Re: Riding to Patagonia...starting issue

[ducpainter]

I don't think it possible to adjust that exhaust valve so loose to prevent starting.

That said, I'm glad you got it running.

[Langanobob]

The way it was cranking over sounded almost like the ignition timing was too far advanced, but I don't see how that would be very likely.  Or, if the battery was weak or had a bad connection and the starter slowed way down and almost stopped on the compression stroke.  If the compression was low because the valves were staying open due to misadjustment, the engine would crank faster, not slower.

Sounds like it's working fine now, that's all that matters.

[1.21GW]

Yeah, still trying to understand what happened technically.  Bike running fine, then I adjust (first time) and some problems starting.  So I re-adjust wider (second time) and problem gets worse.  So I re-re-adjust (third time) back to tight range and problem goes away.  Clearly it was the adjustment.  But the mechanics...not sure.  Will see what the DR experts say.

Anyway, thanks for the input folks.  Always helpful.

Correct...you're wrong.

Measure at the starter. On the starer post, not the cable lug.

You need to know how much voltage the starter is getting.

(snip)

Independent of my valve issue, I want to understand this.  What voltage should I be getting at the starter?

[ducpainter]

You want as close to battery voltage as possible. I'm sure there will be some drop, but the less the better.

howie will be by with some numbers re: 'normal range'.

[Howie]

.5 volts for the whole system.  Interesting the valve adjustment made such a difference.  Loose valves usually mean better cranking speed.  Unless they are so loose exhaust gas has a hard time getting out.  You sure the engine was TDC "on the rock"?

[1.21GW]

Thanks, Howie.  I'll do a voltage check just for the heck of it and see what I get.

Regarding valve gap...pretty sure I was dead on for TDCC.  Regardless, the DR650 doesn't need pure, spot-on, TDC for valve check.  There is a small bandwidth where the valves are in the right position.

So this what the DR guys said regarding too wide of a gap:

And realise that the valve clearances affect valve lift and duration... obviously lift and duration decrease as clearances increase. That being said the decompressor mech only slightly decompresses the engine so if your clearances are way off the decompressor does very little to nothing depending on the extend of the incorrect adjustment.

So I think what that means is that the engine wasn't decompressing enough.  Thus the blowback through the airbox.

[ducpainter]

I suppose if the decompressor mechanism is working on the rocker, and the valve is waaaaay too loose...that makes sense.

[Howie]

Yep.  And if you found leeway you were "on the rock"