Carb balancing question

[welshmally]

I decided to re-balance the carbs again this weekend (900SS) as I hadn't done it for a while (how often should you do it anyway?)

Following Steve's advice, I found that the response when adjusting the cable adjusters was very sluggish. The cables are fairly new and are well-routed, but I just felt that the adjustments I made had a very slow response. Also, when I got to the air screws, there seemed to be very little variation in engine speed unless I turned tham at least over half a turn - there were no subtle variations - either OK or stalling. Is this common experience, and if not, what could be the problem?

BTW I use a Morgan CarbTune II

Cheers

Hugh

[BevHevSteve]

Could be time to clean out your carbs and install new kits....

[welshmally]

Thanks Steve,

I gave them the once-over last winter, stripping everything and cleaning except for the accelerator pumps, so they are probably reasonably OK, but probably not race-ready!

What are the 'standard' atomiser and needles that people generally use? I only use the bike for spirited days out, and very rare track days.

Hugh

[BevHevSteve]

what year SS and do you have PHM40s or the pHF 32s?

[welshmally]

Sorry - late '80, PHM's

Would it be a good idea to install a 90 deg elbow to the rear carb to allow more reliable routing of the cable?

Hugh

[BevHevSteve]

no - puts loads or strain on the cable at the sharp bend and causes a ton of stiction....... I would MAYBE put a 40 but definitely NOT a 90

[welshmally]

....and the atomiser/needle?

[Zanetti]

atomiser/needle won't make any difference to idle speeds from your 1st post,
check the idle air bleed passage is not gunked up with fuel varnish, to get reliable idle all the following must be right.
No air leaks at manifold, valves adjustment ok, ignition system timed and producing good spark at low revs, no damage to the ramps on the slide that the idle speed screws contact, correct float level and idle jet size.
For the lack of response from the cable adjusters make sure the thread in the carby tops is not damaged, slides and carb body not worn or have excessive clearance, are there any damping restrictors to your manometer, they will slow response but not indefinitely, from memory a 1/8 turn on the cable adjuster would make a noticeable change on my manometer (mercury) when holding the revs in the mid range.

[welshmally]

Thanks Zanetti,

I can actually get a really nice idle at about 1100 - 1200 rpm, the only little mystery was the fact that small adjustments, particularly of the air screw, seemed to to have little effect. It would be great to get that finly tuned response I'm after - I'll give the air screw another good clean and see what happens. It'll be easier to identify the fault if I do one thing at a time.

Cheers

Hugh

[welshmally]

I think I know what the problem was.......

Got home from a ride the other day and it was popping like a beauty on the over run on the front cylinder. It turned out I was lucky to get home at all - front plug had completely stripped its thread. Considering I was red lining it earlier in the day, it's a miracle it didn't blow the plug out.

Wierdly, this has always been the stiffer plug of the 2 ever since I bought the bike 13 years ago, but has never been a problem, until now, and now I know why!

Head back on soon, with helicoil, and we'll see how much better it is.........