Author Topic: Update: Hard Bang on Starts... new engine? help  (Read 1592 times)

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Offline connie_rider

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Re: Update: Hard Bang on Starts... new engine? help
« Reply #25 on: September 13, 2017, 12:22:38 am »
IT's starting to sound like a #4 rod bearing.
If so, a careful piston height measurement might give indication.

Ride safe, Ted
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Offline Stasch

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Re: Update: Hard Bang on Starts... new engine? help
« Reply #26 on: September 13, 2017, 10:41:52 am »
Couple more things to consider that are my opinion and may be worth just that:

 - A rod bearing can cause knocking, but I'm not seeing how that could impair engine revolution.

 - From the OP's initial info, it seems that many instances of hydrolock have occurred.

Quote
Preliminary: A few hard starts now and then this year, that seemed like things hitting each other that shouldn't be... Similar to a backfire but seemed more like metal connecting. ?

Quote
Event: Following Monday John started the bike to begin work on it, and it did its banging hard-start for him as well. But, it would not turn over for him again. He removed cover and manually turned it over by hand, but found it would not go past one point - back or forward

I think its possible for the conrods between a potential set of offending piston pairs to BOTH be bent, with the potential of similar lowered piston heights.  This could yield a false positive on the piston height test, especially since the test can sometimes be inexact depending on the fabricated tool and method used to measure.

You might initially think that if both rods in a pair were equally bent, the first should have been locking up the motor prior to damage to the second.  However, conrods don't always bend 2 dimensionally.  (see pics)

Therefore I believe its possible one bent rod in a set could have its piston as low as the other bent rod, yet not cause engine contact while the other one does.

The following pics show how conrods can bend 3 dimensionally.  It came out of a high mileage commuter C10 that wasn't exactly loved.  I've been told that this particular example is one of the most severe seen yet.  I'm guessing it wasn't a single event that hammered this thing so out of shape.

It was the #3 rod who's piston height measured a whopping 3/8" shorter than its straight #2 counterpart.  It restricted engine revolution to about 270 degrees either way - within 10 percent or so of the 300 degrees limit the OP states.

You can also see how the top of the rod is offset left / right compared to the bottom, AND when compared with the lines on the notebook paper, its tilted with its extended 'cylinder' no longer parallel with the bottom.




« Last Edit: September 13, 2017, 10:53:39 am by Stasch »
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Offline Merlin97

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Re: Update: Hard Bang on Starts... new engine? help
« Reply #27 on: September 13, 2017, 11:42:56 am »
Thanks Ted and Stasch
Man-o-man, that is one bent rod in your attached. I'm going to show this post in particular to mechanic John.

So, if in the case of a bent rod(s), on a bike that is probably only worth 2-3K if was sold (in working order), would an engine replacement be my better path, or take it all apart and replace the damaged rod(s)? (I won't be buying a new $bike, and don't really want any other used bike. Like ol'Merlin).

I am looking for a garage to use over winter so I could possibly do the work (I have done all but any engine or carb work), but this seems like a job for a real mechanic. ?

I see above there's an icon waving a white flag - don't want to use that little bugger...
As always, I very much appreciate the feedback and assistance here. Thanks all y'all.
At 130 km/h my Connie went 480' without me. I stopped sliding after 220'. The coyote ended up going in two directions at once.

Offline Stasch

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Re: Update: Hard Bang on Starts... new engine? help
« Reply #28 on: September 13, 2017, 12:14:53 pm »
Quote
So, if in the case of a bent rod(s), on a bike that is probably only worth 2-3K if was sold (in working order), would an engine replacement be my better path, or take it all apart and replace the damaged rod(s)?

The replace rods vs. engine replacement decision depends on a couple things.  Rods 2 and 3 can be replaced with engine in the bike and removing radiator, exhaust system, oil pan and oil cooler.  Rods 1 and 4 require pulling the engine and splitting cases.

I've done both.  I only did the case split because I actually looked forward to the experience of digging into it that deep.  Weird maybe, but I was glad I did from the knowledge and experience gained.  I considered the parts costs as well spent tuition.  Note: this was on a parts bike project, over the winter, and not my main ride.  Your preferences could differ.

Another consideration:  Are you comfortable and equipped to do it yourself or will you be paying a mechanic?  If the latter - its probably cheaper time and cost wise IMO to look for a different C10, parting out the one you have.

