Thicky setting up a DMC2
- Thread starter cwis
- Start date
impamentor
Full member
- Location
- New Forest, Hampshire
Chris
try 2 to 2 and 1/4 turns out on the idle mixture/s..........wind back in, a little by little to hit the sweet spot on each cylinder. Worked with mine...
try 2 to 2 and 1/4 turns out on the idle mixture/s..........wind back in, a little by little to hit the sweet spot on each cylinder. Worked with mine...
Well I've had the carbs apart, cleaned all the passages etc. Nothing there to report really...
I can get it to idle at 1000RPM, but opening the throttle makes it want to die (snaps and pops), and it hangs up on revs. Lean condition? I'm not sure it is actually idling on all three so it could be the other one chiming in making it race.
Bit late to make much noise now, so I'll warm it up and set the timing and check both sides tomorrow, and once that is done I'll know I have a carb problem!
Once spot of good news is that it's now charging its own battery when running, thanks to an additional coil from Wolfgang and a Honda Bros reg/rectifier!
Thanks to everyone that has contributed to this thread so far - it is much appreciated!
Chris
I can get it to idle at 1000RPM, but opening the throttle makes it want to die (snaps and pops), and it hangs up on revs. Lean condition? I'm not sure it is actually idling on all three so it could be the other one chiming in making it race.
Bit late to make much noise now, so I'll warm it up and set the timing and check both sides tomorrow, and once that is done I'll know I have a carb problem!
Once spot of good news is that it's now charging its own battery when running, thanks to an additional coil from Wolfgang and a Honda Bros reg/rectifier!
Thanks to everyone that has contributed to this thread so far - it is much appreciated!
Chris
Hi all,
Got the chance tonight to get a bit further with the bike.
I timed it up. I had to remove the generator flywheel and shift the rotor round on the crank - it actually triggers WAY later than midway on the pickup - more like 2/3 of the way past the pickup. I got a nice idle and it sounds very smooth. Idle control is working fine - I could see the timing shifting about.
It looks like the issues I was having were due to being really retarded at idle - so those who said it sounded like a late spark, take a bow!
Next I'll check the middle cylinder is firing at the correct time, and balance the carbs. Then it's curve 11 (I think from past posters on this subject) and a test ride....
Chris
Got the chance tonight to get a bit further with the bike.
I timed it up. I had to remove the generator flywheel and shift the rotor round on the crank - it actually triggers WAY later than midway on the pickup - more like 2/3 of the way past the pickup. I got a nice idle and it sounds very smooth. Idle control is working fine - I could see the timing shifting about.
It looks like the issues I was having were due to being really retarded at idle - so those who said it sounded like a late spark, take a bow!
Next I'll check the middle cylinder is firing at the correct time, and balance the carbs. Then it's curve 11 (I think from past posters on this subject) and a test ride....
Chris
Dellortoman
Hero member
- Location
- Tasmania, Australia
cwis said:
I recall an explanation of the so-called "idle control" from John Wilson a few years ago. According to John, it's a myth. There's no clever electronic wizzardry to regulate the idle speed, it's just a result of how the VR pickups work. The point at which the pickups see the rotor lobe passing actually changes with engine speed. It just happens that these timing changes occur in a way that damps out variations in idle speed.
As the engine increases revs, variations in crank speed are smoothed out by the flywheel effect. So when you connect a strobe, the ignition appears to jump all over the place at idle, but settles to a smooth advance as revs increase.
Cheers,
Cam
Tetley Laverda
Senior member
People that know far more than me advised curve 10 a progressive curve ideal for hi comp 180 jota runs very well on this curve from low down upwards and onwards wonderful
Enjoy
Tetley
Enjoy
Tetley
impamentor
Full member
- Location
- New Forest, Hampshire
Glad to hear alls well now 
Laverdalothar
Hero member
- Location
- Germany
Dellortoman said:
Hi Cam,
not wanting to discredit the man or his knowledge, but there is really an idle control built into the DMC (at least into the models after 1995). The ignition trigger of the pickup-system (DMC1) has two "noses" (DMC2 has a photo-cell with gaps in the rotating trigger plate, basically the same thing just with different signals), first delivers a kind of "calculation signal", second gives the ignition timing. According to the time-gap between these two signals, the DMC identifies not only the RPM but also changes to the RPM. In low revs (like idle) it tries to keep the RPM constant by changing the ignition timing. You can easily recognize that when coming to a traffic light and stop there (or elsewhere). The RPM drop down, the bike idles. All Lavis with especially bad synchronized carbs have the revs going down just a bit below idle and bike stalls at some point. Not so with the DMC. The Revs go down, too, but at a point below 900 or so, the ignition timing changes and the revs go up again. You can easily hear that change of the engine sound...
Friend of mine had that issue on his 750 SF1 all the time when coming to a stop. since he installed the DMC, the issue is gone, though the effect of the bike missing a beat or dropping the revs all of a sudden is still there, but the bike simply returns to idle afterwards.
