G80CS... and the saga continues

Information relating to the Matchless G85 500cc Heavyweight, AJS 7R, Matchless G45 and Matchless G50
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Re: G80CS... and the saga continues

Postby ajscomboman » Tue Sep 18, 2018 10:55 am

Right the mag is definitely a comp one and pulling the lever pulls the cam ring upwards retarding the ignition, ie it rotates the ring in the direction of the arrow which moves the start of the cam ramp away from the heel of the points fibre foot. If it leaks from the head when a copper gasket is being used then I'd suggest you also remove the barrel and lap the head to the barrel with grinding paste to ensure both surfaces are a good fit. Thorough clean down to remove the grit and then anneal the copper gasket for re-use. When setting the ignition it's best not to loosen the mag sprocket as the book advises but pop the exhaust cam sprocket off its taper instead.

First pop the exhaust cam sprocket off its taper. So starting with the basics for timing (forgive me if I'm appearing to be patronising) bring the piston to the firing stroke TDC. Insert your rod in the plug hole and mark it at a convenient point. Remove and remark 7/16th or 1/2" higher up the rod insert again and rotate engine backwards in gear. Go back further than the mark on the rod and then slowly bring the motor forward until it reaches your mark that you put higher up the rod. That's your advance timing mark point. Go round to the points side of the mag and rotate till the points heel is just about to open the points ( a mag timing light is really useful for this as it saves using the fag paper method). Once you've established the opening point go back round to the exhaust cam which you loosened. Put a large socket onto the cam sprocket face and gently give it a tap to put the sprocket back onto the taper ensuring that you didn't move either the motor or the mag sprocket. Then lock it up.

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Re: G80CS... and the saga continues

Postby ajscomboman » Tue Sep 18, 2018 11:01 am

As clanger has mentioned, if your CS doesn't kick back like a mule if you try to start it on full advance then your timing isn't correct. I have many a scar on my bloody right leg where the buggers have bitten me coz I didn't retard them far enough first before attempting to start them.

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Re: G80CS... and the saga continues

Postby Matchymarty » Tue Sep 18, 2018 7:33 pm

Clanger:
Thanks for the descriptive clarification. I think I understand now.
That being said, what with all the oil in the top end and combustion chamber, fouling the plug, would one say fuel/air mix is burning completely or not?

Also, have we not established that my bike may well be actually 'Too Advanced' given that I have to retard it, say around 1/3 or there abouts of the lever travel to find the 'sweet spot'?

I definitely will try without the silencer. Once I pull the head and clean it up, and make sure the valves are seating now, after the weekend's 3 near siezures.

Does it kick back? Yes and no. It's hard to start. Always has been. I've just finished rebuilding my short stroke and it starts first pop. If it doesn't, it sends your leg to the moon.
THIS bike, is hard to start. Doesn't really matter if I tickle or not, the action of the kick starter is 'stiff' and draggy and i'm not sure if thats gearbox/clutch/ or engine related. Though, the piston does not seem to run up and down anywhere near as freely as my short stroke.

That said, without fail, if I start it like as if it's flooded, (ie, with a hand full of throttle and the fuel tap turned off) It will fire my leg half way to the moon. Not as violently as my short stroke, but it does kick back yes.

AJSComboman:
Thank god. Yes, you are correct, when you pull on the lever, the ring rotates as you say, clockwise.
When I time my Matchy's, I use exactly your method, so yes, I believe I am timing the bike correctly.

So, I'm wondering, how the oil fouled plug affects combustion burn and therefore timing.? I would think, that if the plug is fouled, it is NOT completing the burn, resulting in less power. But how does this affect timing and also heat?

I will try and pull the head off this evening when I get home. It's now 5am here in OZ. ;)

Cheers guys for your continuing support.

ajscomboman wrote:Right the mag is definitely a comp one and pulling the lever pulls the cam ring upwards retarding the ignition, ie it rotates the ring in the direction of the arrow which moves the start of the cam ramp away from the heel of the points fibre foot. If it leaks from the head when a copper gasket is being used then I'd suggest you also remove the barrel and lap the head to the barrel with grinding paste to ensure both surfaces are a good fit. Thorough clean down to remove the grit and then anneal the copper gasket for re-use. When setting the ignition it's best not to loosen the mag sprocket as the book advises but pop the exhaust cam sprocket off its taper instead.

First pop the exhaust cam sprocket off its taper. So starting with the basics for timing (forgive me if I'm appearing to be patronising) bring the piston to the firing stroke TDC. Insert your rod in the plug hole and mark it at a convenient point. Remove and remark 7/16th or 1/2" higher up the rod insert again and rotate engine backwards in gear. Go back further than the mark on the rod and then slowly bring the motor forward until it reaches your mark that you put higher up the rod. That's your advance timing mark point. Go round to the points side of the mag and rotate till the points heel is just about to open the points ( a mag timing light is really useful for this as it saves using the fag paper method). Once you've established the opening point go back round to the exhaust cam which you loosened. Put a large socket onto the cam sprocket face and gently give it a tap to put the sprocket back onto the taper ensuring that you didn't move either the motor or the mag sprocket. Then lock it up.

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Re: G80CS... and the saga continues

Postby clanger9 » Tue Sep 18, 2018 7:51 pm

Petrol combustion is “explosive” - it either ignites or it doesn’t. In other words, it either fires or misses (unlike a diesel, where incomplete fuel “burn” is an ever-present problem).
Your oil-fouled plug would normally cause a misfire, though if you get enough glowing carbon on there it could start to preignite like hell. It would run horribly at that point (if at all).

