Tnt cafe racer - sprag clutch???
Benelli Motorcycle Forum - Benelli Bike Discussions - Powered by vBulletin
Page 1 of 2 12 LastLast
Results 1 to 10 of 12

Thread: Tnt cafe racer - sprag clutch???

  1. #1
    fde
    fde is offline
    Junior Member
    Member #
    20723
    Join Date
    Aug 2020
    Posts
    4

    Tnt cafe racer - sprag clutch???

    Hi All;

    I recently bought a Benelli TNT 1130 cafe racer which had been standing still for more than 2 years. Bit of a basket case - although the owner did say that it was running when he put it away.


    I've cleaned all the contacts and installed a new battery. When starting the bike the engine turns over very slowly....


    Please see this link: https://onedrive.live.com/?id=EAF275...F275C2B7921083 to video I made when trying starting the bike.


    After googling I've come to the conlusion that it (might) be the dreaded sprag clutch?


    I am right in assuming this?


    Are there any Benelli guru's out there that can point me in the right direction?

    Kind Regards
    Frank

  2. #2
    Senior Member Rick67's Avatar
    Name
    Rick
    Member #
    16761
    Join Date
    Sep 2017
    Location
    Brynamman ,Wales
    Posts
    907
    Hi ..
    Just watched your video.
    I'm pretty sure that is not a spray clutch issue.
    You'd head a dreadful mechanical noise .
    To me it could very well be a fueling issue, you can hear the bike almost wanting to start .
    Yes it does seem a bit slow turning over that could be anything from the battery being too low an ampage , battery cables need upgrading or the starter motor needs a service or replacing.
    It could be something else but I'd look at the battery /starting circuit first.
    Well done on rescuing another Benelli !!

  3. #3
    Senior Member Engenia's Avatar
    Name
    Errol Kowald
    Member #
    27
    Join Date
    Dec 2006
    Location
    Canberra, ACT, Australia
    Posts
    5,751
    Your sprag clutch is fine as far as I can hear.
    It IS trying to start.
    Check the battery voltage at the solenoid while you are cranking it. I wouldn't mind betting it is less than 10V.
    Double up the positive battery cables to the solenoid.
    Shorten the cable from the solenoid to the starter. On my Tornado it was twice as long as it needed to be.
    Add a second negative battery cable to the back of the engine. The crankcase breather box is a good point.
    Get your battery tested (even if it is new). 400 Amps is ideal. 250 will struggle. Lithium batteries are best.
    There is a gear set from the starter to the sprag clutch. It was replaced with a lower gearing to make it easier to crank in later 1130's. It's a pain to check but if all else fails .....
    hooroo, Errol www.engenia.com.au [139,200 km - and counting .....]

  4. Remove Advertisements
    BenelliForum.com
    Advertisements
     

  5. #4
    fde
    fde is offline
    Junior Member
    Member #
    20723
    Join Date
    Aug 2020
    Posts
    4
    Well;

    checked all the wiring again;

    cleaned and sanded the earth; checked the starterrelay/solenoid (its working)... hmmm

    run 12v DIRECTLY on the startermotor - it still cranking at the same speed!!!! (see video)

    So it looks like its the startermotor??? Am I correct in assuming this?

    Strange - never had this before - mayby oxidation built up inside the startermotor?

  6. #5
    Senior Member Engenia's Avatar
    Name
    Errol Kowald
    Member #
    27
    Join Date
    Dec 2006
    Location
    Canberra, ACT, Australia
    Posts
    5,751
    So what is the voltage at the starter side of the solenoid when you are cranking?
    hooroo, Errol www.engenia.com.au [139,200 km - and counting .....]

  7. #6
    fde
    fde is offline
    Junior Member
    Member #
    20723
    Join Date
    Aug 2020
    Posts
    4
    Quote Originally Posted by Engenia View Post
    So what is the voltage at the starter side of the solenoid when you are cranking?
    Im not realy sure if I measured this correctly - can you perhaps explain how to do this properly...

    for instance; which side(canble) of the relay should I measure?

    Kind Regards

  8. #7
    Senior Member tractorman's Avatar
    Member #
    12818
    Join Date
    Mar 2012
    Location
    Woodstock, Tasmania, Aust.
    Posts
    157
    Hi Frank and welcome to the site. I had a friend with a TNT that sounded very similar whilst cranking. I doubled up the leads, swapped starters, checked relay, all the things you have done. I even retarded the ignition timing a bit more at cranking speed, as it appeared to be kicking back a bit. Eventually, all of a sudden, the sprag clutch let go completely and engine wouldn't turn at all. It was like the starter motor was turning fast enough but the sprag clutch partially slips making it appear that the engine isn't turning fast enough. Its not such a huge job to fit a new one, as long as a few precaution are taken. Nigel.

  9. #8
    Senior Member Engenia's Avatar
    Name
    Errol Kowald
    Member #
    27
    Join Date
    Dec 2006
    Location
    Canberra, ACT, Australia
    Posts
    5,751
    Quote Originally Posted by fde View Post
    .. which side(canble) of the relay should I measure?
    Measure as close as you can get to the contact on the starter motor. that way you see the drop due to the battery internal resistance, the cables and the solenoid switch.
    If you only see, say, 9V at the starter, work your way back, taking measurements at each junction. If you see a major increase, the problem is just downstream.

    I'm still putting my money on the battery, but it could be anything, including the sprag clutch as Nigel points out. I haven't seen a sprag clutch act like that. Generally they grip or they slip, not half way between, but hey, this is Benelli. Anything is possible.
    hooroo, Errol www.engenia.com.au [139,200 km - and counting .....]

  10. #9
    fde
    fde is offline
    Junior Member
    Member #
    20723
    Join Date
    Aug 2020
    Posts
    4
    Quote Originally Posted by Engenia View Post
    Measure as close as you can get to the contact on the starter motor. that way you see the drop due to the battery internal resistance, the cables and the solenoid switch.
    If you only see, say, 9V at the starter, work your way back, taking measurements at each junction. If you see a major increase, the problem is just downstream.

    I'm still putting my money on the battery, but it could be anything, including the sprag clutch as Nigel points out. I haven't seen a sprag clutch act like that. Generally they grip or they slip, not half way between, but hey, this is Benelli. Anything is possible.
    I've tried 3 different batteries - the original one, a new one (yuasa) and a lithium one - so I can safely rule out the battery.

    I will measure the voltage drops all the components again - just to make sure.

    BTW does anybody have experience in replacing the sprag clutch?

  11. #10
    Senior Member
    Name
    Cam Douglas
    Member #
    18563
    Join Date
    Jul 2018
    Location
    Tasmania
    Posts
    338
    Quote Originally Posted by fde View Post
    BTW does anybody have experience in replacing the sprag clutch?
    I don't, but I very much doubt it's a sprag clutch issue anyway. A sprag clutch failure doesn't result in slow cranking. More likely a sick starter motor or voltage drop somewhere between battery and starter motor.

Page 1 of 2 12 LastLast

Sponsors

Posting Permissions

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