• Ciao Guest - You’ve landed at the ultimate Guzzi site. NEW FORUM REGISTRATIONS REQUIRE EMAIL ACTIVATION - CHECK YOUR SPAM FOLDER - Use the CONTACT above if you need help. New to the forum? For all new members, we require ONE post in the Introductions section at the bottom, in order to post in most of the other sections. ALWAYS TRY A SEARCH BEFORE STARTING A NEW TOPIC - Most questions you may have, have likely been already answered. DON'T BE A DRIVE-BY POSTER: As a common courtesy, check back in and reply within 24 hours, or your post will be deleted. Note there's decades of heavily experienced Guzzi professionals on this site, all whom happily give endless amounts of their VALUABLE time for free; BE COURTEOUS AND RESPECTFUL!
  • There is ZERO tolerance on personal attacks and ANY HYPERLINKS to PRODUCT(S) or other competing website(s), including personal pages, social media or other Forums. This ALSO INCLUDES ECU DIAGnostic software, questions and mapping. We work very hard to offer commercially supported products and to keep info relevant here. First offense is a note, second is a warning, third time will get you banned from the site. We don't have the time to chase repeat (and ignorant) offenders. This is NOT a social media platform; It's an ad-free, privately funded website, in small help with user donations. Be sure to see the GTM STORE link above; ALL product purchases help support the site, or you can upgrade your Forum profile or DONATE via the link above.
  • Be sure to see the GTM STORE link also above for our 700+ product inventory, including OEM parts and many of our 100% Made-in-SoCal-USA GTM products and engine kits. In SoCal? Click the SERVICE tab above for the best in service, tires, tuning and installation of our products or custom work, and don't miss our GT MotoCycles® (not) art on the BUILDS tab above. WE'RE HERE ONLINE ONLY - NO PHONE CALLS MADE OR RECEIVED - DO NOT EMAIL AND ASK QUESTIONS OR ASK TO CALL YOU.
  • Like the new V100, GuzziTech is full throttle into the future! We're now running on an all-new server and we've updated our Forum software. The visual differences are obvious, but hopefully you'll notice the super-fast speed. If you notice any glitches or have any issues, please post on the Site Support section at the bottom. If you haven't yet, please upgrade your account which is covered in the Site Support section or via the DONATE tab above, which gives you full site access including the DOWNLOADS section. We really appreciate every $ and your support to keep this site ad-free. Create an account, sign in, upgrade your account, and enjoy. See you on the road in 2024.

850-T3 California fuel tap question

Mark Shelley

Mark Shelley

Just got it firing!
Joined
May 17, 2010
Messages
11
My 1978 bike appears to have a petrol cap of double skin construction. It does not seem to have a little vent hole like most caps, but appears to allow venting via the double skin, up through the middle on the inside and out through the gaps around the underside of the edge. Is this correct? If it is I guess it is unlikely to get blocked.
I have not had the bike long, but have been having an annoying problem with the bike dieing after a mile or so, but then it starts up fine, only for it to happen again after a short distance.
I have checked the little gauze filters on the carb and they are clean as a whistle.
The tank appears to be pretty spotless inside. The bike has only done a few hundred miles since a total professional restoration and had new petrol taps at the time.
Yesterday when it started to die I managed to get stopped before it died completely. In desperation I switched both taps to reserve position just to see what happened and the engine almost instantly came back to life and ran perfectly the 6 miles home. I have ridden 10 miles to work on reserve settings and it ran sweet as a nut. I will need to have a couple more drama free trips before I am absolutely sure, but it looks like there is a problem with the fuel supply in the `on` position.
Any ideas?
 
There are gauze filter at the fuel taps. Remove the taps, unscrew the filters and reverse flush them. You should be good after that. Try not to disturb the little pipes inside the gauze filters. Also while the taps are off, make sure there are no obstructions, perhaps even reverse flush, or blow air through from the outlet.
 
john zibell said:
There are gauze filter at the fuel taps. Remove the taps, unscrew the filters and reverse flush them. You should be good after that. Try not to disturb the little pipes inside the gauze filters. Also while the taps are off, make sure there are no obstructions, perhaps even reverse flush, or blow air through from the outlet.
Click to expand...

