Hey guys, I will add some pictures tomorrow. Long story short. Got a free tiger cub. Has an almost brand new Briggs & Stratton 27hp professional motor on it. Really solid machine. Some how someone removed the chock lever and integrated it into the throttle lever. Why would they do this? Is it because the original engine wasn’t a B&S so there were some compatibility issues? So now all the way forward would be choked and slightly back would then be full throttle. It had new coils put on it last year. But it’s running rough. Under powered and spits like it’s choked. I’m slightly mechanically inclined and can get things done once you kind fellas point me in the right direction lol. I’m going to check the rpms tomorrow. But not sure what to do otherwise. Should I try to figure out how to get a real choke lever back in there? What kind of pictures do you guys need to be able to help? Thanks in advance.
Scag tiger cub running rough
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WinterDeere
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For most of the Briggs engines, there are multiple throttle plate options. So look up your engine and see if you're able to swap it over to a throttle plate that would be more compatible with your mower controls.
That said, just stopping the throttle short of the position where it closes the choke should work as a temporary measure. The Briggs Intek on my log splitter has this type of throttle plate, and I just throttle it up to where the throttle arm touches the choke actuator, but doesn't depress it. That's easy on a log splitter, but maybe not so easy with the engine hiding behind you on a mower.
That said, just stopping the throttle short of the position where it closes the choke should work as a temporary measure. The Briggs Intek on my log splitter has this type of throttle plate, and I just throttle it up to where the throttle arm touches the choke actuator, but doesn't depress it. That's easy on a log splitter, but maybe not so easy with the engine hiding behind you on a mower.
If I’m stopping the throttle short of it closing the choke it seems like it’s way under powered. Do you think this is a governer issues (low rpm’s) or related to the hack of a fix someone put on this thing? Really appreciate your insight.
Going to do done research on the throttle plate options as soon as I get home today
Going to do done research on the throttle plate options as soon as I get home today
WinterDeere
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Could be the engine has some other problem, but before diving into that, it’d be good to at least identify the linkage components and what they do, so you can determine when and where in throttle movement range the choke is closing.
oldnslo
Super Member
There might or should be adjustment on when the throttle engages the choke. You want engine at full RPM before choke is engaged. Some models had a little lip or detent so took a little extra push to go from throttle to choke.
Where is the adjustment? I’m struggling trying to figure out everything lol. I did confirm the choke is opening and closing completely. It’s opening all the way to that stop once I back it out of the choke position. Also rpms where at about 3000 which seem a little low. I’m having a hard time finding much info on the mower with that engine
oldnslo
Super Member
If my memory is correct there was more than one option on how the choke and throttle were integrated. Can you see what activates the choke? That is were I would start looking to see if there is some adjustment screw in that linkage assembly to allow throttle to rev higher before activating the choke.
Otherwise possibly take some pictures of that linkage assembly and that might trigger a memory for someone.
I think some of the older models also had a metal arm that you bent slightly to adjust when choke was activated.
Otherwise possibly take some pictures of that linkage assembly and that might trigger a memory for someone.
I think some of the older models also had a metal arm that you bent slightly to adjust when choke was activated.
WinterDeere
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You should be able to look up the spec's and parts diagrams using the engine model number. Post a photo of the engine label, and maybe we can help.
3000 rpm is a common maximum RPM for many of those engines, but some others are 3600 rpm. It's possible the prior owner of your machine re-powered a 3600 rpm machine with a 3000 rpm engine.
I was going to upload a short video so you guys could hear how it runs. Not sure if it’s just the junk Briggs but it sounds just a hair rough. Maybe too rich. Like I said I’m not a mechanic. Not even close. I just know enough to be extremely dangerous lol. As always, all of you are much appreciated
WinterDeere
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There should be a sticker on the side of the engine cowling with an actual engine model number, probably the same label containing the serial number. That's what the Brigg's experts will need to identify the spec'd RPM for that engine, as well as the throttle plate and choke options.
So you're saying it spits / pops? On these normally one main jet is partially clogged. RPMS are considerably low. The model and type on the top of the valve cover will give you parts info, post it and I can look up the intended RPM. 3350+ anyhow.
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WinterDeere
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Engine model number is 44Q77-0136-G1, it's a very common model, and in fact I think OEM on some Scag models... not that I'm any Scag expert.
Damn near every site that lists that motor claims a different max RPM, but most seem to be either 3350 or 3400 RPM maximum. If this is the OEM motor for that mower, then the shop manual should have a detailed procedure on how to set low and high idle speeds. You'll need a tachometer, but you can pick them up cheap on Amazon.
If it's not the OEM motor, then you can use the Briggs manuals. All can be found here:
www.briggsandstratton.com
Damn near every site that lists that motor claims a different max RPM, but most seem to be either 3350 or 3400 RPM maximum. If this is the OEM motor for that mower, then the shop manual should have a detailed procedure on how to set low and high idle speeds. You'll need a tachometer, but you can pick them up cheap on Amazon.
If it's not the OEM motor, then you can use the Briggs manuals. All can be found here:
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Thanks a bunch for the info. Did you get a chance to listen to the video? Does it sound rough to you? Just wondering if that’s contributing to what seems to be a power issue. I could be wrong but I feel like this thing should have tons of power for that little 48 inch deck? I don’t know if I mentioned it but there was a new carb put on last year. This is just a back up mower for my little farm IE why I don’t want to just pay someone else to figure it out. I have never messed with carburetors before so I’m slightly shy about taking it apart but I’m willing to try. Also the rpm’s were right at 3000. I turned it up to 3400. Not sure if the 400 is going to really make a noticeable difference. Thanks again
That pop is likely due to one of the mains being at least partially clogged. You can clean these externally much of the time in place. Remove the top plate w/ 3 screws, and carefully remove the gasket. Use a razor blade if needed. The gaskets aren't cheap and work well just by flipping and re using them. Once the mating area is clean and you're sure there are no little bits of gasket inside, a burst or two of carb spray with the straw down each main orifice will open them up. Quickly reassemble and test run. This cuts the cleaner with fuel so you don't have the cleaner soften the main rings or fuel pipe seals.
I'll also drain the bowl before this service and after running via the side bowl solenoid. If you decide the little red straw is needed to flush the bowl out, reinstall the solenoid and run it right away. Once a test run shows it's good, back on the shroud goes.
Base idle is 1300, only notes on top speed on your build is 3600 is the alternator test speed. Increasing your running speed 10% makes a nice difference.
I'll also drain the bowl before this service and after running via the side bowl solenoid. If you decide the little red straw is needed to flush the bowl out, reinstall the solenoid and run it right away. Once a test run shows it's good, back on the shroud goes.
Base idle is 1300, only notes on top speed on your build is 3600 is the alternator test speed. Increasing your running speed 10% makes a nice difference.
rholmes69
Bronze Member
One of the things I've heard is that the pulse fuel pump on these if they've been replaced with an aftermarket, it doesn't provide enough fuel. It can idle okay, sometimes it requires a choke or high throttle to get started, but once you start trying to mow and get into the power, it just seems to bog. Might want to do a flow test on the pulse fuel pump...
Thanks a bunch for the info! Should I just YouTube a video on how to do it or do you have an easy way in mind of checking it?
I disconnected at the carb and cranked it and it’s pushing plenty of fuel. That pulse line is in rough shape though, not a great seal at the bottom? Thoughts?
