It's been a while...

3narf · Post by **3narf** » 21 Oct 2007 11:58

Bloody hell, Sport has been off the road for over four years.

I used to be good at getting it to run properly but I just don't have the time any more...

Anyway, it starts with just the rear choke, but won't start with just the front. I put bigger pilots in it (52s) and it will tick over, but dies when I put any sort of load on it, ie into gear and lots of revs.

Checked the timing and the carb balance which isn't a milion miles out, and that's where I had to leave it to make lunch for the kids.

I may get a couple of hours on Thursday morning. Where should I start next, if that makes sense?

Cam is a remanufactured L5, carbs are PHBH 26s with 118 mains, 50 starters and usually 50 pilots. Transducers are Vespa items.

3narf · Post by **3narf** » 31 Oct 2007 19:53

Oh, well. I might have an hour or so tomorrow with a bit of luck.

3narf · Post by **3narf** » 20 Mar 2008 13:01

Well, anyway... Still hoping for a full day to get the thing running properly.

It's been off the road too long. Problem is, it's difficult to think back to when I used to ride/rebuild/play with it intensively.

Even trying to remember the spec it finished off with- it's got Vespa transducers, 372 pistons, L5 cam, NLM 2:1 and 26mm PHBHs but otherwise it's fairly standard, even the cam pulley is set in its standard position.

I went fine last time I rode it- at Cadwell in 2004- so maybe the carbs just need soaking in petrol or something...

3narf · Post by **3narf** » 01 Jul 2008 19:58

Managed to get an hour this morning- got it running, second kick.

It'll run with just the rear choke, but switch it off and it just dies. This suggests to me some kind of blockage with the pilot circuit in the rear carb.

I pulled the carb apart and gave it a flush out. I wish I could remember- is the pilot screw an airscrew or a fuel screw? Must dig out all my DellOrto manuals.

Is there a website with some carb drawings or schematics or anything like that?

I don't think there's a problem with ignition as it starts really well and seems as if it will tick over with the right amount of fuel...

Ta

3potjohn · Post by **3potjohn** » 03 Jul 2008 05:50

http://www.dellorto.co.uk/

TonyH · Post by **TonyH** » 03 Jul 2008 07:40

Hello, thats funny coz i'm having very similar problem with my 350 at this moment in time, but mine won't run on the front cylinder. The pilot screw is a fuel screw (if memory serves me correctly as its infront of the slide, if its an air screw it will be behind the slide). I've cleaned both carb ( Wurth carb cleaner is excellent stuff by the way) but still to no avail, i must persevere tho!

Good luck, Tony

ps i have a dellorto manual at home if you have no luck on web (i could photocopy bits and post to you if needed)

3narf · Post by **3narf** » 03 Jul 2008 14:44

Many thanks!

I do have the manuals somewhere...

So, does yours run on both, but only on choke? When I get to the bottom of things I'll let you know.

3narf · Post by **3narf** » 03 Jul 2008 14:46

3potjohn wrote:http://www.dellorto.co.uk/

Thanks, John

TonyH · Post by **TonyH** » 04 Jul 2008 11:45

Mine runs ok on the rear cylinder ok without choke but the front will only run on choke. I think mine must have a blockage on the idle circuit somewhere, so it looks like i'll be stripping down my carbs agin this weekend - oh well at least the weather doesn't look good enuff for a ride.

I'll check you up to date on my progress too.

tony

TonyH · Post by **TonyH** » 05 Jul 2008 17:09

Hmm still not having any luck with mine! I've cleaned the carbs again, paying particular attention to the idel circuit, set up the floats exactly...but she still won't fire on the front cylinder without choke!!

HELP anyone??? Would low compression cause this sort of problem, i'm starting to clutch at straws now as its baffling me.

Thanks, Tony

TonyH · Post by **TonyH** » 06 Jul 2008 16:03

Well, hooray, i think i may have solved my problem. Before i took any drastic action, i swapped the front carb over to the rear to see if the problem moved with it. And sure enuff it did. So at least i then knew it was the carb causing the problem. So i've stripped it down again, taking extra extra care this time and what i have found is that the idle passage above the idle jet seems to be blocked! Unfortuately i don't have an airline, so i think i will pop over to my friendly dealer tomorrow and see if he can blow it clear for me.

Hope you've had some luck with yours.

Tony

3potjohn · Post by **3potjohn** » 07 Jul 2008 05:41

I was going to suggest try swapping the carbs but couldn't think whether this was possible. I had a similar thing last year with a 40mm Bing carb,the bike ran well enough at speed but below about 20mph went onto one.An interesting experience suddenly getting both 500cc cylinders coming on and off in traffic. A blocked pilot jet was found-waxy muck not easily cleaned at the roadside. Beats me how the idle jets work as well as they do most of the time.

3narf · Post by **3narf** » 09 Jul 2008 20:19

I soaked it in injector cleaner overnight. I don't have a compressor either, but it seems to be clear now.

Now I just need to find time to try it before it gums up again...

Thanks for all the info & ideas. It's been off the road way too long, now.

Really Aardvark · Post by **Really Aardvark** » 16 Jul 2008 08:36

Hi 3narf

Best carb cleaner I've used is cigarette lighter gas especially the can with the range of nozzle tips in the cap. It squirts through all jets and carb passages, its a hydrocarbon (butane) so it dissolves all sorts of c**p and then evaporates without leaving a residue. Oh and its cheap!!!

Sounds like your bike is very close to mine. I started turning a knackered Strada into a 'Benjy Straw" 3 3/4 nearly 20 years ago. It finally made it into one piece of bike last year and now I need to tune it. Any chance you could let me know what size jets, needle, atomizer you have in your 26mm carbs?

Jem · Post by **Jem** » 17 Jul 2008 20:41

I sorted major problems by fitting the latest floats. They are very different from the original floats and give a much better mixture and starting.
I have also just fitted 45 pilot jets which seem to give much better running. I have used a Colourtune to set up the mixture with good results, my Sport seems much better on idle and pick-up.