Terrible running on a Petter M

Hello everyone

This is my first post on here. I've a number of old lumps, and enjoy running them and putting them to work. I'd describe my mechanical experience as amateur, at best.

Was hoping to ask you all for advice on a 2.5hp Petter M, watercooled, 1923.

The engine is new to me, a lovely old fella down the road offered it for sale and I couldn't refuse. It's very smart, clearly had a lot of love over the years. He told me it's in fine running order and as good as the day it was made. Which I think is mostly accurate.

I've had it running, but it's very reluctant to start on either parafin, petrol, or a mix (obviously just pure petrol in the carb bowl). When it does run, it'll run OK for about 10 mins, then just die. It's lifting fuel into the bowl so the pump is OK. But on removing the plug it's very oily, so I clean it and put it back, then it goes again, for about another 10 mins then it's dead again.

Even on pure petrol, the mixture is clearly very oily. the exhaust spits oil droplets everywhere. I've got the drip-feed lubricator set to almost nothing. The mixture wheel doesn't seem to make any difference. Old black oil oozes out of the air intake at the back.

The spark at the plug is present but very weak, gap set to 20 thou. It's a BTH mag, looks to me in good order. He said he'd recently had it professionally overhauled.

I would welcome any advice on how to get the old girl running properly!

Thanks

Miles

"Appletop" should be able to give you some advice on your Petter M.

Thanks Blue cat

Hopefully Appletop will notice my suffering and take pity soon

Whack a multi meter set at 20kohms on the HT lead and measure to the magneto body, if its below 3kohms it needs a rewind.

Not sure which oil system you have on the 2.5hp, does it have the wells on the crankshaft and Are these running dry fast?

Have you drained the sump of oil petroil mix? I used to have a tap on mine to blow off while running to keep it a bit cleaner.

Are you using clean petrol (not mixed with oil) I wouldn't bother with paraffin unless you are running loaded.

Get the hottest plug you can find, Lodge BBL for petrol. For paraffin Petter used the 3BL.  Champion D21 is a suitable alternative.

Finally the M needs to be well loaded to run right. Decent size rotary/centrifugal pump or dynamo is the best option.

HTH

Cheers, Steve

Ahhhh the joys of Petter M ownership!!!

As Steve said, an M needs a really good spark, I had a 1.5hp Peartop and that had a weak mag and would oil up and stop and was just a pain in the but.

I would think if it is a 1923 then I would assume it has the pressure lubricator? Although from what I can remember the pressure lube had the Thompson Bennett mag and you say you have a BTH?

Taking it as the right BTH mag and ring oilers mains if you fill the left side oil bath every time you run it then you are over oiling the engine, that side feeds the mains and big end and is topped up with the drip oiler set at around 15 drops, if you top this up before starting then the extra oil is fed into the engine and it will "oil up" the plug and stop.

There should be a drain tap on the back of the crankcase, open that and let all the extra oil out, if you do this before starting rock the flywheels back and forth so it pushes all the oil out.

Assuming you aren't mixing oil with the fuel?

A good way to set a Petter M up when running is to hold a rag on the flywheel to give it a "load" you can then shut the mixture screw down until you hit the sweet spot when it'll 2 stroke nicely, it should be about a 1/4 turn out from fully wound in.

Finally, plug choice is important, as Steve said, a Lodge BBL (Good luck finding one!) or a Champion D21 seem to work ok.

Crack on, see if that helps, if not then come back with a video and photos if possible and we'll have another look....

Thanks so much guys, really helpful advice!

Not tried the multimeter yet, but I did change the plug for a new one I had spare for my Lister A. But I've ordered a D21. There is a spark but it's very dull.

The oiler is the little cast iron tank on the left side with a drip-sight. I've wound it off for the moment so I know that it's not making the oil situation worse.

There is no drain for either the crank case or the fuel tank unfortunately. Or at least I can't see one!

