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Monty 247 cylinder removal

Posted: Sat Aug 25, 2018 7:33 am
by Glen N
Hi,

Novice question, restoring a Montesa 247, removed head and now trying to remove the cylinder. Having a little trouble, tried gently tapping and it hasn’t moved. Keen not to destroy it.

What’s the best way to remove the cylinder? I don’t want to remove the bore liner.

From what I understand there is only 4 locating studs that hold it on, do I have to split the crankcase.

Be nice if a manual existed!!

Thanks in advance

Re: Monty 247 cylinder removal

Posted: Sat Aug 25, 2018 9:28 am
by David Lahey
With the head is off, have a look down the holes that go through the fins and you should see four cylinder nuts, one in each hole. They are 7mm internal hex.

Manual available here
http://southwestmontesa.com/manuals.html

This is what the nuts look like
https://www.inmotiontrials.com/product/ ... -set-of-4/

Re: Monty 247 cylinder removal

Posted: Sun Aug 26, 2018 11:01 am
by Glen N
Oh excellent thanks, now I see them and now they appear seized. I can’t budge them for love nor money. I’ve sprayed some wd40 down so might see if this helps.

Re: Monty 247 cylinder removal

Posted: Sun Aug 26, 2018 6:54 pm
by outforfun
If you have seized bolts.

Spray WD40/RP7/Yield/your favorite possum pee on it. Let it soak in for a day or two if you can and keep spraying it, wet with spray is good. Give it time to soak in and help you.

If you can get a impact socket on the head or an inhex into it, grab a cheap impact screwdriver (supercheap - or expensive auto and yard stuff sell them) take the screwdriver attachment off, their either 3/8" or 1/2" drive usually put in your impact socket, check direction of operation and give it a good tap. It can loosen seized bolts without using the 3/4" drive rattle gun on it.

Good luck with it mate.

Re: Monty 247 cylinder removal

Posted: Wed Aug 29, 2018 11:20 am
by Terryg
Perhaps get a small chisel and try and split the nuts.

Re: Monty 247 cylinder removal

Posted: Wed Aug 29, 2018 7:18 pm
by Rod
They are not a hex nut that you can get to with a chisel, they are a cylindrical nut that takes a 7 mm allen key as others have stated. WD 40 etc down the hole and then a set up like this should do the job..............
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Re: Monty 247 cylinder removal

Posted: Wed Aug 29, 2018 8:01 pm
by David Lahey
Rod wrote:They are not a hex nut that you can get to with a chisel, they are a cylindrical nut that takes a 7 mm allen key as others have stated. WD 40 etc down the hole and then a set up like this should do the job..............


Ooh yeah that looks the goods Rod
I remember doing a Cota 348 motor and didn't have a 7mm internal hex drive. I ground an 8mm drive down and it worked a treat. Still have it (ready for the next one)

I'm waiting for the questions to appear about removing the gearbox sprocket and removing the primary drive pinion 8) :montesa

Re: Monty 247 cylinder removal

Posted: Wed Aug 29, 2018 9:03 pm
by Rod
Yeah your right David, pulling a Cota apart is not straight forward, not only do they have those bloody 7 mm barrel bolts, you then got to deal with the stuff fitted on tapers. Fun times ahead for some.

Re: Monty 247 cylinder removal

Posted: Thu Aug 30, 2018 5:04 pm
by Glen N
It’s killing me this thing, so far I’ve soaked in wd40 for the last 4 days. I’ve got a 7mm hex with breaker bar, no joy, impact driver on 7mm hex, no joy.

I’m thinking my next option is poor petrol on it and light a match.

Thanks for the feedback though,it has been helpful.

Dumb question it isn’t a left hand thread?

Re: Monty 247 cylinder removal

Posted: Thu Aug 30, 2018 6:05 pm
by David Lahey
No it's right hand thread.
Temperature cycling is a good thing for this situation. The differential expansion of the metals helps things to move.
You have probably already tried tightening the nuts but if not, that can help too. Any movement in either direction will help your situation.
Don't despair, if you can't remove the nuts the normal way they can always be drilled away along with the studs and new studs fitted once you have it apart
Another thing I just thought of is to make a soft (brass, copper or aluminium) drift small enough to fit down the hole through the fins and give the nuts a touch-up. This can help loosen the thread because an axial impact takes some load off the thread momentarily and by using a flat ended soft drift, you will not damage the internal hex