From a cost analysis, the 2 - $3000 sale value you are using is high IMO even when well farkled out.  C10's are great bikes but used market prices have really fallen off lately.  This is good news as there are some well sorted and maintained examples out there to be considered.  Check the Emporium - some REALLY nice ones are available.

If you replace rod(s), you need to match rod weights as indicated by a letter (H through L, IIRC) printed across the lower rod / connector union.  Lower conrod bearings are color coded by size - a place to start as you plasti-gage them with replacement rod(s) to ensure within specs.
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Offline works4me

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Re: Update: Hard Bang on Starts... new engine? help
« Reply #29 on: September 13, 2017, 01:04:38 pm »
At this point, I would pull the head off to get an
accurate measurement of piston heights.
This will give you a much better idea of what's wrong.
Since you're likely replacing rod(s) or the entire
engine anyway this would be a good place to start.
Best case you're out a head gasket.

Offline Merlin97

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Re: Update: Hard Bang on Starts... new engine? help
« Reply #30 on: September 13, 2017, 01:33:22 pm »
Head is off and will measure piston heights.
Bike value was just a ballpark CND. I've replaced front and rear suspensions, wire harness, front rotors/brackets/callipers, redone cheek and case reflectors as running/indicator LEDs, bar extenders and other bits and pieces - could just transfer all that to a newer Conk10.

All in all this is not a great experience - not to mention no riding summer vacation along NB's coast, Gaspé run and Maine this Fall...
Gracias again amigos

and the learning experience would be good... but need a workspace.
« Last Edit: September 13, 2017, 04:54:29 pm by Merlin97 »
At 130 km/h my Connie went 480' without me. I stopped sliding after 220'. The coyote ended up going in two directions at once.

Offline Stasch

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Re: Update: Hard Bang on Starts... new engine? help
« Reply #31 on: September 13, 2017, 03:40:50 pm »
Ah, CDN $ and the mods do make a difference.

Never fun to have your ride down during riding season.
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Offline Mike

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Re: Update: Hard Bang on Starts... new engine? help
« Reply #32 on: September 17, 2017, 08:54:14 pm »
Will it rotate beyond 360 with the head off? A spun or stacked rod bearing or bent valve could be the answer. With the head off, your minutes away from an answer. With Ted's help, Rev's assistance, 4 books, this forum, and Steve's encouragement, I took it on like a rookie and finished it in a month of spare time (waiting for parts was a lot of it, no one stocks the parts locally and it was a week delay for every order). You won't have to pull the motor or split the case for the two center rods.

Offline Merlin97

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Re: Update: Hard Bang on Starts... new engine? help
« Reply #33 on: September 19, 2017, 12:59:24 am »
Thanks all.
Mechanic has removed everything that could interfere. He's an experienced guy who's worked on all makes and years of bikes. He's built drag bikes and raced I think. Also measured piston head distances and they all match up. Valves and cam are good, cam chain is also fine and unattached from the cam. So it's down to turning the crank manually without anything else involved, and that's where it goes clunk and does not turn completely all around. Back and forth is smooth and fine until that point <clunk>.

  So we'll remove it, upside down it and look in it from the oil pan to hopefully find the something simple or something stupid cause.

 Thanks for your encouragement Mike, appreciated!! I'd take on the challenge in a shot this winter, but without my own garage space (as we had in our previous houses) I'll have to let my mechanic work it.

 I'll renew this thread when I have something to share.
At 130 km/h my Connie went 480' without me. I stopped sliding after 220'. The coyote ended up going in two directions at once.

Offline m in sc

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Re: Update: Hard Bang on Starts... new engine? help
« Reply #34 on: September 19, 2017, 01:05:17 pm »
heres my mantra: "every failure is a chance for an upgrade."

might be time for some trick internals since you're going to go thru a full rebuild (it sounds like).

always look at the silver lining.

Offline connie_rider

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Re: Update: Hard Bang on Starts... new engine? help
« Reply #35 on: September 19, 2017, 09:52:35 pm »
Merlin, here's a wild thought.
Check the pick up on the timing plate.
Is it possible that the plate is hitting it?

Ride safe, Ted
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03 Connie (Buddy)

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Offline Merlin97

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Re: Update: Hard Bang on Starts... new engine? help
« Reply #36 on: September 22, 2017, 04:09:59 pm »
Will check that Ted, might as well because this situation has turned out to be a real head-scratcher.
thanks!
At 130 km/h my Connie went 480' without me. I stopped sliding after 220'. The coyote ended up going in two directions at once.