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Author Topic: Intermittent engine noise, hard starting  (Read 1039 times)

mattjohnson207

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Intermittent engine noise, hard starting
« on: April 14, 2013, 05:30:57 PM »
'09 AVL ,  sounds like an exhaust leak at the head, but no evidence of soot, a mechanic at work suggested unseated ring, which would score the piston.  The oil was quite clean, but became black after only 300 miles.  Can be very hard to start in morning, no more one kicks.  Sounds like loose nuts on the front fender, removed them, no change, so it is mechanical.  Mostly happens under load, 3rd gear and up. 8300 miles. Almost entirely spent its life doing short 8 mile commute to work, or coffee shop.  Could it be  due for decarbonization? Considering getting an aircraft leak down tester from aircraft spruce.  No smoke from exhaust.  I can feel puffs of air coming from my duckbill breather.  Drained oil, no broken parts. Riding bicycle now.  Ready for a teardown if necessary.  Thanks,  Matt

Kevin Mahoney

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Re: Intermittent engine noise, hard starting
« Reply #1 on: April 14, 2013, 05:42:27 PM »
The loose nuts could be detonation in the engine. Very harmful if not attended to. Also noise can really telegraph it's way around these bikes so look hard to loose nuts and bolts. I think a plug would be where I would start, de-carbing maybe, try better gas.

Bullet Whisperer

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Re: Intermittent engine noise, hard starting
« Reply #2 on: April 14, 2013, 06:32:33 PM »
It may also be a blowing head gasket, by your description of the noise and the fact it is most prominent under load. This would also explain the harder starting - does the compression feel softer than before?
 B.W.

ace.cafe

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Re: Intermittent engine noise, hard starting
« Reply #3 on: April 14, 2013, 07:27:52 PM »
My routine would be to very carefully go over everything that is external, and make sure that all adjustments and things that you can easily access and adjust are in good working condition.

If you can access a compression tester(not a leakdown tester), it might be nice to see what compression it has. If not, then you can just proceed with the other method below.

Then, if nothing turns up, you can get a gasket kit for the top end and cylinder barrel, and remove the head for a decarbonizing. While it's off, do all the checks of everything in there, including valves and guides, and also remove the barrel and check the rings, piston, and head gasket too.
If you find anything bad, then you can deal with it correctly at that time.
Then use new gaskets and put it back together properly.

« Last Edit: April 14, 2013, 07:42:45 PM by ace.cafe »
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Kevin Mahoney

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Re: Intermittent engine noise, hard starting
« Reply #4 on: April 15, 2013, 06:34:39 PM »
What he said!

mattjohnson207

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Re: Intermittent engine noise, hard starting
« Reply #5 on: April 16, 2013, 01:45:56 AM »
Ah!  a road map... will first try compression tester...Thanks

dampking

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Re: Intermittent engine noise, hard starting
« Reply #6 on: April 16, 2013, 06:37:11 AM »
Facing same issue in mine too but no starting problem. When the engine is under load (with pilllion) there comes a weird metallic sound from the head part, right under the tank. Compression is really good tho, when the engine is hot, it gets really tough for anyone to kick start the bike.

-Sanket

Bullet Whisperer

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Re: Intermittent engine noise, hard starting
« Reply #7 on: April 16, 2013, 12:19:17 PM »
Hi Sanket,
 Your machine is 'pinking' [pinging]. Could be too lean on the carb settings, too advanced on the ignition timing, or just too much compression - even a combination of a couple of these. The compression can be lowered not only with barrel spacers, but also by retarding the inlet timing, if appropriate.
 B.W.
« Last Edit: April 16, 2013, 12:22:07 PM by Bullet Whisperer »

dampking

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Re: Intermittent engine noise, hard starting
« Reply #8 on: April 16, 2013, 12:54:47 PM »
My carb is running rich. 30 pilot, needle in 4th slot, mainjet 220.

I think I will play with the valve timings and try to get better results out of it. I also checked the big crankshaft nut which you told me to check, it was a bit loose.. tightened it during my last service.

Also, I have this weird tendency to rev high and fast, maybe I should stop doing that on a stock engine.

« Last Edit: April 16, 2013, 01:09:24 PM by dampking »

Arizoni

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Re: Intermittent engine noise, hard starting
« Reply #9 on: April 16, 2013, 07:30:57 PM »
If my bike was showing signs of pinging the first thing I would try is to break down and pay the extra cents to buy the highest octane fuel I could get at a filling station.

This alone could solve your noise problem when the engine is under load.

If the high octane fuel didn't solve the problem, then I would start frinkling with the timing.
Jim
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mattjohnson207

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Re: Intermittent engine noise, hard starting
« Reply #10 on: April 20, 2013, 03:33:54 PM »
As Sanket said, I too have found starting near impossible when it's hot, ever science new.  Would like to try a different carb than my ucal 29,stock came with my 09 AVL.  Something a neophyte could set up with ease and precision.  Currently have a small k&n filter, megaphone exhaust, 7 inch perforated pipe removed.  Lots of backfiring.  After I try the hi test gas, if no improvement, will do a decarbonization. Just picked up a freeway bike, so I can do this job at my leisure, and install Chumma's  remote oil cooler.  Thanks for all the great advice...matt

dampking

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Re: Intermittent engine noise, hard starting
« Reply #11 on: April 21, 2013, 09:41:33 AM »
I am pretty much sure that in my case it's the rich mix which probably added a lot of carbon deposit and bumped my compression and while doing some research.. I found that water/steam can be used to de-carb the piston crown and Cyl head? I am not sure about this but found a doc where I found some good info on the same.

Here's the document - https://attachment.fbsbx.com/file_download.php?id=569474423065444&eid=ASvgtvXLKKicaO9QdxxHKAU5P3VDYYcYQgAtM6Yt_6CutcdKPbSiJhPbWsBopnpzb30&inline=1&ext=1366537163&hash=ASs9VtpkKV9m6XYp

and here's another video of water decarbing - http://www.youtube.com/watch?v=jWqN8pBHJhE



DanB

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Re: Intermittent engine noise, hard starting
« Reply #12 on: April 21, 2013, 04:55:28 PM »
Regarding the hard starting, could this be float related? Especially if you've had the carb on and off a lot. Could have knocked the tang slightly and raise the fuel level?  I was just reading this on a fireball in the IB forum. How much does float adjust impact carb setting, especially at starting?
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barenekd

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Re: Intermittent engine noise, hard starting
« Reply #13 on: April 22, 2013, 05:56:03 PM »
If the float level is too high, fuel can be running into the cylinder as it sits. Makes flooded starting quite difficult. Also will cause rough running at low RPM, in particular.
It doesn't even have to be a high float level, a leaking needle and seat can cause the same issues.
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Re: Intermittent engine noise, hard starting
« Reply #14 on: April 22, 2013, 09:54:02 PM »
Sanket: Other than just off idle, starting and running are two separte fuel circuits which could be independently rich or lean.

The quickest way to do it right is to buy both lean and rich jets and take it to a dyno. Get it done and ride. Other than that its good practice to start rich and do plug chops for each throttle position. Ensure they are no exhaust or intake leaks first and that your timing is spot on.