1926 Chater Lea face cam 350 timing

martymoose

martymoose

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Location
Sydney, Australia
Ok some intereting problems here.  Chris has it sort of running, but as there are only 3 of these in the world, and one running in Switzerland, what do you guys reckon.  No markings anywhere, not sure how they measured originally, velocette list 30-35 thou opening to measure the cam timing.  Others use 50 thou. 
Magneto timing is interesting as well.  Velocette quote 38 degrees maximum advance for their 350 MAC. 
What do you guys think is good valve timing for a 350 single?  If 38 if maximum, what does it start at?  10?

All info gratefully accepted.
 
Here we go. All of these measurements were taken at zero tappet clearance. ie a valve opening means the degree wheel is read at zero tappet clearance. A valve closing is read on the degree wheel when tappet clearance starts to happen.

Inlet Valve
Op. 50 BTDC
Cl . 20 ABDC

Exhaust Valve
Op. 80 BBDC
Cl. 30 BTDC
 
Interesting. If you compare the cam timing the figures for e.g 750GT (low state of tune) on Laverdamania, it sounds like they are a bit out of balance. You could try advancing it a tooth and it would be closer to the Lav figure (but the exhaust would close very late). If you sketch them out it makes it easier to compare. Is it OHV or what? One cam or separate? Any OHV you should always check clearance through overlap. I have never managed to get opening and closing figures to match those quoted for Laverda cams on my twins, I use max lift at half way between the opening and closing figures IIRC.
The ignition timing sounds ballpark, and I reckon 10 at idle would be fine. 
 
This one Sir:

Chater-Lea.jpg


Jeroen
 
Hi Marty,

38? full advance sounds quite normal for old singles, typical range for the Matchys I muck around with.

Is individual cam timing possible, ie, seperate cams for in/ex?  My quick sketch shows your 20? valve overlap well before TDC, I'd place it evenly around TDC to start off with.  Inlet open ca. 10? BTDC, ex closes ca. 10? ATDC.  These old bangers weren't very sophisticated as far as cam timing went.

I'm currently working on a 1926 Triumph Riccardo 4-valve.  Not many of those left either... :D

piet
 
Valve timing is s real pain, 2 dinner plates with bumps ( face cams) 15 degrees between bevel gears but to adjust split the cases. No adjustment between the two plates
 
An interesting exercise on an interesting bike.

The exhaust valve closing at 30? BTDC is way off what would be "normal". Are you sure that isn't ATDC?
Exhaust opening at 80? BBDC is way early too, which actually makes the closing figure of 30? BTDC look like it may be correct. I reckon the exhaust cam needs to be retarded by around 40?.

Inlet valve opening at 50? BTDC also looks way early, as does the closing time of 20? ABDC. I would have expected something like 10 and 55(ish) respectively. So the inlet cam looks like it also needs to be retarded by about 40?, same as the exhaust cam. That's very convenient if exhaust and inlet cams can't be moved separately.

I was wondering if your 15? steps in cam timing (per tooth in the cam timing gear) was at the crankshaft or camshaft. But it must be crank timing. That would mean 12 teeth on the crank gear and 24 teeth on the cam gear, correct?
15? at the camshaft would mean 12 teeth on the cam gear and only 6 on the crank, which seems very unlikely.

So, assuming the 15? intervals are measured at the crank, you could retatd the cams by 2 or 3 teeth (30? or 45? respectively). The cam timing would then be:

Retard by 2 teeth
Inlet Valve
Op. 20 BTDC
Cl . 50 ABDC

Exhaust Valve
Op. 50 BBDC
Cl. 0 BTDC

Retard by 3 teeth
Inlet Valve
Op. 5 BTDC
Cl . 65 ABDC

Exhaust Valve
Op. 35 BBDC
Cl. 15 ATDC

It's a pity you can't get something in between 2 and 3 teeth adjustment, or adjust the inlet and exhaust cams separately. But looking at the above numbers, I'd suggest retarding the valve timing by 2 teeth on the bevel gear would be reasonably close sensible timing.
 
Just noticed, your figures have no overlap at tdc, exhaust valve is already closed. Piet?s and Cam?s comments make sense. Do you have to open the case to set the cam timing?
 
Yes only 3 positions at the cam box but bevel gears inside the cases give 15 degree adjustment per tooth. Next job is to remeasure the timing with 35 thou clearance as per velociette. The measurements we have are with 3 thou clearance. Will also get figures at 50 thou as per most modern manufacturers
 
Jeroen that looks a bit side valve to me. If it is a face cam 350 do you know the owner? 
Click to expand...

Don't know him personally, see him one's or twice a year, he lives in the same area and I have his name, so should be able to contact him.

Since this is in Switzerland, and after your first message thought maybe this is the Chater Lea you are refering to.

Just give me a shout and I will try to contact him
Jeroen

 
 
Beucars said:
Don't know him personally, see him one's or twice a year, he lives in the same area and I have his name, so should be able to contact him.

Since this is in Switzerland, and after your first message thought maybe this is the Chater Lea you are refering to.

Just give me a shout and I will try to contact him
Jeroen
Click to expand...
Opening an old thread. Spoke with the owner today and promised me to copy info on the Chater Lea in post #4. Let's see and wait
 
"I'm currently working on a 1926 Triumph Riccardo 4-valve."

I know where there is one, its in my home town of Westerham and concreted under the foundations of a 1960's housing estate, I can pin point it, but for retrieval, demolition will have to take place, was not thought worth moving from the site, at that time, when the nursery shed it was in got demolished and cleared for the development, the owner was my dads cousin, it could have been mine if I wanted it, but at 12 years old I already had a shed full of runners, all of them motor cycles rather than motorized cycles, what a missed opportunity!
CLEM
 
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