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420carb

A

Anonymous-0

Well-known Member
Can somebody help me with a tsx688carb the correct location for the jets ,Ipulled the carb off the tractor to rebuild it but I have had no luck at the same time we put new plugs and wires on and made sure that the timing was correct but it still sounds like it is out of time because it will backfire do you know how LOUD this can be inside a shop HOLY COW. I keep thinking that it is timing but I have checked several time, and tractor will idle for a few seconds then quit ,but only do so with the choke on that why I think I have other fuel problems any help would be greatly appreceated,Iam about to go postal on this it's got my goat
 
Check your coil. If it is bad it can act like a timing issue. Weak spark will only fire a real rich fuel mixture. That could why you have to have the choke out all of the way.

Also check the shaft bushing in the distributer. It can be worn and allowing the shaft to move. This will change the points setting and effect the timing.

Check the static timing. Just a few degrees makes a big difference on some of these engines.
 
Like almost everything else 1 & 1/2 rounds out on the jets is where you start.

If you're using a timing light you should see SPARK in the center of the window at full throttle. If you're using static timing use the TC or DC mark.
 
Well I tried that with no luck I found the c mark and sure that I was on compression stroke,then turned the dist. Until I just see a spark and backed it up just a fuss, the I rolled the motor over until I was on the high part of the cam lob on the dist. and set the points at 18thou I have a It manual and it told me to set the timing on the spark not the c or d what you said makes why more sence to me, but the thing still backfires and will only run at idle speed with the chock out.
We had also rebilt the carb and Iam wondering if I got all the jets back in properly We put it a can of carb cleaner in the basket but I'm thinking that I missed one,I put one in the bottom of the bowl and two on the other side of the carb, If anybody can help me see the light that would be great

This is my 14 year boys first John Deere I don't want him to hate green.
 
Are you sure the plug wires are on correctly? If it's timed right the no 1 post will be on the front side and no 2 just a tad left of center. BTW don't pay the manual any attention when timing cause it's wrong. Set it like I posted but the point gap has to be set first. 19 to 21 is what it should be. I would put in new points and condensor if you haven't.

On the carb the slotted head screw with a spring is your idle screw. The load screw is near the bottom & is an L or T end for adjusting. It's just a drain petcock on the bottom. There is a screen filter in the elbow where the fuel iine go's into the carb. It must be clean. The nozzle is under the load adjusting needle and bushing. Takes a BIG screwdriver to remove and clean it.
 
Was the carb body stripped to the bare casting and every passage rodded out? Float level is critical. I agree there is likely ignition problems and maybe valve lash concerns.perhaps even a leaking intake manifold or gasket.
First of all throw the fool I&T manual away and obtain the JD manual.
 
Thanks both of you guys for your time and help! I will check out the elbow on the fuul line but whenever I take the bowl off it's full can you give me the correct way to adjust the points and also are carbon wires a big no no,I just can not believe that this can be that tuff I do heavy equipment repair for a job and I cannot think of anythin that has been this frustrating,I did as you said about, number one on comp then found the c mark on the fly wheel turned dist so point just started to open and locked it down there but if the points need to be adjusted first then the timeing is wrong anyhow Correct?
 
Set points first because opening or closing the gap will change the timing. I would set them at 20 on the high lobe. Turn the rotor to check and make sure the advance isn't stuck. Just to get her running you can cheat on the timing & it will be dang close when you check it with a timing light. Stand directly in line with the distributer. Turn it so that the No 1 plug wire post is at 10 till 3. The No 2 plug post will be at 10 till high noon or just left of center.

You do need copper plug wires and a new set of autolite 216 plugs if you don't already have them.
 
Thanks for your help M-Man We got the thing running runs really good until we get about half throttle then we have to pull the choke out all the way to stop it for slobbering.I have change the points condenser wires and plugs, set the float in the bowl,the only thing thatIam in question about are the two small jets in the carb interchangeable I was wondering if I could have them in the wrong spot, I know ther is one is bigger so I cannot screw that up Thanks
 
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