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maspito |
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maspito Derestricted Danger
Joined: 22 May 2017 Karma :
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Posted: 09:28 - 23 May 2017 Post subject: Stumped! Calling all you trouble-shooters! GN250 won't start |
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Hi experts!
I come to you as I am utterly stumped and not sure which way to move with troubleshooting of my sick Suzuki GN250.
I was riding her the other day, pulled out of a junction and as I changed up gear, something went clunk and the bike died. After pushing her for 2 miles home, I started trying to figure out what has gone wrong...
1) Changed gear and think I heard a sort of clunk noise then died. Refused to restart.
2) Start switch doesn't activate the starter motor. When pressed, a single click can be heard from the starter relay, but then all power seems to fade - green "neutral" light goes out and no further click on subsequent attempts. After a while, power seems to return.
3) Battery checked and is good.
4) Main fuse checked and is good.
5) Jumping the starter motor, directly from the battery, spins the starter motor and turns engine, but nothing more. Engine doesn't fire up.
6) Engine can be turned manually using a ratchet and socket on the crank, so doesn't appear seized.
Any advice on what I should check next would be greatly received! |
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jaffa90 |
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jaffa90 World Chat Champion
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maspito |
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maspito Derestricted Danger
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maspito |
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maspito Derestricted Danger
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Teflon-Mike |
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Teflon-Mike tl;dr
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Posted: 10:47 - 23 May 2017 Post subject: Re: Stumped! Calling all you trouble-shooters! GN250 won't s |
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Not tackling these i order:-
maspito wrote: | 5) Jumping the starter motor, directly from the battery, spins the starter motor and turns engine, but nothing more. Engine doesn't fire up. |
I would imagine that the GN250 has a self exited ignition, like most smaller/older bikes, so sparks come straight from the magneto, when crank spun up.
How did you 'jump' the starter? Was the ignition switch 'on'? Did starter spin engine fast enough to make sparks? Have you checked at the spark-plug?
maspito wrote: | 2) Start switch doesn't activate the starter motor. When pressed, a single click can be heard from the starter relay, but then all power seems to fade - green "neutral" light goes out and no further click on subsequent attempts. After a while, power seems to return. |
Classic syptoms of a Dodo-Battery.. might give 12v on the terminals, but without the amps in the acid, not eough beef to do more than latch the solenoid.
Dimming of the neutral lamp, also says that the terminal voltage is dropping big, when starter circuit made.
Putting two-and two together here, It's a common conundrum; a 'tired' starter motor, sucks more amps than it should; carbon brushes on the armature wear, and the carbon dust starts bridging contacts between wingdings; so the starter starts to such more amps from having more winding's effectively connected to the battery at any one moment, and those errant winding as well as taking power from the ones that should be shoving motor around, are fighting against the ones that are, slowing it down. Meanwhile the extra load the starter puts on the circuit, sees the solenoid start to 'arc' and pit as it makes contact; that increases it's resistance, so chokes power to the starter. Meanwhile, to get engine 'started' with a lazy starter motor, that wont spin t up so fast, and sucks more amps to do it, strains the battery, as it will have to provide more amps than it should, and usually for a lot longer before the engine 'catches'. This kills the battery.. So, eventually owners replace that, as 'obviouse' fault.. and problem seems 'solved'... only it isn't! Battery ow is good, but still struggling to deliver the amps demanded by tired starter, the new battery decays quickly, until problem recurs... ad owners, peeved, blame the battery as 'shit' and buy a new one... a-gain.. ad the cycle repeats until the starter gives out completely, or the solenoid is toast.
THAT is far too common.and likely 'part' of the problem you have. GN250 has a kicker, too, though doesn't it? Might be worth circumventing e-start using that. If not certainly for fault finding, using a car-battery on jump-leads, rather than rather diddy and possibly knackered little bike battery.
Meanwhile; be worth checking the solenoid, and making sure it is making the circuit when actuated; probably stripping and cleaning it; and having a poke in the starter motor, checking state of brush wear, probably replacing them, cleaning carbon off the comutator, cleaning up the contacts on that, greasing gear-pack and bushes etc.
BUT....
maspito wrote: | 1) Changed gear and think I heard a sort of clunk noise then died. Refused to restart. |
It went 'Clunk' and died.... split out the refusal to re-start, and certainly potential e-start issues. This is not relevent to why it conked out.
maspito wrote: | 6) Engine can be turned manually using a ratchet and socket on the crank, so doesn't appear seized. |
Good call; but doesn't actually tell you the engine's didn't seize, just it's not locked solid. Is a good confidence check; but don't read more into it than you truly know. Means engine still turns; nothing more; engine could have nipped up, and or lost a ring, or dropped a valve; possible maladies are many, and you wont 'know' until you start digging nto it.
