DS650 won't start

[Cavemanhands]

I hate to be that guy that signs up only to ask for help, but I am at my wits end. I am working on a 2000 DS650 that quit running after the rider dumped the clutch repeatedly.

I had to fix a few things to get where I am now, cranks but doesn't start.

New starter clutch
New CDI
New coils
New trigger coil set at .003
New spark plugs set at .026
New rectifier

Verified TDC, used locking bolt and pulled cam cover to verify valve timing which seems good. While I had it locked at TDC, I did a compression leakdown test which showed a loss of only 4@100psi
Compression test shows about 112#
Carb had clean gas, but pulled jet and blew through passages, all clear and clean
All this thing does is spin. Nice, bluish/white spark at the plugs, added fuel through spark plug hole and used ether, both failed, not even a hiccup or fart, just keeps spinning.

Someone please give me some ideas here before I pull out my gray hair?!

 

[davefrombc]

The  only  thing  I could think  of  is it somehow  firing on  TDC  exhaust rather  than  TDC  on compression ?  You seem to  have  eliminated  everything else .

[Cavemanhands]

thanks for the reply, I am pretty certain it is TDC on compression/power stoke, all cam lobes are horizontal and opposing each other with all valves closed. Also, My leak down test would have dumped out the exhaust.

I should add that I am a bit perplexed that the trigger coil pad is no where near the trigger coil while locked in place..

[davefrombc]

OK...

4 hours ago, Cavemanhands said:

 

I should add that I am a bit perplexed that the trigger coil pad is no where near the trigger coil while locked in place..

That is not good .. Check to  see  if  possibly the   key on the  rotor has sheared  and allowed it  to  turn  on the  crankshaft.  That would explain why  the magnet is nowhere  near  the  trigger  coil  at   TDC compression.

"Dumping  the  clutch" several  times could  have   caused  the  motor  to abruptly   drop  in  RPM  putting  a  lot  of  inertial  torque   on the  rotor  subsequently  shearing  the  key ..

Edited July 28, 2017 by davefrombc

[Cavemanhands]

I think I figured out where I went wrong. When I replaced the starter clutch and gear, I clocked the mag in the wrong location. Can anyone show me or tell me where the pad should be with the lock bolt installed at TDC? The manual said about 10 degrees at most or something, but should the pad be forward or behind the trigger pad?

I just took it apart again. the key is fine.

Thanks for the reply!

[davefrombc]

Since it works as a magneto, I would say  after. Ignition systems usually  fire   a  few  degrees  before  TDC to  give  maximum power. The higher  the  rpm,  the   earlier  the  spark . . Low  rpm   motors  sometimes use  a retarded spark   for bottom  end  power .  The  magnet  of the trigger pad  should  pass the  pickup  before the  piston reaches  TDC to  produce the  advanced spark.  The    manual  should specify  the timing , and  I would suspect  there should be  a  timing mark on the  gears.

[davefrombc]

I  found a service manual  for the  Bombardier DS650  and downloaded  it to  the "Other ATV"  in the  service manual list.

  I'm  not impressed with it  as  far  as the  ignition system  is concerned..  There is no  timing  mark  for  the  magneto. There  is nothing  stating  where  the  magnet  and  pickup  coil  should be   positioned at  TDC. Just the  gap  is  mentioned.

[Cavemanhands]

there is no adjustment on the timing other than the trigger gap. The mag can only be clocked one way, evidently. I clocked it so it appeared as this pic on Ron Wood's site. It now fires up and runs, although it has a significant "cough" every now and then that will kill the engine. Not really sure what's up with that yet.

I am just glad it will start and rev.

[Cavemanhands]

well, it is back together and ready for whatever they wish to do with it. I am very grateful for the help from this forum!
The cough was due to the springs falling out of one of the coil wires, I believe. I replaced those pieces and it seems to idle and run very well.
 

[Frank Angerano]

Great job. Bike looks crazy! 

Hopefully it's all fixed up and no more clutch dumping !!!!!!!!

 

[davefrombc]

Great  to  learn  you got it  running ok..    I see   with that  picture  it  is the rotor  itself that  is  keyed to the  shaft  and the gear  behind  bolts to  it,  so now  I  know why  there  was  no  mention  of  how it was timed.

[Shane Stump]

Ok guys needs some help asap ready to set this thing on fire..thing would never start valves were tight i adjusted the calves to correct shims on intake n exhaust have plenty of clearance in between cam lobes n shims..problem is i done set tdc about 10 times now its dead on..will not fire one hiccup sprayed gas into carb while cranking n while not all it does is make a loud backfire n some flames come out. Its like valves are tight but there not.idk how it could be firing wrong with it at tdc. I need help asap carn is clean have plenty of spark bright blue.