430 Darmah vs 860

Post your 'Carburettor & Fuel System' FAQs, comments & questions regarding Ducati motorcycles here.
Post Reply
Elliot
Cucciolo - the Lil Pup
Posts: 20
Joined: Tue Apr 18, 2006 10:19 am
Location: Christchurch, New Zealand

430 Darmah vs 860

Post by Elliot »

Gents I have been reading the threads in this website for a few years and have recieved some fantastic advice and knowledge form its contributors.

I am hoping you can come through with some more great info for me.

I have a 78 Darmah running 36mm Delortos with a 2 into 1 pipe. It has been off the road for a few years and last ran like a single. Since then I have
1)Cleaned and rebuilt the carbs with new jets.
2)Checked the ignition pick ups using the gauge, and measured the continuity of the pick up at approx 230ohms (250 ohms when hot).
3)Replaced the inlet manifold gaskets
4)Fitted new exhaust gaskets.

I have just tried tuning the carbs iaw the direction on this site as posted by Steve. This proved to be unsuccessful as the rear cylinder was not firing.

When I pulled the plug it was very wet. I used an ifra red thermometer on the pipes when it was running and the front cylinder was heating to approx 170 degrees C whereas the rear exhaust header was approx 50. I suspect that this is the heat from compression only.

I have swapped plugs, checked the spark from the plug by earthing it whilst starting, swapped the ignition pick up wires into the advance unit,
checked the compression on the starter etc.

Additionally the rear cylinder vacuum gauges mostly read zero when it was running whereas the front cylinder had a good vacuum.

I am contemplating replacing the coil and the ignition advance unit from spares that I have.

If the carbs were not balanced I would have thought the rear cylinder would still fire albeit badly.

Has anybody got any other ideas that may assist?

The Paeroa street race is on in a few weeks and I would like to ride down for the day!
Owner of two 78 Dramahs as I can't afford a 900SS or a Greenframe!

Grover
Parallel Twin
Posts: 102
Joined: Wed Jun 21, 2006 3:50 am
Location: Grafton NSW Australia

Darmah drama

Post by Grover »

If you do not have rear manifold vacuum with the engine running on the front cyl, I would be checking your valve clearences, valve timing etc.....the plug being wet indicates you should have fuel or really bad oil bypass, youve seen the spark as well. Do you have decent compression in that cyl? You need at least 130PSI for it to run....ideally 180PSI. Try starting the motor with the rear cyl sparkplug OUT and while its ticking over by itself push the compression guage in and see what you have. I have seen many motors have good cranking compression but poor compression when running
If you were to run the engine again you could try spraying some aerostart or carby clean into the rear carby, if the cyl picks up you know you have a fuel problem....be carefull you don.t get a backfire and burn yourself though.
Keep us informed, always good to hear what the outcome is with these probs. Steve
The older we get, the more toys we collect!!!

Lumpy
SD900 Darmah
Posts: 327
Joined: Sun Mar 25, 2007 5:49 am

no start

Post by Lumpy »

A whiles back i left the ignition switched on overnight on my 82 SS. In the morning there was some melted wax on the floor from the coils. I started it on the centre stand and she fired first kick, idled sweetly but I was worried as to the condition of the coils. I replaced them. What happened then was she would idle sweetly but any revs over idle would backfire pop and finally run on front cylinder only. I don`t want to tell you the amount of grief this fault caused me in finding what was going on. After much horsing around I found the insulation on the wires to the pick ups had turned to poop, soldered in new wires and away she went. Althought this fault sounds a little different to yours, what I`m trying to illustrate is that I checked my pick ups for resisitance, all good, checked them for current leakage to earth , all good, checked them for current leakage across to one another, all good. In short, there was no good reason that I could find to replace these wires. It was pure desperation that sent me that way. By fitting a ignish timing tool and strobe light I could see she was not advancing on the back pot. I guess what I`m trying to say is that I`m not sure that this is your problem, but chances are the insulation on the wires from your pick-ups to your advance boxs will be rat sh*t and needs to be replaced anyhow or they will cause you issues. This fault is very common and is not an issue of if but when they will cause you problems. By the sound of things your no mug, know your way around an internal combustion engine and have tried all thats humanly possible. Slice the outer insulation down the side and check the wires within. Particularly down near the engine as thats where the heat and oil happen. It`s the wire inside the rubber outer thats the issue, don`t go by the wire condition inside the cover before it goes into the rubber outer. I ended up doing my alternator wires after that too, but strangely the insulation near the engine was pretty good but up further near the reg you could easily break it off. Keep us posted on your progress. The more problems AND their solutions that get posted here the more of a useful database this forum becomes.

Lumpy
SD900 Darmah
Posts: 327
Joined: Sun Mar 25, 2007 5:49 am

you gotta be joking

Post by Lumpy »

Hey check this thread out while your about it, only just saw it today. What an evil cow. Talk about kicking a guy where it hurts. Make sure you have`nt p*ssed some female off. Hell hath no fury........................
http://www.bevelheaven.com/~BB/phpBB2/v ... php?t=1943

wdietz186
Cagiva Alazzura
Posts: 703
Joined: Sun Sep 10, 2006 5:40 pm

Post by wdietz186 »

+1 on Grovers comments. It sounds like you have a leaking or burnt valve. Possibly a holed piston. The problem with resurrecting an old bike you parked years ago is you forget exactly why you parked it. If it limped home on one lung after a high speed run you were probably just happy to make it home. I would start with a compression test then inspect the valves for proper clearance. If the vacuum gauge just wiggles you have a pretty big leak. My guess is a burnt exhaust valve.

Elliot
Cucciolo - the Lil Pup
Posts: 20
Joined: Tue Apr 18, 2006 10:19 am
Location: Christchurch, New Zealand

Post by Elliot »

Gents thanks for the info.

I have swapped the plug from the ignition pick ups and can confirm that the rear cylinder coil and ignition unit works on the front pot ignition pick up. Both coils and ignition units run on the front cylinder.

This means I have traced the fault back and it lies with ignition pick up for the rear head despite the fact that it measures out at approx 230 Ohms across the pick up.

When I pulled the cover off the pick up wires have had some work previously and do not appear to be bad visually. It may be an option to Megger the pick ups iot determine if there is an earthing problem but this is not my area of expertise so I am asking some of the guys at work.

Additionally when I turn the engine over on the starter the rear cylinder has a great spark from the plug so I am a little confused. The pick ups are also in timed correctly using the gauge.

I am going to borrow a borescope from work and have a look inside the rear cylinder for the valve/ piston problem as described above.

Will keep you posted.
Owner of two 78 Dramahs as I can't afford a 900SS or a Greenframe!

Post Reply

Return to “Carburettor & Fuel System Shop”