Author Topic: Breva 750 What The Heck Moment  (Read 195 times)

Offline MikeW

  • New Goose
  • *
  • Posts: 81
    • Mike's Machines
Breva 750 What The Heck Moment
« on: May 03, 2021, 04:54:56 AM »
The missus had been complaining recently that her Breva 750 wasn't idling properly for the first few miles on her daily commute. I finally got around to checking it out over the weekend.

I started the bike up and it was having difficulty idling even with the fast idle lever set at the maximum. It was also backfiring through one of the throttle bodies intermittently. Hmm that sounds a little lean I thought to myself. What's going on here I wondered as I got the bike lift out and raised the Breva up to where I could take a closer look.

I removed the plugs and they looked ok but a bit elderly so I replaced them just to be safe. Next I removed the two balance screws and connected up my gauges. On firing up the bike I noticed that the right hand side had hardly any reading at all at idle on the gauges.  That's odd I thought as I blipped the throttle a few times trying to keep the bike to running.

That's when I noticed that the top mounting bolt for the right hand inlet manifold was missing. I looked underneath at the lower bolt and it wound out by around 5mm. No wonder the bike wasn't idling. The only thing holding the manifold to the head was the pressure from the throttle bodies. I was surprised that the bike ran at all in this state. Next I went round to the left hand side and surprise surprise, Both bolts on that side were loose too. Now I know for a fact that these bolts have never been touched since the bike left the factory so I can't explain how this happened.

So I replaced the bolt, tightened everything up, checked the throttle body balance, reset the ECU and the bike settled down to a nice steady idle.

The moral of the story is that when the missus complains about something wrong with her bike don't put it off. There may actually be something wrong with it  :grin:
Mike's Machines on You Tube
Motorcycle News & Reviews
Motorcycle Service Videos

Offline SIR REAL ED

  • Guzzi Hero
  • *****
  • *
  • *
  • Posts: 1166
  • uh.... it's personal....
  • Location: Forest, VA
Re: Breva 750 What The Heck Moment
« Reply #1 on: May 03, 2021, 05:01:47 AM »
The missus had been complaining recently that her Breva 750 wasn't idling properly for the first few miles on her daily commute. I finally got around to checking it out over the weekend.

I started the bike up and it was having difficulty idling even with the fast idle lever set at the maximum. It was also backfiring through one of the throttle bodies intermittently. Hmm that sounds a little lean I thought to myself. What's going on here I wondered as I got the bike lift out and raised the Breva up to where I could take a closer look.

I removed the plugs and they looked ok but a bit elderly so I replaced them just to be safe. Next I removed the two balance screws and connected up my gauges. On firing up the bike I noticed that the right hand side had hardly any reading at all at idle on the gauges.  That's odd I thought as I blipped the throttle a few times trying to keep the bike to running.

That's when I noticed that the top mounting bolt for the right hand inlet manifold was missing. I looked underneath at the lower bolt and it wound out by around 5mm. No wonder the bike wasn't idling. The only thing holding the manifold to the head was the pressure from the throttle bodies. I was surprised that the bike ran at all in this state. Next I went round to the left hand side and surprise surprise, Both bolts on that side were loose too. Now I know for a fact that these bolts have never been touched since the bike left the factory so I can't explain how this happened.

So I replaced the bolt, tightened everything up, checked the throttle body balance, reset the ECU and the bike settled down to a nice steady idle.

The moral of the story is that when the missus complains about something wrong with her bike don't put it off. There may actually be something wrong with it  :grin:

Good diagnosis!  I had a similar situation on my Nevada 750.  The boot between the carb and the engine wasn't fully seated.
"There's two kinds of people in the world; those for whom no explanation is necessary, and those for whom no explanation is possible."

2016 KTM Duke 690
2019 Beta EVO 250
1982 Yamaha Seca 650
1999 Suzuki DR 650 w/790cc kit
1976 Kawasaki KE 175
1986 Honda XL600R

***Wildguzzi Official Logo High Quality 5 Color Window Decals Back In Stock***
Shipping in USA Only. Awesome quality. Back by popular demand. All proceeds go back into the forum.
http://www.wildguzzi.com/Products/products.htm
Advertise Here
 

***Wildguzzi Official Logo High Quality 5 Color Window Decals Back In Stock***
Shipping in USA Only. Awesome quality. Back by popular demand. All proceeds go back into the forum.
http://www.wildguzzi.com/Products/products.htm
Advertise Here