[mitchell]

Hi all.
  My bike , 1972 350 bullet, had issues in June, so I had to do my road trip by car. Just got back and trying to address the issue.  The bike  ran, died. I replaced some parts including the decompressor.  It ran beautifully for about 20 minutes. Idling, I heard some "crunch" /mechanical sound and it just died. I left the next morning with the car.

Three months later to now...

   Thought it might be the push rods/tappets, so today I opened the cover and...they are spinning perfectly. So, it ain't them.
   Bike is in neutral but the kicker is "stuck".

  What would be the next plan of action?

 I thought about the kicker spring but I don't think that the spring would create the sound I heard when it died.
Horror  of horrors, could it be a frozen piston, or the gear box?
I am out of my element if so and out of money to get a pro mechanic who knows these bikes.

Any help will be really appreciated
Thank you,
 Mitchell

[cyrusb]

Pull in clutch and operate kicker. If it moves its not the gearbox.
 Next I would remove the primary cover and try to rotate the crank.
  That should do it.

[tooseevee]

Hi all.
 The bike  ran, died. I replaced some parts including the decompressor.  It ran beautifully for about 20 minutes. Idling, I heard some "crunch" /mechanical sound and it just died. I left the next morning with the car.

   Thought it might be the push rods/tappets, so today I opened the cover and...they are spinning perfectly. So, it ain't them.
   Bike is in neutral but the kicker is "stuck".

  What would be the next plan of action?

 I thought about the kicker spring but I don't think that the spring would create the sound I heard when it died.
Horror  of horrors, could it be a frozen piston, or the gear box?
I am out of my element if so and out of money to get a pro mechanic who knows these bikes.

Any help will be really appreciated
Thank you,
 Mitchell

           Oooh Bummer!

            I'd look into the combustion chamber first.

           This is just a SWAG and I'm guessing it ate a valve or part of the decompressor. But it should still turn over? Just guessing remember.
     
           I hear there are tiny borescopes now that plug right into your telephone. Who'd believe it?   Whatta world 

[Bilgemaster]

Pull in clutch and operate kicker. If it moves its not the gearbox.
 Next I would remove the primary cover and try to rotate the crank.
  That should do it.

I don't know about "that should do it", but our man 'Cyrusb' offers the easiest way and place to start looking for the culprit. A broken primary chain or something else jamming up or otherwise awry with the clutch assembly in that primary case might  cause the symptoms you describe. You would do well to hope  it's just something goobed up in there, since it's likely to be the easiest and cheapest of the other more dismal possibilities to fix--only minor surgery hopefully.

But indeed, it COULD be something a bit more dreary and major like a banged up or dropped valve, fragged piston, thrown crank or some other more internal mayhem. And I'm more than a little concerned and leery that you wrote, "I replaced some parts including the decompressor". After all, a dropped decompressor valve or other bits of its assembly fallen in there wouldn't do your bike's guts any favors. So, if pulling the primary cover doesn't reveal some hopefully relatively easy to mend problem, and you want to peer in there, here's a bunch of little cheapo endoscopes or borescopes from Amazon that'll plug into Android phones, arranged by price low to high: https://www.amazon.com/borescope-android-phone/s?k=borescope+for+android+phone&s=price-asc-rank&qid=1634002682&ref=sr_st_price-asc-rank. Wallyworld also sells similar for less than like a case of Bud.

[Willbrunei]

I had kickstarter problems on my 500 bullet. It was the kickstart shaft that had fractureddue to a kickback and jammed pawl. I know yours is a 4 speed but could be a similar issue?

[mitchell]

Thanks. I had replaced the clutch plates, the primary gasket and decompressor back in June. It all looked fine and ran perfectly... for ten minutes. I will pull the primary cover and have a look-see. If it all looks fine,  then the problem will be something really bad?
If the kick spring had broken  am I correct in thinking the kick start would be totally free? ie. no tension at all.
I will get back to you.
Thanks much

[cyrusb]

Can you kick it through with the clutch pulled?
 You're on the right path, removing the primary should tell a lot.
 A basic rule of thumb when trouble shooting and a good place to start is to go back to the last thing you did.