Pull the spark plug.... this should always be first course action'; what was the engine doing immediately before t conked? Compare to chart.
Whilst plug is out, turn crank over carefully on a spanner, or kicker, through a good two or three rotations, does it pump wind out the hole? Do a rule of thumb compression tests, and see if its making any compression.
"Clunk" is intriguing; could hint at the cam-chain going and or a valve being smacked by the piston, or a big or little end bearing going, or even the gearbox just falling out of gear! Instant removal of load, could have made some other weak-link to go, or wicky-worky.... It doesn't really help poit to anything, so you just have to work logically, down the list fro the top....
Engine dont-run... so, spark, compression, fuel... ingredients for life. Which one missing... then dig down.
Valves would be my next port of call; ISTR GN has rockers with screw and lock-nut tappets; I also seem to recall, that it has four-valve head with two-lube OHCam; valves opened by forked rockers... But, I'd pull the rocker cover; check tapets, look for something daft ad obvious like a broken rocker or a lost tappet or tappet lock-nut! Or even a valve not moving!
Before, during or after that, I would probably do a proper compression test, WOT on e-start off a car battery. Could be a HGF... other than a gear jumping out take off load, couldn't count for the clunk and sudden stop; but?
I wouldn't be in too much of a hurry to try and get the engine to re-start, I WOULD be keen to find out why it stopped so suddenly first!
Common on the old two strokes was the engine would nip-up; seize under load, but almost instantly after seizing, be 'usiezed', still gear, back wheel driving engine, momentum wouldmack the piston 'free', engine would 'catch' on the 'bump' and folk wold ride home, ride around an complain that 'something' was wrong... usually piston rings smeared into the piston grooves! "Its making a terrible noise!"
In similar manner, you could have smacked a valve, or lost a main, big or little end, that momentum freed off before you coasted to a halt....
But engine stopping running suddenly o the road, isn't going to be a fault in the e-start system! Its something n the engine... so that's where I'd be looking. Could be something stupid and non-terminal... but liklihood s it isn't and to find not what, the head, and cylinder is likely going to have to come off at some point, to inspect valves, cam-chain, cam, rockers, etc. inspect piston, piston rigs and cylinder walls, waggle con-rod and look for any play in the crank.
But, work logcally; start at the plug; look under the rocker cover, work down; don't be in such a rush to make t run again, find out why it stopped ruining first! And the starter-system, as semi-stand-alone system, is a separate 'problem', problem isn't 'It wont start' problem is 'it stopped running'.. so find out why! ____________________ My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
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Teflon-Mike |
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Teflon-Mike tl;dr
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chris-red |
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chris-red Have you considered a TDM?
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Chris45 Nitrous Nuisance
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maspito Derestricted Danger
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Chris45 Nitrous Nuisance
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maspito Derestricted Danger
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Teflon-Mike |
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Teflon-Mike tl;dr
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Posted: 15:14 - 23 May 2017 Post subject: |
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Does the GN have a battery topped, live-rail ignition though? If so; then genny should be putting all its output through the reg/rect onto the live rail, that will supply the ignition circuit, and once engine running, supplying sparks to keep engine running.
A flat battery should only take excess amps not being drawn by the ignition or equipment to 'charge', so once running engine should stay running on the amps banged out by the genny as long as its spinning... give or take...
Instances it wont, are likely if the motor was running at lower revs where the genny wasn't banging out too many amps, and other equipment like lamps were competing for them. In that situation head-lamp would tend to dim, long before sparks dropped out, and the ignition would more often start to intermittently 'drop out' rather than just 'die' suddenly, unless you co-incidentally turned on some other high-draw equipment, like pressing the brake pedal, turning on stop-lamp.
Battery, could rob amps, and sufficient to make the motor conk, if faulty, and plates warped and potentially shorting, and actually drawing current, but like a head-lamp, wouldn't expect it to suddenly make engine die; if that bad, I wouldn't expect it to start the engine to begin with; after that, I'd expect sparks to drop out intermittently, as it robbed amps from ignition, and make motor conk, most likely when revs drop.
Given how a tired solenoid and starter CAN kill a battery like that, I wouldn't dismiss the suggestion they may be to blame.... But, fact that bike don't start, isn't the same problem as why it stopped running.. that's what needs to be bottomed out.
Starter-motor, and solenoid help start bike, they don't stop it running, so cant 'directly' be the answer to that one. Battery 'may'... among host of possible electrical faults from a bullet connector shaking loose, to a wire fretting and shorting to the frame, through CDi giving up the ghost, or the reg-rect going toast-wise, or loosing a winding the genny. All of which may need to be bottomed out.... after primary course, 'just' checking for sparks, at the plug, on the kicker or a know good, preferably well over-rated car battery, after popping the rocker cover and checking for obvious, like snapped cam-chain, wide tappets or a lost lock-nut! (and performing basic service adjustments, just to eliminate dumb questions later!) And doing basic compression test, even if only rule-of thumb over the hole!
