Cams and ignition timing

Information relating to the Matchless G85 500cc Heavyweight, AJS 7R, Matchless G45 and Matchless G50
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Re: Cams and ignition timing

Postby Matchymarty » Fri Aug 03, 2018 10:20 am

Update:
Just checked both cams - SH. Cam timing is correct.
#3 slide. checked. Is as it should be.
Gearing is 16T G'box sprocket and 21T Engine Sprocket. Standard gearing for the 'CS' is 18 T engine sprocket. 21T is Standard for 'Touring' model - ie. G80S. Would this really be causing my issues with labouring at 50mph and hill performance? Quite possibly.

I just checked timing again, before pulling the cams, and it was less than 1/16" more than 1/2" BTDC. Meaning, it may have been a poofteenth retarded to start. I then retarded it further whilst riding. I've now reinstalled cams and re-timed spot on 1/2" BTDC @ full advance.

The Engine pipe is 38mm OD and flares to 45.75mm to fit head exhaust outlet. The engine pipe goes half way into the silencer, all but to the baffle end. The baffle end has been cut out, so silencer is basically open.

I will run the bike tomorrow and see what happens. Might take the air filter off after half way on the ride.

Also, it appears the flakes on the top of the piston, appear to be the ceramic coat lifting off the piston crown. (I had the piston coated prior to installing prior to the previous siezure. The misfire would have caused this perhaps.)

Yes, I'm not too concerned by the oil around the plug hole. The head gasket leak, is more of a concern, but not the end of the world I don't think.

Plug hole is definitely NOT helicoiled. Think you just noticed the mark where the plug crush washer was sitting.

So, yes, back to where I started.... as always.

What's your thoughts on the gearing?

Also, I'll adjust the tappets again when warm. I did it last time when cold making an allowance, but will check it correctly when warm - in case this makes any difference.

Cheers.

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Re: Cams and ignition timing

Postby SPRIDDLER » Fri Aug 03, 2018 11:43 am

Matchymarty wrote:Gearing is 16T G'box sprocket and 21T Engine Sprocket. Standard gearing for the 'CS' is 18 T engine sprocket. 21T is Standard for 'Touring' model - ie. G80S. Would this really be causing my issues with labouring at 50mph and hill performance? Quite possibly.

The 16T g/box sprocket is standard for all 500's according to the Spares List and as you say the engine 21T is standard for the Touring models. The 21T will obviously raise the gearing but TBH I don't think it should bog the engine down if it suits the Touring models although the comp models do use different inlet and zorst cams vs the Touring models.
Page 10
http://archives.jampot.dk/book/Spares_l ... ingles.pdf

Also, it appears the flakes on the top of the piston, appear to be the ceramic coat lifting off the piston crown. (I had the piston coated prior to installing prior to the previous seizure). The misfire would have caused this perhaps.

I know nothing whatsoever about ceramic coating except the obvious conclusion that it shouldn't be flaking off.

Also, I'll adjust the tappets again when warm. I did it last time when cold making an allowance, but will check it correctly when warm - in case this makes any difference.

Rightly or wrongly I've always set mine cold with zero clearance but free to spin and can't recall ever needing to repeat the adjustment when checked with a warm engine. I have a feeling that the advice to check when warm is because the rods and their cups may settle a bit or displace oil when the engine is/has been running, rather than the effect of expansion when just warm. After all, a just warm engine rather than one at the normal far hotter running temp hasn't finished 'expanding'. I can see though that an engine at normal running temp might be too hot to fettle with.

I'm out of ideas except that perhaps there's some basic error in your carb or ign or cam timing settings (been there a time or two when checking my own work :oops: ) or the highly unlikely possibility that the cams have been modified or the even more remote possibility that the timing side axle/pinion hasn't been aligned correctly in the flywheel (memory's poor but I don't think the axle is keyed into the flywheel), throwing out the valve timing. If the CS is the same as the touring bikes the cam timing dot on the pinion should be at exactly 12 o'clock when the piston is at TDC. Not worth stripping to check but p'raps you could have a look when you next delve into the cam chest......unfortunately the dot is often obscured by the (L/H thread) pinion nut.

