Post carb rebuild shennigans

[vladtheemailer]

Hi All,

Odd one this so I thought I'd throw it out and see if anyone has had the same thing.

For quite some time, my D900 has had a habit of bogging down when the throttle is opened up at high revs.  As I had a couple of days of work, I thought I'd do the valve clearances,grease the headstock bearings and strip and clean the carbs.

Got it all done.  The carbs were stripped, the jets soaked in carb cleaner and blown out, checked the diaphragms etc., put it all back together and it's starts first touch of the button but the bike runs pretty badly.

The tickover is fine, but pull away and get 1/8th throttle open and it start popping like it's running out of fuel.  No problem, must be air screw.  Wound the air screw to its default (1 1/2 turns out, from 1 turn to 4 1/2 turns) and it still does it.  Tickover's dropped so adjust it back up.  Since then, I've tried the pilot screw in every setting, 1/4 turn at a time and it still does it.  The plugs look a bit bleached as if it's running a bit weak but if I wind the screw out, the tickover goes up.

Assuming that I'b obviously ballsed up somewhere, I had the whole lot apart again and check every orifice, spraying carb cleaner through and checking to see if it made its way to other end and it all seems good.

Weirdest thing is thing is that the lower end was fine before the rebuild.  Now the high range is good but it does this low down.  Can't find any air leaks and the air filter is a bit grey so I'd expect it to be a bit rich.

Any comments welcome.

Cheers,

Jools

[m40man]

Apr 6, 2018 15:36:44 GMT vladtheemailer said:

  The plugs look a bit bleached as if it's running a bit weak but if I wind the screw out, the tickover goes up.

wind out a bit & try again, then turning the thumbwheel to turn the tickover back down.

The fact that higher revs are poor now actually suggests to me that on or more of the main jets needs a re-clean.

From cold, do each of the exhaust downpipes heat up at the same rate? If one less so, that will indicate the troublesome one.

[GAv]

Are you sure the diaphragms are seated ok as they can crinkle when the dash pots go back , also what Martin says, also you haven't moved the needle notches AS if they are too low you have to keep the revs up to avoid bogging down as they have to be lifted further in the base holes under the Venturi.
I am having trouble with my Cagiva, and it's a sod to get at the plugs, seat has to be removed ( easy part as it is a key undo job)then the tank has to be lifted back, and the back of the V pot is accessible.
The rad then has to be removed to get at the front plug. I left the bike outside for a while to work on another bike, the flip up fuel filler had water around the opening so I drained the tank, however it had been back in the and started but outside again it did fire but wouldn't catch ,so back to that procedure,tried the fuel pump however the fuse was in tact and I could hear it priming. It is due its MOT Thursday but having spent Nye on 500 quid at the yokel dealers getting my Aprilia Atlantic Scooter sorted, to be fair the wiring was an amateur spaghetti job, not by me, beyond my electric knowledge, then after they thought it was sorted the new battery drained after a short run andI displayed my annoyance so they fitted a Nexus 500 rectifier that was new but not needed on the Gilera as they had thought and so it went onto my Ape /Piaggio X9 based Maxi Scoot. Free gratis.

As as my knees are pretty much knackered, I can do some distance twist and go cruising which was the plan last year however despite inclement weather,torrential back from Liverpool, and down to Ullapool where it sat outside the Hotel in some overnight downpours, OK and putting the wrong fuel in later didn't help, but once home again that was sorted and it hasn't missed a beat till lately. I really do not want to be handing over some more Filthy Luka on the Cagiva however...

I did splash out on a second hand Brembo rear brake system, only really needed the switch wire and braided pipe back to the rear banjo, piston and caliper +carrier, probably saved a hundred or two, on new stuff, just the rear carrier and Grimeca brake parts were 80 pounds on the Sachs 650, the Brembo one has never been right after my stupid off on the Nuneaton bimble ride out. Riding on the back one alone wasn't just hairy but couldn't be properly bled thereafter.

But sorted now, so I guess if I Cannot figure out why the otherwise faultless Suzii TLs engine wants to fire up, but has not continuously even after another new battery, as has the Aprilia Mille and the very nearly completed Sachs has the Raptor one , it's all a juggling act,but I have had to take the B carbs off again as I think that tank has water ingression too, something that rarely gets a mention when starting is a problem.

[GAv]

Decided having drained the tank again, plugs out, pump priming OK that it must be a connector, found an end buried in the spaghetti wiring , couldnt see another but jammed down by the regulator and way down in the dark recess felt a wire the end with the female connector, joined em bike starts.
Much steamy and exhaust smoke in the conservatory, then was reluctant to restart, left it same as the other day with the Mille, no cold start used , fired up, ticked over and hasnt failed to restart today, maybe some water had got in the tank but certainly the steam was from water trapped in the vee looked a bit worrying but it was just excess damp,and probably WD 40 helped dry out the electrics!

[vladtheemailer]

Hi All,

First thought I had was a pinched diaphragm so I dismantled them again and checked all the jets but they seemed OK. The small o-rings were all present as well.

Earlier I took a can of flammable gas out and sprayed the joints by the carbs and the hoses inside the fairing but it didn't seem to make a difference so I'm guessing the pipework is OK. The exhausts seemed to warm up OK.

I've ordered a service kit so It'll be getting new filters, oil and plugs to eliminate the possible of coincidental other faults.

As I didn't touch the settings on the carbs I don't want to fiddle too much but we'll see what happens and I'll post back once I know if it is carbs or if other parts are playing up as well.

Thanks for the advice, I'll let you know what happens when the parts arrive.

[teejayexc]

Have you balanced them since reassembly?