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MTD 990 Twactor Guy
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:banghead3 It's been a long, cold winter up here in Northern Wisconsin, and I was really looking forward to getting the 990 out to do some Spring clean-up.

Before I put it away for Winter, I had picked up a new (yes, brand new) carburator and installed it. Only had time for a "test run" to make sure everything was working correctly - which it was, but it wasn't. It started fine, ran fine, but I had gas coming out of the bottom of the carb. Ugh! Anyway, I put it in the shed with plans of fixing the gas problem this Spring.

Pulled it out of the shed this morning, tore the carb off and checked it all over. Yup, it had a float and the needle seemed to be working fine. Put everything back together, and charged the battery over lunch. After lunch, I was ready to fire it up, hook up the lawn roller, and flatten out the back yard from all the deer coming in all Winter.

Turned on the gas, set the parking brake, pulled out the choke, put the throttle on high, and hit the key. Well, it didn't start - it went "bang" - big ole back-fire. Back to the Spring tear down again to check and see if Micky and Minnie get into the wiring again, re-set everything and try it again.

Is it just me, or does everyone else have problems with these old 990's? Sure doesn't seem to be very reliable! I think the back-fire is due to a timing issue - correct? Any ideas why I'm still getting gas coming out of the bottom of the carb?

Thanks,
Rich
 

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It seems if you don't start them every few weeks, they get mad at you and let you know it.

I try to fire mine up every couple of weeks to keep them happy, even if I do not plan to do anything.
 

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:banghead3 Is it just me, or does everyone else have problems with these old 990's? Sure doesn't seem to be very reliable! I think the back-fire is due to a timing issue - correct? Any ideas why I'm still getting gas coming out of the bottom of the carb?

Thanks,
Rich
Quoting from another post "These old tractors are a lot of work".

Your are right about the problems of these old tractors. I have found reliable is not a strong point with any of my 990s. Points and carb are at the top of the recurring problems list.

Fuel that gets sucked up into the engine while cranking can accumulate and run back down into the carb if the engine does not start. This can be mistaken for a float problem. A sticking float is also common.

Putting a filter in the gas line is a good idea but does restrict flow from the tank. The 990 has a fuel flow issue from the tank as it is.
 

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put a filter on mine next to carb and would stall out at 1/2 tank never did this before put filter on so moved filter to bottom of tank and now was running with less then 1/4 tank now.
1976 990 dayton
 

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I just love your machine. I bet you get a lot of interest when you work the old girl.
 

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ROJ
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I don't think the reliability issue is just 990's,any time you have 40 year old tractors they are a hobby. If your tractor set all winter with untreated gas in the system you may have gummed up jets and needles in the carb.
 

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I also feel todays gasoline is causing problems with old engines. I use lead substitute in the 990s.
 

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The cure to a poorly running 990 is to change the numbers to J2030H. I am willing to bet that will solve the problems.
 

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