I have to ask: Has it ever run satisfactorily?
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Re: Cams and ignition timing

Postby Expat » Fri Aug 03, 2018 5:34 pm

Hi Marty,

That’s a frustrating problem you have there and I don’t have any suggestions that may help, just a couple of observations.

As you say, the plug is a bit sooty but basically not a bad color and I agree that slow riding in traffic, or a period of idling may be the cause of the black.

Must pass comment on your remark about the oil on the head. My ‘60 G3 shows oil in the same place and the next two or three fins lower down, as well as a little around the plug area over a period of time.
I’ve decided that the pushrod adjustment cover weeps ever so slightly and oil gets blown back and around the head. I was convinced it was the rocker cover or head gasket leaking, but how could it be coming from the head?

I’ve no knowledge of your bike model, but if the head and barrel are of a similar design to mine, there are no oil ways etc to leak in the gasket area.


Or am I talking s**te? ;)
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Re: Cams and ignition timing

Postby Andy51 » Fri Aug 03, 2018 8:18 pm

Hi Marty, I think you have bigger problems than ignition and valve timing. Your oil consumption sounds horrendous, and 4/5 seizures equally so. Where is the oil going? Is it being burnt in the combustion chamber (hence sooted plugs and loss of power - oil ring faulty/in wrong), being blown out of the breather (excess crankcase pressure - faulty rings/excess bore clearance), major oil leaks from gasket/joint? Oilways blocked? Seizures - too little oil in bore (normally bore is splash lubricated from big end), too little bore/piston clearance (should be around 4 thou (1 1/2 thou per inch bore diameter or whatever piston supplier recommends)? All these probably require a partial or full stripdown, but you need to eliminate the oil leaks and seizure issues before proceeding. In over 20 years of riding AMC singles I have only had one partial seizure, probably caused by barrel hold down nuts loosening - tightened them up and drove back home after barely cooled down. A quick bore hone and back on the road for many hard riding miles. You seem to have some fundamental undiagnosed proble. Andy

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Re: Cams and ignition timing

Postby Matchymarty » Sat Aug 04, 2018 6:55 am

Update #2.
Just been for a 70 mile ride after - checking cam timing and re-timing the ignition. I also, rode it a little harder than normal to try and get it to trip up again. It had a miss or two and a cough not far from a large long hill. THen, as I was going up the hill and had to change down to third, the throttle stuck open as I got into a left hander, but fixed itself on the other side of the corner. My mid ride destination was only 5 mins further, then had lunch. On re-start, the throttle was stuck open, the slide was jambed. I pulled the carb off and cleaned, and back on. Left the filter off this time.

Well, I got under it a bit on the return trip, and suffice to say it goes better. Also, I kept the revs up more, and consequently, speed, and it did go much better. I'll look at the plug soon. That said, now that I know the front engine sprocket has 3teeth more than 'standard', I can say that is a lot of my problem, as i normally ride around at 45-50mph, where, it's probably over fuelling, lugging, and certainly not using the power, of the SH cams. So, I'm now convinced I need to swap out the cams, or engine sprocket. Cams are easier, as I don't have to change the primary chain. ahahaha. Well, It'd be a good experiment anyway.

SPRIDDLER - No, I don't think it has ever run satisfactorily. I don't know what a good one, or new one SHOULD run like, but my father in law who's always had matchies, always just said "that's what they are like", and riding his flogged out 350 wasn't much different. He finds that acceptable, and yet, I see photos of the compy's spinning the back tyre in the dirt (yes, with lower gearing but still). No way, mine would do that!

ANDY - I've had many problems. OK, so, I've never actually seized a piston. Dam close though. First piston was replaced as it was using too much oil and smokey. Found the piston to be 40thou (yes) too small for the bore. Second piston nipped up, but could ride home, and that was on a new sleave. Engineer used 3 thou clearance and only 4thou ring gap. 3rd piston had 7 thou clearance, but it was supplied with a gudgeon pin too narrow, and it hammered the clip til it hit the bore. I assembled that , but did not notice the gudgeon was too narrow. 4th Piston had good clearance, but when going up a very steep mountain at a rally earlier this year, it began pinking and preigniting, then nipped up . Stuck top ring the result. I pulled apart and cleaned up bore and piston and rings with a file, 1cm square of emry, and a leatherman at camp then rode another 110 miles the next day of the rally.

