V11 backfires when low on fuel

Hi all, I have a problem and call on the collective wisdom of the club…
2002 V10 Scure 14k miles since new; owned by me for 3 months, completed 700 miles – still getting to know bike.
Symptoms: RH cylinder backfires when low on fuel. Rubber inlet manifold between RH carb & cylinder detaches; engine then over-revs [3kRPM] w/ throttle closed.
Conditions: Only happens when v. low on fuel [could it be that fuel starvation causes engine to backfire; back pressure causes manifold to blow off?]
Current solution: let it cool down, refuel, re-fit. If I refuel every 100 miles or so the issue would not occur but would rather find the correct solution.
…or is this just an additional feature of V11 not mentioned in the sales brochure!!!
All comments welcomed!
Many thanks in advance, Noel

PS: I’ve read an old post on the forum re vacuum in tank.

Sounds like an issue with the fuel pump in the tank. Split pipe may be.

sounds more like worn out manifolds.and a lean mixture .Â

I treat manifold rubbers as a service item. They are made for the job and yet have to deal with heat, cold and ethanol vapour.
Worth a try.
Good luck

and , what happened ?

OK, I’ve reached the stage where I cannot ignore this anymore!! The 100 miles between petrol station visits is really bugging me and makes route planning a pain in the whatsit !!! :angry:
I’ll start with the simple [IE cheap] items and work thru the system until the fault is fixed.

Bike is off the road; tank, airbox, side panels, battery, battery rack and anything else that was in my way have been removed. Tank has been drained and is venting [Expanding Tank Syndrome!]. The right hand injector body does not appear to be aligned to the inlet manifold! This could be coz the rubber has been off more times that I care to think about in the last few months. I would have thought the whole injector ‘unit’ would have been fixed to the engine somehow to hold it’s position; It appears to be held in place by just the airbox rubbers and inlet manifold rubbers.

I’m expecting new manifold rubbers this week. I already have a new air filter. Once I have the rubbers, I’ll rebuild & see if I still have an issue - which I think I will :frowning: Assuming I have , next I’ll swap the injectors over [Is this even possible?] to see if that helps.

This will be a slow process but I’ll keep you posted! Obviously, feel free to comment, criticize, suggest, laugh etc. :laughing:
Rgds. Noel

I was going to suggest, try a bottle of injector cleaner. I had an “issue” recently with the Ural (EFI, twin throttle bodies) apparently misfiring and popping and banging on the left side as though an exhaust clamp is loose. There wasn’t. Also trying Brisk spark plugs to replace the NGK (dealer’s recommendation). Only subtlety better. So nothing to lose i thought, bought STP petrol injector cleaner. Bunged in half a bottle into 1/3 tank then went to top up, then went to the club Essex camp, 250 miles each way. Was like waving a magic wand over it, no more popping behaves more like it did 2 years ago soon after I first got it, and went like the proverbial train.

I put the second half of the bottle on return, then went on my Gloucestershire/ mini Welsh tour which I’m still on now.

Hi Mike,
Thanks for the advice, I’ll bear it in mind.
The bike runs smoothly on a full tank; at the 100-140 mile point its backfires & throws off the RH inlet rubber :frowning: . Refit; Refuel & it’s good to go for another 100 miles :slight_smile: . I’m beginning to think it’s related to the weight of the petrol tank, which I know is bizarre & illogical but it’s the only variable!
New inlet rubbers due tomorrow so lets see what the weekend brings!!!
Enjoy your tour, Noel

I agree it’s bizarre, how is the fuel pump arranged, is it internal? Could be something going weird with it

Mike, fuel pump is external on this model. On the recent Lincoln run I stopped for fuel 4 times in 340 miles and still it came off 3 times!!! :angry:
Rgds Noel

Hi Noel, it’s not something reall stupid like the fuel tap? the mannual one seems to take a huge amount of winding to open fully, or the 12mm pipe from tank to pump - I had to change this last year on the LeMans as it had softened horribly . . .
Also, I assume you’ve found these guys http://www.v11lemans.com/forums/ which is the V11 obsessives corner of the internet :open_mouth:
Cheers A.

Hi Andy,
Thanks for your input - I hadn’t even though about the fuel line! The bulk of the rubber fittings on this 17 yr old bike could do with replacing so it’s logical that would include the fuel line but, again, why does it only occur at the 100-140 mile mark?
I take your point on the fuel tap, it is fully open. When I reassembled the bike last Sunday I forgot about the tap &, on start up, wondered why it was turning over fine but not firing!! :blush:
Yep, I’ve found the V11 forum. Useful source of info; pity it’s predominately US centric.

The bike is now back on the road with a full tank for petrol. A quick 20 mile shake down run Sunday evening just to check nothing major was amiss. Now I need to do another 100 miles & see what happens.

Again, thanks for your comments/inputs and taking the time to write, Noel

Hi Noel - 12mm fuel pipe - I had to buy a meter of the stuff (half inch won’t do, trust me :open_mouth: ) message me an address & I’ll send you a length.

Hi, an update…
Took the bike out Saturday morning for a longer run to see if I still have the fault; back home after 10mins & 3 miles! :angry:
1/2 mile up the road & the gear selector return spring failed. When I pulled over, my right leg felt colder than my left - looked down to find I had a fuel leak with a fine mist of unleaded onto my jeans!! :cry: Fuel leak fixed at road side, bike nursed home & am now waiting for a replacement spring from Gutsibits.
A public ‘Thank You’ to Cabernet & Redmog for their advice & offers of parts.
Rgds. Noel

This bike has a curse on it …

No, it just needs some love & attention!!! :sunglasses:
Rgds. Noel

This has now been going on for 7 weeks ??? :astonished:

Actually, over 4 years!!! Unfortunately, I can only devote limited time to it as ‘life’ keeps getting in the way. :frowning:

Any more news on this?

Unfortunately not! :frowning:
Bike is u/s with failed gear selector return spring & off road for last 2 wks. :cry:
Now hv replacement parts so will see what this w/end brings!!
I’ll keep you updated.
Rgds. Noel