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 Post subject: Fast idling with Dell Ortos
PostPosted: Mon Jun 06, 2005 6:51 am 
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Location: Hartbeespoort Dam, South Africa
model: 750 Paso
year: 1987
Skins,

Is this the notch that you were talking about that affects the idling with Dell Ortos ?

Image

Image

I have put two pictures here because they were taken at slightly different angles.

Must I file these smooth ?

Thanks

Paul


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PostPosted: Mon Jun 06, 2005 9:05 am 
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paso grand pooh-bah
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Location: Kapiti, New Zealand
model: 750 Paso
year: 1988
Yep, Paul. That's them all right. The end of the throttle-stop screw cannot work precisely when it's bearing onto a surface like that. It would be impossible to set the idle properly, and the resulting idle would be impossible to predict.

The slide is very soft metal, and is very easily repaired with a needle file. The screw will probably have to be turned in a bit to compensate for the metal removed, but not neccessarily, because you'll be starting from a problematic situation, if you know what I mean.

If you're not used to setting and ballancing the carbs at idle, one of my first posts, maybe the first one, talks about that. I'm happy to answer any specific questions you may have, if I can.

Tell you what, Paul - you and I can see the wear notches in your pics, because we know what to look for. In fact, I myself had to look hard to see them (it's been a while since I dealt with my own). Other people might look at the pics and wonder what we're talking about. Would you know how to put little white arrows into the pics to point them out? I'm afraid I don't.


Last edited by Skins on Mon Jun 06, 2005 9:21 am, edited 1 time in total.

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PostPosted: Mon Jun 06, 2005 9:19 am 
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Location: Hartbeespoort Dam, South Africa
model: 750 Paso
year: 1987
Thanks, I'm going to be doing some gentle filing tonight.

I managed to get the photos directly on the page by using the MSN Spaces facility (free hosting). I struggled with getting the image to display here because the closing "img" entry was always on the following line. This made the address be displayed instead of the image. Once I worked that out, and made sure that the closing "img" entry was on the same line as the address, it was simple.

I see I am now "regular". Must be all those bran flakes.

Paul


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PostPosted: Mon Jun 06, 2005 11:45 am 
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Location: Hartbeespoort Dam, South Africa
model: 750 Paso
year: 1987
I hope this makes it clearer

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Paul


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PostPosted: Mon Jun 06, 2005 8:15 pm 
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paso grand pooh-bah
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Location: Kapiti, New Zealand
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year: 1988
:beer:

Good stuff, Paul. If anyone is still puzzled by what we're on about, it'll be much easier to explain now. Thanks.


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PostPosted: Tue Jun 07, 2005 4:52 am 
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Location: Hartbeespoort Dam, South Africa
model: 750 Paso
year: 1987
Skins,

I filed the notches smooth with a needle file, carefully cleaned off the filings, put on the tank, plumbed in a fuel tap (I'll explain in another posting) and reconnected everything. I then turned on the ignition, pressed the starter button and.... CLICK. I did get it to turn over slowly, but not fast enough to start.

The battery is now on charge (it's been disconnected and not used since about February so I should have charged it first). I will start it this evening. I'm going to try and find your posting on balancing the carbs. I come from the old Mini Cooper days where you balanced them by listening to the end of a bit of tube placed in the inlet. I imagine it must be similar.

Paul


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PostPosted: Tue Jun 07, 2005 6:51 am 
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paso grand pooh-bah
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Location: Kapiti, New Zealand
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year: 1988
:cool:


Yes, a good battery is required to turn over those big high-compression pistons. But she will start very quickly (mine starts in one revolution, hot or cold) when the timing and mixture are right.

When setting up the idle, I listen to the exhaust. I guess different people have different ways, and some like to watch a vacuum guage, but I listen to the bangs. I reckon the bangs are what it's all about.


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 Post subject: Some additional "challenges"
PostPosted: Wed Jun 08, 2005 10:46 am 
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Location: Hartbeespoort Dam, South Africa
model: 750 Paso
year: 1987
Appologies up front, this will be a little long winded.

I plugged in the battery last night and she started first time on the choke. After about 20 seconds she went straight to around 3,000 revs so I shut her down. Whenever I started her up after that (with or without choke) she went straight to 3,000 revs.

I haven't adjusted the tickover since filing these areas smooth so this is the obvious next thing to do (I got home late and it was pitch black and cold). However, my logic is that the carb piston should be sitting lower now so she should either tickover slower than before, or just die. Maybe one of the pistons is getting stuck.

