Talk me down, man....

[leaky]

Glad to hear you've all been out enjoying the summer sunshine (grrrrr)...here's how I've spent my recent quality garage time ....

Problem finally fixed !!! (I think...).

Just in case there's any lessons in this for anyone other than me (doh), here's (I hope) the final part of the story....

1st Weekend:
  Replaced ignition pickup (just in case)
  Replaced carb rubbers
  Reset idle screws to 2 turns out
  Checked compression - 185,190 and 192psig cold which I took to be fine ! - gauge might be past it's best though..
  Removed petrol tap and cut off filters
  Dismantled filler cap and made sure vent clear (had tried running with cap open before so knew this wasn't a problem but did it anyway !). One of the other threads with photo was useful here. The lesson I learnt is don't do this in the back yard with the cap attached to the tank. Just managed to avoid loosing anything before I did the sensible thing and removed the whole cap assembly and worked on table. Hinkley must have a whole Dept devoted to cap design !! Tank now whistles like mad nearly all the time - different notes for air going in or out !

Engine restarted OK but still poping at steady 2-3K and not keen to pull off. Pause for small amount of moderate swearing.
However, Seemed marginally better than before so decided to use for work commute and see if it would improve or get worse with good thrashing...

By Thursday I'd had enough (no change) and returned to using MZ.
Only useful observations from frustrating 4 days were:
a) running definitely improved with slight choke (smooth pull away and no pops at low speed)
b) idle speed was eratic on one day only.

Decided problem must therefore lay with carbs - 3 main theories :
a) slides sticking at low speed and hence bike running lean - therefore improves with extra fuel from choke
b) fuel blockage in choke supply - if fuel pick up from float bowl blocked then opeing choke plungers would let air straight through from carb inlet to downstream of butterfly and results in leaning out - therefore in this case bike is perhaps running rich and applying choke leans out
c) incorrectly assembled pilot screws (!!) is either producing air leak or blocking off proportion of fuel through idle jet - therefore bike is lean and choke adds fuel and corrects.

One of my ex-racing mates reckoned plug colours I'd seen from previous steady 2K rpm runs in garage were meaningless unless engine was under load. I think I've learnt this before ......However, since it's such a pain taking the plugs out when the bike's in a ridable state I didn't bother trying a proper plug chop before dismantling again...

2nd weekend:
   Carbs off and dismantled again (record time !)
   Managed to remove 2 of 3 pilot jets this time and checked standard 40's. No sign of any obstructions.
   Double check diaphragms for splits (again)
   No sign of any stickiness with slides but lightly polished slides with Brasso metal polish (if anything the slides seem quite sloppy in the guides and I was wondering if this could let ambient/high pressure under diaphragms down to region of needles and reduce low pressure enough to slow/delay rise of pistons - any idea what happens when wear becomes very large ? Didn't pursue this as have clocked up much higher milages on CV carbs before with no probs)
    Needle clips left on centre groove
    Put 1/2 can of cleaner through idle and choke fuel passages. The idle ones I'd cleaned out before but can't remember if I'd done the choke fuel lines (ie external brass pipes). For good measure, pumped petrol with syringe through all these circuits and checked flow in all directions through all inlets/exits. No obvious signs of issues although final bits of lawn not previously killed by kids playing football may take some time to recover from petrol dowsing....
    Replace floats and recheck float heights
    Finally - may or may not be important ? - resequenced oring/washer/spring on idle mix screws.

There seems no info in manual and when I'd reassembled last time had done ;
 (innermost first) oring-washer-spring-screw

parts catalogue shows ;
  (innermost first) washer-spring-oring-screw

Hence this time went with parts catalogue sequence although couldn't see would make any difference..
   
Engine starts OK - warm up and readjust idle speed.
Bingo !! - runs fine, will hold any rpm nice and steady with no popping. Her indoors complains about the noise so must be good,

So....not quite sure which bit of operator error this was all down to -  inadequate cleaning or incorrect idle screw asssembly?

Anyway, 4 trouble free days so far this week going to and from work - seems fine - pulls nicely from ~1.5K - no longer need to drive like 350 YPVS.....top end seems fine as well. Small holes in rusty RH exhaust gives nice burble on over-run....

Hope to get a few extra (recreational) miles in now with the last of the spectacular UK summer rapidly approaching and hopefully do Baltic trip next year.

thanks again for the support

At least this whole sad story has given my work mates with fuel injection a good laugh - I'm just waiting for them to get their next flat battery or I get the chance to download a virus into their Power commanders.......

ride safe

[Sin_Tiger]

Thought it had been raining in the UK for so long you had timed it just right  

............. or I get the chance to download a virus into their Power commanders.......

ride safe

:lol:

You didn't happen to notice the markings on teh needles when you had them off did you?

[leaky]

Needles and emulsion tubes I bought new from Triumph (old ones knackered after 37K miles) and are marked :

needles :5E56
tubes :9-0()519
clips in middle of 5 slots ie 3rd up or down !

hope this helps

[Sin_Tiger]

Brilliant, thanks  :icon_salut