One lung FM Z 1 1/2 HP

[Geo46]

Good morning, I am new to the forum and not sure where to post this , anyway we have a Fairbanks Morse 1 1/2 HP Z , someone has removed the original mixer and installed a Flo Jet carburetor, apparently it did run at some point, we are looking for a substitute for this carb as it is prone to leaking, any thoughts?
Thanks
Geo46🇺🇸

[cnr6400]

Welcome to the forum. Have you looked at all on Smokstak.com? Plenty of info there on FM 'Z's , and a sales / want ad bulletin board too. You might try a rebuild kit for the FloJet carb in the meantime, it might help fix the leaks. 

[Geo46]

Hi, yes I am a member of that forum, just looking for other inputs, carb has been rebuilt, they are prone to leaking.
Geo46🇺🇸

[gipetto]

If it were me i think i'd try adapt a motorbike carb to it. Honda 50cc are about the smallest that i know of, they are 4 hp, so they should be a good match.

[Geo46]

Thanks, looking at all options, any idea on Honda P/N?
Geo 46🇺🇸

[Bluechip]

If it were me i think i'd try adapt a motorbike carb to it. Honda 50cc are about the smallest that i know of, they are 4 hp, so they should be a good match.

My Mantis cultivator has a Honda 22cc OHC engine.  Maybe too small ?


https://www.ebay.co.uk/itm/175659641621?chn=ps&norover=1&mkevt=1&mkrid=710-153316-527457-8&mkcid=2&itemid=175659641621&targetid=4584757337008490&device=c&mktype=&googleloc=&poi=&campaignid=431353847&mkgroupid=1298523655396099&rlsatarget=pla-4584757337008490&abcId=9301942&merchantid=87779&msclkid=b28ce512d43017a91e818044e67cec4f

D.

[Geo46]

Thanks, I’ll check it out
Geo46🇺🇸

[Alyn Foundry]

Hi.
I rallied several of these engines years ago. One of which was missing the carburettor. I made patterns and castings for it.

Please see attached.

Cheers Graham.

[Alyn Foundry]

Not sure whether you missed my previous post….

Originally these engines were dual fuel. The carburettor has a small chamber that is filled with Petrol/Gasoline and an inbuilt needle valve to adjust the mixture. Once running the engine would start to get hot enough to transfer to the main fuel, Paraffin/Kerosene which was stored in a large rectangular tank carried between the skids. The Venturi area has a front cover that has a spring loaded valve, effectively acting as a choke device.

I have a set of Iron castings, unmachined, but I don’t think the original style carburettor would be suitable for what appears to be a mobile unit.

   Graham.

[Geo46]

Thanks for the reply, I am well aware of the original mixers, seems like you are more capable then we are, someone retro fitted this with a Flo Jet, I believe it was to get better throttle control as this was used on a small locomotive, my main goal now is to find a carb other than Flo Jet even if it means making a new manifold, not sure how to size a carb.

[Vixen]

It would help if you were to tell us the engines capacity and required operating speed. It should then be possible to recommend a suitable commercial  carb
Mike

[Geo46]

Well it’s a 1 1/2 HP about 450 RPM, open crankcase , 5” piston, intake valve controlled by an external spring.

[gipetto]

I suggested a honda 50 carb before, but given your figures it would be way to small. I would suggest a mikuni vm clone. they are flange mount, sold on aliexpress. I love them as they are more reliable than the pz series. I'm just guessing as to a size, but i had one on a 220cc honda fourtrax and it ran great. to be more accurate, you would have to calculate the horsepower of a motorbike/atv engine at the same 450rpm, not especially difficult since horsepower doubles with rpm.
for instance, a honda recon 250cc generates 15.6hp at 6500 rpm, therefore the same engine will generate 1.08hp at 450rpm because 6500/450=14.4 and 15.6/14.4= 1.08hp
I fitted a mikuni vm22 to my honda fourtrax, so it will run, but you might want a larger model such as vm24.

[Vixen]

 A honda recon 250cc generates 15.6hp at 6500 rpm, therefore the same engine will generate 1.08hp at 450rpm because 6500/450=14.4 and 15.6/14.4= 1.08hp
I fitted a mikuni vm22 to my honda fourtrax, so it will run, but you might want a larger model such as vm24.

If the vm22 can deliver enough air/fuel to run a 250cc engine at 6500RPM then it will be capable of passing about 15 times too much air/fuel for a 450 RPM engine. IMHO, a much smaller carb than a vm22 is required, not larger.

