Newbie jetting questions

doublegarage

doublegarage

Junior member
Location
California
Well, I've been wanting a Laverda since about 1978 and 2 days ago I finally got one.

It's a 1981 Jota series2 (mk2?), from what I've researched on here it seems to be about 50 bikes from the end of 180 production. Probably sold new here in about 1983.

Anyway, it's a mess. Not one scrap of original bodywork (Honda tank, Montjuic seat, unidentifiable mudguards) - let's say it has great potential.  My initial plan is to get it running well enough to put a few hundred miles on it, then decide what sort of project it will be.

The first obstacle to that plan was two completely stuck slides in the Dellortos - one of them came loose with a squirt of carb cleaner, the other one took about 5 hours with every solvent I had, every penetrating oil that anybody on the street had - and finally some attention from the heatgun and some gentle prying. See attached when victory was achieved.

The airbox has been severely messed with, it has a mystery cutout in the front face, no idea why.  It had disintegrating oily foam glued all over the inside. Pretty sure that's not original from research here and some of the debris was inside the float bowls... It also had a screwdriver inside it (not a joke). The horizontal baffle + snorkel was missing, as was the air-filter element itself. So (finally!) my first question:

1) I'll get an air-filter, but do I need the horizontal baffle that goes below it with the  single hole and snorkel?- probably just for noise, so can I use just the filter?  I've read hints that I should ditch the vertical baffle with the 3 rubber nozzles that fits inside the airbox too?

Then, inside the carbs - someone warned me that the airbox mods probably means someone would have re-jetted it and, sure enough, it has 160 mains, 60 idles, AB265 emulsion tubes.  Reading on here it sounds like 145 mains were stock and that's now considered too big, especially bearing in mind I have to run the thing on 2020 California's foul ethanol brew.  I went to blow out the main jet with an airline and the hole was almost bigger than the blowgun nozzle - Anyway, 2nd question

2) what's a good starting point for idle & mains.  I don't want to buy a whole jet-kit and start tweaking, yet.  Just a sensible/safe setup that will work - reading the forum maybe 130 mains and 55 idle jets? Pretty sure 160/60 is way off?

Anyway, many more questions but I'll leave it there for now, thanks for reading this far.

-Richard
Santa Cruz, California.


 

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+1 welcome.  You appear to have done your research well, all your suggestions sound like great starting points.  Bear in mind that if it's a US bike then they originally had low comp pistons and A11 cams - although many were upgraded during their lives to the high comp pistons and 4C cams.  You'll want to pop the cam cover off to give everything a quick inspection and a thorough oiling at least before attempting to fire her up.  A dose of assembly lube on the cam lobes and buckets won't hurt.  While you're doing that you can see what kind of cams it has.

Before starting, ignition box unplugged, spark plugs removed, a bit of oil in the bores and fresh oil in the crankcase, turn it over for a while on the starter motor to try to get the oil system primed up.  Ideally one would strip an engine that has sat a long while, but it's often not done and they're usually fine.

Enjoy the journey and keep us informed of progress.  Oh, and more pics!  I love the screwdriver bodge. :D
 
Hi, Richard.
1.) When buying new slides they most likely have to be modified. If you look
    from the bottom, the distance between the ramps must be at least 28,7mm.
    If it's less it's easy to machine it on a lathe or maybe the dealer might do
    it for you.
2.) First of all (concerning carbs) I always renew the needles and the 265ABs
    as you'll never know how worn out they are.

Good luck with the bike.
Ernesto
 

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Jotas with 4C and HC never did have the internal baffle plate and three (internal) trumpets many ditch the bottom panel and the snorkel, (actually a fourth carb to air box rubber, long type) my own bike still has both but its a 1200, with A11 and LC and has spent many hours being dynoed, not any help to you though, the cut out in the air box looks like a breather modification, maybe it trailed to the rear number plate area at some time., go with Breganzanes suggestions, except I would do the first turning of the motor by hand/spanner, if you feel anything, then you need to stop and rethink.
CLEM
 
Hi Richard. All the advise here is excellent. And you will need to get with Wolfgang. He is in your time zone.

Wolfgang Haerter
Columbia Car & Cycle
357 Shakespeare Road
Nakusp, BC, V0G 1R1, Canada

Ph.+Fax: (250)-265-4502 (office)
Monday to Friday 9am-5pm (Pacific time)
www.laverda.ca
laverda@lightspeed.ca

 
Does the bike run? Doesn't seem like you've had it running so my advice is to assess the mechanical condition of the engine before you spend 5 cents on anything else! Breganzane & Clem offer great advice-next step after that would be checking compression. Post pics when able, sounds like a real mongrel!
 
Thanks everyone - for both the welcomes and the advice.

