RGS Carburettors (AGAIN!)

K

kneeslider

New member
Hello all.

Its been a while since I posted on here, and its also been almost a year since my RGS was on the road, so I figured that it was probably time to have a look at things.

I tried to fire it up a few times, and found it reluctant, a few coughs but nothing of note, the fuel had been in there for ages, so drain it all out, fill with new, and try again, still nothing, so off with the tank, pull the plugs, clean them up, off with the carbs.

At the moment, I'm at the point where I have the carbs in bits. One of the main jets was in the bottom of the bowl (!) time to have a look at the float levels, everything looks clean enough, and nothing is obviously blocked up.

The mains have 108 on them, and the needles are K1 on the middle notch. the pilots are 65s When I ran it, it was doing about 32mpg (imperial).  Which was rather disappointing.

It has always been a tough starter, any suggestions on mixture screw settings, accelerator pump screw settings etc etc?  I think that the slides are synched OK.

The needles have a slight notch on them, only slight mind.

The ignition is stock, and gives a good spark at the plugs, and it seems to be timed OK.  It would often backfire when starting from cold, but from reading the posts of others here, that seems normal...  Then after an unsuccessful churn on the button, another backfire when you switch it off, again, that is normal?

I have just had a look on the Dellorto UK site, and priced up gasket sets x3, needles, x3 and atomisers AB265 x3, this comes to about ?100 +VAT + postage... Hmm, am I on the right track before committing folding?

Any thoughts/suggestions gratefully received!

 
32mpg indicates ridiculously rich running...but should help cold starting  ;)  I always reckon 40mpg for average riding.

Anyway - things to think about re poor starting.  Stock ignition doesn't respond well if the battery voltage collapses due to (1) weak battery (try jumpstarting - 2 batteries in parallel - to check this) (2) poor connections from battery to starter and battery to earth (3) poor starter condition

Bit late now you have the carbs in bits!  Certainly the notched needle jets won't help running, but won't affect starting.  Nor will accelerator pump jet setting (easy to check that the pumps operate...more time consumong to check calibration).  Idle mixture screws should be 1.5 turns out as a good starting point.

Worth checking all the carb drillings are clear - there's been many posts on this - for example http://www.laverdaforum.com/forum/index.php?topic=55185.msg102412#msg102412

And probably the easiest of all - make sure your choke control does actually lift the plungers off their stops!

Good luck

Finally, you will find http://www.myscooterparts.co.uk/ cheaper for the bits you need (if they have them in stock - use their search tool with the Dell'Orto UK part number)
 
I don't think backfiring is normal, certainly not on my Jota 120.
With a Witt ignition it starts first time very time on a stab of the button, even when left a few weeks.

As Rob says you have too much fuel floating around by the sounds of it!
 
Backfiring certainly points to a weak battery or huge battery drain, a fart on switching off is normal.  With the plugs out, you will find they fire when switching off the ignition(Witt DMC, stock Bosch BTZ), nearly always have one cylinder close to firing position at a standstill.  Might be worthwhile to strip and clean the starter motor.  If the battery is in good nick, the starter may be draining too much current and preventing the ignition from firing while it is engaged.

Looks like needles and needle jets need replacing, if there is a notch in the needle, the jet is certainly worn and this would account for the astronomical fuel consumption.  But, as already stated, has not much to do with starting.

While you're at it, :D, check condition of pump membranes, float valve tips and all other rubber components, as well as for slop in the throttle linkage.  A well set up carb will usually return sweet running to any old dog...

piet
 
Thanks for the pointer chaps.

I think that the starter motor  should be OK, as part of the overhaul I took it apart and the brushes, bearings etc proved to be fine.

I think that while everything is in bits, Im going to check the position of the marks on the crank and the ignition backplate, relative to the proper tdc position.  They check out when I strobe it, but who knows?

I have bought 3 carb gasket sets, and managed to save considerably on the recommended prices from Dellorto's UK website.  I found the part number of the kit, and then a little ebay bashing produced the same part number listed for a different carb for ?6 each so ?19 for all three kits.

A similar bit of ingenuity has got me some new needles for ?5 each, from an online supplier.  I'll share details when I know that they are all the correct bits!
 
Bah! I bought an ultrasonic bath from Maplin for ?99, and stripped the carbs down, then found that the screws holding the choke cable stops are all stuck!

I have been soaking them in penetrating fluid, but they are currently preventing the carbs being properly seperated...

Anyone have any hints and tips for removing them without resorting to drilling out?

