Could a bad starter *only* spin the engine with the plugs removed?

[LowercaseJake]

Well guys I received my eBay replacement sprag which came still installed on the oem flywheel. Decided I'd ditch the light FW while I was in there to see how I'd like it. That was most definitely the issue - the old sprag had several rollers that were scored and compromised, and the spring was toast. Starter now turns the motor over properly. As for my other issues - one of my fuel hoses looked like it was getting pinched due to my circuitous routing job, and the breather was only hand tight. Redid the fuel plumbing, replaced the breather crush gasket and tightened. Only thing I'm a little lost on is getting the orientation of the FW right. There's a dot on the crank that I made sure was in alignment with the dot on the FW. With the thrust washer and clutch gear/cog in place the dot is hidden, so I marked the crank to be sure. I also went back over all my ground and power wires, added another washer to the starter nut to be get it nice and tight and filed off the paint at the engine ground lug. Only thing I'm not 100% comfortable with is did I get the orientation of the FW right. I guess I need to get my hands on a shop manual. Appreciate your assistance.

[Howie]

From what you say you should be good with the flywheel.  You did either use a new flywheel nut or aftermarket replacement* and torqued it down to 189 Nm. I hope.  Loose flywheels are not good.
Though unusual if the sprag is bad enough it can jam the starter.

Keep us posted!






* Like this one that is no longer available  https://motowheels.com/search.html?q=flywheel+nut&go=Go   or this one  https://ccrma.stanford.edu/~peer/Nichols/flywheelNuts.html

[LowercaseJake]

Howie, I have a single phase motor, I don't think those jamb style nuts apply to my setup.

Question: if done correctly, should the lump on the flywheel align above the rear most (to the right, facing the engine) pickup? Theres a dot two teeth down from the keyway that I aligned with a dot next to the dogs of the outer face of the flywheel. I'll see if I can post a link to a photo.

[LowercaseJake]

I'm dumb, it needed to line up with the keyway. No idea what the dimple behind on the small crankshaft gear is for but the bike fired right up and runs great. Can't ride it yet because the seal on my Ducabike slave popped out and I can't find it, smdh. Thanks dudes.

[LowercaseJake]

So, the crank is frozen tight. No idea what I could've done wrong, unless the poor running I described was a prequel to things going awry. I will say that when I replaced the sprag, everything spun over fine, pistons valves and all. I'm wondering If I overdid that...cranking the motor with the cases removed and no oil. I didn't think a couple revolutions would be a big deal but I could've thought wrong.

It's odd to me that the crank won't budge a single mm. Ive removed everything I needed to remove from both sides of the engine (a couple primaries and the oil pump.) to gain visual access to the main bearings. The main crank bearings look perfect, there is zero play in the crank. I theres a necessary keyway slot I'm missing I can def check on that. Just seems odd the motor would abruptly die after 3 seconds, all 3 of which nothing was grinding or slapping. Just simply stopped, and now the crank is frozen.There's not an excessive amount of slag on the oil screen or in the oil. Only thing left to do is remove the heads and barrels to gain access to the rods and pistons, see pif a piston threw a bearing and froze up in the cylinder. If the bottom end is ok, new pistons/rings aren't a *total* disaster. And I suppose I could find a used bottom end if absolutely necessary, but its unfortunate bc I had this engine rebuilt from the bare cases up.

[koko64]

Double check your cambelt pulleys for correct timing. Check all the gear teeth where they mesh as you were just in there.

[LowercaseJake]

Cam timing is spot on. 2 piece adjustable hubs were added last year and dialed in. Belts show no signs of jumping a tooth and the valve train operates as it should. Pistons are froze at the bottom of the stroke.

[koko64]

Any luck finding it ?

[LowercaseJake]

Any luck finding it ?

I don't have a very long fuse so I've already begun parting out the motor in disgust. I've already received a decent chunk of my investment back selling the Nichols flywheel, V2 heads are spoken for, vented clutch side engine case cover, a really pretty polished stator cover etc. The tool I ordered for removing the cyl head nuts arrives tomorrow, so I may have an idea what happened then. If the crank operates on a keyway as Speeddog said that "key" may have worked itself loose, who knows. There's some gold slag on my sump screen which could be normal or it could be bearing shells. Who the F knows.

In all honesty, I never had as much fun on this bike as I did on my old 750, and when I borrowed an S2R800 for a week I didn't wanna give it back. The 900 felt "lazy" in comparison to both engines IMHO.

Thx f' asking tho, Koko.

[greenmonster]

You did align this



?

[LowercaseJake]

You did align this



?

No, not initially. I aligned it with a dot on the gear which was wrong. Is that why my motor is dead? I figured at the worst case scenario my ignition timing would  be wack.

[greenmonster]

Agree w ignition timing should be the main issue.
If too off, doubt it would start. Yours did.
Removed heads yet?