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Kubota B7100 Rebuild starts rough

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DKraft4LJT
Join Date: Feb 2004
Posts: 2 Indianapolis
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2004-05-28          87141


I just did a complete rebuild on a 25 year old B7100. The motor was rebuilt by the dealer - rings, valves, bearings,
glow plugs, injectors - the whole nine yards. When first started it runs rough and puffs white smoke for about 30 seconds and then smooths out and runs like it's supposed to. The start-up drives me crazy, anyone got any ideas?




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Kubota B7100 Rebuild starts rough

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DKraft4LJT
Join Date: Feb 2004
Posts: 2 Indianapolis
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2004-05-29          87149


Hey Art White, Are you out there. I've looked at your responses for a couple of months and you seem to know this stuff pretty good. Any ideas on my B7100 post? DKRAFT4LJT ....


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Art White
Join Date: Jan 2000
Posts: 6898 Waterville New York
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2004-05-30          87252


The older the diesel engine the harder the starting and conditions of the start are close to as you described. There are many things that go into a good valve job that makes starting easier and not knowing if they did it makes it hard. Did they use the Kubota head gasket? Did they set the valve protrusions to the proper spec's? A diesel runs on heat and compression and unless things are in the compression departments. Not being able to see it is tough but I'd also give it a little running time at least 100 hours for all the new parts to seat in before getting to nervous. As I said in the beginning 25 years ago diesels didn't start like they do today and for the believe it or not 30 seconds to clean up on some makes would be unheard of! ....


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Kubota B7100 Rebuild starts rough

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KenPike
Join Date: Jan 2011
Posts: 3 Canada
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2011-01-17          176458


My 1980 B7100 (purchased about 2 months ago from a buddy) starts exactly the same way. Alaways starts right up but runs rough & blows white smoke for about 30 sec before it smooths out & runs with no smoke, white , black or otherwise. It runs really well & makes good power. It sat outdoors, neglected & not run for a year before I bought it, but injectors & head were rebuilt a few years ago. Shows 2700 hours, uses no oil & works great. I plan on checking each glow plug when I get it back into my shop. ....


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candoarms
Join Date: Mar 2007
Posts: 1932 North Dakota
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2011-01-17          176463


KenPike,

White smoke is usually a sign of atomized fuel that hasn't ignited. The injector shoots the raw fuel into the cylinder very near the top of the compression stroke. If it doesn't ignite, it goes out the exhaust as a white vapor.

Ignition problems are usually related to cold engines, low compression, too little fuel, or contaminated fuel.

You might want to try boosting the cetane rating of your diesel fuel. There are additives that you can add to your fuel which help to increase the fuel's ability to ignite.

Just be careful not to add too much of the stuff, as an extremely high cetane number will cause the fuel to ignite well before the piston reaches top dead center. This will cause a severe loss of engine power.

I use a product called Power Service Diesel Fuel Supplement. (White bottle with a red cap.) It's sold at most any gas station. When used according to the instructions, it should boost your cetane ratings (fuel ignition) by up to four numbers.

Click on the link below. Add a couple of ounces of this stuff to your fuel tank on your next fill. Give it a try. A bottle of this stuff runs about 10 bucks, but there's enough there for at least 20 tanks of fuel in your B7100.

Let us know if this helps any.

Joel ....


Link:   Power Service Diesel Fuel Supplement

 

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Kubota B7100 Rebuild starts rough

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hardwood
Join Date: Dec 2002
Posts: 3583 iowa
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2011-01-18          176467


There can be problems that a fuel additive won't fix, but along the line of what Joel said I've used Power Service the white jug stuff ever since I've had diesel engines. While we farmed I used to buy it by the case and use it year around according to the label directions. I still use it in my 4310, but don't need to buy a case at a time anymore. I'm sure there are other brands just as good or possibly even better than Power Service, but in all the time we farmed I never had to have an injection pump worked on and can only remember one injector that something went wrong with. I can't say with any authority that the Power Service kept all the diesel demons away, but used to hear of other farmers having injector pumps overhauled, injectors replaced quite often etc. It made a believer out of me.
Frank. ....


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KenPike
Join Date: Jan 2011
Posts: 3 Canada
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2011-01-18          176482


Thanks Joel, but didn't think I had anything wromg with my tractor! From what I've read on this forum & at least 3 others this is a very common start-up scenario with these little diesels. It sounds/works great after the initial 30 sec or so start-up routine & fires right up without excessive cranking, sitting outdoors @ -19C for the last 2 or 3 days. I have been adding a fuel additive (not sure if it boosts my "whatchamacallit") & a glug of ATF, since the old girl sat outdoors for over a year without running. Just ran it for 45 min. pushing back the snowplow banks getting ready for our next snow fall over the next couple of days. ....


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