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Runs on choke only - roughly


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#1 JakeQT17 OFFLINE  

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Posted September 20, 2011 - 08:42 PM

Hi all,

I've started to restore my QT17 and would like your opinion on where to start with tuning the engine. Currently the motor is hard to start and then will only run on full throttle plus full choke. If I drop either the engine shuts off almost instantly. Also when it runs I can hear these dull "dud" sounds. Is that a misfire? It sounds like this errrrrduddududduderrrrdudduderrr ect...

What are my first steps to begin tuning the motor? What would make it so hard to start one day to the next? I've already cleaned everything I could.

Thanks!
Jake

#2 cookiemonster OFFLINE  

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Posted September 20, 2011 - 08:49 PM

This engine is too lean and needs more fuel. Not sure if what you have is a tunable carb or whether you need jets. Also... Cleaning it (inside) may be the only thing it needs. The puff's your hearing are likely it sneezing from being too lean and detonating before the spark plug sparks.

#3 Bolens 1000 ONLINE  

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Posted September 21, 2011 - 05:12 AM

:ditto:

#4 SnowmanPA OFFLINE  

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Posted September 21, 2011 - 09:51 AM

I just ran into a similar situation with one of my QT-16's. Same symptoms...entirely caused by ME as it turns out. My air cleaner housing was seriously cracked around the mount screw holes due to vibration and metal fatigue so I repaired it with two large washers welded on. In doing that I unwittingly covered a vent hole to the float bowl. Once I got the air cleaner mounted on, it ran exactly as you described.

Thinking I had a float level issue, I removed the air cleaner and adjusted the float and tried it again. It ran GREAT! Until I put the air cleaner back on and then it ran HORRIBLE again. I went through this cycle several times, adjusting the float, swapping it with another one, changing the float needle, etc, until I finally figured out that I was blocking the float bowl vent each time I installed the air cleaner.

Once I figured that out, I drilled a hole in my new washers on the air cleaner and I've had no problems since.

So, my lesson learned is to make sure that everything is clean, the float level is good, and the VENT for the float bowl is not obstructed.

Good luck!

#5 JakeQT17 OFFLINE  

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Posted September 21, 2011 - 10:04 PM

Thanks for the tips! I am going to order a rebuild kit and restore the Carb. I'll be sure to watch out for the float vent, my symptoms happen with the air cleaner completely off as well, but who knows maybe the vent is clogged with gunk. I will post pictures, I will start the project in a week or two when I get the kit.

#6 EricFromPa ONLINE  

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Posted September 22, 2011 - 09:16 AM

Ditto on it running Lean.
It's either a partly clogged Jet,Weak fuel Pump,obstructed fuel line,plugged fuel filter,Clogged pepcock in the fuel tank or as Snowman stated,an obstructed carb breather.

I've had quite a few Twin cylinder engines,Briggs,Ohnans and Kohlers that had the same problems.If you get the carb kit make sure you get the one that's $5 more with the Fuel Pump rebuild kit.

Take a Torch tip cleaner and run it through the jet.
Do not use a cheap paper filament fuel filter on an engine with a vacuum actuated fuel pump.The filter will deteriorate and chunks of it will plug the jet,pump and fuel line.
And NEVER use Silicon based gasket maker in or around anything that Gasoline makes contact with.The stuff turns into a slimmy sludge that plugs up EVERYTHING.

#7 HDWildBill OFFLINE  

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Posted September 22, 2011 - 10:25 AM

Ditto on running lean:
The one thing I would add is in troubleshooting I always start off with the easiest simplest thing the problem could be and work towards the harder more complicated areas. I have had so many mowers (push & riding) come in with the complaint it won't run or runs rough and I pull the air cleaner and it is clogged so badly that I just chunk it in the garbage. I'm sure the air cleaner is not your problem but I'm just saying sometimes it is the simplest things that will cause the problem.

#8 JakeQT17 OFFLINE  

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Posted October 03, 2011 - 09:20 PM

Well the carb rebuild did the trick. After putting it all back together it started right up and ran like a champ with choke completely off. Thank You! But, I must have put the throttle cable on wrong because when I went to give it full throttle I snaped the cable. I have been looking through the parts list and can't seem to find a replacement cable. Im beginning to think that I may be able to but a once size fits all cable and cut it down to size. Do any of you have any experience with this?

Another question, I noticed that my "breather" hose is broken. What is the hose used for? It doesn't seem to important... Thanks in Advance!!

#9 cookiemonster OFFLINE  

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Posted October 03, 2011 - 10:15 PM

Well the carb rebuild did the trick. After putting it all back together it started right up and ran like a champ with choke completely off. Thank You! But, I must have put the throttle cable on wrong because when I went to give it full throttle I snaped the cable. I have been looking through the parts list and can't seem to find a replacement cable. Im beginning to think that I may be able to but a once size fits all cable and cut it down to size. Do any of you have any experience with this?

Another question, I noticed that my "breather" hose is broken. What is the hose used for? It doesn't seem to important... Thanks in Advance!!


These guys may know where to get an exact replacement, but if you want to fit a universal or custom cable, measure it and take a picture of the ends and tell/show us. The breather hose lets oil vapors off the valves and into the carb to burn off. Broken won't cause any problems other than it will allow unfiltered air into the carb and will allow that little bit of oil to build up on the engine around the break. Best to fix it or... filter the breather and block the tube going into the carb.
  • Bolens 1000 said thank you

#10 Bolens 1000 ONLINE  

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Posted October 04, 2011 - 05:21 AM

:ditto:

If you dont want a replacement cable,

You can check with Bob (bhts) he may have a NOS throttle assembly.

#11 HDWildBill OFFLINE  

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Posted October 04, 2011 - 08:51 AM

You may need a tool to make the "Z" on the end. If you do the local parts house may cut and "Z" the end for you.

Glad you got it running, it is always a good feeling when you cans say I fixed that especially when you don't have the experience. Congratulations!

#12 JakeQT17 OFFLINE  

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Posted October 06, 2011 - 08:55 PM

Well, I talked with sam from sam's bolens and he said the cable is not. Myavailable . I guess my only option is to rig up my own. He is "bob" and how do I reach him? You right about the satisfaction that comes with this stuff, its addicting! Thank you much for your help!

#13 Texas Deere and Horse OFFLINE  

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Posted October 06, 2011 - 09:20 PM

Bob is member "bhts" and he is a site advertiser here. If you look on the home page , down the right side, you'll see his Ad. Bob's L and G Tractors




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