94' 616 with briggs engine got questions

[trialsguy]

first thanks for any info in advance.

I just picked up a used 616 with probably several hundred hours on it.
Where do I find the model number for the engine. It seems to run a little rich and I only found one adjusting screw in the center bottom of the front of the carb. It doesn't run smooth at any rpm, not bad, but not smooth.

I took the carb cover off tonight to see if it was gummed up or full of dirt but didn't see anything out of the norm. I sprayed the carb down and cleaned out what needle jet that I could find. I have a tube that comes off the front top of the carb that has a piece of rubber hose with a screw plugging it. What did this hook up too?

Not sure what I would call the brass tube that connects to the top of the carb that goes down into its own hole when the top is on, but it has several varying size hole, but it was slightly bent so I straightened out and reinstalled the top. Doesn't seem to run any better if not maybe a little rougher and richer with maybe some black smoke.

Thanks a bunch
Bob

 

[ILENGINE]

The model number should either be a sticker or medal plate on the blower housing. Depending on engine could also be stamped in a valve cover or cylinder shield. Assiming Vanguard engine, the carb should have two brass looking fittings on it. One is were the fuel line hooks to and the other should be the carb vent. I have seen people reverse the lines on occasion. I don't think they are reversed from your description. the other brass fitting, mostly likely with a 90 bend in is should be the carb vent. If that is the one with the hose and screw, remove either the hose or screw and see if it runs better. If the vent is plugged for some reason it can cause rich running. I bet somebody plugged the vent because there was gas coming out of it because the needle valve was leaking.

 

[trialsguy]

I unplugged the vent so I will see if that makes a difference while running. I only ran it for a little while to see if it made a noticeable difference but couldn't tell anything. The screw on the bottom is screwed out 4 1/4 turns, What is this screw for? I can turn it all the way in without making a difference, this doesn't seem right.

Oh, and by the way it is a vanguard engine. I didn't see a name plate with model number and I didn't see anything on the valve covers. I will look a little better this afternoon.

I picked up a manual for the mower deck and the mower but it appears I have to get a manual for the engine as well. I am going to check the valves to see if they are adjusted correctly. I have done a little searching and found some clearance specs of .012 for intake and .014 for exhaust, does this sound right?

Can the muffler come apart internally? There seems to be a lot of noise coming from the back of the mower, at different rpm ranges, like loose metal shields or something like that.

With all theses questions it sounds like I have a piece of junk, but this thing looks nearly new and mows really well. Just trying to get the bugs worked out
Thanks
Bob

 

[ILENGINE]

Valve clearances should be .004 for both. the internal baffle could of broke loose and would create a rattle and also louder exhaust noise.

Model number tag should be a riveted medal strip just above the flywheel between the v's of the blower housing.

 

[trialsguy]

Thanks, I found the model # 303447, I wasn't looking hard enough

Question on adjusting the valves. Tell me if my thinking is off. Usually on finding top dead center I would watch the intake valve open and close then put a rod or whatever in the cylinder and watch it until it gets to the top telling me its a TDC then my valves should be loose right?

when I check my intake with a feeler gauge at .004 it is close but if I push down on the top of the rocker slightly and release pressure it widens the gap considerably to say around .014 does this seem right?

I don't know if its that far off but I would think me being able to push down on the rocker arm and creating more of a gap means the valve is not set right. Keep in mind that I am releasing the rocker with my finger, not continually applying pressure when getting a measurement

Thanks
Bob

 

[ILENGINE]

Your thinking of find TDC is about right on, but then turn the crankshaft until you are about 1/4" past TDC compression stroke and both valves should be loose. If the gap is changing that much sounds like something preventing valve from seating properly, unless you are picking up on rocking motion from side to side which can cause varying valve clearance readings.

 

[trialsguy]

Checked the left side and they seem to be set at about .006 close enough as far as I am concerned. But... I believe there has been some monkey business on the right side which is the first side that I started with. I am afraid that I cant get the valves to adjust far enough in to take up the slack and still leave enough room to tighten the 13mm nut to down, not enough threads on allen head screw. The intake pushrod is different (thicker) looks like a automotive style push rod to me, and the exhaust rocker arm has had some grinding and welding done to it.. I have a thought and wondered if anyone has switched the securing nut to the underneath side of the rocker arm to compensate for the lack of threads. Obviously this isn't the correct way to approach this to fix engine. But... I would like to at least get the rest of the mowing season with it before I have to rebuild the whole dang thing.. I have a picture if I can get it loaded.

As it is set now I was able to get the exhaust set to .004 but the intake is at .018 whats your thoughts on this.
Thanks
Bob

 

[ILENGINE]

The left rocker has sure been cobbled on. The right side push rod looks like it an aluminum intake push rod out of an intek engine. Should be an fairly cheap and quick job to change out the wrong push rod and the cobbled rocker. For all we know somebody may have ground down the stems on the valves while they were at it.

Something is definitely out of kilter someplace with that setup. Normally the adjustment screws stick out of the top of the locknuts a few threads, or at least level with the nut.

 

[trialsguy]

What I am hopping is, I can get a intake pushrod and a exhaust rocker. But looking at the ground on rocker I am thinking it was cut loose from the side moved forward a tad and re-welded thus giving a little more adjustment in the rocker arm. What confuses me is what is wore out causing the lack of adjustment. Cam lobe? Or is it the wrong parts all together? She smokes a bit and doesn't run too smooth. Would a intake valve set at .018 cause it to run rich or a little rough?
Thanks for your thoughts on this
Bob

 

[ILENGINE]

Too much gap in the intake will effect the timing, causing the valve to open too late and close too early. That much gap could be caused by a push rod problem being wrong push rod. If that isn't the case I would be thinking that maybe the seat has come out. either could cause rough running, and oil usage. Possibly coupled with a blown head gasket on that cylinder.

Misfiring, and low power on one cylinder can and will cause oil usage. Have an uncle with a generator with a vanguard engine that was using a quart of oil every 8 hours because of a bent intake push rod on one cylinder.