Trouble lighting Monitor 2-pint silent (15?) Stove

Maybe George, kerophile, will prove me wrong but I don't think a 3 or 4mm gap between top of outer cap and pan would cause underburn or the flame to extinguish. I have a Primus 5 that runs fine with a small gap between pan and cap.
All of my silents start with only 1 or 2 pumps. Having to pump 10 or 20 times just to start seems excessive and sounds like the pump system isn't up to par. If I pumped 10 times before lighting, there would be too much vapor and I'd like an initial flare up.

 

Hi @Macaroon . The reason I asked about the gap size was because it looked rather small in the photos you provided.
I believe that a silent burner will run with only a small gap (or even with the kettle balanced in contact with the outer cap)
However, I was concerned that you might have touched and moved the top cap when putting the kettle on the trivet, allowing the flame to jump under the bottom lip, putting the stove into under-burn.

Good luck with the new cups when you receive them.

Best Regards,
Kerophile.

 

The last weekend and few days were rather too busy to try out the new burner, however I had a spare minute or two tonight.....

So I fitted a brand new jet nipple to the NOS burner and fitted this to the riser. Primed with meths twice, pumped and lit at the cap (which was definitely fitting snugly) and the result? Sadly underburn once again! I tried 3 times without getting it to light at all. Either this stove is jinxed or I am!

I'm at a loss completely - at least with the original burner I got some results once I'd fitted a new jet nipple and tried pumping harder.

Seems like I'm at the end of the road and I'll have to stick to my 210! Anyone want to take over with this Monitor?

 

@Macaroon - what part of Kent are you in?

 

@Macaroon .
I wonder if you have a leak at the joint where the burner seal is between the riser, preheating dish and burner.
If you have a new seal there it doesn't guarantee that you have a good gas tight seal. If there is the slightest leak there it will cause flashback then under burn once the gas reaches the top of the operating burner.

I use a small pencil type blow torch and use the fine blue flame to play around the joint(including under the preheating dish) to check if that is the problem(while the stove is going).
If the flame turns from a nice blue to yellow anywhere around the joint it shows you have a leak.
If that is the case, you may be fitting the new seal(s) incorrectly.

I have in some severe cases applied a little exhaust cement to the cleaned burner thread(directly under the spirit dish and its seal) and once fully assembled, used the same fine flame from a pencil blow torch to cure and dry the cement before trying to operate the stove again in the usual way.

Being a silent burner, the preheating flame must be allowed to be fully extinguished before you next close the air bleed screw and pump a little pressure into the tank, then light the gas at the TOP of the burner. Let the stove run for about a minute to get the burner operating hotter then pump up further to get the desired flame level.
Hope this helps. John

 

Pity I’m in the States. There has to be a simple problem being overlooked.

 

Are you getting a good fuel flow to the burner from the riser? Your problem could be in the fount.

 

Thanks for the helpful comments people. Interesting point made by @threedots because I have put a high quality new washer (from the Fettlebox) above and below the spirit cup. Maybe I have indeed fitted them incorrectly; I didn't have any trouble fitting them to my Primus 210 but hey I guess I may need to try your trick with the lighter to be sure! The term flashback seems to describe what I experience, with a flame between the jet nipple and the underside of the burner as well as the flame around and under the caps.

What is puzzling me is that after priming and then pumping in readiness for lighting I am getting plenty of smelly paraffin vapour coming out of the burner caps which I gather indicates that vapourisation is happening correctly. With the original burner and enough pressure I was able to get this to light correctly, before putting the saucepan on. With the new burner it is just roaring from the start, no proper hissing burn at all.

@Go Scout I am in the Tunbridge Wells area.

 

@Macaroon

In a ramble round my unread posts I re read this one.

https://classiccampstoves.com/threads/old-roarer-burner-heads.6479/page-4

I've had silents that took a few attempts to settle, possibly because of loose bits dragging through. Not that I'm suggesting the decoking methods described
in the thread but a thorough clean of the burner may prove useful.

It's something that a couple of my silents would benefit from thinking about it.

On a roarer the hot bits you can see ejected, on the silent they just end up in the gas mix between the caps.

I've certainly taken several goes to get one or two to finally play ball.