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 Post subject: newbie w/a 750, lots of questions
PostPosted: Thu Sep 09, 2004 5:14 pm 
whats up all you seasoned duck riders out there, my name is chris and im from az. just bought an 89 750 paso and its my first bike. (sorry to all those that perscribe to the learner bike agenda, which i respect, but you have to respect my meager means and how cheap the bike was). i know my way around an engine for the most part (though i still cant figure out how the desmo stuff works) but i still got a lot of questions for you guys.

engine: had it checked out and the boys say the valves are spec (@ 18000 miles) and its got good compresion, so the engine seems to be alright. however, it still has some trouble, mostly at start up and in 1st. i know the kill switch trick (god bless italian electrics) but some times the thing refuses to start after a good cranking, or will only run w/ the the throttle pulled. basically it wont idle, but only sometimes. also, when accelerating from a stop it sometimes lags, like it cant catch its breath, then all of a sundden the power comes on. or it sounds lide it shoots air back out the filter, like a cough or something. its not a power band issue, its goota be fuel delivery, right? also, usually when these two things occur the bike just feels weak in any gear, and it backfires and sputters when you let off the gas. yet this stuff only happens 50% of the time. anytime else she runs like a top. ive read around on this site a little bit, and are these syptoms of a weber carb? im pretty sure thats what mine has. or do i have a bigger problem?

oil: the shifter can be cranky sometimes, but apparently that can be fixed with mineral oil? ill have to try it. also, after i had the oil changed the thing leaks like a sive from back and front. the plates over the cams were taken off to check the valves and i had to replace some of the seals, but is this a usual spot for oil leakage? are there some hot spots for oil leaks on the bike? (i haven't gotten around to taking off the fairing yet to check). just want to know if i should look somehwere specific.

clutch: she's got a heavy clutch, doesnt she? except that mine sometimes hooks up when i have the clutch completely depressed. nothing huge, but enough that the bike starts moving forward and the engine strugles with the brake on. is this just a clutch bleeding issue?

body: the body is in pretty good shape with only couble dings and good paint. but, some of the bolt holes in the fairing have cracke or broken open. is all lost on these plastic pieces or can they be fixed w/fiberglass (i have a little experience with it). it would suck to not be able to bring them back to new condition because a 1/4 inch piece of plastic broke off.

for parts, i thought i saw something about a place in virginia that stocks paso parts? i could use a new turn signal lens and some of the fairing hardware, but nobody in az has paso stuff.

thanks for any help guys, you have your work cut out for you.
oh yeah, and nice site. good to see somebody loves these bikes besides me.


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 Post subject: Repairing the fairing
PostPosted: Fri Sep 10, 2004 10:44 am 
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Joined: Fri Jul 16, 2004 12:00 am
Posts: 187
Location: Hartbeespoort Dam, South Africa
model: 750 Paso
year: 1987
Don't try to fix the fairing with fibreglass as it probably won't be that successful. If you have all the plastic pieces that broke off you should be able to take them to a plastic repair shop who specialises in this. Most modern faired motorbikes (and scooters) have plastic bodywork and there are several shops specialising in this work here (South Africa) and I am sure you should be able to find one locally. I found a repair place by looking in a local motorbike magazines classified section. I have subsequently found another while driving around. You could try asking at any motorcycle dealership if they know where you could get this work done.

What they do is melt the broken plastic with the equivilant of a soldering iron and when it cools it is as good as new. My son sent his scooter down the road and broke / scratched just about every panel. After plastic repair, filling and painting it looked as good as new (until he dumped it down the road again !).

Paul


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PostPosted: Fri Sep 10, 2004 12:26 pm 
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Joined: Wed Aug 25, 2004 12:00 am
Posts: 19
Location: Houston, TX
Check your intake rubber boots adjacent to the carbs. Look for cracks and such. The rubber gets brittle and lets in air. Not sure if it would cause your "intermitten" problem though. Good to check them out anyway. I replaced mine with cut radiator hose. It saved me $$$ :ugh:


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PostPosted: Fri Sep 10, 2004 7:17 pm 
So C-Dogg where in Az are you. I'm in Phoenix and have a '88. It has become a project bike. I need to find the time to do the front forks seals, clean out the dead gas in the bike and get it to pass the Az smog check

I've worked with mine a bit in the 8 years that I've had it.

Clutch, I have the same problem with it dragging, can't shift in to neutral unless the bike is moving. A quirk I learned to live with.

The coughing could be fuel related or connections to spark circuit, spark plug wires, boots, coils or the connections to the coils from the electronics module.

Just some thoughts,

Bill


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 Post subject:
PostPosted: Fri Sep 10, 2004 7:37 pm 
thanks for the info guys.

bauhaus, another paso owner in az? and i thought i was the only one. im in E mesa, usin the bike for asu transport. great motorcycle parking. i heard there is a ducati place over there, like phoenix international or something. have you checked them out?

today the clutch was worse than it ever has been. it seriously would not even dissengage. down shifts were immediate, with power there before i even let go of the clutch, and the only way to upshift was to rev it and speed shift (i hear this is a pretty common way to shift with motorcycles anyway, due to the diferent tranny configuration). at the lights it would stay in gear even with the clutch depressed, so the thing would shake like mad because i had to jam the breaks in. what the heck is goin on?!?! if there was air in the system, wouldnt the clutch lever be pretty loose? its still firm. geeze, i gotta try something, the commutes are killing me.

anybody got an answer for the weber carb? ill check the rubber, thanks mach5er. but from what ive heard, arent they impossible to keep tuned? if so, is it an absolute mikuni (is that the name?) switch? how much and where at?


