Valve Stem Seal Replacement

[seb421]

Works mechanic is adamant its the stem seals that's worn, leaking oil from the cams / valves and down through the stem seals and into the cylinder hence the smoke on start up

Got him to follow me down the road while i opened it up to see if it was smoking on the throttle etc, no sign of it on the gas just predominantly on start up

ill get a comp tester at weekend and check the comp too as suggested.

Other than a Valve Spring Compressor is there any other tool I'm going to need to buy

Can the seals on front and and rear cylinders be done in place or will i need to drop the engine out again

Ill take pictures along the way and post her when done for those that have not done this also.

Thanks

[carmanbikes]

Works mechanic is adamant its the stem seals that's worn, leaking oil from the cams / valves and down through the stem seals and into the cylinder hence the smoke on start up

Got him to follow me down the road while i opened it up to see if it was smoking on the throttle etc, no sign of it on the gas just predominantly on start up

ill get a comp tester at weekend and check the comp too as suggested.

Other than a Valve Spring Compressor is there any other tool I'm going to need to buy

Can the seals on front and and rear cylinders be done in place or will i need to drop the engine out again

Ill take pictures along the way and post her when done for those that have not done this also.

Thanks

Hi what mileage has it done im rebuilding one at the moment and wonder is it worth doing the seals as the head is off,Cheers Lee

[seb421]

42k mate

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[seb421]

Spends a lot of time in winter stood in freezing weather at work so don't know if that will accelerate any wear on internal perishables?

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[VTRDark]

You don't need to drop the engine Seb, but heads will need to come off so you can get the spring compressor on and remove the valves.

Keep the valves, springs and the collets that hold the valves in place in the order they came out. Get yourself some cardboard to poke the valves through and number them so you don't get them mixed up. While the heads are off give it all a de-coke and get rid rid of all the carbon off the tops of the pistons and on the heads etc. When putting it all back together you my want to lightly grind the valves back into the seats. Just get one of those stick type things that look like they have a plunger on the end, a bit of valve grinding paste. It should only cost you fiver for that! And roll it between your hands on the head of the valve with it loosely back in with a little paste around the seat. Only go lightly though just to get rid of any pitting that may be around the seats and valves. Give the top of the block and the base of the heads a good clean with some wet n dry to get rid of any old gasket stuck on there.

Carmonbikes if you have it all apart you may as well change them as they are cheap. They are only rubber seals with a little coiled wire inside the circumference of them that pop over the valve stems and onto the head.

(:-})

[seb421]

Cheers Carl was hoping to be able to just remove the cams and get at them with the heads still on, didn't want the hassle of taking heads off, gutted

I'll have a look at the bits I'm going to need when I get it in from work tonight

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[lloydie]

And don't use wet&dry on the gasket faces as you will fook it up !

[VTRDark]

Cheers Carl was hoping to be able to just remove the cams and get at them with the heads still on, didn't want the hassle of taking heads off, gutted

It depends on your valve spring compressor. The only ones I have used are shaped like a big C and one end sits on the valve head and the other on the springs at the the other end. But what's to stop the valves falling out once you remove the springs with the heads in place.

I think some 180/240 wet n dry would be fine Lloyd to get the most off and then go onto 320. It's better than using a blade where there's a chance of it cutting into and scoring the soft ally.

(:-})

[tony.mon]

Cheers Carl was hoping to be able to just remove the cams and get at them with the heads still on, didn't want the hassle of taking heads off, gutted

It depends on your valve spring compressor. The only ones I have used are shaped like a big C and one end sits on the valve head and the other on the springs at the the other end. But what's to stop the valves falling out once you remove the springs with the heads in place.


(:-})

You maybe could if you set the piston to tdc, then compress the top spring plate (like a big washer) down far enough to release the collets.....
But probably it would all go horribly wrong, tbh.
For the cost of two head gaskets, just do it properly.

But for getting nice flat head mating surfaces, use some valve grinding paste on a sheet of plate glass.
It'll wreck the glass, but the head will be perfectly flat.

[bsabloke]

Not tried this, but heard from someone who has.
Use some thin rope. Remove plug, set piston just below top. Stuff a measured amount of rope into plug hole. Tie off end of rope. Turn engine pushing piston to top. Compressed rope holds valves up.
Not sure if i would do it myself, maybe if needs must. Make up your own mind!
Richard

[popkat]

There is a tool that can compress the spring so you can get the collets out with the head on, It's combined with air in the plug holes to keep the valves shut, can't remember what the tools called but guess it won't be cheap and you'll need a compressor for the air.

Engine tuners will say you shouldn't lap the valves in with grinding paste but should get the seats properly cut. If you do use grinding paste you twizzle (cracking word, lol) the stick back and forth then lift it up, turn it a bit twizzle again, turn and so on, this is so you do it evenly.

Use gasket remover and a stanley blade to clean up the mating surfaces of the head and barrels, but scrape the blade away as you don't want it digging in, then some fine wet and dry lightly just to finish up, if you have a slight lump of gasket at this point don't go at it with the wet and dry go back to the blade, be careful.

[VTRDark]

If you do use grinding paste you twizzle (cracking word, lol) the stick back and forth then lift it up, turn it a bit twizzle again, turn and so on, this is so you do it evenly.

I couldn't have explained that better myself. Nicely put. Twizzle Iv'e not heard that before.

[youtube][/youtube]

I've also done it with a bit of masking tape around the stem of the valve and a drill attached on low speed. Makes it easy keeping it square on and pushing it in and out. I'm not sure I would recommend that though.

(:-})

[bluestoesonnose]

If your only smoking on start up I'd forget about it, if it's smoking on over run then I'd be a little more interested. I have changed stem seals by blowing compressed air into the cylinder and using a very special Vv compressor. This was on a marine engine and to be honest it was a pain in the @$$.

I'd wait until the guides start to wear and then whip the heads off, do the guides and seals at the same time. Or if you're a little more anal, buy a second pair of heads, go mental on them (flow them, new Vvs, three angle Vv seats, bumpier sticks, etc, etc) and then fit them on a rainy Sunday in the winter, a set of cans, free flow filter (you can have a modified air box ready to go as well) and then a re-jet on a dyno the weekend after.

Anyway, back to the SV, where did I put the polish? Matron, I think the tablets are wearing off..

[Pete.L]

Just a thought!
If you remove the carbs and exhaust could you hold the valves stems in place by going in through the ports? Might save taking the heads off. Mind you, you'd probably need a really fat mate to come around and press the springs down whilst you've got your fingers down the ports

Pete.l

[VTRDark]

you'd probably need a really fat mate to come around and press the springs down whilst you've got your fingers down the ports

Either that of very long and strong fingers to reach and hold against the pressure of the springs.

(:-})