All through, I've had big oil consumption. The C'case relieve valve works, and is always dripping with oil. It smokes on over run down hills, so I suspect intake guide. It gets plenty of oil up top, and intake valve always shows signs of dripping oil on top of valve. Top of piston always has thick crust of oily crud. So it burns oil.

I've used the same rings each time, as I can't seem to find good rings. I suspect partly intake guide, partly oil ring which is a cruddy solid ring with slots in it from JP Pistons. Big end might not be too flash either, but doesn't appear to have any excessive wear up and down. I'll re-build the engine fully after i get my other matchy running right . (it's a short stroke G80CS).

So yes, I'm constantly chasing my tail with this bike. I think I should just gear it down, as mostly, at rally's etc, we ride around at 45-50mph, and as such, the lower gearing would put the engine in a happier place with the SH cams. But then... ugh. Dunno. Stock cams would make it happier all around I think!

Thanks all for comments.

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Re: Cams and ignition timing

Postby SPRIDDLER » Sat Aug 04, 2018 11:46 am

Well that really is a sorry saga. I don't think you can get much further without addressing the two main issues, so to recap:

1. Various/numerous piston problems and over-oiling.

I think it's essential to start with a new piston complete with matching rings and pin, even if it means another rebore. Substantial over-oiling of the combustion chamber (probably piston blow-by) is upsetting carburation and fouling the plug.
Incidentally, a long time contributor to this Forum, 'ITMA', always maintained that a rebore should be done from the cylinder base, not from the top. I can't quite remember his reasoning but I think it was that the cylinder base will always be square to the bore, plus there will be more of the lower part of the cylinder unworn relative to the top.
In the absence of the piston manufacturer's spec'n (as with Club pistons) I have always used a rule of thumb for piston/bore clearance on 350 and 500 singles of 1.5 thou per inch of bore diameter which is either correct or I've just been lucky. I'm not out to achieve speed records, preferring reliability, so happy with a trace of piston slap (if any) when cold. I aim for a ring gap of between 10 and 15 thou rather that the 7 thou which you mentioned.

2. Gearing and cams

In view of your run speeds I'd either fit the CS 18T engine sprocket (might make the engine a bit too 'buzzy' for relaxed runs), or softer cams if you can find some decent ones. Depending upon the year you could borrow your Father-in-Law's from his 350 as if it has the HL cams they are the same as the 500 Touring but you just use different marks on the cams. I haven't checked but you'll probably need to re-jet the carb to the Touring cam settings.
If you haven't seen it this article on cams may be of interest:

http://archives.jampot.dk/technical/Gen ... e_Dots.pdf

I think I'd do the same as you and sort all the changes at the same time, although I probably couldn't resist first giving it a go with the softer cams.
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Re: Cams and ignition timing

Postby Matchymarty » Sun Aug 05, 2018 9:00 am

Thank you again Spriddler for your tireless help and support.

I agree with all your comments however will just add the following.

My latest piston is a 'Ceramic coated' JP Piston +40 thou. It was set up with 7 thou clearance, so, that would mean 3.250" + 0.0040" + 0.007". Given your 1.5 thou per inch, that should mean 4.6-5 thou. Given I have 7thou one would expect piston slap, but no. It has been my and the engineer's experience that these particular pistons expand a lot, and, unevenly, so, we have had to go to this clearance. Engineer actually heated up the piston to temperature to test its expansion prior to clearancing the bore. He gapped the rings to 12 thou. Apologies if I was unclear about that previously. 7 Thou mentioned was piston/bore clearance. Also, don't forget, it is hot in Australia, and we have garbage fuel.

The over oiling is an interesting one. I actually went out for a ride today and rode father in law's bike for most of the 70 miles. Quick story was, that i was following him on my matchy, and I noticed his RH rear shock was somewhat 'separated' and the top and bottom jampot covers had caught on themselves, and looked rather kinked in the middle. Anyways, I checked that quickly and decided I'd ride it and he could ride mine. He is 86, so don't want him riding something potentially dangerous.

So, I got to follow my bike which I dont' often get to do. Basically, it blows smoke a lot. Always, on deceleration, overrun and occasionally, when the clutch is pulled for a gear change. No smoke appears when motoring along normally, but smoke burbles out when the throttle is shut off. I suspect this to be one of two things. Either, the oil ring, being a solid type, does not control the blow by sufficiently, or, the intake valve guide is flogged out. I had the head checked some time ago, but the guy said, the guides were 'within tolerance'. Not sure what tolerance he was referring to as he wouldn't have any access to Matchless spec's.

To be honest, I'm only looking for a reliable good running club bike too. I've given up chasing the oil use at the moment, but will most likely pull the engine down and do a full bearing, bush and top and bottom end o'haul after this rally season. I hate the fact that it smokes so much. It's bad for my missus who rides behind, and it's not a good look in general.

Yes, I could borrow a set of cams. But, I do have a 19T engine sprocket I can try, which may well suit my needs being only 1 tooth more than stock. So, I can try that maybe with the SH cams. I do have an old SS intake cam, but they are different to the 500 Touring ones as far as I know.

So yes, I guess a few things to try. Though, I must say, for the short time I rode it today, and 70 miles yesterday, things are on the up, knowing, that keeping the speed up, made it run much better, so, perhaps with a shorter gear on the Engine sprocket, most of my performance problems would go away. Knowing, it was quite heavily over geared, helps, as when it beings to labour, you can then feel it as being gearing not so much as carburetion or ignition issues. Also, I had no misfiring issues whilst keeping speeds and engine revs up .

Cheers... more experimentation to be done!

Incidently, where do you guys get good quality rings from? (ideally 3 part oil rings) and good quality profiled compression rings. The rings I have been using are square profiled comp rings and single solid oil rings with slots in them. The comp rings aren't even tapered, they are completely square.


SPRIDDLER wrote:Well that really is a sorry saga. I don't think you can get much further without addressing the two main issues, so to recap:

1. Various/numerous piston problems and over-oiling.

I think it's essential to start with a new piston complete with matching rings and pin, even if it means another rebore. Substantial over-oiling of the combustion chamber (probably piston blow-by) is upsetting carburation and fouling the plug.
Incidentally, a long time contributor to this Forum, 'ITMA', always maintained that a rebore should be done from the cylinder base, not from the top. I can't quite remember his reasoning but I think it was that the cylinder base will always be square to the bore, plus there will be more of the lower part of the cylinder unworn relative to the top.
In the absence of the piston manufacturer's spec'n (as with Club pistons) I have always used a rule of thumb for piston/bore clearance on 350 and 500 singles of 1.5 thou per inch of bore diameter which is either correct or I've just been lucky. I'm not out to achieve speed records, preferring reliability, so happy with a trace of piston slap (if any) when cold. I aim for a ring gap of between 10 and 15 thou rather that the 7 thou which you mentioned.

2. Gearing and cams

In view of your run speeds I'd either fit the CS 18T engine sprocket (might make the engine a bit too 'buzzy' for relaxed runs), or softer cams if you can find some decent ones. Depending upon the year you could borrow your Father-in-Law's from his 350 as if it has the HL cams they are the same as the 500 Touring but you just use different marks on the cams. I haven't checked but you'll probably need to re-jet the carb to the Touring cam settings.
If you haven't seen it this article on cams may be of interest:

http://archives.jampot.dk/technical/Gen ... e_Dots.pdf

I think I'd do the same as you and sort all the changes at the same time, although I probably couldn't resist first giving it a go with the softer cams.

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Re: Cams and ignition timing

Postby Andy51 » Sun Aug 05, 2018 9:16 am

I use a JP piston, bought about 12 years ago (a present from my son who lives in Brisbane) and it came with all rings. The oil control ring was a slotted one-part one that has worked excellently since fitting. The piston came with boring instructions - long lost but if I remember rightly they advised 4 thou clearance - very similar to the old rule of thumb of 1.5 thou per inch bore diameter. Andy

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Re: Cams and ignition timing

Postby SPRIDDLER » Sun Aug 05, 2018 11:40 am

More than happy to ponder this with you. It has been 28/30 occasionally 33 degs daytime for several weeks now which is simply too hot for me to feel the slightest bit inclined to get all my protective riding kit, boots, helmet, gloves on. I guess those temps are nothing to you. I never did and will never ride without it since my acquaintance with the 30 something guy in the hosp bed next to me who had been there 6 months. He had been riding at about 45 in shorts and shirt when knocked off his motorbike and his arms, legs, and back were damn near shredded. His donor graft and receiving areas of his body had suffered constant infection and failure. Virtually helpless, he had become almost suicidal.

