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Old 5th September 2011, 14:48   #1
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Default Knocking noise on a Mach 500 LB only in a warm engine

Guys, I really need some help here.
I have owned and have been riding Enfield for close to 16 years now. The last one I purchased was a Machismo 500 LB, 2 years back.
The bike was doing excellent, until about 6 months back, when a weird sound started coming from the engine. The moment I rev the bike and the RPM is coming down, it makes this strange tak-tak-tak noise. This even happens when I am doing gearshifts.
This only happens when the engine is slightly warm, maybe just done 4-5 kms. This noise does not come when the engine is at extreme temperatures, like a cold engine in the morning, and a heated engine after 10-15 kms.
Have spent close to 23k and got the engine opened twice, at a company owned Service center in Bangalore, but the sound still remains.
Has anyone faced a similar issue ? and what can be the probable cause for the same ?
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Old 6th September 2011, 13:31   #2
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Default Re: Knocking noise on a Mach 500 LB only in a warm engine

It sound like piston slapping. It basically affects worn pistons. I had it some time back on my 1978 Bull. The bike was still running on its original factory installed piston. Got my piston checked. It needed replacement. Got it change. And now the sound is gone.

Last edited by Leepower : 6th September 2011 at 13:38.
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Old 6th September 2011, 14:51   #3
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Default Re: Knocking noise on a Mach 500 LB only in a warm engine

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Originally Posted by Leepower View Post
It sound like piston slapping. It basically affects worn pistons. I had it some time back on my 1978 Bull. The bike was still running on its original factory installed piston. Got my piston checked. It needed replacement. Got it change. And now the sound is gone.
Thanks @Leepower....will check with the guys at the service center and see. By piston slapping do you mean that there is a gap between the piston and the bore ? I did read a few online articles on the same, and it seems more related to the Piston rings.
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Old 6th September 2011, 17:08   #4
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Default Re: Knocking noise on a Mach 500 LB only in a warm engine

Carb issue. Remove, clean and replace. Issue would be solved. Check airfilter and routing too.

Why the heck did you open the engine and what did you replace for 23k? Piston slap or whatever could have been made out the first time you lifted the head.
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Old 6th September 2011, 17:21   #5
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Default Re: Knocking noise on a Mach 500 LB only in a warm engine

Is it a sound like 2 metals rubbing together? Could be an issue with the worn out cams. The AVLs are notorious for their cam wearing out, I had this problem thrice in my AVL350, and finally sold it off..
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Old 6th September 2011, 17:23   #6
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Default Re: Knocking noise on a Mach 500 LB only in a warm engine

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Originally Posted by Spitfire View Post
Carb issue. Remove, clean and replace. Issue would be solved. Check airfilter and routing too.

Why the heck did you open the engine and what did you replace for 23k? Piston slap or whatever could have been made out the first time you lifted the head.
Thanks for the suggestion. Will try that too. But do you think Carb would have a link with the engine temperature and the issue.

I use a K& N RC1060 filter with a 130 jet. Will check the routing also

I know, 23k is a lot of money, but being the authorized service center, I usually believe their work. The first time I gave the bike, they checked the Cam etc and did a bot of lathe work. The second time I gave, they said its an issue with the Crankshaft bearings, and replaced the same. The labour charge was also inevitable both the times. This time I am not going to pay a single buck to them, and am pretty angry about this whole episode...

Lets see what happens ?


Quote:
Originally Posted by jingaboysr View Post
Is it a sound like 2 metals rubbing together? Could be an issue with the worn out cams. The AVLs are notorious for their cam wearing out, I had this problem thrice in my AVL350, and finally sold it off..
Yes. I think that might be the issue. Am trying to add a sleeve to an old LB Cam that I have and see if it works. Else, will order a new one, which takes more than two months to source.

But I don't want to dispose off this one because I think LB's are the best machines RE ever came up with.

Thanks for your inputs though
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Old 6th September 2011, 19:34   #7
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Default Re: Knocking noise on a Mach 500 LB only in a warm engine

I have seen 2 particular cases with this kind of noise. One if the camshaft and rocker arm being defective of or worn off. and the second being a shaft in the gear box. Its a very thin shaft in the gearbox. It fits into a small orifice in the gearbox and at the end of it is a ball similar to that of a ball bearing. I don't know the exact name etc. This was the problem with my bike. The mechanic changed the ball and the noise went away. It was a constant clacking at mid temperatures just as you said.and now its been close to 8000 on the odo and there's still no noise.
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Old 6th September 2011, 20:58   #8
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Default Re: Knocking noise on a Mach 500 LB only in a warm engine

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Originally Posted by navpreet318 View Post
I have seen 2 particular cases with this kind of noise. One if the camshaft and rocker arm being defective of or worn off. and the second being a shaft in the gear box. Its a very thin shaft in the gearbox. It fits into a small orifice in the gearbox and at the end of it is a ball similar to that of a ball bearing. I don't know the exact name etc. This was the problem with my bike. The mechanic changed the ball and the noise went away. It was a constant clacking at mid temperatures just as you said.and now its been close to 8000 on the odo and there's still no noise.
Hey Navpreet. Thanks a lot for your inputs. Will definitely be checking on these two possible causes highlighted by you. I have somehow had this feeling right from the beginning that the issue is not related to the Cam, and is something to do with the gearbox. Will keep you posted.
Cheers
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Old 6th September 2011, 23:50   #9
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Default Re: Knocking noise on a Mach 500 LB only in a warm engine

If you are opening up the engine check oil rocker, tappets also. If engine oil is not circulated properly, then also strange noises can come. My 78 Bull used to make strange noises while on the move. Took it to lot of service centres, couldn't get it solved. Finally took it to St. Jude Motors in Wanowrie, Pune run by Pramod Sonawane. He diagnosed the problem and fixed. The fault was the lack of oil circulation.

Last edited by Leepower : 6th September 2011 at 23:56.
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Old 7th September 2011, 01:24   #10
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Default Re: Knocking noise on a Mach 500 LB only in a warm engine

I have an LB500 for a little more than 2 years now. Its all brillant.

Had a Thunderbird before this and i faced the problem you are talking about.

It was fixed by replacing the gudgeon pin. To know more about what this is : Gudgeon pin - Wikipedia, the free encyclopedia

I would advise you to get the gudgeon pin checked and also get the tappets re-adjusted.

23K sounds like an enormous amount of money - how many kms has your bike done and where all has she been ?

May be a change of mechanic is the most important thing to do now :-)
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