Mike

3mm (correction 6mm) diameter is about 1/15 the area of 22mm diameter. Therefore, the carb from Bluechip's Mantis cultivator, which has a Honda 22cc OHC engine would be much closer to the mark


https://www.ebay.co.uk/itm/175659641621?chn=ps&norover=1&mkevt=1&mkrid=710-153316-527457-8&mkcid=2&itemid=175659641621&targetid=4584757337008490&device=c&mktype=&googleloc=&poi=&campaignid=431353847&mkgroupid=1298523655396099&rlsatarget=pla-4584757337008490&abcId=9301942&merchantid=87779&msclkid=b28ce512d43017a91e818044e67cec4f

[gipetto]

Well I could be wrong, but I think my math is correct, since it's not especially difficult to calculate. The only issue i can see is that a vm22 may not allow the engine to idle at that slow a speed, the pilot jet could rev higher than the max rpm of the engine. from a quick search, polaris atv idle at 1200 rpm.
I guess to avoid the idle issue it would be better to go small. It may run, but the power it produces will be abysmal.

[Geo46]

One problem with the cultivator carb, it has a primer bulb which may be a problem to retofit , tank is a 1 gal mounted on the top, rather not have primer if possble, another problem I just incountered is that the engine was submersed in seawater during Ina, not sure what the results are at point, these engines are pretty tuff, I will still need a carb.

[fidlstyks]

Did you find a carb, they are common here in US, where are you? There is always one on eBay for sale, I am sure I have one extra.

[Geo46]

Hi All, I am beginning to think that we should try and find an after market Flo Jet That is mounted the same way as the problem child, throttle linkage could remain the same, hopefully, any suggestions?
Thanks

[Geo46]

Hi All, I have installed a GX160 carburetor, modified a manifold, not getting fuel into the cylinder, however I placed a small piece of gas soaked paper into the throat of the carb and turned it over and I got a couple of pops, thinking of increasing the size of the main jet, any suggestions?
Thanks

[Admiral_dk]

I'm pretty sure that the cultivator carb isn't working as it needs to be connected to the Crankcase for the pumping action (a small hole not far from the Venturi) ....

As for the Honda Carburator - first check that it gets fuel to the Float Chamber etc.

A good guide (from Honda) can be found here : https://www.honda-engines-eu.com/files/files/carb-check-gx120-390-gxv140-390-en.pdf

Hope that you get it running. Oh - and please try with a brand new Spark Plug too (I haven't got a number for how many times I've been had, by seeing a nice spark outside the Engine, but no inside).

Per 

[gipetto]

there could be vacuum leaks between the carb and the engine. ensure that you are using good gaskets, even if homemade at every joint. it's ok to use some easy start to see if it will fire. first check to see that compression on the engine is good. it can be much easier to start an engine with an electric drill, maybe in your case it's too large to do so. you might need to choke the carb also.

it would be better if you could see the carb running on a gx160 so that you know it is good.

[Geo46]

Hi, from my calculations it appears that it engine about 58 ci,  17 CFM and the suitable carb would be  7.3 CFM , where would I find a carb that size?
Cheers!

[Geo46]

I have compression, sealed all around manifold, it will pop when I spray starter fluid, not getting gas from carb, will try changing main jet.
Thanks

[Geo46]

Hi All, after further investigation, the cyclinder bore is 4” stroke is 4” and the RPM’s are 500.
Can someone check my figures it seems I come up with 800 + cc’s.

Thanks

[gipetto]

wolfram alpha says the volume of a cylinder of 4" diameter by 4" length is 6.28 cubic inches or 103cc

[Vixen]

wolfram alpha says the volume of a cylinder of 4" diameter by 4" length is 6.28 cubic inches or 103cc

Who or what is wolfram alpha?

Pi * r squared * h     says the volume is 50.272 cu inch or 823.81 cubic centimetres

[crueby]

wolfram alpha says the volume of a cylinder of 4" diameter by 4" length is 6.28 cubic inches or 103cc

My math comes up with 50.266544 cubic inches, 828.63417757 cc's. Your answer of 6.28 is way too small for a 4" bore. You forgot to square the radius, and then multiply by pi, and then the length of the stroke. 

[Kim]

I'm not an IC guy, but isn't the volume of a cylinder calculated (Pi) * R^2 * H?  So if the R is 2", and the H is 4", I get

3.1415 * 2^2 * 4 = 50.264 in^3

and 1 in^3 = (2.54cm)^3 = 16.38cm^3

So I'd come up with ~823cm^3

Is it somehow different for engines?
Kim
 
----------------------------
Oops - my post overlapped with Chris's AND Mikes.  And I think their answers are right.

[gipetto]

wolfram alpha says the volume of a cylinder of 4" diameter by 4" length is 6.28 cubic inches or 103cc

Who or what is wolfram alpha?

