Bing carb questions

[SteveM]

I've just decided to address a poor starting and running problem with my '89 GSPD and so I bought a carburettor refurb kit from the chaps at Motorworks as shown below.



After having cleaned the LH carb thoroughly both inside and out I reassembled it in the same way I disassembled it, only this time I used the new jets, gaskets, diaphragm and 'O' rings provided in the MW kit. The only real problem I had was that I couldn't find a home for the arrowed 'O' ring in the picture below. Has anyone any ideas where it should go?



Anyway, I proceeded to do the second carb and noticed that one of the slides (LH) had a big 'O' ring round it and the other didn't. Is this normal? Can't see why it would be. Any ideas anyone? Cheers Steve.

 

[Rob Farmer]

The o was fitted to the 91 on carbs and shouldn't be on your model at all. You will never get it to run properly with one O ring fitted. Take the needles out and make sure they are the same length. The needle that was fitted to the later carbs was much longer to compensate for the O ring.

Is there a cutout under the O ring on the slide with it fitted? Apart from the O ring being fitted do both slides look identical?

 

[SteveM]

Hi Rob, thanks for the reply. I'll take a closer look tomorrow.
Any idea about the largest 'O' ring in the MW kit? (pic.1)

 

[PaulRS]

That O-ring would fit around the brass piece holding the main jet, don't know it's original name.
Or around the shaft inside the choke housing.

Paul.

 

[SteveM]

The o was fitted to the 91 on carbs and shouldn't be on your model at all. You will never get it to run properly with one O ring fitted. Take the needles out and make sure they are the same length. The needle that was fitted to the later carbs was much longer to compensate for the O ring.

Is there a cutout under the O ring on the slide with it fitted? Apart from the O ring being fitted do both slides look identical?

As you can see from the photo Rob there is a recess for the 'O' ring to sit in on the slide, and their overall lengths are identical, also I measured both the old needles and they were the same length. Is it possible to just discard the 'O' ring and continue to use the slide or should I order a replacement do you think? There is a slight shoulder above the 'O'ring recess on the slide but I don't think it prevents it from bottoming out in the carb body.



And PaulRS I think you're correct about the left over 'O' ring. My original picture above was wrongly arrowed, the 'O' ring I have left over is actually the second biggest one and it must go on the butterfly shaft. Unfortunately I don't have any new screws to replace the flap if I take the original one out. Apparently the screws have their ends peened over to prevent them falling out and getting sucked into the engine, meaning you have to file off the protruding back part of the screw flush with the shaft before unscrewing them to prevent knackering the threads. I'll get some screws ordered I think as the shaft 'O' ring 'could' be 27 years old

 

[Rob Farmer]

That's a later paralevers slide. Do your carb Bodies match?

Just bin the o ring and make sure they both sit down where they're supposed to. If it doesn't you'll have to refit the o ring and fit a genuine later needle until you can find an 81 on slide. Check the cutaway in the slide to make sure they are both the same if they are all should be good. No wonder it ran rough, the jetting would have been all over the place.

 

[SteveM]

The carbs seem the same, except of course them being mirror images of each other, and the slides do seem to seat identically so I'll do as advised and junk the 'O' ring and see how I get on. Thanks.

 

[SteveM]

All back together now and running way better than before. The only fly in the ointment is starting from cold. It won't run on full choke, and it won't idle properly till warm. Is this normal? I have the air screws 1.25 turns out, standard jetting, needle on clip 3 out of 4 etc etc etc. I toasted the battery getting it going this morning (about freezing), by the time I'd recharged the battery and everything was a little warmer it reluctantly started - eventually. Any thoughts?

 

[Kenny]

All back together now and running way better than before. The only fly in the ointment is starting from cold. It won't run on full choke, and it won't idle properly till warm. Is this normal?

Yes, normal. Air screws are about right ( if bike 'pops' when knocking off the power, then back out the air screws a further 1/4 turn )

 

[Beemerboff]

Could be float levels are a bit low, as a rough check the fuel should be around 14 mm from the top of the bowl when you remove it.
You have to remove/ replace refill the bowls one side at a time or the fuel all drains into the second one.

 

[Rob Farmer]

Don't pay any attention to the recommended pilot screw settings. It's fine for getting the bike going initially but after that forget it!

If you have vacuum gauges set the carbs with a fast tickover (around 1200 rpm) once the engines at normal running temperature, turn the pilot screws one at a time until you get peak tickover rpm. Once it's there you can back off to a normal tickover using the tickover screws. You may have to repeat this a coupl of times with a ride on the bike in between. I have a standard run I do stopping off a couple of times for adjustments.