Too advanced will also cause hot running/lack of power (for similar reasons to retarded running, ‘cept the combustion pressure peak arrives to early for the force on the piston to turn into maximum torque), but normally you’d hear it knocking/pinking and your spark plug would look very different.

The oil contamination is a worry, but you have so many issues with this engine it’s hard to tell if it’s a cause or a symptom!!

I guess you need to strip it (again) and build it up with everything as *standard* - jets, timing, plug, everything. Then you can work from there...

Good luck!
1966 AJS Model 14 250 CSR "cafe racer"
1993 Ducati 750SS

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Re: G80CS... and the saga continues

Postby Matchymarty » Thu Sep 20, 2018 7:33 am

Ok, so I've pulled the motor down.

I'm getting good at this, so didn't take me long!

Observations:
1. Head gasket ok.
2. Exhaust valve is slightly warped and seat area is covered in crap - hence lack of compression over the weekend.
3. Photos tell the rest of the story.
4. Inlet valve stem 0.3725" - Inlet valve guide @ top :0.3765" = 4 thou" wear. (I don't have tools to measure bottom of guide.
5. Exh. Valve stem 0.3725" - Exh. valve guide @ top : 0.378" = 5.5 thou wear.

I'm guessing this is where my issue is. Oil going everywhere and you can see from the piston crown and valves, that there is HUGE amounts of carbon and crust. This was cleaned up around around 500 miles ago.

I'm guessing i'm up for a rebore and +60 piston, and a head job. Not of the 'nice kind'. Also, As my exhaust valve is warped and quite thin, I'm guessing I'm up for a new valve.

So looking at this... can we conclude that OIL in the combustion chamber is my issue affecting power, heat, and ultimately reliability?

Note: You'll see in the bore an oval indentation. I'm expecting this is left over from previous nip up, and subsequent HONE did not take it all out for fear of taking too much out and requiring next size piston.

Looks like I"ll need to take it to next size this time. Piston #5!

M

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Re: G80CS... and the saga continues

Postby Matchymarty » Thu Sep 20, 2018 7:35 am

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Re: G80CS... and the saga continues

Postby Matchymarty » Thu Sep 20, 2018 7:37 am

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Re: G80CS... and the saga continues

Postby ajscomboman » Thu Sep 20, 2018 4:07 pm

Now we're getting somewhere. The barrel appears to be like a ploughed field and definitely will need a bore and new piston. The head requires an overhaul. The valve guides are clapped out, the running clearance I'd expect would be 1.5 thou inlet and 2 thou exhaust, you're double that and more plus the valve seats definitely want re-cutting after new valves and guides are fitted. Also the head gasket shows oil around one of the studs but not the other 3, is that just by accident or was it leaking from there. The rocker box is either cracked or the gasket has gone as the oil looks to have been pouring out from there as well.

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Re: G80CS... and the saga continues

Postby clanger9 » Thu Sep 20, 2018 4:11 pm

Your valve seats are completely gone. No wonder it wouldn't pull, it has no compression...
Sounds like the guides are u/s as well, hence the oil everywhere. Definitely needs a head job & a rebore!
1966 AJS Model 14 250 CSR "cafe racer"
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Re: G80CS... and the saga continues

Postby Matchymarty » Thu Sep 20, 2018 6:55 pm

Thanks Guys.
I was wondering about the valve guide clearances.

The rocker box has a couple of hair line cracks in it, but does NOT seem to leak.
The oil around the plug and on the fins above the plug comes out of the plug hole and mostly is a result of those long pulls up hills.

AJSComboman: Yes, very observant of you! You're right. There apears to be oil leaking from the head gasket at the rear/near side barrel stud. Now that you point that out, I'll investigate further. I use a torque wrench when doing up the bolts, so it is not that. Perhaps the head is not flat on the underside, so I'll have to get that addressed.

For reference, whenever I go up big hills or, 'get after it' a little on a ride, oil ends up on the fins from that near/rear bolt area. My father in law says "aaaah marty don't worry about it, just bloody ride it, it's nothing... at least you know it's getting oil!".

This is the advice I get most of the time. ! It's hard to learn with advice like that!

As for the bore, well, it looks a lot worse than it feels. I'd say the scoring is from this weekend's nip up, but it's actually not that bad. Should have seen it when i nipped it up at the previous rally, when the top ring stuck in the piston groove! I honed it by hand in the paddock and ran it another 120 miles the next day! ahahahah (hence the hollow mark in the bore now.) Either way, I'm up for a +60 or ANOTHER Re-sleeve.

I've found some information that says :
1. Valve stems should be 0.0375" (in - 0.0035" and ex -0.0045"). * So valve stems are already worn 0.0025" - but are within tolerance of low sizes.

(Condemnation Guide for Army G3L)
2. Guide clearance to Valve INLET -High 0.003" - Low 0.0025". Acceptable O'haul 0.005"/ Condem 0.010"
3. Guide clearance to Valve EXH - High 0.005" - Low 0.003". Acceptable O'haul 0.007"/ Condem 0.012"

So Given my 0.004" inlet clearance (front to back- less for side to side), and 0.0055" (front to back) exhaust clearance, I'm well within Condemnation limits! ;)

So do I need to get my guides sleeved to 1.5 thou inlet and 2 thou Exhaust?? Or go to the manual which says 2.5 thou Inlet and 3 thou exh?

Cheers. And once again... thanks everyone!
We Might bet getting there !

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