HTH
The Three Dellortos
Hero member
jotacorsa said:
The Three Dellortos
Hero member
That is horrifing....... What sort of plugs are you using.... They look more like a TIG Welding torch than a sparrk plug !!
Tm
Tm
Hi everybody,
Just a quicky update.
Last night I stuck the tank on backwards using long fuel lines and marked a TDC for the centre cylinder.
I warmed the bike up on curve1, and checked that the centre cylinder (and the other two) are firing at the correct time. They were.
Off the choke, the bike idled perfectly at 1000 RPM - very clean, each cylinder perfectly audible. It's never done that before!
I switched to curve 10, and the idle sounded rougher. Response just off idle also was more hesitant compared to curve 2 (before 1500 RPM when the advance cuts in) I'm not sure why - any ideas?
The bike also hung up slightly returning to idle from 3K - I turned the idle jets out an extra 1/4 turn (2 1/4 turns in total) - this seemed to let it return to idle a bit better. It didn't do this on curve 1 either - again I'm a little mystified.... Maybe I need to back off the idle slightly - perhaps the idle control is retarding the ignition because idle is set too high and the advance once above 1500 RPM is keeping the idle up?
The bike is back together now awaiting a test ride..... Things may well be clearer once the engine is properly hot.
VERY excited!
Chris
Just a quicky update.
Last night I stuck the tank on backwards using long fuel lines and marked a TDC for the centre cylinder.
I warmed the bike up on curve1, and checked that the centre cylinder (and the other two) are firing at the correct time. They were.
Off the choke, the bike idled perfectly at 1000 RPM - very clean, each cylinder perfectly audible. It's never done that before!
I switched to curve 10, and the idle sounded rougher. Response just off idle also was more hesitant compared to curve 2 (before 1500 RPM when the advance cuts in) I'm not sure why - any ideas?
The bike also hung up slightly returning to idle from 3K - I turned the idle jets out an extra 1/4 turn (2 1/4 turns in total) - this seemed to let it return to idle a bit better. It didn't do this on curve 1 either - again I'm a little mystified.... Maybe I need to back off the idle slightly - perhaps the idle control is retarding the ignition because idle is set too high and the advance once above 1500 RPM is keeping the idle up?
The bike is back together now awaiting a test ride..... Things may well be clearer once the engine is properly hot.
VERY excited!
Chris
impamentor
Full member
- Location
- New Forest, Hampshire
Great news....
After a run, mine needed just a little (tweek) adjustment to the idle mixtures just to get the smoothest running I could at 1000rpm.
G
After a run, mine needed just a little (tweek) adjustment to the idle mixtures just to get the smoothest running I could at 1000rpm.
G
sfcpiet said:
Hi Piet,
I will! Test ride is now scheduled for Saturday afternoon - I have booked a mate of mine to be my wingman on a modern bike.
What is the difference between curve 10 and curve 7? Are there any other curves I should try? There is a local shop with a dyno - should I book some time on there or would the results be misleading? I read somewhere that someone set up their ignition on a rolling road and found it pinked in the midrange when out on the open road...
Best regards,
Chris
Chris,
Many years ago, when I first fitted a DMC system, I wasn't sure about my engines' ignition requirements. I temporarily hooked up the box and taped it to the tank top. Armed with a tiny screwdriver and a list of curves I wanted to try out (also taped to the tank), I took the bike on the autobahn where I could hold constant speeds or accelerate from varying speeds without endangering or hindering anybody, especially myself. I went through my selection of curves with a defined procedure while on the move and quite soon found one that worked satisfactorily under all circumstances. Took maybe 1/2 an hour, later tests on a dyno confirmed my seat-of-the-pants choice.
Usually, what feels right, is right.
Curve #7 has a flatter, more gradual advance compared to #10 Both top out at 32?, which you should adhere to for the time being. A dyno run with either a CO or lambda tester wil show if you can cope with less advance.
piet
Many years ago, when I first fitted a DMC system, I wasn't sure about my engines' ignition requirements. I temporarily hooked up the box and taped it to the tank top. Armed with a tiny screwdriver and a list of curves I wanted to try out (also taped to the tank), I took the bike on the autobahn where I could hold constant speeds or accelerate from varying speeds without endangering or hindering anybody, especially myself. I went through my selection of curves with a defined procedure while on the move and quite soon found one that worked satisfactorily under all circumstances. Took maybe 1/2 an hour, later tests on a dyno confirmed my seat-of-the-pants choice.
Usually, what feels right, is right.
Curve #7 has a flatter, more gradual advance compared to #10 Both top out at 32?, which you should adhere to for the time being. A dyno run with either a CO or lambda tester wil show if you can cope with less advance.
piet
Hi all,
Well I got the chance to take the bike out on Sunday. I tried curve 7 and curve 10. After warming the bike up properly, the high idle resurfaced. I ended up leaning the bike off at idle from 2 1/2 turns out (so the revs climbed) and then backing the idle speed screw down. I think the throttle was too open at idle, and the carb was using the transition/progression circuit rather than the idle jet and fuel screw alone.
