900 SS -as temperamental as other Italian women

[brian cornford]

After lying dormant for a couple of years, and only brief movement to keep it turned over for a couple before that (de to moving, workk change etc.) she has not forgiven me. Front pot seems to run reasonbly well, but back pot is spasmodic. Both carbs were taken apart and cleaned up, and this helped with the first symptom-

backfiring.She still backfires a little, especially when I have the rear carb adjusted to what seems the right mixture using a colourtune-although t be honest I find this very hard to judge and might well be out with this.

Engine pulls well sometimes, but a lot of the time feels more like a single- and it can chop between the two giving surges of power and uncertaintyof what is going to happen when I open the throttle! this seems to be linked to throttle opening to some extent-larger openings can cause full power to be restored.
after a lay off of 3 yrs, much misfiring (carbs cleaned in petrol, didn't seem blocked with goo-improved things a bit. Front pot ok, rear cuts in and out with some misfiring under load. She seems bad at the point where the ignition advance changes.....is this about 2800 rpm from memory?Motor won't tick over and I need to keep blipping the throttle at 1800 rpm -below this she will usually die. Perhas she is running only on accelerator pumps at this point? Throttle stop adjustment doesn't make any difference, on either pot. Both are screwed right in. Plug not a good guide(only very short trial runs) -looks wet when I remove it. front pot plug is showing a little colour, though. Wet black runny stuff is emerging from joints in the exhaust system for the rear pot.I think it's too runny and black to be fresh oil (just changed, straight 40). A little smoke on start up, from both pots, but very quickly this vanishes. I tried colourtuning the rear pot mixture, but couldn't judge the colour well. Compression not brilliant, has been waning for years. Any ideas? Thanks,Brian

[Craig in France]

Hi Brian,

2 thoughts:

1. The carbs are not as clean as you might believe. In particular, the idle air drillings could still be at least partially blocked - they are especially difficult to clear. Without these operating cleanly, you will find it next to impossible to achieve a tick-over or smooth low running.

Cleaning the carbs just in petrol in unlikely to do the job properly, especially if the bike has been stood for a while. Copious quantities of carb cleaner, carefully applied in the right places, is normally the minimum required; but an ultrasonic bath is really the best way to go.

I don't know which country you're in; but if the USA/Canada, I would advise you to get Steve A. to clean and re-set the carbs to original spec. He has the right equipment and expertise, as well as access to any parts you might need. If in the UK, Mike at JRS offers a similar service.

2. The insulation on the pick-up wires is coming off. This is a well-known fault, courtesy of Bosch. It causes misfires and intermittent (permanent, eventually) cutting out on the affected cylinder.

It's an easy fix, basically using heatshrink and epoxy resin ... EXCEPT it involves removing the pick-ups, and their replacement requires the use of a special tool to ensure the timing is correctly set. Again, if you're in N. America, talk to Steve. If in UK, try Tony Brancato (but I know he is flooded with work at the moment).

You can also buy the special tool form V2 in Oz - and possibly from Steve? Or hire it from the DOCGB where the tool hire guy, one Steve Wynne (Who he? :-) will also advise as to its correct use.

HTH

Ciao

Craig in UK

[brian cornford]

Molto Grazie.

Thanks for sharing your expertise and knowledge.

Brian

[Geoff]

Something else worth considering is loss of effective rear oil scraper rings; while my 900SS had a good compression leak down, it practically poured oil out of the rear exhaust nut and joints! I had tried swopping leads (Rita so ok to do that), and swapping carbs - no difference. So I deglaze honed and renewed the rings - all ok, oilly mess and rear misfire went away.

See my pics and comments (bottom of first page and second page):

http://www.bevelheaven.com/~BB/phpBB2/v ... 45&start=0

Cheers
Geoff