Page 1 of 2 12 LastLast
Results 1 to 15 of 19

Thread: Guzzi Lemans Plug Fouling

  1. #1
    Join Date
    20th January 2008 - 17:29
    Bike
    1972 Norton Commando
    Location
    Auckland NZ's Epicentre
    Posts
    3,554

    Guzzi Lemans Plug Fouling

    My Guzzi Lemans 2 has been WIP for a year.
    LH plug fouls after about 30 KMS.
    I've checked the ignition, valve clearances, stripped and cleans the carbs ( multiple times)
    Tonight I printed off the specs and stripped and wrote down all the jets and needle numbers, all as per spec.
    Then I thought i'd swap the carbs over and see if the problem was the engine or the carb.
    Ran ok for about 20 kms then started to bog down.
    The problem had moved to the other side so its the carb.
    I've played with Dellortos on my BMW and this is first time I've stuck this.
    Wise words welcome
    DeMyer's Laws - an argument that consists primarily of rambling quotes isn't worth bothering with.

  2. #2
    Join Date
    14th July 2006 - 21:39
    Bike
    2015, Ducati Streetfighter
    Location
    Christchurch
    Posts
    9,082
    Blog Entries
    8
    Stock air filters or pods? If the later is one a dirty bitch and the other a clean nun?

  3. #3
    Join Date
    20th January 2008 - 17:29
    Bike
    1972 Norton Commando
    Location
    Auckland NZ's Epicentre
    Posts
    3,554
    Quote Originally Posted by AllanB View Post
    Stock air filters or pods? If the later is one a dirty bitch and the other a clean nun?
    It came with cone shaped K and N pods. I have just cleaned and oiled them.
    DeMyer's Laws - an argument that consists primarily of rambling quotes isn't worth bothering with.

  4. #4
    Join Date
    24th November 2005 - 12:40
    Bike
    anything I can get my grubby wee paws on
    Location
    Outside
    Posts
    1,497
    Worn needle and/or seat
    =mjc=
    .

  5. #5
    Join Date
    13th June 2010 - 17:47
    Bike
    Exercycle
    Location
    Out in the cold
    Posts
    5,624
    Standard PHF36's ?

    Possibilities are:
    blocked air correction jets/passages
    Worn needle/needle jet combo
    Crack in the carb body - below fuel level on the central tower carrying the jets.
    If the problem only shows up hot, this could be it...
    Do the floats carry the same numbers ?
    Float needle jet fitted correctly into the body ? Any crack around that ?

  6. #6
    Join Date
    20th January 2008 - 17:29
    Bike
    1972 Norton Commando
    Location
    Auckland NZ's Epicentre
    Posts
    3,554
    Quote Originally Posted by Grumph View Post
    Standard PHF36's ?

    Possibilities are:
    blocked air correction jets/passages
    Worn needle/needle jet combo
    Crack in the carb body - below fuel level on the central tower carrying the jets.
    If the problem only shows up hot, this could be it...
    Do the floats carry the same numbers ?
    Float needle jet fitted correctly into the body ? Any crack around that ?
    List for tonights investigation.
    floats are both the same, 10 grams
    next on list is checking for worn parts and cracks.
    This is why we love old bikes...isn't it....keeps the brain active....
    DeMyer's Laws - an argument that consists primarily of rambling quotes isn't worth bothering with.

  7. #7
    Join Date
    4th November 2003 - 13:00
    Bike
    BSA A10
    Location
    Rangiora
    Posts
    12,711
    Check the accelerator pumps as well
    "If you can make black marks on a straight from the time you turn out of a corner until the braking point of the next turn, then you have enough power."


    Quote Originally Posted by scracha View Post
    Even BP would shy away from cleaning up a sidecar oil spill.
    Quote Originally Posted by Warren Zevon
    Send Lawyers, guns and money, the shit has hit the fan

  8. #8
    Join Date
    13th June 2010 - 17:47
    Bike
    Exercycle
    Location
    Out in the cold
    Posts
    5,624
    Quote Originally Posted by Kickaha View Post
    Check the accelerator pumps as well
    Thought about that - Dellorto take the fuel up and over the top to the nozzles in the bore. I don't see how there can be a bleed of fuel through the system while running. I'd check the pump ramps in the slides in case one side is a very long ramp...
    Mikunis, Yes, with their system there can be a fuel bleed if something sticks. Bloody Dellorto pumps are hard enough to get to work in the first place...

  9. #9
    Join Date
    24th June 2004 - 17:27
    Bike
    So old you won't care
    Location
    Kapiti
    Posts
    7,879
    Also check the choke mechanism - they are VERY prone to sticking....

