Using Loctite/Silicone on the Top End Gaskets

[Gazbo72]

Just wondering it is better to use something extra on the gaskets like loctite or silicone when rebuilding the top end.

If so what do you use ???

Gaz.

[drunkmunkey6969]

Yamabond/Threebond.

[WINTERMODEL150]

I use loctite 5910 or 5920 Halfords sell them ,or as suggested by drunken monkey .

Dean

[wack 63]

Or this http://www.ebay.co.uk/itm/Wellseal-Gask ... 20cabe28a4. Never had a problem with it and easy to clean off.

[Gazbo72]

Thanks for the above info guys.

I found some Loctite in the garage. The front sticker was all worn off so took a punt It was orange and gooey .
I am sure it was gasket sealant from the last engine build. I put a thin bead on both sides of the base gasket a tourqed it all up and left to cure.

Checked the squish and got between 1.5mm and 1.8mm. I didn't put any sealent on the top gasket as I wasn't sure the squish would be okay. I am two minds to leave the top gasket with out sealant as the squish is right. Does any one else not bother with out any thing apart from the gasket to seal it. It is a 200 alloy barrel with a steel liner kit withan alloy 1mm gasket.

Gaz.

[rosscla]

Things like loctite have a shelf life. You need to watch the exp date. Some use it on the head particularly if lapping the head for use without a gasket

I use hi temp silicone on both base and head, even put some on the spigot.

You need to be careful with the head and try to ensure not to get the stuff in the bore, especially if it's loctite...

[Darrell Taylor]

ive found the problem with many motors and lambretta engines(in the limited time ive worked on them)is the crankcase base gasket surface is regularly untrue and in need of skimming and many of the cylinders are the same some are as cast and have not even been machined then on performance top ends the 4 stud fitment isnt really up to the job so as a result of the above i find the use of a sealant with good gap filling properties is needed if none of the above are being sorted out,i recommend loctite 5900 or 5910 as its been my sealant of choice for around 10 years now and never fails to impress me,approx 5 wks ago i had a stud pull on a mates 34bhp rb with fairly high compression and as a short term repair to get him home sealed the head down with this as i normally do but this time applied a thick bead around the outer edge and left to cure for a few hours,a few days ago he got round to stripping the motor after regular use to find it had held tight on only 3 studs!
ive recommended this to many people who have been amazed with its performance
Use sealant on everything to do with top end / crank housing,most see it and consider it a bodge but until youve carried out leakdown testing on a regular basis and get fed up of stripping a motor down to seal it airtight only then do you realise it warrants doing first time
ps the loctite is not marked as been fully petrol or oil resistant on the packaging but in use ive found it to be one of the only ones that actually is

[drunkmunkey6969]

I only use the 5910 where a gasket is also in use, and yamabond for gasketless metal-to-metal contact....for exactly the same reasons as noted above.

So for example I might use 5910 and a base gasket at the bottom of the cylinder and yamabond at the top on the cylinder head with no gasket.

I also use threadlock on various studs/nuts, and retaining compound on crank pins and some bearings (rear hub for example).

[Gazbo72]

Picked up some loctite 5920 today. Its got me thinking is it worth stripping the top end, getting a new base gasket and starting again. Just in case the old loctite goo was out of date. Or not fit for the job. Engine is still on the bench, So i suppose it is easier to do it now rather than it failing once it is back in the scooter.

The old loctite was in a bottle about 4 inchs high and has like a bellows for squeezing the orange goo out.

Gaz.

[Tom Russell]

The old loctite was in a bottle about 4 inchs high and has like a bellows for squeezing the orange goo out.

Gaz.

That sounds like Loctite 574, which was recommended to me and I used on my Dave Webster Group 4 engine to seal cylinder head to iron barrel (which by the way was a work of art)