"New" bike

[Kelvin]

G'day,

I've been lurking here for some time, I didn't put up an initial post because I was unsure of where to put it.

However, I recently picked up a second bike so perhaps now is a good time to introduce myself?

I rode an R65LS in the 1980s when I was a uni student. Financial constraints required that I do all the work on it myself. Although I had a number of other bikes after that I was looking for a bike in 1996 and found one identical to the one I'd sold in 1988. Recently I found another, slightly newer, bike, this one with 135k km on the clock and many of the mods necessary for bikes of this age (SS pipes, SS brake lines...) and what I thought was a reasonable price (AUD 6,100). I've just gone though the process of getting it from Melbourne to Sydney and fixing a few minor issues.

It had a major issue with carburetion, not functioning properly above 4k revs and not at all above 5k (but beautifully below 4k). As is usual I was able to fix this with considerable help from the historic threads on this forum: many thanks for this!

Both bikes are on historic (club) rego, so I get 60 ride days per year. This is two rides per week with the pair of bikes. They're running with only minor differences at present. I live in NW Sydney, so fairly regularly ride north up the old Pacific Highway and west to the Putty Road.

Cheers,

Kelvin

[skippyc]

Nice looking bikes Twin, twins

[ged in oz]

Nice work Kelvin. You’re spoilt for choice.

What was the issue with the carbs?

[Kelvin]

Dismantling showed that one of the needles was corroded, and the springs were old/rough/corroded. I replaced the needles, needle jets and springs and got a bike that functioned above 5k but not below. After some reading and substitution I have it running happily with the new components but the needles raised two notches to position 4 (original was position 2, my Haynes manual and the BMW workshop manual say position 3).

With the needle in position 3 the bike idled and worked above 5k, but 3k to 5k it would lag when the throttle was wound on. It would accelerate, but it would pause first.

There was a bit of crud in one of the main jets, and although the carbs had recently been serviced (and the outsides were beautifully clean) the main jets were stuck to the main jet holders: I think the carbs were serviced but not completely disassembled. I'm not entirely sure that the whole saga was not caused by that tiny bit of crud.

It's also possible that the needle was dropped to position 2 during the recent service by mistake, and that this wasn't picked up because the bike was not ridden at highway speeds after the work. 

[Barry]

With the needle in position 3 the bike idled and worked above 5k, but 3k to 5k it would lag when the throttle was wound on. It would accelerate, but it would pause first.

Assuming float levels are correct that's a sure sign that it's running weak at position 3.  One needle position is a very big change though. Another option is to go one size up on the needle jets which is much smaller change.

When you consider these bikes were set up relatively weak by the factory and then if there is any ethanol in the fuel it will make them run even weaker, it's no surprise that the mixture is marginal at the book settings.

[Bob_Roller]

Do you have any idea what work was done, parts replaced when the carbs were worked on ??

Sounds a bit like a tear or hole in a carb diaphragm .

[Kelvin]

The recent carburettor job was to replace the O-rings and clean, my guess is that the diaphragms were not replaced. They're fine at the moment.

The needle jets are the correct size as per the book, so I'm not in a hurry to replace them. As it stands at the moment the bike is running sweetly, but rougher than I can usually get it. I'm going to run a few tanks through it and see if it settles down. I want to see what sort of fuel economy it gets and also confirm the needle configuration of the other LS.

Fortunately we're just coming into summer in Oz... :-)

[Kelvin]

my guess is that the diaphragms were not replaced.

Or perhaps not. RHS diaphragm was not oriented correctly, so the piston was 30 degrees out. I now think that the PO replaced the diaphragms, but (very) inattentively. No wonder I had difficulty tuning it.

I'm currently working through a problem with fuel dripping out of the LHS float chamber while I'm riding it. I replaced the float needle, to no avail. Current hypothesis is that corrosion on the spring clip caused it to jam, I should receive a pair of these tomorrow (and I should've replaced the $2 items when I did the float needles!).

[ged in oz]

Ewww. A CV carb is not going to enjoy that!

The diaphragm installation doesn’t give a lot of confidence in the previous carb rebuild. I suspect it warrants double checking everything, particularly float heights. That might expose the source of your leak too.

Little by little Kelvin.

[Kelvin]

Little by little Kelvin.

And a little more. The leak was stubborn, I eventually stripped both carbs, had the float needle seats replaced, and reassembled them. The leak persisted. I replaced the floats, checked their operation, no help.

However, the float chamber from the other bike was fine. The two float chambers were identical, no cracks, no irregularities. Filled with fuel on the bench they had identical patterns of moistness around the top.

So, I got a new float chamber from motobins. It leaked. (At this stage I'm starting to go nutty.) But, it didn't leak on the "old" bike, only the new, so I put the chamber from the "old" bike onto the new, and the brand new float chamber onto the old bike. And now both are working reliably. Touch wood.   [smiley=1drink.gif]

[ged in oz]

Well, I’m glad to see that you sorted it Kelvin. Persistence and perseverance are like an unstoppable force sometimes!

You have to wonder where the issue was though? It’d be very difficult to get even a slight deformation in the base of the carb body I would have thought. Anyway, as long as it’s sorted.

Difficult getting bits out of Moto Bins at the moment with the airfreight industry seized up. My last order from them took 4 weeks to get here! So, I went to Munich Motorcycles in Perth for my next order and the service was excellent - I originally forgot to order a sump gasket, so I rang the next morning and they added it to the order without drama - and it was delivered to my door within 48 hours. Their prices are a bit rude though.

[Kelvin]

Their prices are a bit rude though.

Yes, but cheaper than a dealer!

With the time difference to WA I've been able to dismantle one day, place an order, and reassemble the following day. I doubt it would work in the covid times, but it's made things really easy in the past.