Briggs 19hp single stumping me....rev limiter?

BuggyMasters

Member
Joined
Aug 4, 2017
Threads
1
Messages
10
This is on my friends craftsman mower. The machine is a 2014 model.

The machine backfires and pops through the carb under load. Checked the valve lash, all good. Nothing sticking. He has replaced the carb with a brand new one and brand new coil too. Starts and idles fine. If you try to go to full throttle it starts breaking up. While running and having the problem, I hit it with carb cleaner and the effect was minimal but leaned towards chocking it out vs picking it up so it was not starving for fuel. The more I played with it the more it appears that it was purposely being limited. If you have ever had a Polaris ATV as an example where they have a rev limiter for reverse, that is what it is acting like. As if it has a rev limiter. However it's not getting anywhere near an RPM that it SHOULD be limited on. This machine has a "tractor" mode on it. Seems the safety measures are all or none (it either runs or doesn't). Nothing I would think of that could act like a limiter.

Where should I look? What am I not thinking of?
 

BuggyMasters

Member
Joined
Aug 4, 2017
Threads
1
Messages
10
It is conventional overhead. Has regular ol' rocker arms. I will check the throttle and I will let you know. I suspect it will make no change because it's being held back via ignition
 
Joined
Jul 22, 2017
Threads
21
Messages
2,154
The only way it can be held back via ignition is that the magneto coil is not gapped right. Check it with a buisness card. Regap it with a card is what i mean.

You might have a blown head gasket also. I would almost bet good money on the gasket.
 

bertsmobile1

Lawn Royalty
Joined
Nov 29, 2014
Threads
64
Messages
24,647
And what the @#!*!#* is it fitted to ?
no engine has any sort of rev limiter except the EFI ones everything else is in the mower.
And being that there are 3 different OHV B&S engines rated at 19Hp an engine number might be a bit of a help too.
 
Joined
Jul 22, 2017
Threads
21
Messages
2,154
Buggy there is no rev limiter on that engine at all. Well the governor is a limiter in a way. But I don't think that's your issue with your engine.

I have worked on many of these, that's why I asked you if it was a OHV type engine. I myself don't a engine number,it's on the valve cover if you look at it good.

The reason you are getting blow back out of the carb is that the head gasket is blown right there between the cylinder and valve rod valley. The compression is coming back out thru the carb via the rod valley. When you take the gasket off it will have a bad spot on the back side of the gasket.

Rotary parts has a better gasket than the OEM ones. It is beefier and last longer..

Be sure to check/change your oil also. Gas can get in the crank case because of the gasket being bad.

Bert will agree with me on this. We have been working on these things for a long time. We do this for a living.........
 

BuggyMasters

Member
Joined
Aug 4, 2017
Threads
1
Messages
10
I will check it out again in person tomorrow. The guy said the model number is a 33R877.

He did tell me that he took the head off to make sure that everything looked ok. The valve lash if I remember right was .003 and .005. The guy is no dummy either. Seems if it was a head gasket, it would be a pig to start and would never run good at all. I mean it fires and idles fine and you can slowly start running the RPM's up and it is fine until it gets to a certain point and then it starts running like crap.
 

BuggyMasters

Member
Joined
Aug 4, 2017
Threads
1
Messages
10
And what the @#!*!#* is it fitted to ?
no engine has any sort of rev limiter except the EFI ones everything else is in the mower.
And being that there are 3 different OHV B&S engines rated at 19Hp an engine number might be a bit of a help too.

It's a craftsman mower. I didn't THINK there was any kind of ignition limiter on it but figure if they have gone that far with a mower now a days you guys could school me on it. That is just what it reeked of when shooting it with carb cleaner had nearly no effect on it. My thoughts are that it had nearly no effect because fuel is not what it's problem is.
 
Top