Help - Breva 750 - rough running

Hello there,

I’ve been having issues with my Breva over the last 2 months and have been trying to resolve myself based on info from many of the posts and technical docs around. I have now exhausted my list and thought I’d share my ‘work’ to date and see if anyone can advise on my next steps please?
It’s a 2005 Breva 750ie that I bought in June 2020, it has 22k and is standard except for a pair of Mistral’s (baffles in place).

First off - lumpy running and big hesitation.
Replaced plugs to start, then noted water in filler (assumed in tank too) so as week two, booked in for service and check over.
Tank was drained
New filter (metal)
Valves set
Throttle bodies balanced
Oil/filter too

Came back just fine
6 weeks later, refuses to start after a 20 mile run out. Luckily when warm and dry. After 45 minutes of trying every 5 mins or so, took off seat. wiggled all the relays, fuel pump connector etc. It started. Was it me? I don’t know, just started for a laugh as the RAC arrived as it woke up!!!

Got it home, checked All connections, cleaned up spades on the injector relay (they needed it). Saw no signs of any issue that could have caused it?? Starting to loose a bit of faith now.
Week later;
Hesitation starts again. Similar, if not the same as before. Start a list of checks.

Air Filter - replaced (it was pretty dirty) No change
Checked plugs - Engine definitely running Lean
Replaced Lamba Sensor - no change (now realise this wasn’t necessary)
Checked tank again - syphoned out and found signs of water again!
Tank off - noted both vent pipes loose. Out with Fuel, filter and pump out.
Totally drained Tank - New filter _ again! in case
Vents cleared (overflow was partially blocked so explained water ingress, tank vent pipe was pinched in pipe so hoping that was it) and then blown through
Cap vent checked too
Checked HT leads
Tank back on (has anyone else experienced the lengthening tank palaver?)
New fuel, no leaks, test run and…same again, no change

So, now looking at GuzziDiag and Lonelec
No error codes or anything I could see of concern
TPS reset and throttle learning set up.
No Change
Contacted Beetle (Mark) who kindly sent me a basic map for no-pop and Lambda Off.
Mapped this, TPS reset, throttle learning
Ran better than it has been…but still ‘missing’, not regular but easier to hear around 3-4k revs, and feel when riding…
Last ride just now after Beetle got back to me with a variation for Temp with our UK climate.
Remapped, reset TPS etc … and no change.

I have now run out of my ‘very’ limited knowledge of where to go next. If anyone has any thoughts or options, no matter how small, that would be very much appreciated. Feel free to point out the obvious too as this has been just Me Vs Breva until now, and I think I know who’s winning.


They say a problem shared is a problem two people now have!

I have got an expanded tank. Ratchet strap from the bottom yoke round the tail of the tank buckles it back on.

I had intermittent charging problems with my B11. It turned out to be a hairline crack in one of the fuses. So, replace all fuses and relays?

Good suggestion - will try next time, thanks

Thanks for that. I have taken them all out and checked but not swapped out so I’ll give this a try too. Cheers

Injector cleaner?

Thanks. If you mean added to tank stuff then yep, tried that too.


I take it that the Breva has a plastic fuel tank ? If so, then the answer is yes. My V7 Classic had a plastic tank and it expanded. Like Topsy it growed ! Trying to make it fit one day, I managed to hole it. I had to replace the tank with a second hand one. The problem appears to be the ethanol in the petrol that causes the expansion. I don’t know if you can “dry” the tank out by draining it over winter and leaving the tank cap off. Removing the petrol pump assembly from underneath the tank would get a better airflow. It is a nuisance. Is a metal tank available ? However, I did find that to be a too expensive solution, given the age of the bike.

But this does not fix your running problem.

What happened, if anything, two months ago that might have caused this problem to manifest itself ?

Check all electrical connections again ?

Are the injectors working correctly ?

Hi Jeff,

Thanks for replying. Yes, the plastic tank is a bit of a strange one. I liked the earlier reply of ratchet strap across the yoke, next time maybe.

Two months ago was when it stopped, and never ran properly after that. I found water in the tank which had to be rectified, but that wasn’t it. When I had the tank off I checked al the connections underneath too.

Good point re-checking all the electricals again. I have this week gone back to the injector relay (one in the middle of the 5). Again, took off, checked connections and got the multimeter across the +=. This time I got only 15 ohms!! All I have read says it should be 50-100 and I found a Hella PDF for the closest new one saying 85 Ohms! New one in the post from Gutsibits, due tomorrow. Fingers crossed.

Maybe replace all the relays - if still factory fitted originals, will be 15 years old. Contacts inside could be messed up.

New replacement Injector relay, no change. In fact the resistance was the same as the original one so I now have a spare.
Fair point they are all 15 years old. I’ll add them to the shopping list.

I’ve been reading about poor connection at the air temp sensor on the air intake box affecting running. Is it a tank off job to get to it to check does anyone know? I can’t see it.

Thanks for all comments

Hi Matt,
May I suggest you look through the “Hhhelp with my Sttttuttering” thread in the CARC section of this forum and my entry of the 8th September. The problem with the Norge was that it refused to start two weeks after some throttle body adjustments were made. The obvious conclusion was that the adjustments were the cause of the problem, but, no, it turned out that one of the rubber hoses on the fuel pump assembly inside the tank had collapsed and no fuel was reaching the injectors. It will be worth seeing if this might be the case with your problem.
A quick way of checking if this is a possibility in your case, is to remove the spark plugs, squirt some fuel into each cylinder, replace the plugs and if the engine fires then it points to a lack of fuel being the root cause of the problem. We did this with the Norge and it ran, but we never thought the problem went back to a blocked pipe within the tank and still believed it was something wrong with the throttle body settings. How wrong we were?!?
Hope this helps,
Cheers Phil

My Breva 1100 did some strange things when the TPS went FUBAR

Perhaps plug GuzziDiag in and trace the throttle position I.e. slowly open and close the throttle and see if the trace shows any unexpected steps or jumps

Hi Phil,
Thanks for the reply - oh yes, read your post many times over. Very informative and I followed it too. So when I went down the ‘water in tank’ route for the second time I replaced the fuel filter and checked all the pipework and all seemed fine to me. Definitely getting fuel out to the cylinders and it runs, just still rough running.
Cheers for the nudge, I just hope to not empty the tank for the 3rd time!

Thanks Tris.

I’ve run the GuzziDiag with engine running after TPS reset and learning jobs. I know what you mean, but not sure i know what i’m looking for. It rises up when slowly revving and drops back to the set 3.1.
I did read though (Beetle) that a TPS reset should be followed by a gentle open of the throttle and release, then rest again. That’s on my list for this weekend. I’ll take on board your suggestion and see what I can get from the readouts.

Last weekend i thought i had it - RH injector was ‘loose’! removed it, bit of crud on the end, cleaned it off and popped back in, tightened the securing bracket properly. No change but daylight faded and back to work.

I have confirmed that my injector relay was slowly failing though and have new HT leads, caps and coil end caps on their way…

Cheers for the suggestion