I also experienced another problem last night. The bike has been standing without being ridden since November (she has been started a few times but I have been preparing my house for sale so she has been left to sit). Normally when the revs rise like that I pull in the clutch, put her in gear and ease the clutch out to drop the revs. Once they are down they stay down, even when I pull in the clutch again.

Last night I pulled in the clutch, put her in gear and I was able to let the clutch right out without it "taking". After switching off I could put her in gear, leave the clutch out and push her around without any engine compression (although on one occaision I did get compression until I pulled the clutch in and let it out again).

My thought is that the dry clutch has some rust (?) on the shaft or basket that is stopping the plates from re-engaging, because it has sat so long. I have heard of clutches getting stuck "engaged" but not "dis-engaged". What do you guys think ? Is there somthing that must be greased ? if so, which item and what should I grease it with ?

Can I take off the clutch cover without dismantling the hydraulics ? What should I watch out for (any little ball bearing likely to drop out ?).

Any suggestions appreciated.

Thanks

Paul


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PostPosted: Wed Jun 08, 2005 5:25 pm 
As long as you take care you should have no problems stripping the clutch.

"Gerhard,paso750" wrote about how to carry this out and I think its someware on this site, or at least linked to it someware.

Just do not pull the clutch lever with the clutch cover off, otherwise you will pop the piston out!

Strip it down give it a good clean and rebuild in the same order. Just do not mix the plates up as each will ware to each other.

If you need it I can send you a word doc file of his instructions, am sure he would not mind.


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PostPosted: Wed Jun 08, 2005 8:52 pm 
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paso grand pooh-bah
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Location: Kapiti, New Zealand
model: 750 Paso
year: 1988
:cool:


Paul, about readjusting the throttle stop screws: I wrote in my first post in this topic that 'you'll be starting from a problematic situation'. If you think about the size of those wear notches (they looked huge in the pics to me) you will realise that someone has been progressively turning the scew in to compensate for the notch it was making in the slide, and now that the contact point on the slide has been restored, the screw needs to come back out. After that, you will take it back in slightly further than where it was when the bike was new.

If you don't quite follow me, it boils down to this: with the size of those notches where the metal should have been flat, your adjustment was a mess. I think I cover this situation in my old post on balancing the carbs. Did you find that post? (the link at the bottom makes it easy to find).

Re the clutch: doesn't sound good, I'm afraid. But I hope you find it's something simple. Yes, you can take the cover off without dismantling the hydraulics.

My old carb balancing post is the second from the bottom in: http://forums.ducatipaso.org/viewtopic.php?name= ... &start=405

Oh dear. That link just failed to work for me, although it seemed to when I put it in. Anyway, if you click on 'find all posts by Skins' in my profile, then go to page 28, it's the second from the bottom. There's a lot there, in the instructions, and in fact you'll have to do even more for yourself, when it comes to 'the same kind of adjustments with the idle mixture screws' in paragraph 6. But if you can do it, you might wind up with a bike that is very smooth and quick, like mine. I'll be happy to answer and further specific questions on the carb setting and balancing.


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PostPosted: Thu Jun 09, 2005 4:57 am 
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Location: Hartbeespoort Dam, South Africa
model: 750 Paso
year: 1987
Matiztab,

Thanks for the advice. When I got home from cycling last night it was dark but I thought "let me have one quick look". I put her in gear and tried to move her and I had compression back. The clutch has released itself. I engaged / disengaged it lots of times and it still worked. I suspect something had got caught on some rust, or other build up, and freed itself during the day. I am hoping that all the engaging / disengaging last night has cleared the obstruction.

Skins,

Thanks also for your advice. I managed to find your article on the 28th page as you suggested. I won't be able to attempt this over the weekend as we have another show house, but next Thursday is a public holiday and I will attempt it then. Next Thursday is the 29th anniversary of the 1976 Soweto riots (16th June). Wasn't it in New Zeeland where they flour bombed the Springboks ?

My thought regarding the idle stops was that as the metal has been removed the piston has to be lower than it could have been before, even if the piston grooves previously landed perfectly on the screw thread. A lower piston should give a lower idle.

However, I am going to follow your instructions and have a bike that works properly.

