Head Gasket

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jotajohndude

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First up my mechanical ability or rather confidence does not go as far as replacing a head gasket, so lets get the laughing out the way first.

A triple engine has a slight weep from the head gasket. Assuming that there is no fault with the head and the best case scenario is just a straight replacement any ideas what a recognised Laverda shop would charge, how much labour involved. I assume the part is cheap enough.

This is just a hypothetical question, as present I am Laverda(less) though the Sf on eBay looks nice
 
My old 3C always had a slight weep from the head gasket area. I never did manage to fix it. The consensus back then was that the later gasket with the o rings would sort it out but it didnt fix my problem. Had the head skimmed slightly too but that never helped. It was probably porous. After nearly 100000 miles I swapped the engine for a wonderful low mileage oil tight motor. Trouble is it was nowhere near as fast! Regards Pat.
 
jotajohndude said:
First up my mechanical ability or rather confidence does not go as far as replacing a head gasket, so lets get the laughing out the way first.

A triple engine has a slight weep from the head gasket. Assuming that there is no fault with the head and the best case scenario is just a straight replacement any ideas what a recognised Laverda shop would charge, how much labour involved. I assume the part is cheap enough.

This is just a hypothetical question, as present I am Laverda(less) though the Sf on eBay looks nice
Click to expand...

Piets advise is excellent..use it!

[size=10pt][size=10pt][size=10pt]When re-torquing, you should first slacken off the nuts, one at a time. 

You'll probably also find conflicting torque values.
I use 22Nm for the outer M8 studs, 28Nm for the long M9 studs through the cam bearing blocks and 32Nm for the short M9 studs.  The M7 studs each side take 15Nm.  Most manuals state considerably higher values, but I've found my figures to cause less strain on studs and casing threads and result in an oil-tight seal nevertheless.

HTH,
piet[/size][/size][/size]
 
Guys,

Thanks for the advice. I had seen a bike with a slight weep from the head, I was considering buying.  Given I am no Gerry Burgess with spanners i walked away not knowing if it was a simple thing or possible a typical 80's bike with a cylinder head fault.

So my search for another Laverda continues (over and above the one I am currently after). Will have to make do with my 'umble Hinkley Bonneville when she comes back from the tuners (aka Bob Farnham), for my two wheeled thrills.
 
Weeping head gskets are usually caused by the cylinder liners standing slightly proud of the cylinder gasket surface.  Unfortunately, this is a result of the many temp. cycles the cylinder has gone through in its' life, the alloy has shrunk a wee bit.  Not an easy fix, either on a milling machine with a turntable or removing the liners and machining the retaining spigot a bit.  This should only be done if the cylinders are to be re-bored afterwards, no way they can be replaced and remain as true as they were before.  The liners need to be at least flush with the sealing surface, better still would be a recess of 0.1-0.2mm to give the gasket a little space.  This results in even pressure on the gasket over the entire face.  If the liner stands proud, the gasket seals perfectly around the cylinders but is missing pressure on the oil sealing surfaces.

Simple re-torquing seldom gives the desired results, only strains the gasket and studs further.

piet
 
Paul Marx said:
A slight weep won't keep you from using it.
If it works, don't touch it.
Ciao
Paul
Click to expand...

+10,

wait for winter ; )

In the mean time check compression
check torque of cylinder head nuts ( bearing in mind Piet's advice )
check compression again.

No probs ?.....ride and enjoy

I have read that a little weep is quite typical on Jotas ??

rgds
joe
 
Quite often a leak that manifests itself as a drip from the front external stud is caused by a crack in the head where the two thin portions meet in the middle - this then weeps along and forward to this stud due to the natural cant of motor. Have known many owners replace head gasket to be met with the original leak again. It's a relatively simple job to repair for someone with good TIG skills - Regards - Phil
 
and of course can be a poorly sealed exhaust pipe, which causes a minor leak, with oil being drawn down the exhaust valve guide, and then puddling on a fin, and getting blown back (uphill) along said fins to the side of the block.
CLEM
 
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