LM MK2 Carb synchronization |
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Lemon 2 Junior
Senior Member Joined: 04 Feb 2016 Location: Ystradgynlais Status: Offline Points: 222 |
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Posted: 09 Feb 2016 at 17:17 |
So valves sorted, now onto the carbs..they need setting from scratch, wife helped with throttle and slide sync and slides seem to be in order, I've read the dellorto manual and to be honest, was a little beyond me...Any advice on where to start with concerning idle and mixture...Bike will start on choke, but right carb is blowing fuel vape and popping from pipe...Any help.much appreciated.
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Doug
Senior Member Joined: 25 Sep 2014 Location: North East UK Status: Offline Points: 246 |
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Make sure valves are adjusted correctly and timing is spot on before anything else. Give the carbs a good clean and ensure there are no manifold air leaks. If the exhaust is stock I'd begin with factory settings.
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Mike H
Senior Member Joined: 21 May 2014 Location: East Anglia Status: Offline Points: 8733 |
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Yes really start by stripping cleaning and checking the carbs, can eliminate 'unsolvable' problems when it comes to setting up. Any hard green or brown deposits needs removing and check all jets and airways are clear. This can be difficult as the deposits can reduce the diameter of jets so they still look OK. Guess how I know! If in doubt, get a whole new set of jets.
Check float heights are correct and equal (metal arms parallel to float bowl flange when in the closed [up] position), also that both floats are the same weight (should be embossed on). Ideally need vacuum gauges and 6mm adaptors for the intake 'manifolds' to balance the slide heights. Start by getting both slides at the same height, and with a small gap (for idle). With carbs off can use e.g. a 1mm drill bit to set the gap. Thereafter when changing the throttle stop screws always turn BOTH BY THE SAME AMOUNT. Except: where fine balance of the throttle stop screws is done with help of the vacuum gauges. Exact reading doesn't matter so long as both are equal, as near as is practicable. After that, can set the throttle cable adjusters in the samec way, when slides are hanging on the cables (just off idle). Mixture screws start at 1.5 turns out. That is to say, screw all the way in, then anti-clockwise 1.5 turns. This is a beginning position only as it may not be enough, 2 - 2.5 turns out tends to be more common. You adjust these until engine idles without you having to use the twistgrip then you can revise the throttle stop screws BUT note that engine needs to be properly warmed up to get absolutely right, which is rarely possible on the stand in your garden, so expect idle to be bit high after a few miles of actual riding. If so throttle screws can simply be screwed in a bit to compensate (both by the same amount). After a while with age air leaks may occur down the idle screw threads and interfere with the mixture but you can get small O-rings to put in. In fact carb overhaul kit should include them. On the LM's the accelerator pump diaphrams could be failing so need checking and replacing if necessary. HTH |
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"Chicken nuggets don't dance on a Tuesday."
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Pharisee
Senior Member Joined: 24 May 2015 Location: Bedfordshire UK Status: Offline Points: 119 |
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I had a couple of problems balancing the carbs on my LM2 recently. The first problem was actually getting the blanking screws out of the inlet manifolds. They would only unscrew two or three turns before the head of the screw hit the underside of the cylinder head cooling fin. In the end, I had to remove a tiny bit of the fin with a Dremel to allow the blanking screw to pass by. Anyone else had that problem?
The second was that my vacuum gauges didn't come with any M6 adaptors. I had to turn a pair up out of some 6mm brass rod. All very inconvenient |
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Light travels faster than sound which is why some people appear bright until they open their mouth.
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Lemon 2 Junior
Senior Member Joined: 04 Feb 2016 Location: Ystradgynlais Status: Offline Points: 222 |
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Using a drill bit for slide height adjustment is a good idea, will give that a go... been well over twenty years since the bike was last ridden, perhaps a carb overhaul kit may be in order...distributor was replaced as it was found, and all connectors have been checked and clean on rebuild, valves were done yesterday, so perhaps some TLC on the carbs is needed....she does fire up and revs out well, just struggling on transfer from pilot to main by the sounds of it... Dad gave me a 1963 Triumph Thunderbird as when i first past my test nearly twenty years ago, didn't really grasp the whole concept of pre ECU bikes, so many thanks for your help...between you lot and Dad, should hopefully get a basic grasp of old school bikes...i did get some slight trouser movement from side movement as i was warming her up in the shed earlier today, which was nice.