It now idles happily at 1000-1100 RPM after a long ride and drops there quickly. Response just off idle at very low throttle openings is a bit fluffy, so I might richen up slightly, and increase the idle speed a bit to compensate. It looks like I'll have to rebalance the carbs too.
As to the ignition, there was only a very slight difference in response between the two curves - curve 10 seems to be slightly better up to around 5500RPM - better throttle response. I couldn't detect any pinging at any combination of throttle and revs.
Torque seems much improved - I'm now noticing the loooong throttle pull as I can use more throttle and it actually has an effect. There also seems to be a fairly distinct step in the power output at just over 6000RPM - I've not really experimented here yet, as the speeds the bike is going and the acceleration makes it difficult to hold on, and my crappy shocks make the whole plot seem quite wobbly and scary, frankly.
On a slightly different subject, it looks like I need to remove my extended clutch lever and replace the cable - as the bike warms up, neutral is harder and harder to find.. Oh - and I need clipons so I can drop the forks through the yokes!
Next step is a longer ride with a voltmeter attched so I can confirm it is charging, and then clutch cable replacement. And shocks. And handlebars....
Thanks to all that have helped me get this far!
Chris
Well I got the chance to take the bike out on Sunday. I tried curve 7 and curve 10. After warming the bike up properly, the high idle resurfaced. I ended up leaning the bike off at idle from 2 1/2 turns out (so the revs climbed) and then backing the idle speed screw down. I think the throttle was too open at idle, and the carb was using the transition/progression circuit rather than the idle jet and fuel screw alone.
It now idles happily at 1000-1100 RPM after a long ride and drops there quickly. Response just off idle at very low throttle openings is a bit fluffy, so I might richen up slightly, and increase the idle speed a bit to compensate. It looks like I'll have to rebalance the carbs too.
As to the ignition, there was only a very slight difference in response between the two curves - curve 10 seems to be slightly better up to around 5500RPM - better throttle response. I couldn't detect any pinging at any combination of throttle and revs.
Torque seems much improved - I'm now noticing the loooong throttle pull as I can use more throttle and it actually has an effect. There also seems to be a fairly distinct step in the power output at just over 6000RPM - I've not really experimented here yet, as the speeds the bike is going and the acceleration makes it difficult to hold on, and my crappy shocks make the whole plot seem quite wobbly and scary, frankly.
On a slightly different subject, it looks like I need to remove my extended clutch lever and replace the cable - as the bike warms up, neutral is harder and harder to find.. Oh - and I need clipons so I can drop the forks through the yokes!
Next step is a longer ride with a voltmeter attched so I can confirm it is charging, and then clutch cable replacement. And shocks. And handlebars....
Thanks to all that have helped me get this far!
Chris
78jotadave
Hero member
Trust me I am not wanting to steal cwis thread but I am experiencing my own DMC Witt woes
First I bought my DMC afew years back from Wolfgang came complete with coils, spark plug leads and charging coil.
So now finally getting around to installing it, I also upgraded to a SH530-12 Rectifier.
Using all the excellent information on this site I have installed the unit and followed the advice of all those who went before me.
Battery is good, all connections clean and I believe correct but I get nothing I mean zip, nada, zero....F..k!
Tried the screw driver test to check for spark and there is nothing so I tried reversing the pick up wiring as it says to do that in the instructions still nothing.
The only time there is any spark at the plugs is when I turn on the ignition key and then operate the emergency switch to the run position there is then a small spark just once at all 3 plugs at the same time.
What is going on ? The unit is labelled DMC2+/NORM code 12388 LAV 1000software. The bike was running great before I removed the old system now not even a spark. Inside the DMC unit the program adjuster is a small dial numbered 0 thru 9 then ABCDEF.
Anyone out there able to tell me whats going on, Thanks Dave.
First I bought my DMC afew years back from Wolfgang came complete with coils, spark plug leads and charging coil.
So now finally getting around to installing it, I also upgraded to a SH530-12 Rectifier.
Using all the excellent information on this site I have installed the unit and followed the advice of all those who went before me.
Battery is good, all connections clean and I believe correct but I get nothing I mean zip, nada, zero....F..k!
Tried the screw driver test to check for spark and there is nothing so I tried reversing the pick up wiring as it says to do that in the instructions still nothing.
The only time there is any spark at the plugs is when I turn on the ignition key and then operate the emergency switch to the run position there is then a small spark just once at all 3 plugs at the same time.
What is going on ? The unit is labelled DMC2+/NORM code 12388 LAV 1000software. The bike was running great before I removed the old system now not even a spark. Inside the DMC unit the program adjuster is a small dial numbered 0 thru 9 then ABCDEF.
Anyone out there able to tell me whats going on, Thanks Dave.