Help with Kerzel H&M engine

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creast

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Hi guys,
I have built the Kerzel Hit and Miss engine and am having serious problems getting it to run. I have good compression (bounce) and have tried the carburettor with petrol (gasoline to you USA guys) and I have tried the Jan Ridder vapour carb but no luck. The spark plug has been tested at presure and the engine does try to run with the odd cough. Any ideas?
Also, should I set the exhaust to open from BDC or before? The cam profile seems a bit quick.
What did happen to Dave Kerzel? I have tried emails and the site but it seems the Florida site is going terminal.
Any help would be most appreciated.
Rich
 

Ogaryd

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Hi Rich, Your exhaust valve should start to open just after bdc & close approx. at tdc, If the exhaust valve is opening a little early or closing a little late you can increase the valve lash to correct that. Ignition about tdc. You should hear the intake valve make a burping or sucking sound on intake stroke. My Kerzel runs well on Jan Ridders vapor carb. I use coleman camping fuel, I believe naptha is about the same. Start with a lean adjustment and richen till it fires. Hope this helps. Regards Gary
 

creast

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Gary, another quick question. Do you use oil in your fuel and if so what ratio?
Thanks
Rich
 

Ogaryd

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I don't use oil in the fuel, I used a silicone oring for the piston ring. Silicone is much softer rubber than viton and still holds up to the combustion temperatures. When first starting my engine I used generous amounts of oil in the rear of the cylinder & on the valve guides. I believe that friction is the largest problem with getting these small engines running. Mine will bounce back and forth 2-3 times. Another thing is keeping your valve seats very narrow, they will seal quicker & tighter. Gary
 

creast

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I don't use oil in the fuel, I used a silicone oring for the piston ring. Silicone is much softer rubber than viton and still holds up to the combustion temperatures. When first starting my engine I used generous amounts of oil in the rear of the cylinder & on the valve guides. I believe that friction is the largest problem with getting these small engines running. Mine will bounce back and forth 2-3 times. Another thing is keeping your valve seats very narrow, they will seal quicker & tighter. Gary
Thats really interesting Gary.
I fitted an O ring to try and check the max possible compression eliminating any leakage past the piston. I was tempted to try and run with O ring but found the friction too high. I have now temporarily fitted an O ring with a PTFE cap ring and the compression seems reasonable. Its difficult to measure the actual compression because any adaptor and the gauge adds significant volume. God knows how many times I have lapped the seats to get them where they are now. They are not too wide either. I suspect my inlet spring may be slightly too strong but it does make a gentle burp on inlet stroke. So far, the engine has just fired intermittently. I will try the Coleman fuel and maybe a silicone O ring too. Thanks for your input.:)
 

Ogaryd

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I cut the oring groove till the oring barely touched the cylinder, The cylinder was lapped to a glass smooth finish the auto buffing compound.Gary
 

Ogaryd

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Hi Rich, I just remembered the problem I had was battery voltage when I first started my engine, it would fire once or twice then quit. added a charger and life became much better. I hope this helps. You will have it running soon. Good luck, Gary
 

creast

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Hi Rich, I just remembered the problem I had was battery voltage when I first started my engine, it would fire once or twice then quit. added a charger and life became much better. I hope this helps. You will have it running soon. Good luck, Gary
Thanks Gary.
I must add that I did not opt for the points option and have gone for the Ridders blokker ignition of sorts but triggered by a Hall Effect switch.
To be honest, that has caused me countless hours of grief too ... lol!
The ignition circuit seems ok now after countless faults to sort but there are so many variables on this to get it running that I am trying to eleiminate all the possibilities. The fact yours runs ok on ridders carb and Coleman fuel is a good start.. its nice and simple. I may even resort to a commercial miniature plug despite having tested mine at pressure in a similar way to Dave Kerzel.
I will press on regardless. Many thanks for your help
Rich
 

popnrattle

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The exhaust valve should open at least 30 degrees BEFORE bdc, and close after the piston starts back down on the intake stroke. Just like a full-size engine. I think you can use the inertia of the exhaust somewhat to start the vacuum needed to open the intake valve before the piston starts moving down.
You might reconsider using a mini-plug(cm-6 NGK) because I have experienced my GM points ignition system creates such a good spark that it will jump from the terminal to the hex flats(half inch or so distance) and make the engine stall. I even tried to close the gap to about .020 with only slightly better results, but still happens sometimes. Cleaning the ceramic with contact cleaner just in case there was a carbon tracking thing going on helped slightly. The smaller plug looks great, but if I want it to run all day I have to put the full-size motorcycle plug in.(M10x1 thread, also).
So, if your mini engine is running erratically, consider looking for this. I have also seen miniature engines stall because the spark jumps to one of the valves and/or rocker arms because they are in close proximity to the high-tension wire. Later, RT.

[ame]http://www.youtube.com/watch?v=p3LxjE8sWWg[/ame]
 

creast

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The exhaust valve should open at least 30 degrees BEFORE bdc, and close after the piston starts back down on the intake stroke. Just like a full-size engine. I think you can use the inertia of the exhaust somewhat to start the vacuum needed to open the intake valve before the piston starts moving down.
You might reconsider using a mini-plug(cm-6 NGK) because I have experienced my GM points ignition system creates such a good spark that it will jump from the terminal to the hex flats(half inch or so distance) and make the engine stall. I even tried to close the gap to about .020 with only slightly better results, but still happens sometimes. Cleaning the ceramic with contact cleaner just in case there was a carbon tracking thing going on helped slightly. The smaller plug looks great, but if I want it to run all day I have to put the full-size motorcycle plug in.(M10x1 thread, also).
So, if your mini engine is running erratically, consider looking for this. I have also seen miniature engines stall because the spark jumps to one of the valves and/or rocker arms because they are in close proximity to the high-tension wire. Later, RT.

http://www.youtube.com/watch?v=p3LxjE8sWWg
Thanks for the tips.
My problem is not erratic running, just not running at all really. I have had it run for a few seconds only and then nothing. It seems highly sensitive to fuel air ratio even when running on the Ridders vapour carb. The engine definitely tries but never quite makes it. I did play with the exhaust valve timing too and it does bear some effect. I will try the valve timing as you recommend but the useful cam lift may not quite stretch to the range you quoted. The cam is to Kerzel drawing.
I did ponder on a plug change and do have a 1/4" thread miniature plug which I possibly could fit with some mods to the head.
Once again many thanks.
 
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