75 860GT ignition question

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ducadini
750 Sport [BEVEL]
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Location: Antwerpen

Re: 75 860GT ignition question

Post by ducadini » Mon Jul 25, 2016 12:36 am

Best start checking it from the bottom down : teke the alternator cover off and look for the timing marks on the gears. As already said : it might take a few turns of the crank (counterclockwise) to align the marks. (see manual 860 fig 81-83) Then check the marks on top of the heads to see of they align.

have fun
ciao
ducadini
Nego i ricordi peggiori
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blaine.hale
Mariana
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Re: 75 860GT ignition question

Post by blaine.hale » Mon Jul 25, 2016 5:15 am

ducadini wrote:Best start checking it from the bottom down : teke the alternator cover off and look for the timing marks on the gears. As already said : it might take a few turns of the crank (counterclockwise) to align the marks. (see manual 860 fig 81-83) Then check the marks on top of the heads to see of they align.

have fun
ciao
ducadini
Bottom end is fine. I went to break into that the other day and it was still factory untouched. No one had ever been in there! Super nice. This bike, by the way, only has 13,000 original miles on it.

Thanks for the top end tip, guys. Sounds like I need to reproach that. I'm thinking I was rotating the wrong way, as stated. I'm used to BMW and Moto Guzzi.

blaine.hale
Mariana
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Re: 75 860GT ignition question

Post by blaine.hale » Mon Jul 25, 2016 2:23 pm

wdietz186 wrote:Blaine, The dots on the horiz. cyl. should be lined up when the vert. cyl. is at TDC. The intake valve will be open on the horiz. cyl. with the dots lined up on that cyl. There is a service manual on this site that will explain it all. When you adjust the valves on the horiz. cyl. you need to watch the intake close and then bring the piston up to TDC. Set the valves to .004" in and .005" ex. One thing that confuses everybody is that on the bevel drives the crankshaft turns clockwise, [backwards as you view it from the left side] unlike most every other bike [even the belt drives] which turn counterclockwise.
Apparently I did the process right. I went back and checked per your notes.
Lined the dots up on the horizontal cylinder and noticed the vertical piston was, indeed, TDC and that the intake on the horizontal was open.

How does the rotation effect setting the valves? I did everything via the motor spinning counter clockwise (looking at the crank on the the left.) This meant rotating the rear wheel the opposite direction of operation (reverse.)

wdietz186
888
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Re: 75 860GT ignition question

Post by wdietz186 » Mon Jul 25, 2016 6:33 pm

The crank spins clockwise on the beveldrive engines, unlike the beltdrive engines which spin counter clockwise. So sitting on the left side of the bike the crank will turn towards the rear when the rear wheel is turned in the forward direction. If you start with the dots lined up on both cylinders [the vertical cylinder at TDC,valves closed] and turn the crank clockwise [turning the rear wheel in the forward direction] until the horizontal cyl. intake opens fully then closes with the horiz. piston at the top of its stroke, that will be TDC on the front cylinder[both valves closed, on the compression stroke] then check/adjust the valves.

blaine.hale
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Re: 75 860GT ignition question

Post by blaine.hale » Tue Jul 26, 2016 4:45 am

wdietz186 wrote:The crank spins clockwise on the beveldrive engines, unlike the beltdrive engines which spin counter clockwise. So sitting on the left side of the bike the crank will turn towards the rear when the rear wheel is turned in the forward direction. If you start with the dots lined up on both cylinders [the vertical cylinder at TDC,valves closed] and turn the crank clockwise [turning the rear wheel in the forward direction] until the horizontal cyl. intake opens fully then closes with the horiz. piston at the top of its stroke, that will be TDC on the front cylinder[both valves closed, on the compression stroke] then check/adjust the valves.
Ah-hah! See...I'm sure I read "the motor runs clockwise" about a million times and it still didn't register and I STILL did my order of operations with it turning counter clockwise. I'll recheck my order of operations tonight with the motor turning in the right direction.
Out of curiosity, though, what would the motor direction effect when I'm setting valves and timings? I'd think a compression stroke is a compression stroke no matter the engine direction.

