Monitor (not so) high speed picnic stove

I’ve been doing my best to fettle my late model Monitor high speed picnic stove. I’ve replaced the lead washers and cap cap seal as well as the pump leather and NRV pip.

It will start and runs alright. However I wonder if it should have a little more power.



It also has an intermittent pumping gremlin. The issue is that around every third pump the pump pushes in to easily without moving any air. I think that the assembly which holds the leather occasionally catches in the ‘open’ position on the inward stroke. I’ve cleaned it totally and checked for and debris. I wondered if perhaps the leather wasn’t giving a good enough seal so I tried reinforcing it with a little extra leather which helped a little.

Once pressurised it runs ok however as test I pitched against an Optimus 96. I have two virtually identical kettles so I filled them both with the same quantity of water and set both to boil. Needless to say the Optimus won by nearly 2 minutes.
I maybe expecting to much from the Monitor but I still feel it should run better. Any advice would be very welcome!

 

Some of my stoves have pump issues too, I think it is the leather is too hard and/or not sealing every stroke. Remedy seems to be a new pump cup.
Duane

 

That’s what I thought to at first to but I’ve tried replacing the leather twice now, both times with replacements from fettle box.

 

I'd suggest giving it a leak test. Empty of fuel, finger over jet orifice, pump up to pressure, immerse in water. Look for any bubbles, report back.

It should put out as much heat as it's Swedish friend without bother.

 

I have a Monitor 17b touring that absolutely was weak and anemic after a rebuild. Just could not figure it out. Dunk test showed bubbles out of the NRV even after a rebuild and gasket change. Switched the NRV to a primus NRV I had that was a new-made unit from Japan. Problem was gone. Dont know why it didnt like the NRV it came with...maybe it was the spring or some manufacturing flaw but would not run right at all. Take the pump out before the dunk test (pump it really quickly with the screw loose and pull the pump out) as I didnt see the bubbles the first time as they must have been really small and held by the pump leather.

 

Thanks for the advice, I’ll try the submersion test and report back!

 

I’ve been squirting denatured alcohol into any pump tubes when checking for leaks, saves getting any water into the NRV/CV and tank, it only washes any lube that was used to help the pump slide, easily reoiled.
Duane

 

Try wire brushing then soaking the pump leather in oil. May give it a bit more oomph.

I've put a couple more in post to you just in case.

 

Thank you! I’ll give that a go.

I’m away from the shed for a few days so will try various tests and replacements next week

 

Update: the dunk test didn't reveal any leaks, but I thought I'd try replacing the NRV and pump leather anyway just to be sure. HOWEVER: unfortunately I cannot now test if these solved the issue as I did a stupid thing: I left the shed door open and dropped the circular brass slotted nut which holds the pump leather in place. 2 hours on my hands and knees searching through the grass yielded no results. Sadly this means I cannot currently reconstruct the stove... oh dear.

 

If it helps, you are not alone. I did something similar (lost the small retaining nut from the end of the pump shaft) with a monitor stove of my own a couple of years ago!


-R

 

Thank you, that makes me feel (a little) less daft. What did you do for a replacement? being a different set up to Primus / Optimus etc i can't seem to find a readily available part to swap in?

 

@optiben80 I too have made similar mistakes thankfully I spotted it as it fell and it didn't bounce too far.
It's amazing how far things can travel when dropped from a workbench. Nuts and washers seem to bounce in direct relationship to how urgent the work is and inverse proportion to their physical size. And often made worse by the grey or light blue floor coverings in many of the labs I've had to work in making the perfect camouflage for tiny steel items.
Are there no metal detectorists that you know of nearby?
Regards
John

 

Sadly no detectorists nearby that I know of! I think I may have to accept that it has become an unintentional offering to the stove gods.

I just have no idea how to source a replacement! Any suggestions would be welcome!

 

@optiben80
I'm unable to search my workshop in my present condition as it's a hazard on crutches but sure I'd have a comparable one. I have a memory like a sieve so drop me an email in 3 weeks time to remind me.

 

@optiben80 The Monitor 17B (I believe) is the same exact stove other than your stove has buttons for legs and mine has folding legs. Parts are interchangeable. That being said I pulled my 17b and did some measuring. The pump shaft on mine is 17.3mm.

Why is this nice to know?

Because the primus number 1 and any other large 2 pint stove is 17.2mm in my collection (variance of a 10th here and there)

So....you are not out of luck. Try calling Mike at Basecamp UK Pressure stove, lamp & Lantern index and tell him you need a complete pump leather holder for a Primus number 1.

I just put mine into my 17b....and it pumps air. You can get your stove back working for VERY cheap as these are super common parts.

You can probably get that to work. Worth a shot as it tested ok here.

 

thats really kind of you thank you!

 

Thank you so much for going to all that effort, I really appreciate it! I got onto Mike at Base Camp and he said he has a used Monitor part that might work so fingers crossed! If it doesn't work i'll go down your suggested Primus number 1 route! many thanks to you all for all your support!

 

Sadly the Monitor part from Mike at the Base Camp isn’t going to sit my stove so whenever you’re ready

 

I have stacks of pump bosses & a Monitor High Speed to check them against. I'll get on it after Newark