Rtv excessive black smoke and loss if speed

Ngwarrington

New member
A couple weeks back I picked up a used RTV 900, 920 hours on it. Its also much louder than my other RTV 900 and puffs black smoke upon start up and also when drive around. I searched these forums for a week or so and have done everything I’ve read and could think of. All new filters, oil, cleaned out fuel tank checked intake, remove spark arrester, cleaned out the muffler. Still black smoke and speed still limited. Engine bogs down at 3/4 or more throttle untill i pull back and engine rpms climb again. What now
 

aurthuritis

Well-known member
Site Supporter
does it overheat? black smoke is un burnt fuel. several possibilities for you to explore and check off your list. have you replaced the air filter? is the HST pulling the engine down with excessive drag? are the brakes stuck?"place in neutral with the engine off and see if you can push it easily" also need to check the fuel screw on the front of the engine fuel pump side to see if the tamper proof has been messed with.

does the engine smoke black with the transmission in neutral and the throttle revved all the way? do this test with the hand throttle not the peddle. let us know what you find
 

bordercollie

Gold Site Supporter
Gold Site Supporter
I'd look at the air intake and make sure it wasn't blocked also. I have had a lot of trouble with dirt dabbers and yes.. even rat and bird nests in the intake areas. collie
 

Ngwarrington

New member
All air ways are clear and cleaned including air filters. I adjusted fuel screw in and out made no difference still excessive black smoke. I will try that test next time i go to shop.
 

bordercollie

Gold Site Supporter
Gold Site Supporter
Did you change the fuel filter too? I know you likely did but am eliminating everything possible.
 

v10rick

Active member
Site Supporter
Injectors are not normally a problem with this engine. But if you don't know the maintenance history I would remove and have them checked. Any diesel shop will be equipped to test and refurbish if necessary.

Plan B...
I installed new china injectors from ebay, considerably less than OEM Kubota. With several hundred hours the engine runs as it should.
 

hondajoe

Member
Black smoke

Injectors are probably not your problem unless it has a miss.You should check to make sure your return line going back to the tank is not plugged from the injectors.As far as the rack adjustment screw that screw will make a huge difference.Mine was lean from the factory just one turn out made the difference.So if they screwed it out a bunch you might back in range yet to lean it out.I would go in 2 turns at a time to see if this helps and no more then 6 turns in and mark your turns.Mine smokes just a little at full load or wide open.I have heard of the springs breaking in the injection pump plungers causing this kind of problem at high rpm.JOE
 

aurthuritis

Well-known member
Site Supporter
Injectors are probably not your problem unless it has a miss.You should check to make sure your return line going back to the tank is not plugged from the injectors.As far as the rack adjustment screw that screw will make a huge difference.Mine was lean from the factory just one turn out made the difference.So if they screwed it out a bunch you might back in range yet to lean it out.I would go in 2 turns at a time to see if this helps and no more then 6 turns in and mark your turns.Mine smokes just a little at full load or wide open.I have heard of the springs breaking in the injection pump plungers causing this kind of problem at high rpm.JOE

this very good advice. especially knowing that the fuel screw has been messed with. have you verified that the engine is able to develop full rpm under load?
 

Ngwarrington

New member
I did check brakes and they are all free. I removed the injectors and the back injector had a build up of white corrosion like substance around the smooth part above copper gasket. Im thinking it might have something to do with IP so I guess ill remove that and take everything at once. I can see the return flowing pretty well back into fuel tank so i assume its flowing properly. Btw thanks all for your input ill keep you updated
 

Ngwarrington

New member
I haven't gotten a chance to have IP and injectors tested yet but idk why i failed to mention that there was a good amount of water in the fuel tank and some sludgy material in fuel filter. I Removed and thoroughly leaned tank and lines. Before testing it last time.��������
 

D&D Farm

Gold Site Supporter
Gold Site Supporter
The black smoke indicates to much fuel for the system to burn??? So what causes the fuel delivered to the cylinder NOT to burn efficiently???
 

aurthuritis

Well-known member
Site Supporter
I would guess that you have a broken spring in the injector pump.

as Colorado mentioned. there is a spring that connects to the fuel delivery screw "I THINK". anyway i know there is a spring but it has slipped my mind exactly what it attaches to. if it is broken or out of place the consequences fit your pattern.
 

Ngwarrington

New member
Like I said the machine is so loud compared to our other RTV we have, like really loud it doesn’t sound mechanically bad it’s just a loud engine.
 

aurthuritis

Well-known member
Site Supporter
there can be two causes of black smoke.
1. if everything else is normal then there is to much fuel being delivered. ie. the fuel screw has been messed with.
2. if the transmission or other parasitic load isn't allowing the engine to get up to operating speed then the governor will call for more fuel up to the setting of the fuel delivery screw and an over fueled condition called lugging will occur.
 
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