I drained the tank down via the taps and the flow rate was good and consistant. I removed them anyway and they look brand new, which they are of course!
I put it back together and took it for a spin. The problem still exists.
I may well book it into Haywards in Cambridge when I get chance, but I am off to St Andrews to start work on The Open at the weekend so it may be a while. Has anyone got experience of Haywards with the older bikes?
 
john zibell said:
You original post didn't say anything about having new petcocks.
Click to expand...

Without wanting to sound like a pantomime Dame......Oh yes I did! ;)
 
Confusing thing to me is that it runs fine on 'Reserve' but not on 'On'. at the risk of offending what position are the taps in on 'On'?
Peter
 
Mark Shelley said:
john zibell said:
You original post didn't say anything about having new petcocks.
Click to expand...

Without wanting to sound like a pantomime Dame......Oh yes I did! ;)
Click to expand...

Sorry, missed it.

OK then, new taps. Are they original type? If so, handle down is on, handle up is reserve, handle forward or back is off. You said flow rate was good in the on position. When you drained the tank, was the cap open or closed?
 
OK then, new taps. Are they original type? If so, handle down is on, handle up is reserve, handle forward or back is off. You said flow rate was good in the on position. When you drained the tank, was the cap open or closed?[/quote]

They are the original type as shown on this link http://www.stein-dinse.com/bilder/artik ... 5461-z.jpg
and they are not up for reserve. It is down for on, reserve and off are horizontal, I can`t remember which way is for which without looking.
I think the reserve thing was another one-off occurrence as it happened again on my way home last night with it on reserve position!
 
I have the same cap on mt T3 marc and the vent did get blocked up with rusty crap a few years ago.Can't remember where the hole is but you can take the top part off and then it shoud be obvious ...I think it is right in the centre.
In my case she would run for a few miles and then start to get starved of fuel and run on one,backfire and be a complete bitch.
 
Orright then. The taps illustrated actually look like after-market replacements for the original sugar-cube type taps fitted to the T3 but that shouldn't make any difference. Next time it starts to die, pop the fuel cap open and se if it picks up. If it does, your cap's not venting.

Peter
 
Mark Shelley said:
OK then, new taps. Are they original type? If so, handle down is on, handle up is reserve, handle forward or back is off. You said flow rate was good in the on position. When you drained the tank, was the cap open or closed?
Click to expand...

They are the original type as shown on this link http://www.stein-dinse.com/bilder/artik ... 5461-z.jpg
and they are not up for reserve. It is down for on, reserve and off are horizontal, I can`t remember which way is for which without looking.
I think the reserve thing was another one-off occurrence as it happened again on my way home last night with it on reserve position![/quote]

Actually those are from a newer bike. The origi8nal T3 had a round valve stem into which an arm was screwed in. Anyway, that is not important. What is is the post from Chris A. He may have something with the vent becoming blocked. I've personally not seen that, but it could happen.
 
I've not seen venting problems on a bike (sheltered life) but have had the problem on cars and lawn mowers. Popping the cap should prove the theory.
 
The vent being blocked threw me for a couple of weeks even though I had encountered exactly the same issue years before with another bike.A good mate with excellant diagnostic skills sugested it and he was dead on the money.
 
I just went thru something similar with my V7 Sport, but mine was loosing power at higher cruising speeds as the flow was poor due to a blocked cap and never actually died. I have the flip-up style cap. Mine has the rubber seal sandwiched between two metal plates and is screwed together with one screw/nut in the center.

The metal plates have a simple maze that allows the cap to vent, but the air must travel thru the maze to get out. each plate has a small hole and the rubber gasket actually has two. Mine had built up dust, some rust and some deformation of the rubber seal was causing me grief.

I unbolted the the assy, cleaned up the dust and corrosion and then flippped the rubber gasket so that the side that was deformed and appeared to have been possibly blocking the maze of one of the plates now was facing the other plate. I used thread lock on the little center screw/bolt so that I was sure to not overtighten and squeeze rubber seal into the maze channels.
 
You must log in or register to reply here.
Back
Top