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Reboring a Venom Alloy cylinder #678672
12/22/16 9:58 pm
12/22/16 9:58 pm
Joined: Oct 2015
Posts: 56
Western Australia
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barry2 Offline OP
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Joined: Oct 2015
Posts: 56
Western Australia
Hi Mates
Just rebored my Venom Clubman c/ alloy cylinder , using a 020" Aerco piston bought in the UK, spot on .004" clearance but it still has a noise like piston slap, it had it before with .008" wear ( big end etc were ok), it's a noise you can alter with power etc, noisy on over run ie not on power/ pulling but when you bring the throttle back , any thoughts on the matter?
All the best
barry

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Re: Reboring a Venom Alloy cylinder [Re: barry2] #678738
12/23/16 11:39 am
12/23/16 11:39 am
Joined: Nov 2006
Posts: 400
Wisconsin, USA
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franko Offline

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Posts: 400
Wisconsin, USA
My son, Brian, had this on his Norton. It turned out to be the rotor outer was pulling loose of of it's center. The knocking was most pronounced at idle. HTH

Re: Reboring a Venom Alloy cylinder [Re: barry2] #682791
01/27/17 1:48 pm
01/27/17 1:48 pm
Joined: Jan 2017
Posts: 3
Uk
5
57clubman Offline
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Uk
A similar rattle that you describing can be caused by the big end cage they tend to wear abainst the crank pin, this can sometimes be detected by side to side movement on the conrod, they will run to enternity like this but it may not make for a pleasant ride.

Last edited by 57clubman; 01/27/17 1:50 pm.

Bob
Re: Reboring a Venom Alloy cylinder [Re: barry2] #719914
12/24/17 2:21 pm
12/24/17 2:21 pm
Joined: Feb 2006
Posts: 625
Ontario , Canada
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RGSROB Offline
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Posts: 625
Ontario , Canada
check the side play on the cam gear and idler . You can get a noise almost like a worn big end from excessive play . It should be ideally about .002".
I also run a venom but with an iron cylinder and it does have piston slap which does diminish as the bike warms up.
Does your noise change as the bike warms up.?
The alfin type cylinders can be subject to quite a bit of distortion and even separation of the iron from the aluminium jacket. You may have to have a really good look at that.


Re: Reboring a Venom Alloy cylinder [Re: barry2] #719955
12/24/17 10:28 pm
12/24/17 10:28 pm
Joined: Jul 2016
Posts: 227
Australia
Joolstacho Offline
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Joined: Jul 2016
Posts: 227
Australia
Several possible things it could be I guess, -but I agree with Rob to check the meshing of the camdrive idler pinion. This can be adjusted to give nice neat meshing in the geartrain.
I believe it makes a clacking noise when there's too much clearance between the pinions, and it would come and go with engine revs/load I would think.
These gears should always, if possible, be changed as 'sets' because they 'bed-in' as a set. Have any of your timing gears been changed?

Re: Reboring a Venom Alloy cylinder [Re: barry2] #719966
12/25/17 3:54 am
12/25/17 3:54 am
Joined: Feb 2007
Posts: 646
Ewing. NJ
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edunham Offline
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Posts: 646
Ewing. NJ
I had something similar when the idler shaft hole in the crankcase wore oval. Didn't want to strip a good running bike, so I used some miracle Locktite stuff. Still nice and quiet 5 years later.

Ed from NJ

Re: Reboring a Venom Alloy cylinder [Re: barry2] #720141
12/27/17 4:14 pm
12/27/17 4:14 pm
Joined: Feb 2006
Posts: 625
Ontario , Canada
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RGSROB Offline
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Posts: 625
Ontario , Canada
Hi Jools, just to clarify I am not talking about mesh of the gears. I am referring to linear movement of the idler and/or cam on their shafts. The helical gears will cause the gears to hammer back and forward on their shafts. if there is excessive clearance.

Re: Reboring a Venom Alloy cylinder [Re: RGSROB] #722067
01/14/18 11:50 pm
01/14/18 11:50 pm
Joined: Oct 2015
Posts: 56
Western Australia
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barry2 Offline OP
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Posts: 56
Western Australia
Hi Mates
Getting back to the engine noise , stripped the engine down again, the big-end Had .003" up and down wear ( not all the time though I had to move it about to get it) anyway , stripped the flywheel and put in a new big end,on assembling the fly wheels, (Radialy) one disc is spot on but the other is about ,002" ( in the vicinity of the crankpin ie not 90 to it)
Axial run out is about .005" , hoping that would be OK ( near enough?) not sure where to apply pressure to recifiey if not, any comments would be welcome
Barry

Re: Reboring a Venom Alloy cylinder [Re: barry2] #724751
02/08/18 2:32 pm
02/08/18 2:32 pm
Joined: Feb 2006
Posts: 625
Ontario , Canada
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RGSROB Offline
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Joined: Feb 2006
Posts: 625
Ontario , Canada
ideally ,after assembly, you should aim for no more than .001/.0015 T.I.R.of the shafts at or near the main bearing locations.
If you get some discrepancy when clocking up the od of the flywheels it is less important.
When the OD of the individual flywheels were machined there is a good probability that they may not be Concentric with each other.
After flywheel discs were machined,Velocette mounted the shafts to each flywheel then balanced those individual assemblies prior to fitting the big end .



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