VH metallic tapping noise at TDC

Singles, twins and fours.
ralfpenkert
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Re: VH metallic tapping noise at TDC

Post by ralfpenkert »

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Brian_Walker
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Re: VH metallic tapping noise at TDC

Post by Brian_Walker »

Most common problems with monoblocs is idle passage, taking the jet out and blowing out with air doesn't work remember the idle screw effects the air flow for the mixture not fuel. pilot jet cleaning does not always solve the problem sometimes the passage is blocked which requires a fine piece of wire, I use a oxy jet cleaning tip. Thumping is often associated with too much fuel so problem could come back to the carby now you mention increasing advance effecting engine running.
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Re: VH metallic tapping noise at TDC

Post by nevhunter »

Long shot but is the plug the right length or extended core? Nev
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Re: VH metallic tapping noise at TDC

Post by paul.jameson »

When checking the exhaust valve clearance make sure that the valve lifter is not holding the rocker down. If it does, you can have quite a clearance between top of pushrod and the rocker which can be noisy.
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Les H
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Re: VH metallic tapping noise at TDC

Post by Les H »

Thanks for your answers Will, much appreciated. I spent all day yesterday, getting it ready to ride. It does start easily using the recommended method of releasing the de-compressor during the kick...this is a different method to what I've been using for years on big singles. A friend came round and though the rattling was not that bad but a trial run up and down my drive had me shaking my head as to me, there is quite a loud "clack" sound during hard acceleration. If it's not big end noise, it must be the piston slap I guess, so a bill of around 300 quid expected for a piston, rings and re-bore coming up then? :(
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Re: VH metallic tapping noise at TDC

Post by Les H »

Thanks Nev and Paul, I will check out your suggestions. As far as I remember I think I removed the decompressor when the clearance was re-set. I re-ground the seal on it. The clearances of 6 and 8 thou seem unnecessarily large to me, I can only assume this is to absorb the push-rod expansion as the alloy head will expand too and INCREASE the gap... AMC big singles simply have the gap set as long as the push-rod cups can rotate when hot. Maybe the clearances created for the iron head engines were never adjusted smaller for the alloy head?
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Re: VH metallic tapping noise at TDC

Post by Les H »

Hi Ralf...OoopS. Nearly missed your reply...It seems I am answering them all in a backward style :(... I downloaded your excellent video. Thank you very much. I have to say your engine does sound a bit rattly too but maybe not as loud as my one. Maybe when I have my helmet on and take it for a ride I will not notice it so much. I will try to make a video of my one and try to enter it on this thread, we can both compare them together...Watch this space :)....PS: What position of ignition advance does your engine run smoothest at and what was it set to on this video?...I find the fastest and smoothest is just over 1/2- 2/3 from maximum. Advancing the ignition more makes the engine run more harshly and slightly slower?
Last edited by Les H on Tue Jun 14, 2022 9:45 am, edited 2 times in total.
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Re: VH metallic tapping noise at TDC

Post by Les H »

Also Brian thanks for your tips too. I will remove the carb today as I have an ultra-sonic bath cleaner to hand. I'll also check the jet sizes and settings...
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Re: VH metallic tapping noise at TDC

Post by will_curry »

I would expect your engine to have the cam with ramps which needs
a special technique to set the gaps.

There are both alloy and steel pushrods available and my understanding is
that the steel ones go with iron barrels and the alloy ones with alloy barrels.

I inadvertently fitted a steel pushrod into my all alloy trials bike many years ago
the row was deafening.
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Re: VH metallic tapping noise at TDC

Post by Simon.Gardiner »

will_curry wrote: Tue Jun 14, 2022 2:55 pm I would expect your engine to have the cam with ramps which needs
a special technique to set the gaps...
Adjust inlet tappet with exhaust valve just opening and exhaust tappet with inlet valve just closing, according to the handbook.
...There are both alloy and steel pushrods available and my understanding is
that the steel ones go with iron barrels and the alloy ones with alloy barrels.
Mmmm - possibly written by someone who's only owned all-iron or all-alloy engines! Those of us mere mortals who have to use iron barrels with our alloy heads also need alloy push-rods ;) :D

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