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Author Topic: Extra vibration, extra exhaust noise and loss of power  (Read 2951 times)

TwistedPhil

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Extra vibration, extra exhaust noise and loss of power
« on: April 23, 2008, 08:39:59 AM »

Hi, my bike is 6000kms old, I took it on the freeway for the first time and its been running like a dog since.  It shakes so much sometimes I cant see out of the mirrors and it sounds louder.  When it gets warm it suffers real power loss, like I'm running on 1 & 1/2 cylinders and it makes a louder lower exhaust note, like one cylinder is worn out.  I don't know whats wrong.
I have taken the front cylinder apart looking for the problem, i thought that was where the noise was coming from. Everything in there was within tolerance though.

Fires on both cylinders - no misses
compression over 160 psi - both bores
fresh oil
Valve lash spot on
Cam timing right

I'm lost!

Has anyone had these symptoms ( vibration, exhaust noise, power loss - worse when warm ) or found a solution?

I owe you a huge debt, anyone who can help.
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kezza69

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Extra vibration, extra exhaust noise and loss of power
« Reply #1 on: April 23, 2008, 09:28:17 AM »

have you looked at your carb's . My 650 ran ruff and lacked power down low until my mechanic found that one of my primary jets was blocked with crap.
cleaned and wella :D
runs like a dream. :twisted:
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GT250RIDER

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Extra vibration, extra exhaust noise and loss of power
« Reply #2 on: April 23, 2008, 11:32:42 AM »

just wondering have you loobed up your chain l8ly??? that might do the trick or dirt/stuff in your fuel blocking up your filter and making it hard to pump fuel around?? or yeah id take a look at carbs.....did you notice it over time or straight away?
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JackComet

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Extra vibration, extra exhaust noise and loss of power
« Reply #3 on: April 23, 2008, 04:29:07 PM »

Quote from: "kezza69"
have you looked at your carb's . My 650 ran ruff and lacked power down low until my mechanic found that one of my primary jets was blocked with crap.
cleaned and wella :D
runs like a dream. :twisted:


+1.
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TwistedPhil

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vibes / noise / powerloss
« Reply #4 on: April 24, 2008, 02:59:51 AM »

It happened 'suddenly', as in before I took my bike on the freeway it was ok, someway into the trip the vibrations were worse than I had experienced, but then so was riding in 5th on the freeway.  By the time I got off the freeway it was running loud, overhot and gutless, and a new vibration problem.  I stopped to let it cool.  Hasn't been the same since.

Your right about the carbys and I'll have them checked, except I heard I must eliminate any possible ignition problem or valve timing issue before I look at the carbs.

Has anyone seen a crankshaft in peices?  Is it possible for the timing chain driver gear to slip on the shaft?  ( Just a private nightmare. )

Can the CDI alter its timing / spark advance settings on its own?

Can the magneto rotor slip on its shaft?

Any help is really needed.  I love the bike. Shame to replace the engine for what might be a relatively minor problem.

 :what:

Look at the carbs first ?      8O
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Mike on the Rock

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Extra vibration, extra exhaust noise and loss of power
« Reply #5 on: April 24, 2008, 05:16:18 AM »

Hi   Twisted Phil

Sorry to hear about your troubles; and welcome to Korider.

As for your bike I am thinking it is a GT250 we are talking about, so what year, how many K, new or used and where is the bike?

You have posted compression and that looks good, was this done before or after the noise started? Sort of sounds like someone has sort of opened the engine up?

As for the magneto slipping, it is keyed on and I do know of one that slipped and this caused a loss of power, but that was about it, as for the chain, if the tensioners are not set correctly the chain can jump teeth and put the cam out of time, this will create a lot of noise.

Lack of fuel also has the same [noise/jerking/missing] symptoms  :oops:

I have posted a picture of the crank separated, makes lots of noise and locks up the rear:evil:

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wirafals

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Extra vibration, extra exhaust noise and loss of power
« Reply #6 on: April 24, 2008, 06:48:14 AM »

snapped/cracked muffler? i had almost same problem before with my previous bike, suddenly it sound loud and lost power, couldn't really remember about the vibration tho. when it's could it's fine but when its hot it lost its power and the sound louder. took it to the bike shop and they foud out there a crack on my muffler just next to the flange where it connected with the engine block. they said when the bike cold, the crack was still closed when its get hotter the crack was open. i don't know if that make sense or not, but that what the mechanic told me.
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TwistedPhil

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I think its ignition timing
« Reply #7 on: April 24, 2008, 07:25:28 AM »

Hi Mike,

I bought it second hand with 4000 kms on the clock and its got 6000 kms on it now. Bike is in Melbourne.

The compression was done on a warm motor, full battery W.O.T. , after the noise started and after I opened the engine up.

Your right, I was fretting about the crankshaft.  

Trouble is the whole engine is making the vibration, and the noise is an altered exhaust note like what youd get from a flogged motor.  I cant find anything mechanically wrong though.
Each cylinder works on its own, no more noise no less noise.

So Im looking at a timing issue, valves or spark.

Your picture of a crank reassured me its not the crank, the valve lash is still right so its not the cams. The chains are in the right tooth with the timing mark set to TDC.

This means I am left with the ignition timing.

There is an induction sensor ( thingy ) in the magneto side of the crank case, which tells the tacho and the CDI that one rev. has passed.

Its gotta be either the sensor or the CDI.

Cant get a dwell meter to work on the ignition though.  Ill try to swap this CDI  with a working one I guess.

Thanks for your help and the tip on synchronizing the carbys.   :cheers:

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I didnt feel like I knew my bike until I took a look inside.
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TwistedPhil

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I think its the timing
« Reply #8 on: April 24, 2008, 07:32:28 AM »

Hi Wirrafalls,

I wish it was the exhaust.  

If its not the CDI / sensor I may have to push it off a cliff.  :wink:
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TwistedPhil

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found the problem
« Reply #9 on: April 25, 2008, 03:58:32 AM »

Ive got soft valve springs.

Must've been cooked sometime.

Thanks for the help.
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