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Briggs 21hp Intek issues...too rich

#1

M

marinegrunt

I have 21hp Intek that's on a Craftsman ys4500. Model number is 331877. I got the mower for free due to a broken connecting rod. I went ahead and did a carb kit, rings, light hone, lapped valves, and all new gaskets too. It fires right up and seems to idle okay but it's experiencing a rich condition which causes it to run rough and black smoke. If I slowly increase the throttle it seems fine but throttle too fast and it boggs and you get the black smoke. I took the carb apart again but seems fine. I might put all of the old carb parts back in just to try. It definitely seems like a fuel issue but could it be anything else?

Also, can anyone tell me for sure if the aluminum push rod goes on the exhaust? The previous owner had the engine torn down. He put it back together and had the aluminum on the exhaust and marked with ex on it. I know most have them on the intake but a few have them on the exhaust. The reason I ask is I keep getting the hard start and have to adjust the valves. Seems to work for awhile.

Thanks!


#2

I

ILENGINE

Did you check the flywheel key. If it locked when the rod broke could of sheared the key and is now out of time.


#3

Boobala

Boobala

marinegrunt said:
I have 21hp Intek that's on a Craftsman ys4500. Model number is 331877. I got the mower for free due to a broken connecting rod. I went ahead and did a carb kit, rings, light hone, lapped valves, and all new gaskets too. It fires right up and seems to idle okay but it's experiencing a rich condition which causes it to run rough and black smoke. If I slowly increase the throttle it seems fine but throttle too fast and it boggs and you get the black smoke. I took the carb apart again but seems fine. I might put all of the old carb parts back in just to try. It definitely seems like a fuel issue but could it be anything else?

Also, can anyone tell me for sure if the aluminum push rod goes on the exhaust? The previous owner had the engine torn down. He put it back together and had the aluminum on the exhaust and marked with ex on it. I know most have them on the intake but a few have them on the exhaust. The reason I ask is I keep getting the hard start and have to adjust the valves. Seems to work for awhile.

Thanks!
Click to expand...

See this link.....https://drive.google.com/file/d/0B6NaqjIxWV1ySkZjTTA5TGltZEE/view

SEE Section 13 ....PAGE 5 .... Installing Cyl. head ... INTAKE pushrod = ALUMINUM

The "BLACK" smoke suggests a carb out of adjustment , might want to read through the carburetor section in the above mentioned manual ..


#4

M

marinegrunt

Thanks for the replies. Key is okay. Atleast it was when I put everything back together. I will check again just to make sure. I adjusted the air/fuel mixture screw the other day but it didn't seem to help. Makes me wonder if there's an internal carb issue. I wish I had another nikki carb to try.

The linkage looks okay but could it be the issue? It's weird how it runs okay until you increase the throttle quickly. If you ease the throttle up it's fine. Although, it does eventually act up. It's the quick throttle increase feeds extra gas into the cylinder. I wish I could find a cheap aftermarket carb for this mower to try. I hate to spend $70 on an oem unless I know it will fix. Might have to tho.

Thanks again for the tips


#5

M

marinegrunt

I'm an idiot. When I rebuilt the carb the kit came with a fuel transfer tube. It's the white plastic piece that's in the bowl. I didn't transfer the main jet over to the new. I'm surprised it ran at all. I'm glad it was something simple.

I'll have to see about the hard starting. It's a brand new battery but might've been drained from all of the starting and not running it much.

Thanks


#6

T

Tinkerer200

Valve adjustment is critical especially the Intake. Also, camshaft/compression release failure is common with this engine causing hard starting.

Walt Conner


#7

Boobala

Boobala

marinegrunt said:
I'm an idiot. When I rebuilt the carb the kit came with a fuel transfer tube. It's the white plastic piece that's in the bowl. I didn't transfer the main jet over to the new. I'm surprised it ran at all. I'm glad it was something simple.

I'll have to see about the hard starting. It's a brand new battery but might've been drained from all of the starting and not running it much.

Thanks
Click to expand...

Don't forget the PUSHROD ..... Aluminum is the Intake Rod......


#8

M

marinegrunt

Is there a way to tell if the compression release has failed? I've adjusted the valves a few times.

Does the intake always have the aluminum push rod? I've read other posts in the past where some briggs engines use aluminum on the exhaust. Since this engine was torn down by the previous owner I can't say for sure. I just went by how he had it labeled along with some info I dug up online. From what I read most use aluminum on intake but not all. I personally don't know tho.


#9

I

ILENGINE

Remove the spark plug and turn the engine over by hand, and what the intake valve, which on the single cylinder engine is the bottom valve in the head. You are watching for a bump off right before TDC compression stroke. Just will open the valve a few thousands for a short period of time.

Some use it on the intake and some use it one the exhaust. You can use the steel rod for both and it won't hurt a thing. If you decide to open the engine up to inspect the camshaft for proper operation just put a new camshaft in and be done with it. I have seen too many cases where it appeared to be working properly and would actually be hanging up.


#10

M

marinegrunt

Thanks ILengine. I think I might do as you suggest and just install a new cam. Mower is in perfect shape. You can tell it was waxed yearly and cleaned all the time. Just had the broken connecting rod and parents neighbor was going to take it to the scrap yard. I only have about $100 in it. Well worth throwing another $70 at it.


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