Restoring 500GTV

If you need technical information or help with your parallel twin Ducati GTL 350/500 or Sport Desmo 350/500 engine - post your FAQs, comments & questions here.
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Cucciolo - the Lil Pup
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Joined: Wed Mar 31, 2004 9:29 pm
Location: Brisbane Australia

Restoring 500GTV

Post by Tigersteve »

I am restoring 500 GTV and I understand that they were no the most loved bike in the Ducati range, However it was my Fathers and will never leave the family.

I believe that there are a number of modifications that can be made to the engine to make it more reliable, if any one can suggest any I would appreciate it

Thanks all

Am new here love the concept will post some pics soon

Cucciolo - the Lil Pup
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Joined: Sat Apr 24, 2004 11:23 pm
Location: Melbourne

500 GTV

Post by Ray »

also known as the SD500 (Sport Desmo)
Hi Steve,

I have one, my second, so someone loves them.. maybe just me.
I can only advise that they need a lot of TLC.
Oil should be changed every 1000 to 1500 km max.
You can use an early Honda CBR900 oil filter.
IKON are making period style rear shocks and they work great. The original marzochhis used to last 5 or 6 months before collapsing.

I had the entire electrical system re-wired using Dukeletrix (a DOCV member has been running this business for some years). This is essential as the original loom is crap.

I have a few spares but nothing much to speak of.. you can obtain a lot of advice and detail work in Melbourne from Bob Brown (no use to you really)
and parts from EuroBrit in Melbourne and Gowanloch in Sydney.
I typically just buy whatever I come across adn thus have an array of busted and broken or worn out parts,but they give me hope for rebuild if needed. I have a spare frame but no triple clamps and no forks. I have the remants of a head and an engine cover. I have a spare gear selector box.

The 64,000 buck question, do you have any parts you dont need?
Do you have an original exhaust? It is black not chrome.

I still use the SD500 but not regularly. It is a bit too old for day to day use.

I have an electronic image of the brochure but that is likely not much use!

I am keen for a replacement seat unit including saddle. I was thinking of having one build in carbon fibre as the cost for building a new seat is high anyway. Interested?
In a Parallel Universe

Cucciolo - the Lil Pup
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Joined: Sun May 09, 2004 3:43 am
Location: Gympie


Post by rgs650 »

Just joining in here without helpful information but as my project proceeds I will post information on anything I find.
I have finally got hold of a 500 desmo ( 500sd manufactured 11/77) after many years of searching and a couple of years of hassling an owner of one who finally succumbed to my pleas .
I've been involved with bikes for about 40 yrs and make a living making or parts or restore /repair of obsolete items so unobtanium parts are not totally unobtainable. I have spoken to an ex owner of a springer models who is a very competant mechanic who thrashed it around for 18 months or so and couldn't break it. However I am aware of the parallel twins reputation for mechanical fragility but can no find hard facts on this. As I still own 350springer + 450 desmo singles (30 yrs, raced +road ridden) I know about fragility ,but found it acceptable for the enjoyment of the machines. I'm aware of the camshaft tunnel oil sealing problem (evident in a spare engine) ,a modification very minor to overcome, if indeed a problem.
If any one has hard information on mechanical problems on these machines which I can overcome/modify b4 assembly I would appreciate a reply. This does not include any electrical problems as these are all self evident as it is a 70's italian machine and I've been sorting these out for years.
As a post script I've owned ridden , raced ,every type British Japanese Italian motorcycle made ,I even still have my old tz350d yam, 350 bsa,suz katana ,450 desmo etc and have been around the traps this is the first 500sd I've seen in the flesh and and have lusted after one from photo's and reading roadtests and specifications (plain bearing, 52mm Stroke , triple brembo, mags, plus pretty damn good styling etc).
I diverge please .Please post a reply with all the problems for rectification, and I'll do the same after Rebuild

Cucciolo - the Lil Pup
Posts: 3
Joined: Sat Apr 24, 2004 11:23 pm
Location: Melbourne

Things That Go Wrong with the Parallel Twin

Post by Ray »

Hello Brian!