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Lemon 2 Junior
Senior Member Joined: 04 Feb 2016 Location: Ystradgynlais Status: Offline Points: 222 |
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how did you get on? was looking at a carbtune, but for £70 i would hope I wouldn't have to bugger about with adapters. |
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Pharisee
Senior Member Joined: 24 May 2015 Location: Bedfordshire UK Status: Offline Points: 119 |
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Once I'd got the M6 adaptors, it was fairly easy. I only have a cheap carb balancing kit that I bought off eBay but it did a reasonable job. Adjusted the slide stops to give the same reading on both gauges (at a tick-over of about 1100 rpm). It was a bit subjective as the gauge needles were bouncing about a bit. Once I was happy with that, I adjusted the cables so that both slides lifted at the same time when the throttle was opened slightly. Made sure that both gauge needles moved at the same time. I've not had the Lemon very long so I'm no expert but it ticks over nicely when it's warmed up. |
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Light travels faster than sound which is why some people appear bright until they open their mouth.
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Lemon 2 Junior
Senior Member Joined: 04 Feb 2016 Location: Ystradgynlais Status: Offline Points: 222 |
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ah good, yep slightly different to modern bikes, I can tune my Triumph Sprint ECU with my mobile phone, but can't tune a set of carbs manually...sums it all up.
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Phil
Falcone Joined: 20 Jan 2016 Location: Yorkshire Status: Offline Points: 29 |
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Just to add, when you balance the carbs using vacuum gauges once you have got them balanced on tick over, try swapping the gauges from side to side to make sure both gauges read the same as each other. When you do the revving up test make sure the bars are straight ahead, depending how the cables are routed you will find that putting the bars on full lock will alter the carb balance on an open throttle
Good luck |
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Brian UK
Moderator Group Joined: 13 May 2014 Location: Surrey Status: Offline Points: 17641 |
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Best and cheapest setup for balancing two carbs (or FI) is a manometer. Never goes wrong and far more accurate than vacuum gauges. See how to do it in the FAQ section.
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Brian.
Better 5 minutes late in this world than years early in the next. |
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Dukedesmo
Senior Member Joined: 17 Apr 2015 Location: Leics Status: Offline Points: 856 |
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I have a (Morgan) Carbtune, bought it for my Ducatis. Works fine on the LM and was supplied with both M5 and M6 adapters. |
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Le Mans 2
Ducati 916 Ducati M900 |
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red leader one
Senior Member Joined: 07 Oct 2014 Location: Cullercoats Status: Offline Points: 4466 |
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Pretty heavy then.
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Dukedesmo
Senior Member Joined: 17 Apr 2015 Location: Leics Status: Offline Points: 856 |
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Indeed, chain required to restrain the beast.
Funny thing is that I made a short video of the bike running that day to try and capture the noise through the 'solo per competizione' Lafranconis. I set up the camera (my phone) on the bench to the rear and right side of the bike and revved it a bit but the pressure waves from the exhausts blasted the phone onto the floor. Luckily the phone didn't break so the whole episode is captured on video...
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Le Mans 2
Ducati 916 Ducati M900 |
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Pharisee
Senior Member Joined: 24 May 2015 Location: Bedfordshire UK Status: Offline Points: 119 |
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Your threaded holes appear to be in a different place to mine Mine are on the edge that face directly towards the rocker box. Is it possible that my inlet tracts have been swapped over (left cylinder to right cylinder) at some time in the past? |
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Light travels faster than sound which is why some people appear bright until they open their mouth.
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Dukedesmo
Senior Member Joined: 17 Apr 2015 Location: Leics Status: Offline Points: 856 |
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Certainly looks odd, I've not tried swapping them but assuming the holes are equally spaced it might be a possibility? Here's a close-up of mine; Really easy to get at.
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Le Mans 2
Ducati 916 Ducati M900 |
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