**Edit: I just realized this probably means my exhaust valves are opening when the intakes should be. Big ol' facepalm.

blaine.hale
Mariana
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Re: 75 860GT ignition question

Post by blaine.hale » Tue Jul 26, 2016 2:19 pm

Just went through the valve process again. 2 discoveries and corrections. The ball on the intake valve adjuster on the vertical cylinder was flipped around so that the spherical side was against the valve stem and the flat spot was up in the adjuster cup. Whoops! Second issue was the horizontal cam index marks were off by just one tooth. Fixed that. They line up perfect when the vertical cylinder is at TDC and the horizontal intake valve is open.
All that sounds great! Sadly, still no start. I'm getting back fire on the vertical cylinders carb every 5 or so kicks now, though. So there's that..

wdietz186
888
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Re: 75 860GT ignition question

Post by wdietz186 » Tue Jul 26, 2016 3:02 pm

Ok, now we are back to square one. Time to investigate the ignition options. Unless Steve has something tucked away it's time to send some money overseas.

blaine.hale
Mariana
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Re: 75 860GT ignition question

Post by blaine.hale » Wed Jul 27, 2016 4:50 am

wdietz186 wrote:Ok, now we are back to square one. Time to investigate the ignition options. Unless Steve has something tucked away it's time to send some money overseas.
Steve kindly pointed me to the Elektronik Sachse ignition. I assume that means I need to go back to coils as well. Going to be majorly expensive :(~
I've heard the gland and adapter they provide can be the wrong size too.

ducadini
750 Sport [BEVEL]
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Re: 75 860GT ignition question

Post by ducadini » Wed Jul 27, 2016 9:20 am

As I understand it : You have ignition while kicking on BOTH cylinders ? And the engine is huffing and puffing while starting ?
Noticing that there was a bit confusion about the LEFT side CLOCKWISE rotation : check the timing of the ignition like in the manual pag 154 onwards.
Check the wiring going to the boxes.
Check the wiring to the plugs.
Those can be switched without problems (except a little kickback :-)

Keep us informed
ciao
ducadini
Nego i ricordi peggiori
Richiamo i migliori pensieri

blaine.hale
Mariana
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Re: 75 860GT ignition question

Post by blaine.hale » Wed Jul 27, 2016 9:48 am

ducadini wrote:As I understand it : You have ignition while kicking on BOTH cylinders ? And the engine is huffing and puffing while starting ?
Noticing that there was a bit confusion about the LEFT side CLOCKWISE rotation : check the timing of the ignition like in the manual pag 154 onwards.
Check the wiring going to the boxes.
Check the wiring to the plugs.
Those can be switched without problems (except a little kickback :-)

Keep us informed
ciao
ducadini
You think maybe the transducers could be switched? They were disconnected when I got the bike. The PO drew a little diagram as to which lead out of the gland nut went to which transducer (one was marked "red stripe")

My current status is I'm kicking with choke on and hearing a lot of air sucking in but I don't hear anything igniting in the cylinders when I kick. Just like spinning over a dead motor, to my ears. Now that the valve lash and cam timing are proper, I get a kick back and back fire out of the vertical cylinder probably every 5th kick I give it.
Time was set according to my manual. Found TDC and used a piston stop to get that even more accurate on the degree wheel. Moved the engine to about 90 degrees the rotated it slowly back to 35 degrees BTDC. Adjusted the ignition unit until the holes lined up on the flywheel with the unit. That put the adjuster screws just about mid-way on their adjustment slots. Getting pretty nice spark on the plugs as well. Blue and white.

wdietz186
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Re: 75 860GT ignition question

Post by wdietz186 » Wed Jul 27, 2016 5:02 pm

It is possible the wires from the pickups were switched,but it makes one suspicious, why were they disconnected in the first place? Was the bike a basket case when you bought it? Or were they disconnected while chasing a [non] running problem?

blaine.hale
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Re: 75 860GT ignition question

Post by blaine.hale » Wed Jul 27, 2016 5:47 pm

wdietz186 wrote:It is possible the wires from the pickups were switched,but it makes one suspicious, why were they disconnected in the first place? Was the bike a basket case when you bought it? Or were they disconnected while chasing a [non] running problem?
The PO tore it down to paint the frame and had planned to restore the bike. He replaced the pistons and rings, and got it back to rolling chassis state. I'm finishing it off. Built a wiring loom for it and using all motogadget gear. The ignition system is still separate and all stock. Don't even have the engine stop relay on it at the moment.
Guess I'll try swapping the transducers. At this point, it's probably the only thing I haven't done.

