guzziriders.org - moto guzzi forum Homepage
Forum Home Forum Home > Technical > Small Blocks
  New Posts New Posts RSS Feed - B750 - odd low speed 'misfire'
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

B750 - odd low speed 'misfire'

 Post Reply Post Reply
Author
Message
Andrew_C View Drop Down
Senior Member
Senior Member
Avatar

Joined: 14 May 2014
Location: Hampshire
Status: Offline
Points: 298
Post Options Post Options   Thanks (0) Thanks(0)   Quote Andrew_C Quote  Post ReplyReply Direct Link To This Post Topic: B750 - odd low speed 'misfire'
    Posted: 17 Sep 2017 at 17:58
OOK - scenario.
At 2500 rpm ish, the bike is misbehaving. Not really a misfire, but a hesitation. High speed it seems fine. One pipe (nearside) looks bluer. ISTR from my spannering days long ago this indicates that cylinder is running hot. Plugs look OK, the other side maybe a bit sootier around the insulator, but tips look the same.

Any thoughts about where I should be looking first? I have got a cable and Guzzidiag.
Back to Top
Brian UK View Drop Down
Moderator Group
Moderator Group
Avatar

Joined: 13 May 2014
Location: Surrey
Status: Offline
Points: 17641
Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 17 Sep 2017 at 18:22
Firstly put some injector cleaner in the tank, be generous. See if that improves it over a few miles.
Next I would check the balance of the throttle bodies.
Brian.

Better 5 minutes late in this world than years early in the next.
Back to Top
Andrew_C View Drop Down
Senior Member
Senior Member
Avatar

Joined: 14 May 2014
Location: Hampshire
Status: Offline
Points: 298
Post Options Post Options   Thanks (0) Thanks(0)   Quote Andrew_C Quote  Post ReplyReply Direct Link To This Post Posted: 17 Sep 2017 at 18:53
Ta. I'll give that a whirl.
Back to Top
Andyb View Drop Down
Senior Member
Senior Member
Avatar

Joined: 02 Jul 2016
Location: Nottinghamshire
Status: Offline
Points: 602
Post Options Post Options   Thanks (0) Thanks(0)   Quote Andyb Quote  Post ReplyReply Direct Link To This Post Posted: 18 Sep 2017 at 09:19
My 750B always had a flat spot, but a little higher up the rev range, at around 4000rpm. Never sorted it out, which was a shame as it ruined the bike for me. The later V7 with 1 TB is much better.
AndyB

Edited by Andyb - 18 Sep 2017 at 09:25
Back to Top
Andrew_C View Drop Down
Senior Member
Senior Member
Avatar

Joined: 14 May 2014
Location: Hampshire
Status: Offline
Points: 298
Post Options Post Options   Thanks (0) Thanks(0)   Quote Andrew_C Quote  Post ReplyReply Direct Link To This Post Posted: 18 Sep 2017 at 17:08
Nah, not a flat spot.  A definite fault.
Back to Top
theoneandonly View Drop Down
Senior Member
Senior Member
Avatar

Joined: 24 Jul 2014
Location: london
Status: Offline
Points: 661
Post Options Post Options   Thanks (0) Thanks(0)   Quote theoneandonly Quote  Post ReplyReply Direct Link To This Post Posted: 18 Sep 2017 at 22:45
empty the tank , there will be water , check plug caps for resistance , unplug lambda sensor add contact cleaner , make/break 5 times , make/break tps connector .

take for a good (15 miles ) thrash 

then plug it into someones diagnostics , see if lambda is working .
https://www.facebook.com/BaldricksWorkshop
http://baldricksworkshop.co.uk/

motorcycle slut, if it has wheels and an engine , i will ride it .
Back to Top
Andrew_C View Drop Down
Senior Member
Senior Member
Avatar

Joined: 14 May 2014
Location: Hampshire
Status: Offline
Points: 298
Post Options Post Options   Thanks (0) Thanks(0)   Quote Andrew_C Quote  Post ReplyReply Direct Link To This Post Posted: 24 Sep 2017 at 13:44
Originally posted by Brian UK Brian UK wrote:

Firstly put some injector cleaner in the tank
Well, without wishing to count chickens,  or tempt fate, that seems better. Weather permitting,  I'll ride to work this week, and see if it really is sorted.

