Re: Riding to Patagonia...starting issue

[1.21GW]

Looking for some mechanical advice.  I posted on a DR specific website but I like you guys more so here you go:

I checked my valves about a month ago.  Had never done them and it was like 22k miles since I bought the bike.  Seemed well overdue (Suzuki recommends every 7.5k miles).  For the record, the bike was running fine.

Anyway, checked them and made adjustments.  She started after but with a little difficulty.  This kept up for a day or two.  Then I parked the bike for a month and didn't use it at all.  

Started her a few days before my departure and noticed the same trouble starting as before.  Googled some stuff, read forums, and learned that if the valve gaps are too tight (i.e. more play) the engine can have trouble starting because not enough compression builds up.  So I open her up and check the valves and adjust the gaps to the wider/looser end of Suzuki's specs.  I've ridden her a bunch now and the startup problems continue.  When running she runs and sounds fine.

Oh, and I checked the battery and it's fine (13.95V this morning when I measured before attempting to start), I don't think it's a battery issue.

Below is a video of my startup attempt today.  As you can see, the gap between the engine trying to turn over gets shorter and shorter after starting very slow and sluggish.  Also, after I turned the camera off and tried to start it again, I got a big puff/blowback of air through the airbox (the box top is open and I had the seat off, so I could hear and feel the air rushing out of the box).  This happened again on two more attempts.  I turned the camera on to record it and of course it didn't happen and she started up right away.

So it appears that something needs to "build up" to get her started, and with the blowback from the airbox I'm guessing it's compression related.  Which leads me back to valves.  I'm going to open her up today and adjust them to the other end (i.e. tighter gap) of the recommend gap range and see if that helps.

Anyway, wondering if you have any thoughts?  I could be having the classic error of target fixation, where because I did the valves I'm focused on that as the problem, but it could be that the problem is elsewhere and just occurred coincidentally when I did the valves.

[ducpainter]

I don't think you have a 'battery' problem, but you might have a voltage drop problem. Loose/dirty connection somewhere in the starter system.

Also, too tight is not enough clearance. If you have clearance cold, and you set the valves at the bottom end of the spec, it's possible, if you missed on the tighter side, that when hot the valve could be too tight and affect compression, or even burn, but shouldn't affect starting, until the valve is burnt. How's that for a run on sentence? That isn't likely to happen in a very short time.

Do you have access to a compression tester?

[1.21GW]

Nope.

I checked the V when I started this morning and it dropped to like 12-something so I'm guessing the voltage drop issue is not in play.

Curious why there would be blowback in the airbox.  If the valves were too tight (i.e. gap too wide) could there be a decompression issue?  Or am I making things up?

[ducpainter]

Nope.

I checked the V when I started this morning and it dropped to like 12-something so I'm guessing the voltage drop issue is not in play.

Curious why there would be blowback in the airbox.  If the valves were too tight (i.e. gap too wide) could there be a decompression issue?  Or am I making things up?

If the valves are too tight, the gap is too small, not too wide.

Where are you measuring the voltage drop?

[Speeddog]

Is this problem consistent with cold start, hot restart, neither?

Similarly for cold, hot ambient temp?

What altitude are you at?

[1.21GW]

I'm testing battery(red) to frame and watching it drop on the multimeter while I try to start the bike.  Wrong?

[ducpainter]

I'm testing battery(red) to frame and watching it drop on the multimeter while I try to start the bike.  Wrong?

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.

I'm thinking I should split this part out and move it to Tech. howie, and Nick, and all the smaht guys will be more likely to see it.

[1.21GW]

Is this problem consistent with cold start, hot restart, neither?

Similarly for cold, hot ambient temp?

What altitude are you at?

Hot restart (like when I stop for gas and restart) is fine.  So that would normally make me think it's a carb issue or something.  Temperatures are really cold here nor really hot, so not a wide range of ambient temp.

Altitude is like 200-500m.  My carb has been fine and unadjusted at sea level and at nearly 5000m, so its set up in a way that works in a wide range.

[1.21GW]

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.

I'm thinking I should split this part out and move it to Tech. howie, and Nick, and all the smaht guys will be more likely to see it.

Sounds good.  I'm going to adjust the valves to the tighter end of the spec today and see if that solves it.  If not, I'll post new in Tech Issues.

[ducpainter]

I'm going to move this part of the discussion anyway. Just add any info to it in Tech.

[Howie]

Re check your valve clearances anyway.  Too tight will lead to burnt valves.  A good method for the novice is the "go no go method".  Just to make up a number, let's say the spec is .006".  A .005" feeler gauge should be loose and a .007" shoul go through, but feel tight.  From the video I would rule out valves, at least as far as cranking goes.  The puff in the air box cold be from a tight intake.  Or lean mixture. 

Since your diagnostics have to be more shade tree than shop my ext step would battery voltage directly to the starter and see what happens.  You might have a starter with worn bushings or a bad segment from the way it sounds.   Just a wild ass guess.

[1.21GW]

Thanks all.

I adjusted them to the tight end of the spec and she has been starting fine since.  Tomorrow after sitting all night will be the final test, but I think all is well.

So now I know what a bike that won't start because of low compression sounds like.

[1.21GW]

Thing with DR650 is that the lip of the valve cover part of the motor is above the gap you need to check.  So you have to curve your gap tool over the lip.  This obviously creates false friction.  So you can buy a pre-bent gap tool from Pro Cycle, or just bend your own tool.  Even then, the space is limited and I had to check and re-check and re-check to make sure I wasn't getting false readings.  

Now I'm curious what the valve check procedure on my Duc is like.  Scale of 1 to 10, what is the difficulty level?  And the PITA level?

[ducpainter]

Thanks all.

I adjusted them to the tight end of the spec and she has been starting fine since.  Tomorrow after sitting all night will be the final test, but I think all is well.

So now I know what a bike that won't start because of low compression sounds like.

You have me thoroughly confused.

[1.21GW]

Okay, 80% I understand this all wrong...

But I adjusted the valve to the tight end of Suzuki specs.  I had had them (or thought I did) at the loose end of the spec.  Really, though my talents with a gap tool are lacking apparently.  So they were wider than spec, particularly on the exhaust side.

Anyway, I tightened the gap down within spec and when I started the bike, no issue.  So I think there wasn't enough compression because with wide gaps the valves were releasing too much air.

That make sense?