Pesky 30 year old Dellortos!
 
apply some heat to the casing with a heat-gun. be careful not to overheat them and make sure you mount them in a bench vice first...

might be the DPO applied some locktide to it...
 
I don't know what causes it but the choke slide seizing in place is not unknown. Well I do know it is fuel gums but I really don't know why it happens sometimes and not others. I had a bike that I had ridden every day for weeks and then one day one of the chokes seized.  ::)

Carb cleaner doesn't even seem to help too much.  ::)

You need to get some movement in there. Remember there is a small rubber seal on the bottom of the plunger. With some carb cleaner above the plunger give the top of the plunger a tap with a hammer and a pin punch. Not too hard to destroy the rubber but just enough to move the plunger. Once you have movement you are almost home.

Lothars suggestion has merit too but I have never tried it because this sort of stuff normally happens to me when I'm on a trip.

Cheers

Rod
 
kneeslider said:
Bah! I bought an ultrasonic bath from Maplin for ?99, and stripped the carbs down, then found that the screws holding the choke cable stops are all stuck!

I have been soaking them in penetrating fluid, but they are currently preventing the carbs being properly seperated...

Anyone have any hints and tips for removing them without resorting to drilling out?

Pesky 30 year old Dellortos!
Click to expand...

choke cable stops? You mean the single screw on each carb that holds the choke plunger/cable into the carb?

I would soak in penetrating fluid, apply gentle heat, then hold the carbs securely and hit the screw with a very tight fitting bit in a hammer/impact like this....  http://www.harborfreight.com/impact-screwdriver-set-with-case-37530.html

Paul LeClair
 
Wouldn't recommend hitting anything in that area - pretty thin casting...

The screws are steel and the casting is alloy - not a good combination. The suggestion of moderate heat is a good one. Make sure you have a screwdriver bit that perfectly fits the slot - they are not all the same and a proper fit is crucial in a slot head screw. If that doesn't work, drill 'em out - the screws are pretty soft. Make sure you drill a pilot with a very small bit (1mm or thereabouts)

HTH

Pete
 
Oops, my mistake. I misread the post. Thought it was referring to a stuck plunger rahter than the screw.

I'll try again. Heat is good but I would try to freeze and release it first. There are products on the market like WD40 but they cool as they are sprayed on, contracting the jointing surfaces and allowing the lubricant to wick in.

50/50 acetone and ATF works well too. As the acetone evaporates it cools. Same theory.

I'd get some between the slot bolt and housing then, again with a pin punch  :D, gently tap the screw with a hammer. Don't hit it hard, just tap it. The shock waves help the lubricant to wick in and break the tension.

As offered, proper size driver, heat, etc are all good options. Drilling it out would be my very last.

Cheers

Rod
 
Drilling it out would be my very last.
Click to expand...

Big 13mm SDS drill - 10 seconds and it's out  :D

Seriously though Rod, don't be afraid of the drill - properly applied, it's a really good option. They key is to centre the bit and only start with a very small bit (around 1 - 1.5mm or 16th/inch). Once you have the pilot hole, work up to larger sizes until the size is greater than the screw thread size. Then the head drops off (no, not yours, the head of the screw  ;) ) and you can remove the attached item. You now have the remains of the screw sticking out, which should freely turn out (love the word "should"  - but if it's still stuck in the carb, you would never have got the thing out with the head intact). If it is stuck, more heat (hot air gun, not hairdryer) and it will come out.

Never had it fail yet, but I guess there is always a first time...

Pete
 
Drilling out would be my very last option for a few reasons Pete.  :)

I'm not scared of a drill or a bit of an engineering challenge but experience has shown me that drilling out something that is much harder then the surroundings can be fraut (spelling?) with danger unless you know what you are doing. I was replying to the original post at the skill level I perceived.

From memory the bloody bolts are  non standared thread too. You just can't go down to the local hardware and by a slot head countersunk bolt to suit.  ::)

I'd be surprised if you couldn't get the little sucker out with a bit of cunning.  ;)

Cheers

Rod

 
Thanks for the replies everyone!

I managed to get the screws out eventually, soaking in penetrating oil for a week, then I made an extension for my impact driver to get it nice and snug in the screw...

A few taps, and out they came.

Its all going back together now, so setup wise

18.5mm float heights
New needles in the middle slot
1.5 turns out on the mixture screws.

Any guidance for setting up the accelerator pump screws?

 
New needles alone are only a shortcut... and Laverdas do not like shortcuts!  Fit new needle jets as well.

Accelerator pumps total at 4ml for a 1000 and 5ml for a 1200 at 20 full squirts of the pump.

piet
 
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