Pi * r squared * h     says the volume is 50.272 cu inch or 823.81 cubic centimetres

It's a free AI tool for math, came out about a decade before chatgpt. wolframalpha.com. it has worked in the past for me, but i guess it's become abandoned and the results are not as good.

[Geo46]

Hi All, based on the conversion charts that I just used ,and probably should have before I asked the question, it works out to be 50 cui +/- and 819  cci +/- , so assuming that it is 50 cui. what should I consider for a carb?
Thanks

[Admiral_dk]

Just to clarify : My closest experience to your request is a Suzuki LS650 - A single cylinder Four-Stroke, with a 40mm. Carburator. I'm not sure (no rev counter), but I guess that max. RPM is around 5-6000.

Your Honda Carb will flow approx. a sixth and your cylinder volume is ~25% larger ....

Rough guestimate ; it will allow your Engine to run up to somewhere between 1-2000 RPM (everything else being Equal .... But they are NOT).

For my olde LS650 to go down to 500 RPM - the Throttle would be closed so much, that I can't see any hint of light through it (that is almost the case for 1200 RPM).

I must admit that I'm rather surppriced that the Honda carb don't even give a hint of running when Choked 

There are a few here that actually has full size old work engine and I had hoped that one or two would have chimed in by now .... but then again - a good number of those don't even use a carburator ....

Per         

[Geo46]

Well maybe I not using  the carb right, sounds like you are saying I should be closing the throttle completely, to me that sounds like no fuel would flow into the cyclinder, I have 6 months to figure this out, your correct about the older engines not using carburetors they use mixer which is a form of carburetation

[Admiral_dk]

OK - I should try to explain a few things better.

A number of old engine ran on Town-Gas (or other kinds of gas) - not gasoline - so no carburator.
Others ran on Oil - like old Hot-Bulb Engines - were the oil was injected into the Hot-Bulb (low pressure) - again no Carb. The Kerosene Engines had somekind of Mixer as you mention.

Starting Procedure ; no two Engines designs has the exact same best practice - but in my experience tells me that it is almost completely impossible to start a cold engine with an open Throttle.
In my youth, I used to slowly open the throttle during cranking, from closed to a bit over fast idle ....
If no succes - slowly closing again. I used to be able to hear when I was close to succes - Electronic Fueling and Ignition, has decreased my abilities over time ....

Unless the weather and Engine is warm - I also expect you to have to use somekind of Enrichment function - like a Choke - for the Engine to fire.  Almost all those devices do NOT work if you open the Throttle much over Idle.

As you haven't got the Carburator dialed in for your engine yet - you will have to experiment with the exact Throttle position for starting.

I noticed that your Honda Carburator includes a Fuel valve - I hope that you have it in open position when trying to start the Engine. I mention this as I have never seen any other carburator were this valve is build into the carb itself.

I hope that I'm not telling Granny how to suck Egs 

Best wishes

Per

[gipetto]

when i need to find out if a carb is switched on or not, i simply remove the bowl to check is there a fuel flow. this also works to clean out any bad fuel.
There's no reason you can't run ganged carbs to get more fuel and air, if the honda carbs are easy to come by, and you feel like fabricating a suitable manifold.

[Alyn Foundry]

There were 1000’s of this particular engine manufactured during the early part of the last century. The carburettor is quite a simple affair. A small box along side the Venturi carried enough Petrol/Gasoline to get the engine hot enough to vaporise its running fuel, Paraffin/Kerosene. The front of the Venturi is covered by a spring loaded choke plate. The air is then drawn across the adjustable jets in the Venturi proper. As the Venturi opens out the air is met by the throttle plate ( Butterfly style ) which is fully open when starting. This throttle plate is activated by a centrifugal governor fitted in the halftime gear.

This engine originally had the main fuel tank mounted between its skids, underneath it. The fuel was drawn up through a non return valve. Your engine has a gravity fed fuel system.

Only a week ago a carburettor was being offered, complete with both fuel jets for $15.00 and shipping. There are several FB groups running over the pond for the vintage stationary engine movement.

You could fit a fuel check valve in the line which would allow you to gravity feed the original carburettor without it constantly running. These were fitted to many Asscociated Manufacturers ( Amanco ) engines that had the fuel tank mounted above the carburettor.

   Graham.

[Geo46]

Good morning, I do get fuel to the carb, I will try closing the throttle, never would have considered that, I am thinking of increasing the main jet size to the largest available, won’t be for 6 mths. But still need more suggestions. This is a work in progress.
Thanks

[Geo46]

Another question just came up. The GX160 comes with 3 gaskets which is the correct one for our setup, 2 have a small a small hole which we assume line up with the small port,