"Metal in engine" diagnosed as backfire + sprag clutch

[Mobius]

Remember the distressing part of metal I found inside my engine case when I did the starter motor? And my horror at the "nasty metal sound" the bike sometimes makes when cold? Well, I had thought it was yet another piece of metal caught somewhere in the engine, with stiff/cold oil picking it up and chucking it through various parts...

Well, my buddy listened to it at start up at work the other day, and diagnosed it as a backfire (a slight "chuff" sound) instantly accompanied by a nasty metallic banging sound, which he says is the sprag clutch responding to the backfire.

He said it happens to all Pasos when they backfire - and probably with a sprag spring that's getting a bit tired.

So, that is great news, and I can now clearly hear the single backfire sound quite clearly: the sounds come from two different parts of the motor: the backfire from the top/front, and the metal bang coming from the engine case.

Much worse news is that on the Wednesday night Ride two days ago, I covered about 100 kilometres, and just short of home, with no power being applied, a single gear change resulted in zero drive.

Coasting to a stop, I found every single rear sprocket bolt snapped off. This is very concerning, as 15km previously I had stopped, and inspected the drive chain and sprocket and nothing seemed amiss... I'll post photos in another thread soon. *sigh*

[JWilliam]

Will you have to strip down the engine to repair the sprag clutch then? I take it that this happens on cold start and the engine does not fire. My Paso never backfires when cold or at least it hasn't done it this year, it had done so but I did some modification and it no longer does this - can't remember what it was though. It might be that when it is very cold I use Ezi-start ether and this helps greatly to get the motor running first time.

[englishstiv]

Regarding that rear sprocket have you had the rear wheel off recently, as it sounds very much like the cone washer on the axle rod was replaced the wrong way around or was left off completely???????

[paso750]

Regarding that rear sprocket have you had the rear wheel off recently, as it sounds very much like the cone washer on the axle rod was replaced the wrong way around or was left off completely???????

That`s 907ie specific. The P750 & 906 don`t have that.

G.

[higgy]

I too have had the very same bolts back out on my 906 out of the blue. Since then I Loctite® 222MS™ Threadlocker to the proper torque and check them every time I check my tire pressure which is religiously before every start of a single days ride

[paso750]

I did this


G.

[englishstiv]

That`s 907ie specific. The P750 & 906 don`t have that.

Cheers G ...........I didn't realise this fact

[higgy]

I did this

Damn G,lots of work

[paso750]

higgy it`s not and it`s inexpensive, too.
All it needs is a good 2mm drill and a stainless steel wire (I used 0,8mm). As the bolts are slightly lowered in the sprocket one needs to drill the holes close to the top. (drill through the bolt heads from both sides as if you try to drill them at once the thin drill can cant and snap off. I`d recommend to mark where you want to drill the bolts before removing them). I used special pliers for safety wire for twisting but it can be done with normal pliers (or easier, with clamping pliers) as well. There`re different methods of how to route the wire. Going from right to left as you can see on the picture seemed to be the best for me as all bolts secure each other. If you would untighten one, the two connected to it would be tightened.

G.

[higgy]

Yeah G,I have a well worn safety wire plier,still its a lot of work

[jcslocum]

I did this


G.

Show off!!!

[paso750]

it`s not my fault it`s functional and good looking

G.

[higgy]

it`s not my fault it`s functional and good looking

Oh? then whose fault would it be there G ?

[paso750]

it`s in the nature of shiny things

[907pasonut]

it`s not my fault it`s functional and good looking

G.

thats not a bad idea...I agree, its both functional and simple.
I just checked the 907 (after reading Mobius's post) and it has a different system, I can see 6 threaded (bolts or rods) with nuts, the nuts themselves are about 2mm countersunk into the sprocket, I wonder if I can take the threaded rods (if they are rods) out and fit bolts...ie: copy G's idea
both the 907 and 851 have the same setup