Thanks Brian!
Back to Top
Brian UK View Drop Down
Moderator Group
Moderator Group
Avatar

Joined: 13 May 2014
Location: Surrey
Status: Offline
Points: 17641
Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 26 Sep 2017 at 09:31
Guess how I knew that.
Brian.

Better 5 minutes late in this world than years early in the next.
Back to Top
Andrew_C View Drop Down
Senior Member
Senior Member
Avatar

Joined: 14 May 2014
Location: Hampshire
Status: Offline
Points: 298
Post Options Post Options   Thanks (0) Thanks(0)   Quote Andrew_C Quote  Post ReplyReply Direct Link To This Post Posted: 26 Sep 2017 at 20:43
Hmmm... having ridden to work today, I'm not so sure it is fixed. I'll give it a bit longer, but it does seem to be low speed, when cold that is a problem. Just went out on country main roads on Sunday; in traffic this afternoon.
Back to Top
rapheal View Drop Down
Senior Member
Senior Member


Joined: 13 Nov 2014
Location: west country
Status: Offline
Points: 573
Post Options Post Options   Thanks (0) Thanks(0)   Quote rapheal Quote  Post ReplyReply Direct Link To This Post Posted: 08 Oct 2017 at 20:16
Mine used to do that, I think its something to do with the way the bike is set up for the emissions, it turns the fuel off, I fitted one of those magic gadgets from the dark lord, result a much smoother motorcycle, and better pick up from low revs
also worth checking are the plug caps, and the threaded adaptors on the plugs, these coem loose with the vibration for some reason, I nipped mine up and crimped them a bit
Back to Top
Andrew_C View Drop Down
Senior Member
Senior Member
Avatar

Joined: 14 May 2014
Location: Hampshire
Status: Offline
Points: 298
Post Options Post Options   Thanks (0) Thanks(0)   Quote Andrew_C Quote  Post ReplyReply Direct Link To This Post Posted: 09 Oct 2017 at 14:02
Nope.  This is above and beyond the normal V twin "lumpy at low speed" feeling.  That I've fixed with  a Finbau thingy.

Don't think it's the caps on the plugs either; I've had them out to look at the colour.
Back to Top
Mike H View Drop Down
Senior Member
Senior Member
Avatar

Joined: 21 May 2014
Location: East Anglia
Status: Offline
Points: 8733
Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 09 Oct 2017 at 16:13
Have you done this:

Originally posted by theoneandonly theoneandonly wrote:

empty the tank , there will be water , check plug caps for resistance , unplug lambda sensor add contact cleaner , make/break 5 times , make/break tps connector .

take for a good (15 miles ) thrash 

then plug it into someones diagnostics , see if lambda is working .



"Chicken nuggets don't dance on a Tuesday."
Back to Top
Andrew_C View Drop Down
Senior Member
Senior Member
Avatar

Joined: 14 May 2014
Location: Hampshire
Status: Offline
Points: 298
Post Options Post Options   Thanks (0) Thanks(0)   Quote Andrew_C Quote  Post ReplyReply Direct Link To This Post Posted: 09 Oct 2017 at 16:25
Originally posted by Mike H Mike H wrote:

Have you done this:
I'd missed the post.  Comes from sometimes reading on the phone... 

Some of it, yes.  Lambda stuff fiddled with adding FF gizmo.  I'll look for water and knackered plug leads, TPS etc.

I've got the GuzziDiag tool.
Back to Top
 Post Reply Post Reply
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 12.03
Copyright ©2001-2019 Web Wiz Ltd.

This page was generated in 0.078 seconds.