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 Post subject:
PostPosted: Sun Sep 12, 2004 12:34 am 
Here is a long shot,

Is the hose to the clutch the original rubber? If the hose has gotten old and is expanding instead of pushing the fluid into the slave cylinder you would get partial disengagment. You could try putting on braided steel lines. ProItalia in California had a set a while ago or you may need to have custom lines made if that is the problem

Let's assume the hose is:
ID 3mm
Length 1000mm
Volume of fluid in the hose= 70 cc

1% expansion of the hose = 72 cc

The Master cylinder only pushes 8 or 9 cc at 1% expansion, 25% of the clutch action is gone.

When I had air in my clutch line, it did not work at all. Air compresses a lot more then break fluid.

Does it get worse as the bike gets warmer? Mine does, but not like what you describe.

I'm in No. Phoenix area, Bell and Cave Creek and just moved here in Febuary, so I don't know any Duc shops here yet.


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 Post subject:
PostPosted: Mon Sep 13, 2004 8:44 pm 
In regards to the engine problem, mine had a very slowly dying fuel pump and exibited similar problems, intermitent. When it finally did die I found out they are $289 retail. Local auto parts shop has a basic low pressure fuel pump with identical mounting pattern for $32. Easy fix.


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 Post subject:
PostPosted: Tue Sep 14, 2004 5:40 pm 
do you have the part number for that pump? manufacturer maybe. id like to try it


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 Post subject:
PostPosted: Tue Sep 14, 2004 7:26 pm 
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paso grand pooh-bah
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Joined: Thu May 06, 2004 12:00 am
Posts: 581
Location: NorCal
model: 750 Paso
year: 1988
hey c-dogg in the downloads section is the parts catalog for your bike. you can get your part number from there.


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 Post subject: Paso Quirks
PostPosted: Wed Sep 15, 2004 4:59 pm 
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Joined: Wed Jul 21, 2004 12:00 am
Posts: 66
Location: Windsor, CT USA
I can't make any sugestions about the starting problem, but the problems with idle an power delivery are definitely carb related. If it is a Weber carb, you should pull it apart and give it a good cleaning, or at least run some carb cleaner through it. Check the manifolds and boots for cracks or looseness. Check the tightness of the upper cover on the carb, and the tightness of the fuel line fitting on the cover. After that, rejet the carb. There are several Weber sites on the internet who sell jets that fit the DCNF. Go to size 60 idle jets, set the idle mixture screws at two turns out, and close both air bypass screws. Go up at least size 160 main jets, and down to 160 air corrector jets. If you have aftermarket pipes, go to 165 - 170 mains. This will help your power delivery, and should improve the idle.

Regarding the clutch, first try performing a thorough bleeding. Use the handle of a screwdriver to tap on the banjo fittings at the clutch cover and at the master cylinder while you are bleeding the system, because air can get trapped at the right-angle fittings. If that doesn't work, pull off the clutch cover, and check for fluid leaking around the slave piston. The stock piston seal is just an O-ring, and will fail over time. Also check that the "push-rod" and throw-out bearing in the center of the piston are in good shape. Check the adjustment screw on the clutch handle, to make sure that the master cylinder is being engaged after only a small amount of free play. When your clutch is well sorted out, the hard shifting and low engagement point should go away.


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 Post subject: clutch bleeding
PostPosted: Fri Sep 17, 2004 2:43 pm 
Mike had recomended bleeding the clutch with the clutch cover off. I thought I had bled the system THOROUGHLY before and was still experiencing problems. As soon as I pulled the cover off one more air bubble came out and the clutch feels better than ever now.

Thanks Mike! :thumbup:


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 Post subject:
PostPosted: Wed Sep 22, 2004 12:14 pm 
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 126
Location: Australia
model: 906 Paso
year: 1989
With the clutch problem, go with the advice of chilly_bill. try different things, different angles, don't give up! I have spent hours trying to bleed the clutch and brakes. It would drive you to drink....and I don't need any extra excuses! I think one time I hooked up a pump full of brake fluid and pumped it in from the bleed nut, but it must be totally clean.


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 Post subject:
PostPosted: Fri Sep 24, 2004 1:55 pm 
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Joined: Wed Aug 18, 2004 12:00 am
Posts: 14
Location: USA
model: 750 Paso
year: 1986
On the clutch -
I have a 1990 750 Sport. The o-ring on the slave cylinder needed replacement on mine. A Mityvac greatly simplifies the bleeding procedure.

_________________
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George Betzhold
Scottish Woods Log Cabin Resort
Murphy, NC


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 Post subject: Re: clutch bleeding
PostPosted: Fri Sep 24, 2004 8:40 pm 
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paso grand pooh-bah
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Joined: Thu May 06, 2004 12:00 am
Posts: 581
Location: NorCal
model: 750 Paso
year: 1988
Chilly_bill wrote:
Mike had recomended bleeding the clutch with the clutch cover off. I thought I had bled the system THOROUGHLY before and was still experiencing problems. As soon as I pulled the cover off one more air bubble came out and the clutch feels better than ever now.

Thanks Mike! :thumbup:


glad to help :cool:


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 Post subject:
PostPosted: Wed Sep 29, 2004 3:26 pm 
tried the clutch cover off method and it worked like a charm. at least it has so far. but after a week i think i feel the old clutch grimlins coming back. ill wait a while longer to see what really happens (i might try switching to mineral oil, as that might be the problem) and then try and bleed it again. do bubbles move around the system? i got the one out at the bolt, but maybe there were some smaller ones that have accumulated there again? i hope thats the case, because otherwise ive got a slow leak somewhere. i cant wait to try and track that down!


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