Aircooled Knock under load.

[Davegrohl99]

Hey everyone,

Just back from a 900km trip around “Sunny south east” of Ireland.

I have noticed taking on some very steep hills under harsh acceleration uphill there is a audible ticking noise. When I change down gears the knocking seems to disappear. It’s a bit worrying but seem to be okay when in the correct gear.

Am I not changing down early enough and not holding it in 3rd for long enough.

2.0 CU engine for reference.

Cheers


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[davidoft1]

Sounds like bottom end knock

[Davegrohl99]

"pooh".

Rebuilt the top end this time last year to the day.




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[Davegrohl99]

Maybe it could be pinking? I’m hoping that might be it. The only thing I haven’t looked at since ownership and rebuild is the carbs. Maybe a retune of the carbs and balancing them and maybe run it slightly richer might solve the issue.


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[tobydog]

I would check that the ignition timing is not advanced

My Moto Gucci is meant to run on the old 5 star fuel. If you open it up too much at low revs under load it pinks which sounds like a metalic pinging.

 

[Davegrohl99]

Okay will do.

We only have 95 Ron at best here in Ireland. I religiously use Dipetane as an additive to help keep the engine clean. Maybe I should consider octane booster also?


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[davidoft1]

"pooh".

Rebuilt the top end this time last year to the day.




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did you do the big end bearings too?

[Davegrohl99]

No never split the case. Problem was top end related at the time. I’d be very disappointed if that was the problem as the engine is really performing well. Other than in that situation. I might try what’s been said above before I get really worried.


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[davidoft1]

No never split the case. Problem was top end related at the time. I’d be very disappointed if that was the problem as the engine is really performing well. Other than in that situation. I might try what’s been said above before I get really worried.


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You can do the big ends without splitting the case , it’s not uncommon for the big ends to fail after a top end rebuild , I could be wrong

[T25Convert]

It’s pretty common to develop bottom end issues after a full top end refresh.

I watched a great video (which I can’t find again) of an American changing the big end bearing shells. It went like this:

Remove heads, withdraw barrels but leave them just over the piston so the rings stay compressed. Thin walled socket on a wobble bar between base of barrel and case to undo con rod and cap. Piston and barrel removed complete with con rod and half the bearing. Hand in through the now present hole to retrieve con rod cap. New shells and back together again. Did a whole set of big ends in a matter of minutes.

If it were me I’d want to look at crank and car bearings, but if you are confident of the issue and don’t fancy splitting the case there is another viable alternative!

[Rosie n' Jim]

When the revs are low, and gear is high, there's a lot of torque going through the transmission. If a cv is dodgy it could make a clonking noise. Does your knocking keep time with engine revs or road speed (wheel revs)?

[Davegrohl99]

No the noise is sporadic and isn’t in the same time as the engine. I wrought it was my exhaust rattling but doesn’t seem to be that either.


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[sarran1955]

Hello,

Ticking noise under load...Hmmm

When did you last check/grease/change your CV joints...

Cordialement,

[Davegrohl99]

Hello,

Ticking noise under load...Hmmm

When did you last check/grease/change your CV joints...

Cordialement,

I checked CV bolts were tight before my strip. The CVs themselves I haven’t checked perhaps a rebuild is in order?


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[Robsey]

I think it is the type of sound that matters..

In my " very generic" understanding -

A worn CV joint is more likely to be a ticking or crackling sound.

A worn crank bearing would be a more rumbling type sound.

A more metallic pinking / tinking noise could indicate timing being too advanced by a couple of degrees.

A general rule for me is start out and rule out the easy stuff, and go through the options until you hopefully find the source of the noise.

So in simple terms -
Basic service with timing check etc.

Strip, clean and repack the cv joints.

And last resort, look at the bearing shells.