Nothing is really 'off the menu', but starter systems start engines.. they don't stop them! So not really at the top of the list for proddings and pokings, yet. But that's what needed here, I think; logical prodding and poking, looking at stuff that can stop engine running, once started, not what isn't starting it, and working down the list, methodically, no straw clutching.
'Trouble' with electrics is that they are too easy to tackle, to avoid looking at oily-bits, and then have you chasing your own shadow, rather than actually getting anywhere helpful... like repeatedly replacing battery, when root cause is a knackered starter motor! ____________________ My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
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bypass2 Spanner Monkey
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maspito Derestricted Danger
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maspito Derestricted Danger
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Posted: 14:55 - 26 May 2017 Post subject: |
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UPDATE:
Today I remove and dismantled the Start Motor. She looked clean as a whistle inside. Wiring and connectors were undamaged. I saw evidence that the brushes are making good contact. There were hardly any carbon dust (so I suspect the previous owner had replaced this part not too long ago). Most importantly, there was absolutely NO sign or arcing or other electrical failure.
Therefore, I will rule out the Starter Motor as being faulty.
Once reinstalled, I tried to jump the Starter again. This time, the ignition was turned on, the Spark Plug removed and grounded to the Engine... but sadly there was NO spark
The battery had no issue to keep turning the engine over and over like this, so I am also ruling a bad battery our of the equation.
I've ordered a new Spark Plug to cut that from the equation (I know, probably should have been my very first action!)
The good news was that while she was turning over with the Spark Plug removed, I was able to feel air pumping out of the Spark Plug hole, so there is compression (exactly how much will obviously need further investigation)
I've also checked the entire Wiring Loom and find no signs of failure.
So once I receive the new Spark Plug, I will resume testing! Any further comments would be greatly appreciated! |
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maspito Derestricted Danger
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Posted: 12:18 - 05 Jun 2017 Post subject: |
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UPDATE: NO LONGER STUMPED!!!
So, after checking every single electrical component for correct resistance / continuity, I was non the wiser. All the electrical components checked out work (FYI 24 kOhms was a good measurement).
At this point, I'm really starting to hate this machine!
So I start playing around aimlessly, and notice that the sound of the engine turning over had changed - I could now hear the starter spinning freely but the crank and engine was no longer trying to turn over. So I remove the LH engine case and see that the Rotor Generator wasn't spinning with the Start Motor. I guess something is up with the starter clutch not engaging, so I pull the Rotor Gen off to find a rather classic problem: a sheared Rotor Gen Clutch bolt. I've attached pics below.
Now we have explanations for all the effects I experienced:
1) The clunk noise: This was the noise of the bolt shearing.
2) Immediate loss of power: Sheared bolt head jamming the Rotor Generator and Starter Driven Gear, slowing down the Rotor Generator (maybe even driving the Starter Motor), reducing electrical generation / power.
3) Not activating the starter motor and draining power: Sheared bolt head jamming the Starter Driven Gear, causing the Starter Motor to be unable to turn, yet sapping battery power.
4) I think the Sheared bolt head eventually worked loose when I was manually turning the engine on the Crank, which allowed subsequent efforts on the Starter Motor to turn the engine, but as the Starter Clutch was not engaging, no power was being generated to kick the engine into life.
So this (I think) explains EVERYTHING!
There were no signs of Locktite on these bolts, which I believe they should have. Luckily, I have a complete spare engine! So I'll rob the parts to replace all the damaged ones and will put her back together later this week. |
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pepperami Super Spammer
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Posted: 12:58 - 05 Jun 2017 Post subject: |
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This thread does not end until you come back and tell us that it's running again.
Pictures/video or we come round your house late at night wearing hockey masks ____________________ I am the sum total of my own existence, what went before makes me who I am now! |
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maspito Derestricted Danger
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Posted: 14:42 - 18 Jun 2017 Post subject: UNHAPPY FACE :( |
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Hey guys... Still having issues!!!
I rebuilt the flywheel generator, installed a new woodruff/flywheel key, put everything back together, started her up and...
STILL!! The starter motor just spins. The flywheel generator stays stationary and doesn't seem to pick up on the starter gear.
Now, to be clear, I rebuilt the Sprag/Start Clutch correctly, torqued the 3 bolts that attach it to the Magneto, lined the Magneto/Starter Clutch Assembly up on the Woodruff key and torqued the main nut holding it all in place.
The Starter Motor and Idle Gear are spinning clockwise, which I believe is correct.
So all I can think of is that the springs/rollers of the Sprag/Starter Clutch aren't doing what they should be doing. Any thoughts? |
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Old Thread Alert!
The last post was made 6 years, 313 days ago. Instead of replying here, would creating a new thread be more useful? |
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