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My other green is JD
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259 Posts
Discussion Starter #1
Maybe there is a better place to post this question, but I'll try here first....I notice very little activity on the ZTR front mount forum......

I have a ztr with a Briggs and Stratton Vanguard Model 261777 Type 001601

Today, it started right up, but then quickly dies....I immediately thought fuel....so I checked the level and even changed the filter.

It will crank over and cough through the carb...

I pulled the flywheel to makes sure the key had not sheared....it was OK. I pulled the valve cover and everything appears to be ok - no loose valve stems, etc....everything seemed to work fine when I cranked it over.....

It's got good consistent spark.....

Any ideas what's wrong? I can't find much info on this engine.....is there an electronic module, etc??

Thanks........I can't believe it went from running fine to dead in 2 seconds....:thSick:

I don't have a compression tester.....
 

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10K and Climbin!
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12,344 Posts
take an eyedropper or pour a bit if gas into the carb bore and try again.. If it runs a bit fuel is your problem,

Your engine has magneto ignition and if you have spark things are well.. all parts moving correctly rules out internal failure.. Valve lash should be checked/set since you have it apart.. :dunno:
 

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Premium Member
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630 Posts
Sounds like fuel not getting through carb. Does it have a solenoid on the bottom of the carb bowl? If yes listen for it clicking when you turn the ignition on and off. If its clicking, or doesn't have one, then make sure you have fuel getting to the carb by pulling the fuel line and cranking for a split second. You should get a spurt of fuel. Be careful as it is flammable.. If yes then a spoon full of fuel down the carb throat an see if it fires. If yes you need to pull carb and clean it. If still no then I'd look at the ignition..


Sent from the MTF Free App
 

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My other green is JD
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259 Posts
Discussion Starter #4
Tried pouring a little gas in the carb....still no go....almost acts like it's out of time....just coughs and snort through the carb???? Could I have broken rings or a hole in the piston?

Thanks for the pointers!

Bright blue snapping spark......
 

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Certified Technician
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8,420 Posts
Had one today do this...key was sheared 90* advanced.
 

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My other green is JD
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259 Posts
Discussion Starter #6 (Edited)
Could valve adjustment be the issue? Is it possible for valves to get out of whack that quick? Thanks

UPDATE:

I tried cranking it after it sat overnight....it fired up and ran at about 100 rpm - about as slow as an engine can run and not die......ran for about 2 or 3 seconds like this and died....

It's almost as if some sort of compression release is stuck open? Is this possible on this engine? :dunno:
 

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10K and Climbin!
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12,344 Posts
Could valve adjustment be the issue? Is it possible for valves to get out of whack that quick? Thanks

UPDATE:

I tried cranking it after it sat overnight....it fired up and ran at about 100 rpm - about as slow as an engine can run and not die......ran for about 2 or 3 seconds like this and died....

It's almost as if some sort of compression release is stuck open? Is this possible on this engine? :dunno:
Did you check the key? DO that FIRST. You will do more harm than good if it is sheared. RED's 'da man!

If it is OK then:

Get out your flashlight and mark the crankshaft @ TDC of the piston for one of the cylinders. Now with the valve cover off, rotate the engine by hand in the direction it runs and observe the valves action as you make 2 rotations. 1- the intake stroke
2- then compression stroke
3- then the power stroke
4- is followed by the exhaust stroke..

**Watch the valves carefully as the release will involve one of the valves staying open a tad during the start of the compression stroke. That is when your Compression Relief happens.. Take a look-see as from the discussion the method vary's but it's always on that particular stroke.. Hope this makes sense..

:goodl:
 

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Proud Wheel Horse Owner
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3,213 Posts
Here's what you know:
-Flywheel timing is correct......you verified that (unless you messed up putting it back together and the key fell out as you slid the flywheel down the crank. I've seen this happen.

-You have spark.....but you can only check that outside the engine.

-Fueling the engine doesn't help......so you know it's not a fuel delivery problem.

Okay, so at this point, it's time to stop guessing and go to work.
-Buy a $20 compression tester and test compression. You should get about 70psi on an engine with a compression release.

-Buy a new spark plug. I've seen spark plugs fail to where they spark great outside the engine, but they will not spark under the pressure of compression. The engine will run just as you describe; popping through the carb, super low rpm.

If these 2 things don't get results, come back.

BTW, you usually don't need to take the flywheel off. Just remove the big bolt and look a the keyway. There should be a matching keyway in line with it, cut into the crank. If you don't see that, you know it's slipped.
 

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My other green is JD
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259 Posts
Discussion Starter #9
I do believe I have pin-pointed the problem....

Ran a compression test as suggested - surprised to see 150#

Pulled the valve cover again for a closer look - this time I realized the rockers were pretty loose.....I was in a hurry, so just snugged them up a little until I dig the feeler guages out.....

Snap! One of the adjuster nuts broke.....I wonder if it had been cracked and jumped a few threads.....

I was still able to snug it up a little......

Put the valve cover back on and SHAZAM - IT STARTED!

Ran a little rough, but I'd have to blame that on poor valve adjustment.....

Now I need to order a adjuster nut assembly....or whatever they are called...

Thanks for the tips.....this site is great.
 

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My other green is JD
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259 Posts
Discussion Starter #10
Now I am pulling my hair out trying to locate parts!

Anyone know where I can get a "rocker nut" for this engine?

Briggs Part 491511

Looks to be discontinued.....would a nut from a different model work or am I forced to machine my own? Could I get by with some sort of lock nut on the rocker stud? I still have the ball shaped portion that the rocker "rocks" on....just the portion that houses the set screw is what broke off flush

Thanks
 

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Certified Technician
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8,420 Posts
I dont see it available through anyone online...discontinued and not available, with no superceded number..
 

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My other green is JD
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259 Posts
Discussion Starter #12
Yeah, I'm starting to thinks it's creative fab time.....:dunno:

I guess either I try it or else I have a new boat anchor:Disgus:
 

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10K and Climbin!
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12,344 Posts
Yeah, I'm starting to thinks it's creative fab time.....:dunno:
I guess either I try it or else I have a new boat anchor:Disgus:
Post a thread in the Wanted to buy or for sale forum.. maybe somebody has a grenaded engine with good heads laying about
 

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My other green is JD
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259 Posts
Discussion Starter #14
Well guess what!?!?!


After all of the headache....taking things apart, checking EVERYTHING.........

It was something SO simple.....

Spark plug wire had been laying against the muffler.....


I was at my wits end and decided to take the muffler off thinking it may be plugged.........it fired right up and ran like brand new!!!

The spark plug was getting just enough fire to spark....but was shorting out too much to run.

Leave it to me to have something so frustrating happen....


Runs like a champ now....!!


Just about threw it in the creek.....:ROF
 

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Registered
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288 Posts
do you still need the valve adjuster nut? if so pm me and Ill try and get one for you at the local brigs dealer he had them in stock.
 
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