  10. #10
    Join Date
    20th January 2008 - 17:29
    Bike
    1972 Norton Commando
    Location
    Auckland NZ's Epicentre
    Posts
    3,554
    So got home and stripped the LH carb again.....
    Checked out the main suspects, needle, needle jet and idle jet.
    Found in my BMW racer bits box another PHF 36 and it looked less munted.
    As they are not the same mounting took out the bits needed and compared them.
    Visually no real difference.
    Found a drill bit that was a sliding fit into the needle jet and it was a bit sloppier on the old one.
    What the hell I thought fit them and go for a ride.
    I did the same 30 kms as last night, bit of mean streets of Onehunga and Mangere plus a few strops up and down the motorway.
    Initial impression was smoother, no popping from exhaust, seemed to pull better and happier to run a higher gear at lower revs.
    Pulled out plug on the actual spot I did it last night and not sooty.
    Rode back thru urban area and it would feather along at 60 KMPH/2000 rpm without issue in 5th ( try that on your Ducati )

    Conclusion: when you buy an old bike fit new jets.
    Gong to order all new ones.
    Thanks for all your advice and tips, always appreciated

    Photo from a while back.
    Its a lardy thing compared to the R90s but its got lots of ommph and old blokes come up and talk to you...
    Click image for larger version. 

Name:	IMG_02391_zps4kbuxijy.jpg 
Views:	39 
Size:	171.2 KB 
ID:	328011
    DeMyer's Laws - an argument that consists primarily of rambling quotes isn't worth bothering with.

  11. #11
    Join Date
    13th June 2010 - 17:47
    Bike
    Exercycle
    Location
    Out in the cold
    Posts
    5,624
    Guy who lives around the corner from me has a Laverda 3C. Carbs needed a refresh.
    He got someone else to supply and fit the new brass and slides - not cheap..
    He came round to me with them in his hand asking why they wouldn't synchronise - and what the hole in one new slide was.
    They wouldn't sync because it had the short cables in the gantry of 2 different lengths...
    The hole in the slide was at the bottom of the ramp and is supposed to have a plug in it with a spring to stop the needle fluttering.

    He found cables of the same length and fitted them. I made up a brass plug for the slide and pressed it in. Never heard of that missing in a new slide...

    The guy who did the job apparently lives in Rolleston and i'm told is a truck mechanic. He knows how to charge....

  12. #12
    Join Date
    13th September 2012 - 20:50
    Bike
    2014 BMW G650GS
    Location
    Auckland
    Posts
    178
    A good result John.

    Do you think that new jets would sort the Vespa front end?

  13. #13
    Join Date
    14th July 2006 - 21:39
    Bike
    2015, Ducati Streetfighter
    Location
    Christchurch
    Posts
    9,082
    Blog Entries
    8
    Quote Originally Posted by Voltaire View Post
    Rode back thru urban area and it would feather along at 60 KMPH/2000 rpm without issue in 5th ( try that on your Ducati )

    Not a chance in hell - it would buck me off - I've recently gone from a 15 to 14 tooth front sprocket - it would still pack a paddy. At last I can run all 6 gears at sub walk home speed on the open road (but still get a ticket speed...).


    Carbs. I have one somewhere in the garage. Oh my Lawnmower still has one.

  14. #14
    Join Date
    28th January 2015 - 16:17
    Bike
    2000 Ducati ST2
    Location
    Lower Hutt
    Posts
    1,274
    Quote Originally Posted by Voltaire View Post
    Rode back thru urban area and it would feather along at 60 KMPH/2000 rpm without issue in 5th ( try that on your Ducati )
    Click image for larger version. 

Name:	IMG_02391_zps4kbuxijy.jpg 
Views:	39 
Size:	171.2 KB 
ID:	328011
    Since fitting the Keihin FCR41's I can tootle around at 2,500 - 3000 RPMs quite happily. Simply wouldn't have happened with the stock Mikuni's. Not sure about 5th gear at 60 though... massive driveline backlash, high gearing and all...

    Nice looking Guzzi btw, love the classic styles.

  15. #15
    Join Date
    28th January 2015 - 16:17
    Bike
    2000 Ducati ST2
    Location
    Lower Hutt
    Posts
    1,274
    Quote Originally Posted by AllanB View Post
    Carbs. I have one somewhere in the garage. Oh my Lawnmower still has one.
    Carbs. Had new slow jets arrive today, looking forward to doing some more tuning. Sometimes crude and stinky is good

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •