Timing marks I'm rather odd

thirdwheel · Post by **thirdwheel** » Fri Apr 22, 2011 11:21 pm

Hi all
Went on a voyage of discovery today as bike (AJS 18s 1953)really not running that well but good enough if you see what I mean.
So this afternoon took the head off and ground in the valves, had a peek at the bore and piston - hum I can see the shiney top surface of the top ring and the piston moves in the bore would even say it could be the wrong size piston. put it all back together and decided to lookand see if the valve timing was set up ok. Well I never had a chance to look as the cams came out with the timing cover. Much head scratching the timing marks are nothing like what I have found in books or on here! The inlet only has one mark with a "2" by it and the Ex only has one mark with a "1" by it I stared and stared at them willing other marks to pop to the surface of the metal but nothing happened, the cams have no other marks or markings on them. So I've used what I have - seem to make followers sit right on the start point of the ramp of the lobe when lined up with the marks. Will time up the mag in the morning and see how it goes. Annoyingly I still get gas hissing back through the carb when I bring it up on compression - the valves looked real fine when I ground them in.

Ok it looks like I may have a bitsa but I will sort it as it's a nice bike but what are the cams has anyone any thoughts.

What great weather for being outside on the bike

George

SPRIDDLER · Post by **SPRIDDLER** » Sat Apr 23, 2011 12:02 am

(First para deleted by me as it was a complete red herring resulting from a cocktail of Oramorph and haste )
What it should have said is that the inlet valve opens whilst the piston is still rising towards TDC on the exhaust stroke, therefore it's possible that air will momentarily escape from the cylinder 'back' out of the carb intake.

A 'Search Forums' search for 'Valve timing' will bring up loads of info and links such as the following (thanks to the much respected, but late 'Biscuit':

[[Without knowing the details of your cams, ie markings or keyway or not keyway etc. The following method works for me when fitting cams from God knows where to engines of equally doubtful provenance.

With the mark on the half time pinion (HTP) at the top, the piston is at TDC, this will be TDC at the end of the exhaust stroke, where the exhaust valve has just closed, and the inlet is about to open.
Turn the engine back until the mark on the HTP points to the inlet camshaft bush. Take the inlet cam, and with the cam peak pointing to the right as you face the engine turn it anticlockwise until the cam is forced against the tappet foot. Identify which cam wheel mark is nearest the HTP mark, that's the one you want.

Similarly with the exhaust cam,turn the engine forward until the HTP mark points towards the exhaust camshaft bush, but this time have the
cam peak pointing to the left and turn it clockwise against the tappet foot, again identify the mark nearest the HTP mark and insert.

Never fails for me, and you don't have to worry about which mark, which year, mag in front or behind, whether the cam has a keyway or whether the cams were original fitting.]]

Edited by - SPRIDDLER on 22 Apr 2011 11:13:55 PMEdited by - SPRIDDLER on 23 Apr 2011 8:14:47 PMEdited by - SPRIDDLER on 23 Apr 2011 8:41:26 PM

thirdwheel · Post by **thirdwheel** » Sat Apr 23, 2011 11:21 am

Thanks you I did a major search on these and other forums befor posting and much head scratching. When I lined up the marks that I do have the lobes of the cam were as you have written so I was hoping it was as it should be. Thanks for the info about the inlet valve and it opening befor TDC - I never thought to look at the timing chart - I will do now. I think the engine is a sum of parts as would have happened to a bike that was used over a long period of time when money was very tight - you just used what you could get to keep you on the road to get to work, it's kind of honest really. The piston has a raised crown and there are no markings relatig to size. I renovated a matchless in the late 70's and this had a flat top piston but this was an iron head, found the thing buried in a pals garden and it ended up with a CCM front end but thats another story.

Thanks again
George

rex.webb · Post by **rex.webb** » Sat Apr 23, 2011 8:35 pm

NO!!!!!!!!!!!!!!!!!!!
NO!!!!!!!!!!!!!!!!!!!
NOW MR SPRINDLER ?? SPRIDDLER !!!!!!!!!!!!
NO INLET VALVE OPENS ON THE
"COMPRESION STROKE " ???????????
Sorry but how did you get that infomation.

P.S. YES IT OPENS BEFOR "TDC" on the "EXHAUST" stroke

Ride with Care and Live Long.

SPRIDDLER · Post by **SPRIDDLER** » Sat Apr 23, 2011 8:56 pm

quote:
NO INLET VALVE OPENS ON THE
"COMPRESION STROKE " ???????????
Sorry but how did you get that infomation.

Calm down, Rex! IT'S MY MEDICATION!!!!! . Addled me brain. I've also been thinking all day that it's Sunday, too.
As you say; on the zorst stoke when the piston is still rising towards TDC it opens just before the 'suck' cycle starts - (bit like a Werther's Original).
I've edited that bit on my post in case it misleads anyone. Which it would, of course

Edited by - SPRIDDLER on 23 Apr 2011 8:07:00 PMEdited by - SPRIDDLER on 23 Apr 2011 8:47:29 PM

rex.webb · Post by **rex.webb** » Sun Apr 24, 2011 7:48 am

Hi youg Spriddler !
"Happy Easter" to you and ALL fellow Motrcyclist,s out there.
Hope all our Valves keep working OK ?
We have an Excellent Workshop here called
"PAPWORTH Hospital" verry good with fitting new Valves to Heart,s .
Ride with Care and Live Long.

SPRIDDLER · Post by **SPRIDDLER** » Sun Apr 24, 2011 12:01 pm

'Twas a Happy Easter for me, Rex.
Went out to a club run meeting point yesterday. With a bit of medication, grunting, pushing, shoving and wobbling I managed to get on 't pillion of my son's Kawasaki yesterday. First time on a bike for 8 months (me, not my son!). Only about 10 miles but a landmark nevertheless.
Crikey, these modern humped pillion seats seem a long way up in the air! Especially with only one arm to hold with. No 'sack of spuds' riding style on these bikes!
Yes, Rex - Great Easter

thirdwheel · Post by **thirdwheel** » Sun Apr 24, 2011 12:15 pm

Some feed back
Mag timed up well first time I've hit it first go!
The bike runs better and will tick over - just the valve timing might have been a tooth out. The inlet still hisses gas on the compression stroke - could be someting to do with the loose valve guide that I noted when I ground the valves in and thought I would suck it and see as I had set myself 24 hours to try and get this right without spending loads of money apart from a decoke set. The weater is sooo nice and I just want to bimble about the kentish lanes before having to go back to work (school) and my time is no longer my own 24/7. Perhaps I can pick up a new (different) head tomorrow at ashford.
Thanks again chaps and don't be so hard on spriddler as he means well!!

George

Merlin · Post by **Merlin** » Sun Apr 24, 2011 12:46 pm

Thanks again chaps and don't be so hard on spriddler as he means well!!

Blimey a real Gent on our forum,well I never

rex.webb · Post by **rex.webb** » Sun Apr 24, 2011 1:13 pm

No i am sure we all can say "Great News" Nevill. When i had a Big Bike Accident in 1958 !. I had 10 month,s off work.BUT i still
"LOVE TO HAVE A RIDE ", hopefully in Dry warm weather.
Ride with Care and Live LONG !