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Started the Ybravo to see how it would run, well it surges and I am not surprised.

I have to clean the carb. I know how to do this, but I am not sure if it will fix the surging and I don't feel comfortable playing around with mixture screws (remove them while cleaning the carb). Also, I've heard about a surge spring on the carb. Where is that?

I tried to find info all over google, but couldn't find much. Even on youtube. Any help on how to do this would be really appreciated.

Well to start, hopefully this link will bring up a blowup

buykawpower.com

To start, I would just remove the bottom bowl nut and drop the bowl off and have a look. Part#92154 Get a can to catch the dribbling {hopefully} fuel.

Fish said:

To start, I would just remove the bottom bowl nut and drop the bowl off and have a look. Part#92154 Get a can to catch the dribbling {hopefully} fuel.

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My FH451V would only run with choke on and would surge and/or stall with the choke off. I pulled the carb off but in hindsight only needed to pull the bowl as stated. The needle the float is connected to has a small hole in it where the fuel enters from the bowl. It was mostly plugged. Cleaned it out with a small piece of wire, reassembled, and has been running perfect ever since.

Thanks a lot guys! Gonna look at it soon and come back with an answer!

I was able to remove the carb. It would of been fun to have a fuel cut off valve... Removing the fuel line was a PITA.
Now I removed the bowl and looked at the float pin... I dont see much. I cant even remove the float pin, it is real tight in there. I am gonna start by removing the jets and clean them.

Today, I opened up the carb and it was very clean. But, I still removed the main jet and the lower jet and cleaned them both. In all holes I was able to see light thru them. Then, I shot some cleaner thru the fuel line tube and also cleaned the hole where the needle float goes. I assembled everything again and installed it on the mower. I tried starting it and it didn't want to. I removed the air filter and changed the spark plug with a similar one (Champion) and still wouldn't start much. It would really puff slowly like it was dying. Then, I added oil, because it needed some. After messing around with the throttle linkage to get it wide open, it started. It ran like crap sounding a little low on the revs. I stopped it and it didn't want to restart. Alltho, cleaning the carb seemed to fix the surging.

I guess the final thing to fix would be the valves? Well, I am not sure how to do that and I would need to get the tool to calculate valve clearance. I am really getting discouraged here with this motor. Any help would be appreciated.

I adjusted the vavles yesterday with a feeler guage that I bought. Before adjusting the vavles, I couldn't get the feeler gauge thru, so I guess the vavles were way too tight. I had to pull may times and it still did not run right. Any other ideas?

I also considered that maybe because of the cold, it isn't running right and that is why it is so hard to start?

We need to re-explore your valve adjusting, did you check the clearances after you made sure that the piston was at TDC?

Flywheel key?

What is the fly wheel key?

As for TDC, yes it was. I tried my best at getting it at close as possible to the spark plug hole. I then unscrewed the set screw, adjusted the adjusting nut and once I was done I tightened the set screw while holding the adjusting nut. Then I cranked it a little to check the clearance at different positions to see if it was still good. Is that fine?

Now, one of the screw holes to secure the valve cover is a little stripped. I am not very comfortable fixing this. This motor is really a headache.

Sorry I not gonna explain it. Someone else can or you can look it up. Prob a vid on YouTube. Easy to check and your symptoms warrant a check.

Well to be specific, it comes to tdc twice, you need to adjust the valves when it is tdc and both valves are fully closed, the other tdc, one valve will just be closing, and the other will be starting to open. As far as the stripped out threads, I use helicoil myself, but buying a kit to do just one screw is kind of prohibitive. Any mower shop should be able to cure it for @ $10.

I've checked for the fly wheel key on Youtube. I dont seem to have the symptom of the pull cord ripping my arm off and I did not hit anything while mowing with it. Before I stored it, it was running really well. But, if all else fails, I will replace it.

Now for the valve adjustment. How can I know it is at the right TDC? I guess I can see if both valves are closed by looking at there previous movements?

I will get the stripped thread fixed by a guy I know who fixes cars. Once it is fixed, I am going to readjust the valves.

Just turn the engine by hand with the plug out and watch the valves, one rocker arm will be pushing the valve down, and as the piston comes back up, it will be letting the valve back up, and as you keep turning past the top dead center the other rocker arm will start moving. That is the TDC that you don't want... just keep rotating
and when you come up to the other tdc, both valves/rocker arms will be still. That is what you want.

Fish said:

Just turn the engine by hand with the plug out and watch the valves, one rocker arm will be pushing the valve down, and as the piston comes back up, it will be letting the valve back up, and as you keep turning past the top dead center the other rocker arm will start moving. That is the TDC that you don't want... just keep rotating
and when you come up to the other tdc, both valves/rocker arms will be still. That is what you want.

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Thanks a lot for the help! This is really appreciated! I will come back with an answer! I just have to ask my friend when he will have a little time to retap the thread for the rocker cover.

I opened up the vavle cover again to readjust the valves. I put the motor at TDC compression (both vavles were not moving like you mentioned). I used my feeler gauge and did a few adjustments. I closed up everything and tried to start it up. After cranking a lot of times, the motor started, but really reved slowly. Really really slowly (it was barely running). I tried it again and it revved a little faster. After a while, it reved at a normal speed, but I was still having some surging issues. It was even over-revving at the end. I am really close to bringning this mower to a shop. I am out of ideas here unless someone here can help me out more. I know my way around motors, but I do have limited knowledge about them.

I asked my friend what he thought about this and he recommended checking the fuel filter. Would this fuel filter cause all my problems? If so, can I just remove it temporarily to see if it is that?

It was the fuel filter!