Wonderful for your dad to be riding at 86. Great stuff!
Your engineer seems to be a very thorough and competent chap to have around.

I can't recall replacing just the rings but always a new piston which is supplied complete with ring set and pin. I must have led a sheltered life as I can't recall seeing a solid oil control ring on my singles.
This knowledgeable and helpful company has an excellent reputation for ring sets:

http://www.fwthornton.co.uk/

Try the 19T sprocket. Even if it's only marginally better at least it'll be a step in the right direction. I suggested trying your dad's cams as that would be a simple job, although changing the sprocket is also very straightforward. The existing primary chain should still fit O.K.

Obviously, the smoky zorst will be due to oil from the crankcase getting past the piston and/or drawn into the combustion chamber through worn valve guides. The oil can't come from anywhere else. There is lots of detail on clearances etc. in the MOD workshop inspection limits document from 1953 linked below. It's for the WD 350 so you need to be a bit choosey at which figures you use but the acceptable clearances, (not necessarily the components' dimensions) for valve guides, shafts, bushes etc. are a useful guide for our 350 and 500 singles.

http://archives.jampot.dk/book/Workshop ... ndards.pdf

E.g: -------Component description-------- High/Low when new--- Acceptable on overhaul--------Condemnation limit.

Valve stem to guide clearance (640x388).jpg


And a later thought, (although I doubt it would cause such problems as you have) but if I was at the engine I'd take 2 mins to check that the inlet valve oiling screw is correct - i.e. with a pointy end........

inlet valve oil dims 009 (740x555).jpg
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Re: Cams and ignition timing

Postby Matchymarty » Sun Aug 05, 2018 6:13 pm

Thank you again Spriddler.

I have a brand new oil feed screw, which definitely has a pointy end on it. Thank you for the measurement though, as I'll check that. I've had the screw all the way in, set as per book, and other settings, and it does not affect the oil smoke and consumption. Perhaps it's too short? Now I have your measurement, I'll check it. Cheers.

Also thanks for the component condemnation manual. Much appreciated. After the rally season I'll definitely pull down and check all engine components.

Yes, i may well try the 19T engine sprocket, however, it's almost easier to change the cams out then open and re seal that pesky primary case! ahahaha. Particuarly annoying on the CS models, as the alloy band is hard to the foot rest, making it most difficult to ensure the seal is even and sitting nicely in the band. Bloody pommy design! Sometimes I think about putting touring foot rests on it!

As for your experience with the scantily clad motorcyclist and subsequent loss of skin - I see this all the time here. We call it 'Gold Coast riding gear'. I live on the Gold Coast in Australia, and, we often see idiots in shorts, a singlet, and thongs - yes, thongs. (Thongs - ie. Jandles, flip flops, pluggas, etc - NOT, the G-string type - although, that wouldn't suprise me either.) I don't own a car (luckily my partner does) and have not for over 10 years, so I ride every day at least, 100 miles return to and from work, rain, hail, sleet, and baking heat. I ALWAYS wear boots, gloves, helmet, riding pants and a jacket. I even refuse to wear the latest 'ankle boots' that some people are riding in. I'm particularly stringent on the old bikes, as one is more likely to have a mechanical issue on an old bike and end up on ones bum. My Sister in law is in wound care in the hospital, and sees horrendous things from bike accidents... so yes, I know what you mean there!

ANDY, yes I see your point RE: the JP piston and rings. I mean, these engines are NOT high tech things, so why would they be so fussy about what sort of piston is in it? I have no idea. I haven't had much luck though. Also, it should be noted, that the old OEM wire wound piston was meant to have 1 thou clearance. That never worked here in oz as well as it did in Pommy land, as I've heard from an original AJS tech who I have contact with. Pitty he's forgotten a lot of things, and is old and over it, so just says "oooh it's running ... leave it alone Marty!" . hehehehe.

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