Accelerator pump diaphragm

[Stevex]

Before stripping my 36mm carbs I noticed both accelerator pumps werent squirting. Ive checked the nrvs and they appear ok. The carb bowl ones can be blown through in only the correct direction and the pump nrvs plastic balls can be moved easily against their springs. The diaphragms, although not holed or cracked seem quite stiff. I replaced them last, about 12 years ago. Would this be enough for them to stop working, bearing in mind they are physically operated via the throttle slide plunger? Anyone experienced similar?

[guzzisteve]

There should be a gasket on the body of carb, most parts books don't show one. Many need priming through the cap on the top of carb, Rebuild w/all new if unsure and still don't work. Good Luck

[Stevex]

Yes, mine have the gasket fitted.
I'll see what happens when I prime to pump.

[guzzisteve]

I never had an issue with mine on LM3 but a customer with LM1 has even with new diaphragms. He has to prime through the top cap each time he goes riding. Once out going no more issues. Seems some are fussy. Never an issue on my 32's.

[Stevex]

I think if the pumps need continuous priming, one or other of the nrvs has given up the ghost. The bowl nrv is easy to check but the pump one, as far as I tried, is not responsive to a suck and blow test.

[wirespokes]

NRV - I'm guessing this is NON RETURN VALVE

I've had many bikes with 36, 38 and 40mm Dellortos and haven't had an issue with the pumps. Then again, I haven't checked for squirt, but if the bike runs as it should, why should I check?

It's good to know what to look for in case I ever do run into that problem.

I haven't had to pull the pumps, but had no idea there was also a gasket along with the diaphram. Where would it go - which side of the diaphram? Is it necessary, especially considering it's not on the parts diagrams?

[Stevex]

Even though my pumps werent pumping I wouldnt say I noticed it during normal riding, but Ive no idea how long theyve not worked for and what felt normal isnt necessarily so. The pumps squirt neat fuel to overcome any lag when the throttles are opened enthusiasically, which on the Guzzi, I dont do that much.

[guzzisteve]

NRV - I'm guessing this is NON RETURN VALVE

I've had many bikes with 36, 38 and 40mm Dellortos and haven't had an issue with the pumps. Then again, I haven't checked for squirt, but if the bike runs as it should, why should I check?

It's good to know what to look for in case I ever do run into that problem.

I haven't had to pull the pumps, but had no idea there was also a gasket along with the diaphram. Where would it go - which side of the diaphram? Is it necessary, especially considering it's not on the parts diagrams?

The gasket is separate, does not usually come w/diaphragm.  The gasket goes on the carb body side. It also is not in many of the parts books or diagrams In different manufactured bikes not only Guzzi's but Ducati's too.
I know of it cause I sold DelOrto carbs & parts to customers that wanted a hotrod Guzzi. It is in all of the DelOrto parts books though.
I had to look up what NRV was also.     

[Frenchfrog]

Even though my pumps werent pumping I wouldnt say I noticed it during normal riding, but Ive no idea how long theyve not worked for and what felt normal isnt necessarily so. The pumps squirt neat fuel to overcome any lag when the throttles are opened enthusiasically, which on the Guzzi, I dont do that much.

I had similar feelings when I disconnected the pumps on mine...but not even sure if they worked correctly prior to doing that. With my A/F set up I've seen that on sharp acceleration the carburation really goes lean for an instant so perhaps they still don't work ? Tried priming etc but not checked if the gasket is there or not...anyhow this discussion as revived my interest in checking and hopefully sorting it out !!!!!

[Stevex]

Gasket, number 63. Dry side of the pump.