I really hope you get your bike up and running and eventually we meet at National Duke club meeting; ... really like to see a couple of them at once on the road!

I get a lot of strange looks with mine. I am sure they all think I have just put Ducati on the tank.

Things that go wrong... hmm, my fist one had a few issues,
the counter shaft sprocket bearing parted company, and cost me upper and lower cases...this I sincerely believe was due to poor chain adjustment, they are finicky here, too tight is my belief.

I too had the oil seal issue in the head.

If the oil level gets too low (I now always 1/2 litre overfill) then the pickup which is high often starves. This leads to premature wear in the head of course.

First gear can slip after take off. I am told by Bob Brown that this is common and he fixed mine by removing one of the gear "notches" (hey so I am not technical, a round node sticking out from the gear, there are two). What would happen is I would take off then the bike would lurch and crunch as if dropping out then into gear (which is apparently what it was doing, slipping off the first notch to which it had not properly engaged). I should have taken a picture of the part but I did not. What it does now is slot in with a bang. I can rerely get neutral once stopped. I can live with that.

The starter cluth is an issue with mine. You will want to know it is in good condition. Unless you know how to fix such an item.

My Del Orto's are quote "worn out", but most parts are available so should be in no trouble to yourself.

The cam chain tensioner can be a problem. If it jams (not uncommon) happened to me, it will flap about which has two results, 1 the chain gets buggered and 2, it lightens the bike (unfortunately in ways that are not so good). The tensioner bears double checking.

According to Bob Brown, they dont like a thrashing, he told me that Mike H when he visited Melbourne (all those years ago) borrowed an SD500 from his shop and retunred it completely effed. At least MH rode one!
In order to reduce the possibility of self destruction I believe a larger base gasket on the barrels reduces the comp ratio, again that is advice from Bob Brown. Mine is standard and still running fine.

The original (I think it was speedline) wheels, they are a greenish gold colour were a problem. On my first SD500 the front split! The replacement wheels which came later appear quite strong if heavy.

That is basically all I know about the down sides. They have a lot of up sides from my perspective. They look great, handle well and of course are unusual.

Does yours have an original black exhaust?

If you work out how to reduce the vibratioin at 5-6 thousand revs let me know. It smooths out nicely above 6 and is nothing to worry about below 5. Unfortunately, 5-6 is touring territory and although nothing like a single, it is a bit annoying.

Best wishes and if you decide to make something or get it made I would consider sharing the cost for most parts if it makes sense for you to have a few made.

There is apparently a new one (!?, well perhaps one never ridden may be a better discription) for sale in Maldon Victoria and I plan a Sunday run to find out how much.

In a Parallel Universe

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Post by DesmoBro »

hey ray wondering if you ever got a chance to check out the Brand New SD500 (half a decade Later)....I have one and i'm wondering if any of these bikes has a numbered gas tank My Tank has the Numbers 00157 underneath the Made In Italy Sticker....trying to find out if my numbers are some kind of Hoax or not

Cucciolo - the Lil Pup
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Joined: Sat Apr 24, 2004 11:23 pm
Location: Melbourne

Post by Ray »

the bike was in fact a GTL not an SD... pity.

as to numbered gas tank. do not know. mine is having some work done and I do not have it to hand to check out when it returns I will let you know.

I hope you are Ducati club member. more parallel twins the better.

it will be interesting to see if ducati are forced by the Rossi element to change from L4 to in line (or parallel 4)... will give the old SD a whole new perspective.. forerunner (ok being funny_
In a Parallel Universe

Parallel Twin
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Location: Australia

Post by radecal »

G'day blokes,
The little bits that go wrong can be frustrating but the cam tunnel plug can be a hand grenade but is easily fixed. One option is to have a circlip groove machined inside and problem solved once and for all. Ian Gowanloch advised that one to me. He also said they can be made to run hot and fast (and reliably) without too much effort.
Knowing Mike Hailwood, he would have ridden to the limits ANY bike loaned to him.

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