Paul


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PostPosted: Thu Jun 09, 2005 7:08 am 
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paso grand pooh-bah
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Location: Kapiti, New Zealand
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year: 1988
I can understand your point about the piston sitting lower if metal has been removed, Paul, but it's not as simple as that. In fact, no metal had been removed until you did so with your file. Up to that point, the metal had merely been compacted, forming the notch. Probably the idle did slow then, and someone turned the screw in to compensate. That made the notch bigger, the idle slowed again, the screw got turned in again, and the cycle was repeated until the huge notch you found was created, and accurate idle adjustment because impossible at that point.

To see how erratic the movement of the piston is on the stop once a notch like that has formed, you need to look down the throat of the carb while very gently lifting and dropping the piston onto and off the stop, using the throttle control - before you have repaired the notch of course. I think I mentioned that excercise somewhere, perhaps in another topic related to idle problems.

I believe that when there is a large notch, the piston can 'ride' on the point of the screw, due to vibration and pressure of the spring, changing the idle speed while the motor is running. You will remember I measured the amount of piston movement required to alter the idle by 100rpm, and it was very small.

PS: With ref to your post above 'piston landing perfectly on screw thread', Paul. The end of the stop screw is more or less a point - perfect for making notches. I have thought about rounding the end of the screw, but that might cause problems. The system works if, once you've got it right, you leave it alone. The fact that she went straight to 3000 rpm means you removed metal only up to the deepest part of the notch, which is good.

PPS: Yes, the flour bombing was in Wellington. I can still hear the sound of that little plane circling overhead, while we tried to run the cops off their feet outside the park, trying to find a way in.


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PostPosted: Mon Jun 13, 2005 5:07 am 
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Location: Hartbeespoort Dam, South Africa
model: 750 Paso
year: 1987
Skins,

Thanks for the extra info. I managed to make a little time yesterday and took the tank off again. I checked to make sure that there was enough throttle cable slack and then I checked when the different carb pistons lifted. The one for the rear cylinder started lifting about 10 to 20 degrees of throttle travel before the one for the front cyclinder, so I have changed that.

Whilst I was poking around I took all the jets out, made sure they were clean and put them back. I set the idle jet screws to 1.5 turns out and the throttle stop screws so that the pistons were barely lifted. Then I ran out of time, so I'll be continuing on Thursday.

One interesting thing that I found, the main jets are different between the front and rear cyclinders. For the front cylinder there is a 152, and for the rear there is a 148.

My logic (admittedly from inline two-stroke Karts) was that the rear cylinder was given a bigger jet to help cool it (it is protected from the air by the front cylinder). However, in the case of Ducati's L-twin the top of the front cylinder is the only part that is cooled whereas the rear cylinder is cooled for its full length, so maybe I am wrong.

Do you know what jets you have in your Dell ortos ? Bear in mind that we are at 5,000 feet so mine may be slightly smaller than your's.


Paul


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PostPosted: Mon Jun 13, 2005 7:21 am 
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paso grand pooh-bah
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Location: Kapiti, New Zealand
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I can't tell you which jets I'm using, Paul. It's four and a half years since I tuned my carbs, and she is running so well, I'm loath to disturb things. I did make several pages of notes in a small note book about throttle stop screw vs idle jet screw positions, and I see I settled on both mixture screws 1 turn out, and the throttle stop screws 5 turns out on the front cylinder and 3 and three-quarter turns out on the back cylinder. However, I did replace one of the idle mixture jets with a different size, and I can't remember on which cylinder. At the time, I looked through carb jetting lists in Haynes Ducati manuals for 750s to give me an idea, and I remember seeing only one model where a jet differed in the front or back cylinder - can't remember which jet it was. However, the main jet size is only going to make a big difference when you're on full throttle.

Your slides lifting 10-20 deg of throttle movement apart sounds really bad! The slides MUST move at EXACTLY the same instant if you want your bike to run like it should. That's where you must start before you do anything else. It can be done (by cable adjustment) the way I describe on page 28, with a finger of your left hand in the rear cylinder carb to feel one slide, while looking into the front cylinder carb to watch the other slide, and easing the slides off the stops with your right hand on the twist grip. The secret is that one cannot SEE two things at the same time, but one can SEE one thing and FEEL another, at the same time, and in this way instantaneous movement can be achieved. I may sound crazy, but I am right. Trust me.


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PostPosted: Mon Jun 13, 2005 8:44 am 
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Location: Hartbeespoort Dam, South Africa
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year: 1987
I managed to get my youngest son to slowly turn the throttle and was able to put one finger in each carb. This is how I picked up the difference. It will explain why she sometimes "hunts" a bit when cruising along on partial throttle.

Paul


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