Author Topic: 2 3/4 running hot  (Read 2104 times)

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Offline Chris54

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2 3/4 running hot
« on: 01 Apr 2014 at 20:08 »
Hi All, on the last throws of my 1911 2 3/4 (Auto Inlet Valves) Model D restoration, 11 days until the Pioneer Run.
Any of you have more knowledge than a copy of the original manual, Have i got the valve timing wrong, the engine runs very hot, very little experience with engines this old so i was wondering if any of you could point me in the right direction, i think the ignition timing is to far retarded and am thinking the valve timing may be a tooth out.
She starts well as long as i advance the spark as much as possible, runs with what i would call far to much crispness, not a racing machine after all. I am taking the engine off the frame tomorrow so i can remove the cylinders to check the timings.
So who can tell me, How far is " Keep on turning the cam till the valve tappet ha absolutely closed. Move forward the cam the least shade further"
Any help from you experienced people will be well received.
Cheers
Chris

Offline cardan

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Re: 2 3/4 running hot
« Reply #1 on: 01 Apr 2014 at 21:08 »

Hi Chris,

The flywheel on a Douglas is very useful when setting the timing, even if you don't have a degree disk. If you have a degree disk, stick it on to the flywheel - I use BluTak. If you have a poor eye, make a pointer (a bit of wire) that points to the flywheel/timing disc at the top. Set the degree disc to read 0 at TDC, or just use a marker to mark TDC on the flywheel.

Take the spark plugs out. Find TDC on the back cylinder on the non-firing stoke. If all is OK, the exhaust valve should be just closing, or should have closed in the 10 (or so) degrees before TDC. (The flywheel goes in the same direction as the wheels.)

A paranoid person will check the other cylinder as well!

Ignition timing - the points should open say 35 degrees before TDC when fully advanced. (If you don't have a degree disc, you can estimate 45 degrees pretty well - half of 90 - then guess 35. Or borrow a dress-maker's tape from the other half and measure the circumference of the flywheel. Multiply this number by 35 and divide by 360 and put a mark on the flywheel this distance before TDC.)

Check for air leaks.

You might find the motor runs better if you restrict the max opening of the inlet valves to about 3/32" - 1/8". Springs should be matched.

Good luck.

Leon

Make sure there are no air leaks

The

Offline Chris54

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Re: 2 3/4 running hot
« Reply #2 on: 02 Apr 2014 at 07:38 »
Hi Leon
Thanks for the info, i am sure i am not advanced enough, will check valve timing first because if this is wrong the engine has to come out, however, to check piston is on TDC i do not think you can get to the piston through the spark plug hole, i seem to recollect that the valves and spark plug are in a chamber to the side of the cylinder, i suppose a piece of bent wire may work, i have another engine in pieces so could bend up something to suit testing this on another cylinder.

The thought of air leaks and inlet valve lift restriction is interesting, will look at these as well.

I will let you know tonight how i get on.

Cheers

Chris

Offline Chris54

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Re: 2 3/4 running hot
« Reply #3 on: 21 Apr 2014 at 14:25 »
Hi Leon
Sorry about the delay in letting you know how I got on but been very busy, now the pioneer run is over I have a little time, not much, repairsvto make.
Your advice on timing the engine helped, got it running a lot better and cooler, think it more due to air leaks than timing but at least I can now astrip and rebuild a 2 3/4 in 2 hours !

The problem I now have is a broken crankshaft, have to find one before I can go through the timing process again.

Anyhow, thanks again Leon for your advice.
Chris

 

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