Problem starting motor

[atheras29]

Crankcase cover leaking - the rings are not seated yet. New engines suffer from this and is a major problem to overcome at start-up. You will probably notice oil fouling the spark plug due to the rings. Spinning that engine by the flywheel, you should feel good resistance to compression - if not it will be very hard to start.

You can set the engine up on your lathe and without the spark plug installed, spin it for considerable time to seat the rings. The engine will become quite warm to the touch while it is being run-in. Then clean out and refill the oil.... Reinstall the plug and note the difference in the resistance to rotation by hand....

just another 2¢ ;D

Oh yes, Whippet, not Whittle....I have a new untouched casting set for one... I also built its big brother the Wallaby. Westbury designs are fine! I had to build a windage tray for the Wallaby and an oil relief due to so much oil thrown up on the cylinder walls. It did much better after the rings seated. I now use it to proof new carburetors.

BillC

Hallow BillC

I did all the above to brake in the motor (bushings and piston rings) before i try to start it. This engine is the first one I attempt it to build and i had a few problems with it from the beginning. I downloaded the drawings thru the Internet and started to make the engine parts. Soon I realized the drawings have some wrong, and missing dimensions without enough information’s for timing
Most of the parts are made on CNC machines and some of them I had to remake them
The more I mess with it, the more I think it is human error
The only think I think can be wrong is the timing.
I changed the carb to a smaller one with (.100”/125” and 150” ID opening) ;D

Test of the cylinder compression read only 31 psi

How can I check to see if the timing is correct?

These are the cams I made, and I am wondering what is the best way to set the timing.
Photo #4911 cam contour details
Photo #4915 camshaft angles
Photo #5246 cam
Thanks

 

[jpeter]

Cams look decent provided you're turning it the right direction. It's required that the exhaust lobe be advanced, comes first, from the intake lobe by 90 degrees or so. Basically, when you rotate the crank in the proper direction the exhaust valve must just start opening at bottom-dead-center (or there abouts) and be closed by top-dead-center which is when the intake valve should start to open. The intake valve then needs to be closed by the next bottom dead center. Then at the next top dead center the ignition fires. Be sure sure the timing gears have the required 2:1 ratio.

Regarding 30 psi, it seems low but maybe with a low compression ratio it might be fine. I don't really know. No doubt someone here knows.

Just trying to help. It sure looks like it outta run.

 

[stevehuckss396]

Move your piston to top dead center.
Fix a degree wheel to the crank shaft.
Set a pointer to point at zero degrees on the wheel.
Rotate the crankshaft in the reverse direction 109 degrees.
Rotate the cam so the exhaust follower is at its peak lift and lock it down.


The cam diagrams are to be used with the fixture to cut the lobes in the correct place on the shaft. There is no detail as to the lobe seperation on this engine but he used 110 degrees on the seal and this looks close to the seal. If you go with the above instructions, and the cam is anywhere near the seal, and cam timing is the problem, it should start with the above instructions.

Disclaimer: I cant say for sure it will work, but this is exactly what I would try if I were in your boots.

 

[Admiral_dk]

Mount a dial indicator on the engine (with a magnetic stand or similar) an let the plunger touch top of the piston - in your case, you need to remove the combustionhead, and locate TDC (Top Dead Center) and do the degree wheel as Steve says.

Next move the dial so the plunger touches the inlet valve and make sure it's closed - if it's at the starting of opening phase, rotate the crank a full turn. Reset the dial to zero and turn the crank the way it's supposed to run, until the valve starts to open (this is a bit of a definition problem, some says it's when it starts to move and others specify the point when it has opened a specified amount - ie. 0.1mm.) your engine is specified to open at 10 degree before TDC, but write down the exact value you measure. Continue turning the crank until the valve is closed again and note this value too - it should be 50 degrees after BDC according to the second picture you showed us. Do the same with the exhaust valve and compare the values with your picture (open 60 degrees before BDC and closes 20 degrees after TDC). A few degrees to either side can be ignored and don't forget that the valve clearance will affect the measured values too.

What kind of fuel are you using ? This engine would probably run on several different fuels, but certainly not equally well with the current "carburetor". And as previously said, the fuel tank / level should be a small amount below the carburetor.

Best wishes
Per aka Admiral_dk

 

[BillC]

The 'rocked' position is where the valves are equally open at overlap where the exhaust is closing and the intake is opening - the piston at that point should be at TDC. Remember that when the engine is turning its designed direction of run - the exhaust valve opens first - then the intake - and that is where you are at the 'rocked' position. The term is actually for rocker arms but with the side valve arrangement of Whippet, you can see the cam followers.

That's the quick and dirty method of cam timing. Once you establish basic timing then do the fine degree wheel tweaking, but I have run engines using this method of timing with these 'mild cam' engines. When you make a cam with lots of overlap and long duration then you will need to be very precise. Your Whippet cam is very mild - the valves actually are both closed at overlap in the 'rocked' position.

You are now at the 'fun' part of building an engine. Everything hits you in the face at the same time.....but the worst is over. Just be systematic and take your time - it will run....

BillC

 

[Admiral_dk]

BillC :

Your Whippet cam is very mild - the valves actually are both closed at overlap in the 'rocked' position.

Something doesn't add up here .... If you look at IMG_4915.jpg camshaft angles. It shows a 30 degree overlap and a rather hot cam timing - especially for a model engine .... But that might be an explanation.

