuel AND air into the flow, for the starting mixture.

As others have mentioned, you should not be using your full 'choke' for anything other than maybe getting the bike initially started. Immediately half close it, once the motor has caught and then close asap thereafter. I close after a hundred yards or so (having not started the bike before I'm seated and ready to get on my way). I use the same method as Alan above, spin the starter, then introduce choke until she fires.

If your bike is revving too hard when on full 'choke' then that is kinda normal. And in the other direction, if it starts but will then bog down when on higher choke openings, the your startr jet is too rich. Bikes that just about start, but then rev too high at half-choke usually have a starter jet that is a bit too lean.

On the subject of rich/lean, the starter jet is long and has some v-small emulsifier horizontal holes around the shank. If a DPO has been very ham-fisted when tightening the jet, then the jet can twist, around the weak section created by these holes and close th holes up a bit - check for that.

HTH

Paul H
Click to expand...
Hi Paul
thank you for the reply , I’m going to try the method of spinning the motor as I gradually apply the choke , bike hasn’t been started for a while as I’m not a fan of starting it up and not riding it but I’ll post on here if this method works ok
thank you Tommy
 
CLEMTOG said:
lets not get confused here, and the American terminolodgy (or Canadian) may have created some variables,
take one float bowl off and dead centre you will see the main jet (it is screwed into the bottom of the emulsion tube) which will not have (much) effect until the throttle is 3/4's open, off centre is what we call in the UK the "pilot" jet this takes care of the fuel coming in on tickover or at teeny weeny (very weeny) throttle openings, not usually refered to as a starter jet in UK, because in PHF carbs THERE IS a starter jet. Both pilot and main jets can be changed from the outside, by removing the float bowls, (it is fiddly, you will lose something under the starter, so dont do it) but since you need to get a good look at the slides (are they all the same? are they scored?) take the bank of carbs off the bike and have a more thorough delv, you will also be able to see what needles you have (are they all the same? is the clip in the correct and same groove on all?) and have good general clean out, replace the float valves and their seats with ethanol proof type, this usually only get done when you have a sump full of petrol (eek).

the starter jet, well its not realy that, more like a "starter orifice" is external, but again fiddly to look at, where the choke cable enters the carb body (top) there is a pear shaped plate with a countersunk screw, remove this and the cable and it adjuster will be in free air, the plunger which seals the orifice at times when the choke is "off" wil be hanging on the cable at the end, the bottom of this brass plunger has a rubber insert, it should be hardly marked, it can be removed from the brass plunger and turned around, but they are cheap enough to buy and replace with new, so that is what I would do, with a magnifyer look down its bore hole and you will see the brass seat with raised edges, this is very unlikely to ever get blocked due to its size, but the "rim" needs to be in reasonable condition.

All of this prompts me to suggest that you remove the bank of carbs, put them in a box and send them to paddy, Be carefull when removing the bank if you have the type where they fit onto a male alloy spigot and are is0lated by a plastic sleeve in the throat of the carbs, DO NOT WIGGLE, pry them of in a very straight fashion, dont thump the bodies with anything, a squirt of WD40 wont hurt, and when you re-install post Paddy, be sure to add some lube to the male spigots to aid the removal the next time. I use 3 in 1. this does not apply if your carbs are the rubber mounted type, that is to say there are two jubillee clips to fix them to the manifolds.
CLEM
Click to expand...
Thank you for your advice Clem
 
Clem,

The starter jet is accessable when the float bowl is removed. It is located imediately under the "choke" slide orifice, which is actually an enrichener slide, or start carburettor if you like.

For all jetting changes on the PHB/PHF/PHM carbs, the bowl needs to be removed. The main jet can be changed with only the central nut removed, providing the bowl remains stuck to the sealing o-ring.

piet
 
I thought that was the dip tube and foot valve. I dont remember ever taking one out of the carb body!
CLEM
 
FWIW, noticed a few comments previous, while the main jet is just that a main jet, if way too big ( ie 145+ ) it will effect the idle/cruise jet and needle transition noticeably. Well i know from sorting out new proper ignition on old Bosch anti pinking jetting for the PHF32's.

Was ever a mystery that overall UK Laverda motors could ride on 145 mains, out here it was anything but a well behaved ride, let alone the dreadful fuel consumption, erratic on road implications. j.
 
Hi Jon. My Jota had 145 mains in it when I got it (PO evidently had little clue about carby tuning). It rode relatively OK (no flat spots or misses) but wasn't making much power and had atrocious fuel consumption. After a few dyno runs we (dyno bloke and I) settled on 120 mains, but the interesting thing is that on an experimental run with no main jets at all, it ran the same as it did with the 145s in it. The conclusion being that a 145 main jet is beyond the fuel flow range of the emulsion tube and needle/jet that sits just above it.
 
You must log in or register to reply here.
Back
Top