Tappets on G2

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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Tappets on G2

Postby davehutch » Tue Jul 29, 2008 12:10 pm

When i set my tappets it said to set piston at TDC and set so rods turn but no up and down movement with engine warm. I have done this but when I turn engine over rods become loose untill TDC again. Is this right ?
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Tappets on G2

Postby itma » Tue Jul 29, 2008 2:29 pm

TDC on firing stroke?

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Tappets on G2

Postby davehutch » Tue Jul 29, 2008 3:44 pm

Not sure seemed to be the same every time piston was at TDC. It starts first time every time when cold but then starts to back fire spit and then cut out. Then have to wait for a while before it will start again.
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Tappets on G2

Postby davehutch » Tue Jul 29, 2008 4:03 pm

At TDC Both valves closed push rods can be turned but no up and down moverment. Then as you go through the cycle one rod goes up oppening valve as the other drops making that rod loose. Is that right ?
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Tappets on G2

Postby SPRIDDLER » Tue Jul 29, 2008 5:28 pm

quote:

At TDC Both valves closed push rods can be turned but no up and down moverment. Then as you go through the cycle one rod goes up oppening valve as the other drops making that rod loose. Is that right ?



"loose"? or do you mean without any up and down movement?
Either way.....
The first rod going up after TDC on the firing/compression stroke should be the exhaust valve opening. Not sure about "the other drops making that rod loose" bit though, that pushrod should already have been 'down' (inlet valve closed, no discernable up and down movement) if coming off the compression stroke.
At no point in the cycle should there be any greater up and down movement on either pushrod than that which existed when you adjusted them (i.e nil discernable movement), provided that you have set the valve clearances with the piston exactly at TDC on the firing/compression stroke.
It is important to realise that the piston must be EXACTLY at TDC on the FIRING stroke since the cams which operate the pushrods have 'quietening' profiles which means that the bottom ends of the pushrods stay largely in contact with the cams at all times, not just when they are lifting/operating the valves.
Bruce and the spider stuff, eh?
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Tappets on G2

Postby davehutch » Tue Jul 29, 2008 6:36 pm

Some thing very wrong then!!
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Tappets on G2

Postby SPRIDDLER » Tue Jul 29, 2008 7:51 pm

quote:

Some thing very wrong then!!



If it has been running o.k. and you've not had the cams out there can't be much wrong. It must be something simple:
Which valve is closing (pushrod descending) in your previous scenario? I looks to me that if one valve is closing (poss exhaust) and the other one is opening (inlet?) you are at or near TDC on the INDUCTION stroke, although in reality the inlet normally begins to open just before the exhaust has completely closed.
Double check that you really are observing the pushrods at TDC on the firing stroke.
Are you turning the engine in its normal direction of rotation when observing the pushrod movements? (My special subject; stating the b******g obvious).
I sense a slap on the forehead moment coming up.Doh! We all 'ave 'em
Your local AMOC section chaps can assist but you haven't indicated where you are.

Edited by - SPRIDDLER on 29 Jul 2008 8:08:02 PM
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Tappets on G2

Postby itma » Tue Jul 29, 2008 8:04 pm

use the rear wheel in 4th gear to turn the engine, when finding tdc.
watch the points, they will be open onthe firing stoke, closed on the TDC which ain't.

If it is not yet clear, there are two TDC in the 4 stroke cycle, on only one are both valves shut.

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Tappets on G2

Postby davehutch » Tue Jul 29, 2008 8:28 pm

The problem is I am at**t it runs alot better when you do the tappets right. Thanks for your help!!
Its running a lot better but is still uneaven (i think carb) any way wife won't let me start it now because of kids next door. shell try tomorrow. And next week goining to my local meet hope i will get some help.
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Tappets on G2

Postby davehutch » Tue Jul 29, 2008 8:47 pm

Its been a long time since i played with bikes. My other bike is a 1200 bandit doesn't need any thing doing to it . Thats why i got this and lookin forward to it. It sounds great when it is running
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