I'm not mixing oil and fuel, it's just fresh unleaded going in now, I gave up with the Paraffin. It's definitely a BTH mag. The previous owner was very keen to tell me that it had just been renovated at some expense, and to be honest it does look in very good order visually, but the spark is barely visible when cranking it over by hand.

I understand that it needs a load ideally. I don't think it'll take much load, I almost stopped it using my bare hands on the flywheel, and I did stop it using my knee with thick trousers. This doesn't seem right, it should have more beans than that.

Is there any way of improving the spark on these? I don't know much about Magnetos. I've got a Lister D and a Lister A that both have them of course, but they've always worked absolutely fine, never bothered trying to tickle them.

Thanks for your help, I really appreciate it.

If you have a very weak spark you may have a faulty capacitor or the magneto needs a rewind.

Maryalice

Coils, point and condenser all must be in good order. If it was renovated proper I'd expect to jump a decent gap.
Easy checks are continuity, make sure there is a path to earth from the HT lead to the engine body, make sure there is no oil/muck/paint on the magneto bracket.

Sound like the timing is out if you can stop it fairly easily. Not been set at TDC as would seem common for many "show" engines.

Get some photos up, let's have a look...

There should (Doesn't mean there is) be a drain but the slightly earlier Victory model has a bung and not a tap as it's a wet sump.

Does sound like your mag is on it's way out though....

Thank you all for the helpful advice, I do really appreciate it.

I have a short video showing the engine and its ancillaries. I am not allowed to post links as I'm a new member so just go to YouTube and cut-and-paste in the video code given below into the address bar when looking at something else, and it should come up.

UVCZxWN_rcQ

Unless a moderator might be so kind as to insert the proper link.

The new plug has arrived but I've not tried it yet. I did a resistance test from the end of the HT lead to the engine body (metal part) and it came out between 600 and 700 kilo-ohms. That seems quite out of the suggested range, am I doing it right?

I wonder if I'm using the mixture wheel correctly to. I turn it clockwise as far as it'll go which I presume is full-fuel, then wind it off a little bit after it starts. I'm not quite sure if that's right!

600kohm? That is a lot! 3-5kohm is the norm depending in the magneto. What range was you in? It's looking like you may need a rewind.

I'd probably take the magneto off and try it on the bench in isolation. HT lead to magneto body and if that's still high, remove the pickup and read from the slip ring.

Your video is set to private.

Can't find UVCZxWN_rcQ ?

Woodsman wrote:Can't find UVCZxWN_rcQ  ?

I'm very sorry for that error! It should be OK now.

StuartTurnerSteve wrote:600kohm? That is a lot! 3-5kohm is the norm depending in the magneto. What range was you in? It's looking like you may need a rewind.

I'd probably take the magneto off and try it on the bench in isolation. HT lead to magneto body and if that's still high, remove the pickup and read from the slip ring.

Your video is set to private.

It's an autoranging multimeter. Hmmmm OK perhaps I will try taking the mag off. Never done that before! But hopefully not too difficult. I believe the dots need to mesh when I put it back

myulz wrote:It's an autoranging multimeter. Hmmmm OK perhaps I will try taking the mag off. Never done that before! But hopefully not too difficult. I believe the dots need to mesh when I put it back

I don't know your engine, but I tend to set mine to a known position such as TDC and take pics of any timing marks, maybe highlight with a paint pen or Tippex.

Key upright iirc

Just had a chance to have a look at you video, doesn't seem to be running bad for an off load Petter M. You won't get it to two stroke off load.
I'd ditch spark plug cap and get a brass/copper terminal instead.

Don't suppose you have a serial number on the flywheel? Normally stamped opposite the key iirc.

I will try again, somehow my previous comment went into the wrong posting.....
Steve is quite correct, get rid of the resistor cap and just use a brass terminal.  This  could account for the feeble spark. Never ever use a plug cap with a magneto.
Eric