It looks like my Dellorto shopping list needs to get longer. I'll get new needles as Ernesto suggests, the one I held in my hand when the slide came out was pretty crusty - the AB265s looked very clean - but I agree, no idea what they look like on the inside. I won't replace the slides for now - that one was badly gummed up but after a quick cleanup they all move very smoothly. Which needles is it supposed to have, K1?

Setup would therefore be: 130 main, 55 idle, AB265, K1 needle (?). Rebuild kits x 3.  I won't bother getting a lower (horizontal) the metal baffle/snorkel, just an airfilter. Maybe leave out the vertical/triple-rubber baffle too (thanks Clem). What spark plug is recommended? The forum seems to have changed its mind over the years.

I've spent 2 days wondering what cams/pistons it has - so Breganzane's suggestion to actually look inside is what I needed to hear. Not sure I'll know what I'm looking at in there but I've got a camera.

Right, cam covers off, oil change, slow cranking, clutch bleeding, that's today sorted.  No pictures of the bike itself yet because I ripped into it 5 minutes after it arrived. 

Thanks again, all.

-Richard





 
That gummy residue on the stuck slide is probably from either a fiberglass gas tank or one that has been sealed somewhere along the line with a substance which dissolves in modern fuel. Your experience sound exactly like what I found when disassembling a set of Amal carbs from a Dunstall Commando with original fiberglass tank. The slide seized when the rider (not me, thankfully) was banked over in a fast curve and it hurt him very badly.

Anyway, I would be very worried about that residue lurking in other parts of the carbs and causing havoc. Be careful. Depending on what the original material was there might be different solvents that would be effective. If you have a friend who is a PhD organic chemist it might be a good little research project!

Eric
 
Some progress today and some concerns.

- I left the oil draining overnight and got about 2.8liters in the pan.  Cleaned up the drain plug and was concerned to see what looked like a twist of aluminium (yes I'm a pom) on it - but turned out to be just grey sealant.  Replaced the plug with a new copper washer while muttering about people who slather everything in sealant, then of course..the plug wouldn't torque up properly at all and I think the thread in the sump is damaged (the plug looked like new).  Ahh well, I suppose the engine was going to come out one day, I just wish it was for a better reason. 

Refilled with 20W-50 to the max on the dipstick (just under 3.0L) -  nothing's dripped out of the drain plug yet but then it wouldn't while it's cold would it.  >:(

- To cheer myself up I removed the cam-cover and looked for cam identification - see attached, "4/C" on each cam. Also stampings under the intake cam side: 2, 0 and 3.  Does that mean anything useful?

- Then turned the engine over slowly, watched the cams, didn't feel any "blockage".  Changed the plugs for a lightly used set of B8ES (from a failed experiment on a car).  Turned it over a few times on the starter and then - it started!

- It needs all of the choke to start, sort of idled ok after a while but I never got the choke all the way off. Probably idle speed setting but also big idle jet? Revs up nicely, but it's all a bit academic with the wrong jets and no airbox so I didn't try for too long. Anyway, it starts, runs, revs, and didn't seize. (shame about the drain plug thread)

-Richard
 

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I perched the bodywork back on the bike to show the overall look.

If someone said to you "it's an '81 Jota with a Honda tank that's been cut/shut/welded and a Montjuic mk2 seat unit but modified with a 2-seat Corbin and a Vespa rear light" you might think...."well that sounds like a dog's breakfast!" but I think it kind of works.

I was told it was a Suzuki tank but I reckon it's from a CB1100R but extensively modified underneath to fit the Laverda frame, plus adding a 2nd petcock.

The story is the bike got side-swiped while sitting at a traffic light, hence all these changes. Other things that are "wrong"?
- Speedo/tacho are reversed and the tacho has the wrong face (they rev that high though, right? :-X). 
- Modified panel between the clocks.
- Marzocchi forks from a 120 Jota or later maybe. 
- Didn't the mk2 180s all come with a right-side gearshift lever, so this has been converted?
- Moto Witt ignition.
- Telefix adjustable clip-ons.
- Some sort of Verlicchi headlamp mount. 
- unidentified front mudguard

The plan is still up in the air - I kind of want it to look like that bike I wanted when I was 18, which means a set of bodywork from somewhere, maybe in carbon-fiber from Boba. No hurry to decide. Meanwhile, it looks pretty cool i think.

-Richard
 

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You're right, the mods work well-bike looks far better than the description! Well done getting it running & happy to hear good news so far. BTW, what's the additional cable on the clutch cover next to the hydraulic line?
 
Which clever person is going to explain the meaning of the 2 0 3 stamp on the cylinder head?  I don't recall seeing that on any triple I've owned, but then again I forget things.... ::)
 
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