 

[BillC]

Yes, you're right and that along with poor compression would make her a bear to start. I believe (if I recall correctly) the cam gear it mounted and retained on a taper so with a bit of tedious adjusting, the difference in the I and E overlap could be precisely placed but a one lunger is so forgiving with valve events....It may be a bit lame but it will run with them set evenly.

BillC

 

[atheras29]

If you're sure that the timing is right (cam, valves & ignition), I would expect it to make a pop or two from time to time when trying to start it - is there any such signs ?

If it cant generate enough power to run it could be leaking compression. Maybe the valves aren't seating or maybe the piston fit is not as good as it needs to be.

Thanks

The problem wash the piston compression
Deep vertical grooves on cylinder liner
I change upper piston ring with mat'l CI and Teflon for the second
I must build a new carb and i hope to have better luck this time

 

[atheras29]

Yes, you're right and that along with poor compression would make her a bear to start. I believe (if I recall correctly) the cam gear it mounted and retained on a taper so with a bit of tedious adjusting, the difference in the I and E overlap could be precisely placed but a one lunger is so forgiving with valve events....It may be a bit lame but it will run with them set evenly.

BillC

Timing again the motor with a dial indicator and change piston rings wash able to start it for a few seconds
This type of cam is a problem to timing because i cut a key on the shaft's taper and the difference in the I and E overlap.
Big deference on cylinder compression with new rings without any leak down

[youtube=425,350]http://www.youtube.com/watch?v=SYPTSi8Sqng[/youtube]

 

[gbritnell]

Dimitrios,
Most of the answers that have been given should be helpful. Whenever I have designed a camshaft I make the overlap at TDC uniform, meaning the intake opens and the exhaust closes at the same amount before and after TDC. Usually this is about 15 degrees. If the cam is made in one piece the lobes would be cut with the proper orientation so it would just be a matter of setting the overlap relative to TDC. As was mentioned you could use a degree wheel, dial indicator or just plain eyeball it. If the cams are made individually then they would have to be set with a degree wheel.
To set the ignition timing you can do this. Find TDC and make a mark on the flywheel and one on the block that both line up. Now find the circumference of your flywheel, Pi x Dia. and make a paper strip that long. Usually I set my timing around 15 degrees before TDC as a starting point. 15 degrees would mean that you would divide the piece of paper into 24 equal segments. Now lay the paper strip around your flywheel and put another mark at 15 degrees BTDC. Now with the ignition hooked up rotate the engine until it sparks. Adjust your timing until it sparks at the 15 degree mark and you're set. Once you get the engine running you can play with the timing to see if more or less advance will make the engine run better. If it's a high speed engine it will generally take more advance to make it run good.
gbritnell

 

[Ken I]

I agree with bearcar's comment about the plug - is the plug over the inlet or the exhaust side of the engine ?
With a conventional spark ignition you want to introduce as much turbulence as possible to help flame propogation - I'm concerned your plug may be located in a rather stagnant area of the head containing exhaust gasses.

Just an idea - 2c

Ken

 

[atheras29]

I agree with bearcar's comment about the plug - is the plug over the inlet or the exhaust side of the engine ?
With a conventional spark ignition you want to introduce as much turbulence as possible to help flame propogation - I'm concerned your plug may be located in a rather stagnant area of the head containing exhaust gasses.

Just an idea - 2c

Ken

Thanks Ken for the advice

If i use the head on photo # 5901 the plug location is over the E side. I change the rotation of the motor from ccw to cw because the fly wheel nut gating loose.
On the design the plug is over the intake valve
For all the tests i dead to start it I used a cylinder head with plug between valves and piston photo #5919
Here is a video with the first start up
(fuel gas with 5% Castor oil)

[ame]http://www.youtube.com/watch?v=SYPTSi8Sqng[/ame]

 

[mu38&Bg#]

I think the bigger problem with the location at the exhaust is that it's recessed. However, engines have used this plug placement and run.

I think the problem lies in carburetion. That looks like a fairly large glow engine carb(Super Tigre?). The needle can have a very narrow acceptable adjustment range when fueled with gasoline. With a carb that large you won't be able to correctly set the needles without a load on the engine. At 10CC I would stay with a carb bore no greater than 5mm diameter equivalent area. I think the original design called for 1/4".

Looks like you're local. I found your stuff on youtube a few months ago. I thought you were in Greece?! Cheers!

Greg

 

[jpeter]

I've had model engine carbs I couldn't get lean enough and had to modify the needle valve to get to work. You might try pinching off the fuel line some to get it leaner. Use a clamp of some sort so you'll have control of the mixture. Also, the fuel level in the tank is quite a bit below the carb spray bar for a carb with that large a bore. There's a good chance its not drawing fuel consistantly. You might try raising the the tank some to get the fuel level about 1/4 inch below the carb spray bar, at least for the initial runs. Another thing to try is placing an o-ring on the piston for one of the rings. That'll help the compression some.

Keep trying.

 

[atheras29]

Thanks to everyone who responded and helped me.
I started the motor and I am now working on the other three of them.I have to make some changes, and new carbs.

The timing AND compression were wrong
Thanks again

 

[mu38&Bg#]

I see the video is up. It sounds great!

[ame]http://www.youtube.com/watch?v=ZXx5hIA-2Aw[/ame]

 

[Ken I]

Great build - nice little runner(s) you've got there.

Ken

 

[atheras29]

Great build - nice little runner(s) you've got there.

Ken

I see the video is up. It sounds great!

I guess it's never too late to thank you.
Three motors are done and i'm working to convert the forth one to diesel.
Thanks again Dimitrios