Leaking Base Gasket

[nicos]

hi everyone!

11 280 raga with about 10hrs gentle riding has a leaking base gasket front right area behind water pump.

removed water pump and checked barrel nuts but cannot tighten enough with an open end 13mm,

is there a special tool?

they seem tight,shall i replace gasket or leave as is?

it is only very slight leak and saw it cos i was riding in dusty conditions.

pls advice.

thanks!

[tankygsy]

1/4" or 3/8th" drive torque wrench with a 'uj' (wobble joint) will tighten it down no problem. You need to remove the coolant hose fitting with (if my memory serves me right a 10mm Allen key) to get access to the cylinder nut.

A spanner is pointless anyway cause you can't torque it correctly.

I'd try and retorque it down first then if leak persists I'd replace the gasket.

[nicos]

thanks for that info!

was gonna try tightening but for some reason cannot get a socket on the front right nut.

i thought maybe there is a special tool for it.

i removed the water pump but with the hoses still on just to get them out the way.

will try again next week and see.

thanks again!

[hrc1]

Keep an eye on this, a few suck the gasket in...........So I'd change it. Also I'd change to the thicker one.

[nicos]

i moded a 13mm spanner today and tightened them but still leaking,the front right needed half a turn which was strange.

gonna park it up till the gasket arrives from trials uk.

which size gasket do you think i should use ?

thanks !

[tankygsy]

To find that out you need to measure the 'squish'. This being the distance between the top of the piston and the inside off the combustion chamber at the perimeter (outside edge of bore).

See:

http://www.trialspartsusa.com/diagrams/Squish.jpg

The norm is to fit the head complete with combustion chamber cap and o rings, screw it down via the cylinder nuts, but not too tight (finger tight is fine). Put a pea sized blob of blue tak or play doh on the edge of the piston and rotate the crank until the piston passes TDC. If it feels really tight your blob of blue tak is too big, don't give yourself a hernia like!

Take the head off again and the blue tak will be squashed.

Use a vernier calliper if you have one to measure it while it's still stuck to the piston (if you lube the combustion chamber earlier it will be) or if you're carefully peel it off and measure it. Record your measurement and repeat a couple of times untill you can repeat the results for accuracy.

With the base gasket fitted the stock setting is a squish of 1.25 - 1.50 mm.

For instance If your blue tak measures 2.15mm then a cylinder base gasket of 0.80mm will put it round about 1.35mm and inside the ball park I.e:

2.15 - 0.80 = 1.35mm

If the blue tak measures 1.85 then a 0.50 mm base gasket will be about right I.e:

1.85 - 0.50 = 1.35mm

Etc etc and so fourth.

Edited May 21, 2012 by tankygsy

[laser1]

You can measure the squish or just replace it with the same thickness (or thicker) that you take out.

[nicos]

update.

i replaced the base gasket with a newer version i got from trials uk,it has a silicon bead so suppose it seals better.

problem was the front right stud was loose cos the threads were gone in the cases,magnesium is too soft i suppose,had to helicoil,used loctite on all 4 and torqued them down.there was a bad sealing from the reed block manifold also so sorted that too.

runs nice now,had me swapping needles and clip positions for ages !