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Craig in France
Cagiva Indiana
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Re: 75 860GT ignition question

Post by Craig in France » Wed Jul 27, 2016 8:37 pm

Hi Blaine,

Reading thru this thread, I think you need to leave the ignition system alone* and start looking elsewhere.

* Bill makes a good point however about whether each pick-up is connected to the correct cylinder. As the workshop manual says (and in bold, note!): "The red cable must be connected to the transducer of the vertical cylinder". 8)

Just to review the situation:
1. You say, "Getting pretty nice spark on the plugs as well. Blue and white". So we know the ignition system is doing what's it's meant to do, i.e. making sparks! So that just leaves the question: Is it doing it at the right time?

2. You say you've checked and re-set the static igniton timing. So, in theory at least: Yes, the sparks are happening at the right time. So there's no more to be done on the ignition system*. However:
.

3. You say that the compression is low: 128 psi +/-. While that isn't critically low, it's true that low compression will make any engine reluctant to start. From the 'oil-down-the-spark-plug hole' test you've done, it sounds like the rings aren't sealing. New rings should be tight. Yours aren't. But is there anything else it could be? You've checked and re-set the valve clearances and also the cam timing. So let's eliminate those. That leaves us with valve guide wear.

Conclusion : at this stage, I would be leaning towards a leak-down test to identify the cause of the low compression. But - and first :-)

4. Fuel supply. (As the old adage says, "99% of ignition problems are carburetor problems - and vice versa!").

You say: "Carbs are rebuilt, with stock jetting, and I can confirm I'm getting fuel in them and into the cylinder. Pumpers are working as well".

These bikes are very sensitive to incorrect fuel supply - and ageing Dell 'Ortos are very good at delivering it! Too rich, too lean, unbalanced, air leaks - all these will stop your beast from roaring into life. So here's the question:

Who re-built the carbs and when? The 'Who?' is important because, if the carbs weren't thoroughly - and I mean: 'thoroughly' as in 'ultra-sonically' - cleaned, then you could be in for a very frustrating time. The carbs need to be really, really clean, especially all the little passages and drillings that are hidden to the naked eye!

I ask 'When' because, if the carbs have been left standing for any time with gas in them, this can very quickly block the small diameter passages that are used at start-up. Btw, the fact that gas seems to be arriving in the cylinders isn't particularly revealing. It has to arrive in the right mix - or 'No Go'. And the pumpers are irrelevant at start-up. Except when an unknowing operator works the throttle, and floods everything ... :doh:. DON'T work the throttle. Simply set the choke. It's all you need to enrich the mix at start-up.

So, if it were my bike, with the ignition system seeming to be working, I'd do what I could to eliminate the carbs as a possible cause. Take 'em off, dis-assemble, ultrasonically clean, check the components for wear and correctness, change the inlet manifold seals (they leak and stuff up your settings). If you're not confident of your abilty to do this, Steve and others offer the service.

HTH - and good luck!

Craig

blaine.hale
Mariana
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Re: 75 860GT ignition question

Post by blaine.hale » Thu Jul 28, 2016 4:32 am

Thanks for taking the time to read and type all that out Craig. You've made some good points that I need to go back and check on the bike! I'll probably have a nice, long session with it tonight.
Just a couple things. The pistons and rings are brand new, probably the reason for low compression because they haven't been seated yet. I do have the fear that the rings might be stuck because the bike hasn't run in the couple years since they were installed.
As for the carbs. I rebuilt those about a month ago. New seals but not new jets as they looked great and weren't gummed up...even the ones with ball valves. They got ultra sonic cleaned and every passage blasted with air to make sure things were flowing. I've rebuilt old Dels a few times and always had great success, but you're right, they can be very picky. The ones on my 77 Guzzi Le Mans are the same model PHFs, just 36mm and setting those just right was painful at first but the bike would at least fire or try to. Float level was very specific.
I think you're pretty right with the ignition. That's set and seemingly healthy. I'm just going to do a quick swap of the transducer leads and see if anything happens.

Tonight's focus is going to be fuel and how much is being delivered. Is the factory default for mixture on these 3/4 to 1 turn out as a starting point?

Vince
750 GT
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Re: 75 860GT ignition question

Post by Vince » Thu Jul 28, 2016 7:29 pm

1 1/2 turns, don't get discouraged. Spent some time banging my head on some stupid things bike wise.

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