HF-301cc ..... the surging / hunting has arrived.

[nyquil junkie 225]

Short history recap....

Engine replacement on the old 855/856. Runs fine, strong. No complaints.

The engine is the HF 301cc 8hp replacement model.

We ran it all day yesterday, pushing mud and cow poo/pack (no pics, will take some next weekend) and for hours, it was doing a great job.

Then it began to surge....hunt... at any speed. Close the choke a little and it runs fine.

A gas feed problem, running lean. Carb jets and whatnot need flushed with Carb cleaner. An obvious and logical conclusion. One I will do on the weekend.

How crud got in a fuel system that is new, and has had nothing but clean stabilized gas put In it is strange. I bet these engines don't have filters.....

This was the first time in hours of break in running I ran the thing at near full throttle. My nephew says these engines have cheap governor springs that stretch if you push the throttle too far forward.

I dunno if that's true. If cleaning doesn't cure it then that may very well be.

Then he said oh... they have crappy narrow jets that run lean out of the box.... drill it out or get a bigger one.

Maybe.... but it was running fine for many hours before it started this surging. So that one makes little sense. (To me anyway)

The only thing I did not do last week was close the fuel valve and run it dry. If a week of sitting made it gunk up then we have some really poorly formulated gas in this country anymore.

Anyone else have issues with these engines suddenly for no apparent reason start to surge and how did you cure it?

I'm thinking a slightly closed choke which does make it stop is the easiest cure if the cleaning doesn't work. I don't think that will harm it any. I can't mess too much with it, for a couple yrs u til the warranty runs out, I will save the warranty replacement (one replacement) for the day it blows up on me.

Also I have no idea where in this HF Carb it would tend to clog up easiest to know where to flush.

I assume, a Honda Carb is nearly identical ?

Edited August 11, 2014 by nyquil junkie

[slammer302 2,154]

I have the 212 predator and have had no problems i didn't use the factory gas tank and i did add a inline filter. My dad has one that does the something you are fighting with i think it is in need of a valve adjustment because i cleaned the carb and even replaced it and still the same problem but it still gets the job done and he only paid 40$ for it

[nyquil junkie 225]

Today I disassembled the entire Carb, cleaned, inspected and resembled it.

It was spotless and it still surges.

Since it ran fine for a while new, then bean this problem I figured it was a fuel flow issue, bit no, all the lines are clear, the gas is new again, stablized..... and its the same.

So I ordered a new carb off eBay, and a set of welding tip cleaners. I will very gently bore the old jet out one size at a time and see if it helps. If yo choke it slightly, it runs OK, right on that knife edge of too much choke and not enough choke...which sucks.

I've done the jet reaming trick on other engines, most of the time to works, sometimes only marginally. I wish I could find parts to this thing and just buy new jets and tubes..... but that's what you get for buying a HF engine.

If this one fails, it goes back to HF for a replacement.

As I read around the go cart and mini bike forums, a lot of people complain these engines run lean out of the box.

But it ran fine until t was broke in. That part bugs the snot out of me. It started this in the middle of a tank of gas, that was spotlessly clean when I drained it today.

It still runs fine, and strong, no stall or sputter, other than the surge. Starts easy....

Anyone know of an online source for parts for these engines? The 212 parts are all over it the parts for the 301..... not so much.

[slammer302 2,154]

Let us know what the fix is

[nyquil junkie 225]

An interesting day of tinkering...

I reamed the cab main jet it a wee bit... didn't help. I reamed it out a little more than I should have after that to just see what will happen... still surges but huffs black smoke... so now that Carb is too rich.

So I put the new Carb I got off eBay from a HF 301 salvage.... runs like new.

It would seem some little passageway is clogged, but since its sealed with brass plugs you cant adjust it or properly clean it.

But it runs fine now.... new Carb.

So on studying this Carb.... I thought I would stop by the hardware store, they sell mower parts and stuff. I ask em... what Honda engine is an 8hp?

He says the gx240 is an 8, the 270 is 9hp more or less, they both take the same Carb.... he pulls one out.

They are identical, HF 301cc carb and the Honda gx240. But the Honda Carb is fully adjustable and you can buy rebuild kits for it.

Now the hardware store wants $75 bucks for a Honda OEM Carb.... eBay you can get them with free shipping for $15.

Go figure.

The HF 6.5 engines are not direct Honda replacement parts, but it seems the new 301s they have..... are.

Good to know. Because nobody on the planet sells parts for the HF301. Not even HF.

I'm gonna order a Honda adjustable Carb to put on the engine, it also has the sediment cup on the fuel on/off valve the clone Carb doesn't. The Honda Carb however also has a fixed main jet, but it would seem the main jet wasn't he problem with the surging.

Even so larger Honda main jets, pilot jets tubes and such are all easy to find.

Who knows... for 15 bucks to solve the problem when or if it ever returns, some questions can be left unanswered.

Edited August 24, 2014 by nyquil junkie

[nyquil junkie 225]

I took the old Carb apart, it may have been a clog in the pilot jet or the air path going to it also. I did not see that jet as it is hidden behind a removable plug and very hard to get out but it snaps right back in. The path looked clean. It the jet has a very tiny hole that may have been clogged or obstructed with a little varnish.

Once I replace the main jet I will pop it back on to see if cleaning the pilot jet and pathway and screw outlet fixed it for that Carb.

[Molon_Labe 731]

Just so you know, I don't sell or believe in "snake oil" but there is nothing in my opinion better than STP Fuel Injector Cleaner to cure a gunked-up carb (black bottle). I put a couple of ounces in every mower gas can I refill along with a healthy shot of Marvel Mystery Oil and my carb problems have been a thing of the past. It won't cure the lack of or a dirty fuel filter but it really works wonders on a dirty carb. For a carb that's giving problems I use a full bottle of the STP in 1 gallon of gas to get it kick started and it has worked every time. My brother collects Cubs and I told him about it after he said he was having trouble with a couple of them and now he swears by the stuff. Hey, for a couple of bucks what do you have to lose?

Edited August 26, 2014 by M_Bailey

[nyquil junkie 225]

I used to put MMO in everything.... I just kinda stopped for some unknown reason .

Good idea to add a little stp in each tank full.... I wonder of it hurts to mix stabil and stp I the same tank.

Mmo kept my trucks running with no issues for decades....

Edited August 26, 2014 by nyquil junkie