Marvel Schebler carb fun (2010 frankenstein crawler)

General help and support for your Lindeman through 2010 John Deere crawler
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magnus
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Marvel Schebler carb fun (2010 frankenstein crawler)

Post by magnus » Tue Apr 28, 2015 5:55 am

I own an early 2010 loader that the float failed in. I had the carb out before and it has what I would call a restriction cone below the accelerator butterfly.

This is not the original engine. From what I can tell someone converted a diesel to a gas with the engine out of something like a generator. Instead of it idling up under load you have to throttle it up and when it loads up it will let it throttle up. It works though.

So I was wondering if anyone else had seen one of these restriction cones in the carb and if I should remove it when I put the new float in or just leave it.

I think the number was a TSX 866? I don't have it in front of me right now.

vtjoe
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your carb

Post by vtjoe » Tue Apr 28, 2015 6:25 am

i think it is a venturi..... not a restriction
a true carb part
1957 420C four roll since 1982

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Stan Disbrow
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Post by Stan Disbrow » Tue Apr 28, 2015 6:47 am

Hi,

I also think you are looking at the venturi. That is a tapered restriction to the airflow. It causes the air to speed up as it passes thru. This lowers the air pressure and, since the outside air pressure is now greater, pushes the gas thru the jet and into the airstream.

All carbs have one, or they do not function at all. On these carbs, they are quite obvious. On other brands, not so much. MS used one carb body to make several models by changing which venturi and jet set they installed. That was their way of dialing in a carb to an engine.

As an aside, I like the MS way a lot better than, say, a Weber. Those things have six sets of jets and fuel/air premix tubes which have to be fiddled with to tune a carb to an engine. The best way to do that is to use glass spark plugs so one can see the color of the burn in the cylinder. You have to load the engine at several RPM points while watching. Oh, and Webers are one carb per cylinder, so tuning takes all day even on a four cylinder. Eights are worse, and I have tuned twelves, which still makes me shudder just thinking about it!

For those who don't know, I spent over twenty years racing, mostly sports cars on road courses. Hence the 12 cylinder engines from time to time.

Crawlers are a lot easier! ;)

Back to the machine we're discussing. Check your governor. Your description sounds like a sluggish governor. It probably suffers from lack of lubrication, a commonly overlooked maintenance item.

As far as an engine swap, those are also common. Deere used the same basic engines in many things. The most common donors are ratty old combines. They often look a little different, many having side covers for valve adjustments since combine engines are tough to do that by removing the valve cover on top.

I do not have a handy reference for which carb goes with which engine.

Stan
Last edited by Stan Disbrow on Tue Apr 28, 2015 7:56 am, edited 1 time in total.
There's No Such Thing As A Cheap Crawler!

Useta Have: '58 JD 420c 5-roller w/62 inside blade
Useta Have: '78 JD350C w/6310 outside blade
Useta Have: '68 JD350, '51 Terratrac GT-25
Have: 1950 M, 2005 x495, 2008 5103 (now known as 5045D)

magnus
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Post by magnus » Tue Apr 28, 2015 7:03 am

I guess it is I just imaged searched marvel schebler exploded view and it is labeled venturi. I'm just not used to seeing one like this. I've rebuilt car ones and I am used to seeing the taper machined in. I actually feel a bit silly now. A drop in for as many different systems as they used these on makes a lot of sense. It still may not be the right one for this application, but it worked ok so I guess I better leave it.

With the mixed parentage of this machine I thought I should check.

Thanks Stan!

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Stan Disbrow
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Post by Stan Disbrow » Tue Apr 28, 2015 8:03 am

Hi,

Well now, I feel a little silly having explained what the venturi does. But, I will leave it in case someone else should be unsure of what it was we were talking about.

Yes, MS carbs are wonderfully simplistic compared to just about any car carb. Even a one barrel from an old six cylinder truck engine. The nice thing is you can manage to tune an incorrect one in good enough unless it is way too large or small for the displacement of the engine cylinder.

I say cylinder because these tend not to care if you have two, four or six of them. Just how much air has to flow how quickly to any one of them. :)

Also, just in case, these are supposed to have a tiny backup fuel filter screen inside the carb attached to the fitting for the fuel line. These clog up and cause all sorts of grief for folks who don't know they are hidden in there!

I say 'supposed to' because sometimes the cleaning method employed is to snip them away. Then, the fine crap gets into the jets causing the need to constantly twiddle the tuning as the fine crap comes and goes....

Stan
There's No Such Thing As A Cheap Crawler!

Useta Have: '58 JD 420c 5-roller w/62 inside blade
Useta Have: '78 JD350C w/6310 outside blade
Useta Have: '68 JD350, '51 Terratrac GT-25
Have: 1950 M, 2005 x495, 2008 5103 (now known as 5045D)

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Tigerhaze
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Post by Tigerhaze » Wed Apr 29, 2015 11:35 am

It does sound like it could be a governor issue, but to be sure you have to make sure the M-S carb is correctly adjusted, especially the "power" screw. All three adjustments have to be made in order or it will act like it has governor issues- I once replaced a governor on my 8N only to find out it was a carb adjustment issue. I believe the M-S carbs used on JD crawlers are similar; you can search for my posts describing ho0w the adjustments work.
(1) JD Straight 450 crawler dozer with manual outside blade; (2) JD 2010 diesel crawler loaders; (1) JD 2010 diesel dozer with hydraulic 6-way blade; (2) Model 50 backhoe attachments, misc. other construction equipment

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Paul Buhler
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Post by Paul Buhler » Wed Apr 29, 2015 5:11 pm

Hi: The MS carb is quite rugged.. I fiddled with mine for quite a while before I was able to get a decent balance between the idle jet and the load jet. Air leaks led me to closing the idle jet completely. Surging as Tiger suggests, (sounds and feels like governor problems) and fouled plugs got me to look closer at the load jet. A 1/4 turn on the load jet makes a big difference in terms of performance and it took me a while to find the right setting so that the machine brings on power smoothly and doesn't foul plugs so it starts easily (I have a recently new load jet installed). Good luck with your exploration into your machine's problem. Paul
Paul Buhler
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chet
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Post by chet » Wed Apr 29, 2015 7:33 pm

One of the problems I ran into when installing the gas engine into my diesel 2010, was the governor that came on the gas engine would not work with some of the interchanges that had do be done for the install. It's been awhile but if I remember right it had to do with the water pump. I installed a governor from a 2010 wheeled tractor and fabricated my own linkage. Could be who ever did your machine encountered the same problems, but wasn't able to get the linkage adjustments just right. I was able to get a 165 gas for my switch, so my problems may have been unique.

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