Engine Swap Electrical Issues

[Plang642]

Hi,

I'm new to the DMF and Ducati's in general and would appreciate help ferreting out what is wrong with the electrical system on my bike.

I recently bought a 2000 Monster 750 with a 900ss motor of uncertain vintage.  The bike has many issues, mechanical and electrical.  My understanding from the guys at the local Ducati shop is that whoever did the swap to the bigger motor did not make any modifications to the electrical system.  This is a problem as I believe the 750 motor had a two phase stator, while the 900ss has a three phase stator.  Is this correct?  If so, I believe this would require changing the regulator from a two phase to a three phase as well??  Other than that, is there anything else that would need to be changed in the electrical system to accommodate the larger motor?  I've been told that since the bike has carbs and not FI there is no ECU to worry about.

Thanks for the help!!

[koko64]

Cool project btw.

A 2000 model M750 actually has a three phase alternator (if it indeed is that year). Are there 2 or 3 yellow wires coming out of the alternator side case and regulator?

What year SS motor at a guess? Are there 2 or 3 yellow wires coming out of the alternator side case (LHS)? Was the SS motor carbed or injected if you can tell?
2 wires=single phase, 3 wires 3 phase.

If unsure post some pics. You'll need a host site.

[Plang642]

Thanks for the info.  Bike is a 2000 M750.  I was told the ss motor is from 1995, but no way to verify.  Other than the engine number starting with LC4 (built for US market) I can't get any confirmation on the year the motor was built or what model it came off of (I'm assuming a Super Sport).

Haven't actually got into it yet, so can't verify color or number of wires.  Just trying to get a idea of what "would" need to be done to make such a swap work properly.  Bike is running FCR 41mm carbs, so I'm assuming the ss motor was originally carbed.  The '95 Super Sport came with 39mm Mikuni's I think.

Bike is burning lots of oil and at a minimum needs new rings.  Debating whether to get a 944 bore kit or replace with oem rings.  I need to ratchet down the exhaust note considerably (running Sil Moto 105db slip ons), so I'm leaning towards going the oem route and swapping the 41mm carbs for 39's (Keihin or Mikuni).  Got the db killers from the mfg in Italy which helped, but still too loud for my 48 y/o ears.

[Howie]

A '95 would be two phase alternator.  As koko said, your bike came with a three phase.  Since your engine is unknown, do count the bid yellow wires going into the regulator.  If your regulator is wired properly and working it will work with the two phase stator, one diode simply will have nothing to do.  Keep in mind two phase is a misnomer  The alternator actually consists of two single phase stators.  Could you elaborate on your electrical problems and any diagnosis you did?  Does the bike start and run?

Your bike came with Mikuni BDST 38mm.  41 mm flatslides may not be the most ideal for your bike, but is the most common size used so there is more wisdom in tuning.  Flatslides are als an expensive and desirable upgrade.  Anyway, I would sort the bike out before spending a lot of money

[koko64]

New hi comp pistons in standard bore could be cheaper than new oem rings and really improve the bikes performance. Retarding the ignition and using premium fuel then becomes necessary. 41mm FCR carbs work well with that combination, but they have no choke and difficult starting in winter is a result. There are ways to mitigate this. Big bore kits are for more maximum effort motors IMO.

FYI, selling the very desirable FCR's could pay for a set of Mikunis and your rebuild.

[Speeddog]

Thanks for the info.  Bike is a 2000 M750.  I was told the ss motor is from 1995, but no way to verify.  Other than the engine number starting with LC4 (built for US market) I can't get any confirmation on the year the motor was built or what model it came off of (I'm assuming a Super Sport).

~~~SNIP~~~

LC4

• .... x will get you the year of the cases, at least, good chance it's correct for major motor bits as well:
  
  http://www.ducatimonsterforum.org/index.php?topic=66797.msg1233363#msg1233363
  
  

[koko64]

FCRs and hi comp pistons make it feel like another bike. Check the condition of the barrels and valve stem seals. Do the valve stem seals while you are in there and look for pitting on the valve seats on a motor that's been layin around.

[Plang642]

Thanks to everyone for the great information!  I've been trying to learn about all of this on the internet over the past several weeks and it's nice to finally have some knowledgeable feedback.  Based on the table posted by Speeddog, the engine is indeed a '95 900ss!

The bike does start and run, but takes about 10 to 15 times to actually start up and just runs rough and is undependable (stalls at lights, etc.).  I haven't done any diagnostics as yet, but the new lithium battery needs to be charged intermittently for the bike to start, which leads me to believe that the wiring from the stator to the regulator is incorrect.  Bike also has been sitting for several months, so carbs probably needs to be rebuilt, cleaned, and synched.

The heads are dual spark and the current pistons are high comp.  The bike is spewing blue smoke on starting and through the rpm range, so probably needs new valve seats in addition to rings.

I will be moving from the sf bay area to LA shortly and will be shipping the bike down to Moto Republic in Eagle Rock so I can work on it there.  Hoping to have it sorted out soon.

A couple last ideas on the sound issue are to wrap the headers in fiberglass and (if still needed) find a fabricator who can customize smaller diameter baffles to fit inside the ones I got from the mfg.  I realize this will reduce power somewhat, but hopefully not by much.

[koko64]

Hopefully the cylinder linings aren't scored and it's just the rings but you'll know when you see it. Twin plug heads eh? Is the ignition two standard black boxes or one larger unit?
FCR carbs having no choke are notoriously hard starters but you can develop a routine to deal with this. I have jetted a set of 41's one to two pilot jets too rich and open the idle speed knob a whole turn with a few squirts of the accelerator pump for the first start of the day. In winter I will open the idle mixture screws a few turns as well and close them as the bike warms up. There are extended IMScrews with a knob to do this by hand that the dirt bike guys use.
Plug colours will tell a story and they are probably fouled with oil or  too rich a pilot jet. Have you changed them out?
All that starting is probably wearing thin on the LiFePo4 battery. What brand is it? If the wiring is ok and not corraded or incorrect then diagnostics around regulator health is probably the first test after the battery. The battery will need a lithium specific charger in nearly all cases.

[Plang642]

I think the battery is a Ballistic Lithium.  I have a lithium charger which works well.  The guys at the Ducati shop said the terminals need to be changed on the battery,  so I'll have to look into that as well.  The ignition appears to be one large unit, but really won't be sure till I start disassembling.

Thanks for the tuning advice on the 41's.  I have to admit I don't really want to change them.  Rolling full throttle is like nothing I've ever experienced before.  There's just this all encompassing WOOSH sensation that is awesome.  Add to that getting on the freeway and looking down to see your going 90 in third gear like nothing at all and you just can't help but get a big smile on your face

[koko64]

I've only tuned a two sets of FCR39's and four FCR41's on Ducatis and all felt great, but starting was a pregnant dog. I have dyno data for good baseline settings, but I found low rpm tuning to really vary with the individual bike mods, ignition set up, fuel availability, climate and rider preference. They rock for instant response. 

You might have an Ignitech ignition if its a single unit

[Howie]

I have a buddy who has a 900 Super Sport with flatsides that starts in cold weather with a couple of pumps and a couple of turns on the idle speed knob.  Problem is when the engine is warm, well, holy hydrocarbons!.  The bike used to be a 966 with high compression and some head work.  The carbs are jetted for that engine