Oiling Problem

Information relating to the Matchless G11 or AJS Model 30 600cc twin
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Oiling Problem

Postby freddie 136 » Tue Jun 23, 2009 7:36 pm

Hello, thanks again for all your information,just to set the record straight, the bike has not covered 500 mile at 30 mph,its done approx 35mile at 35-40mph with out letting the engine labor just nice gentle running seen as i have replaced all the bearings on the crank as wll as having the rebour and new pistons and rings. The pistons are from Jampot spares as was most of my other new parts,bearings etc, and there was no information in the box with the pistons, the person who built the engine back up is a friend who has built many engines including his own race engines.cheers Fred.

Edited by - freddie 136 on 23 Jun 2009 7:37:43 PM

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Oiling Problem

Postby itma » Tue Jun 23, 2009 9:04 pm

Freddie, I wasn't inferring that you had done 500 miles at 30 mph, what I said was that too many folk have that fixed idea.

the standard norm for bike aircooled engines used to be regarded as 0.002 inch of bore
Thats per inch of bore not actual clearance, so on a 3inch bore it would be 0.006 and thats measured fore and aft not at the sides.
I ask reborers to use 3 thou per inch, and accept perhaps a little more oil consumption.

Probably JSL wont give a recommendation from fear of todays blame culture, 'my bike siezed so its all your fault type of thing.'
They have no control over what happens to it as it leaves their stock.

I bet your friend wont use such tight bore tolerances on his race bikes?

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Oiling Problem

Postby paul knapp » Wed Jun 24, 2009 1:45 am

I think that the bottom line to Freddie's problem, is that his .003" clearance is too tight! Best to lift the barrels and have them honed out a little more to....?
If/when you do this Freddie, you will have to check the ring gap, as this will be larger.

My M20 twin has .005" skirt clearance using JP pistons, rather rattly on cold start, but soon quietens down after a couple of minutes running.
I have just had my Triumph barrels bored last week,and the 'expat' motorcycle engineer gave them .004" piston clearance, of which he assured me is OK since I am using original Triumph N.O.S. pistons.
From my Modern Motorcycle Mechanics book, by J.B. Nicholson, he specifies for a 600cc - 650cc twin, a clearance of .0045" for solid skirt pistons. (unknown manufacturer)

Paul
___ďAs a hobby for the technically minded, motorcycling provides great scope.Ē

J.B.Nicholson

Don't worry about the world coming to an end today. It's already tomorrow in Australia!


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Oiling Problem

Postby itma » Wed Jun 24, 2009 10:59 am

I can't emphasise enough that the piston clearance relates to the width of the bore
ie xx thou per zz inch of bore.
so on a Triumph bore of around 3 inch that would need 6 thou.
slack but happy...Triumphs go faster the more they rattle.

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Oiling Problem

Postby freddie 136 » Wed Jun 24, 2009 7:28 pm

Thank you every one for all your input, i really appreciate your answers to my problem. I am going to take the barrels off as soon as possible and have my friend hone them out a little using [ itma's] 2 thou,per inch of bore, and at the same time i think i will replace the oil pump with a referbed one, i will let you know what the outcome is when the job is complete,cheers Fred.

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Oiling Problem

Postby SPRIDDLER » Mon Jul 06, 2009 5:34 pm

quote:

I will email JSL asking for clarification with regard to clearances for their GPM pistons ....


In case you're holding your breath; I'll pass on any info as soon as I receive a reply to my email of June 23rd...
I poke badgers with spoons.

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Oiling Problem

Postby freddie 136 » Tue Jul 07, 2009 9:09 pm

Hi, when i enquired last week they passed me on to T.N.L,engineering for piston/bore clearance,the chaps their where helpful but could not get any further than one to two thou extra per rebore than normal depending on if you have the latest stock of pistons from JSL, TNL say that the latest stock is giving them problems, how do you know if you have the latest stock,don't know that, but i went with the view that i had the latest stock,so had the rebore done to 6 thou, should have it running time permitted in a couple of weeks. Could not find any problems with the oiling system [no gasket glue any where near the oil ways]had the oil pump off cant see why it would not work properly,did not seem damaged or warped in any way,so put it back with a new pair of gaskets on pump face,don't think it can pull any air. The two other gaskets for the pump where the wrong type, these came out of a full engine set that i got from JSL plus some of the other gaskets where of poor quality in my opinion.
cheers Fred.

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Oiling Problem

Postby itma » Tue Jul 07, 2009 10:38 pm

Our late and much missed Biscuit was a fervent advocate of make your own gaskets.

As for clearances in the lack of precise knowledge its best in my view to err onthe side of slack rather than tight.

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Oiling Problem

Postby alanjennings » Wed Jul 08, 2009 5:57 pm

A chap at "Heart of England"has had the same rebore problems!! I agree with "Itma" {for once!!-only joking11} plenty of clearance is better than too little!! If it doesn't rattle, something is wrong!!
Alan [Morini] Jennings

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Oiling Problem

Postby freddie 136 » Sat Jun 12, 2010 2:00 pm

Hi,i am having a problem with oil pushing out of the timing case where the dynamo fits in. I thought at first it was a poor cork washer and not a very good bolt that goes through the timing cover to the dynamo,but i recon i have fixed both and it still is leaking.My bike is a 1958 G11 600 twin, i had new bearings, pistons,and a 20th rebore late last year and after reboring the cylinders a little larger [some of you might remember the topic] all has been well i had a new gasket set fitted along with a new filter. I have done about 1800 miles running her in with no problems, and use SAE 50 oil.So all of a sudden i get this oil leaking from where the dynamo fits to the timing case, i have hade the dynamo off and there was oil in the dynamo cleaned it up tried again and after approx20 miles all was o.k. after 30 miles there was a small run down the engine casing and after 50 miles what looked like a few small runs down the engine and oil in the well that the dynamo sits in, The oil does not leak till after about 20 miles Can any member enlighten me please. thanks in advice Fred

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