HF engine tips and tricks

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FWIW, I purchased one of the 79cc HF motors about a month ago, started it and after verfiying that it runs I then took the whole thing apart to remove the oil sensor and govenor parts. In my opinion I was pretty impressed with the quality of construction on the engine. I also have a Huasheng 4 stroke and the HF engine is much better quality construction.
I think the carb on the HF is POS, however!
As for performance mods I'm thinking (if there is enough valve to piston clearance) the head can be milled to raise compression. Also the HF engine has a big and heavy flywheel. If the flywheel is machined up a bit and lightened, would that help performance?

Bob
 
Hi Bob I also just bought a HF 79 engine I did the same removed oil sensor and gov I havent taken apart a HS have one but I did take apart a HF clone of a Honda 160 and the HF 79 seemed a lot better constructed especally the valves. Quick question when you remove the gov should increase size of valve springs to keep them from floating or are they good as they are when I did the cloine 160 they suggtested uypping the lbs on springs Thanks Larry
 
bird_e said:
FWIW, I purchased one of the 79cc HF motors about a month ago, started it and after verfiying that it runs I then took the whole thing apart to remove the oil sensor and govenor parts. In my opinion I was pretty impressed with the quality of construction on the engine. I also have a Huasheng 4 stroke and the HF engine is much better quality construction.
I think the carb on the HF is POS, however!
As for performance mods I'm thinking (if there is enough valve to piston clearance) the head can be milled to raise compression. Also the HF engine has a big and heavy flywheel. If the flywheel is machined up a bit and lightened, would that help performance?

Bob
Click to expand...

Totally agree w/ the 1st paragraph. Simply raising the compression won't likely give much benefit w/o other complimentary mods. Lightening the crank will give better acceleration and possibly introduce more vibes at the top.

Eldo,

Heavier springs will raise the rpm's at which the valves begin to float but this motor doesn't float the valves at 5000+ rpm's and heavier springs produce more load on the (plastic) cam. I wouldn't attempt any higher rpm's w/o a lot of work. Also valve float is it's own sort of governor!

Cheers!
 
The exhaust exit port on this engine is huge compared the HS 50cc. I know it's a bigger motor (79cc) but it just seems the this engine has alot more performance locked up somewhere, but where? I noticed the carb is about the same size as the HS engine. Could a bigger carb be the answer to get more power out this engine? Has any one tried a different carb?
Bob
 
thats a thought Bird. A Honda carb should match up perfectly.

Man, great stuff. Really enjoying all the information, thanks all.

Will be starting the plug and cap tests this week end. Then cutting off half the fins. I have a spare engine earmarked to replace this one for when I gone an' went to far, snork

The only ways I have to test is tach and laser thermometer. Any ideas on other tests I should try? I am not sure how accurate the thermometer is, but seems close. Cheapie from HF. Non-Contact Laser Thermometer

"Temperature range: -4° F/-20° C to 968° F/520° C
Accuracy: +3° F/+2° C or 2% of reading
Distance-to-spot ratio: 8 to 1"
 
Do some timed runs over a known distance and record the results. May tell you which one runs the fastest. Good luck Dan I hope you find out which one is best and maybe one of them will be "magic".
 
Tyrslider thanks for info on valves didnt wanna change them anyway. Have never taken appart myHS not broke dont wanna fix it. Whats up with the plastic cam can you get a steel one? The clone 160 had a steel one.
 
Elmo said:
Do some timed runs over a known distance and record the results. May tell you which one runs the fastest. Good luck Dan I hope you find out which one is best and maybe one of them will be "magic".
Click to expand...
Will do Elmo. Ray's HF hits 6K RPM. I forgot to ask him if he was using a stock plug.

Have a great industrial road picked out. Kids used to drag race there. Long, st8 and level. Barely used during the week and dead on week ends.
 
Yeah!

Eldo,

Don't know on the cam avail., kinda doubt it. They seem to work fine though. Maybe the 160 is the same, kinda doubt that too.

Dan,

Read the instructions on that laser. I'll check in w/ some of the guys at work too. I think the LaserTherm is most accurate on opaque and dark surfaces and not as much on reflective surfaces. Either way it's more accurate than your bare inner leg!

Cheers!
 
anyone know a hack for running a light off the motor? I'm just using a batter for my headlight. sure would be nice to be able to charge the batter with the motor.
 
Max,

There's no charging/lighting coil, only ign. You'd have to add one or run an external generator/alternater.

Cheers!
 
There ought to be a way to hook up an alternater. Maybe one like the Kubota perm magnet one, it is pretty small.
 
A motorcycle or scooter job is going to be better I think. The Kubota one may work but it'll likely rob a 1/4 or more hp. More the faster you spin it. You don't need that much power.

I just keep an extra set of batteries on my charger and always have some charged. I understand the cool factor but other than that bicycle lights are pretty good these days and don't rob power from your motor.

Cheers!
 
Ya know I never thought of it but I guess when you only got 2or so hp every little bit hurts. Reminds me gotta change my battry
 
Plug upgrade/replacement. Was a busy day and only found one of the plugs and it was cross referenced to one of the ones cross referenced, lol. Auotlite 275. Gapped it to the stock HF plug. It did sound and seem smoother but at first actually lost 1.4 MPH. Latter it bumped up 2 MPH over stock plug but think it was just the quirk of a small engine having a normal happy moment. The RPM stayed in around the same range. So this plug worked, is cheap and readily available but no gain.

The surprising thing was the NGK plug cap. Added .8 MPH on both plugs.

Now running with the Autolite 275 plug and NGK cap. I have no way to quantify but does seem to be smoother with better acceleration. Was thinking it is a new plug and should have more UMPF but stock plug has only 70 hrs on it and has a beautiful brown color.
 
Good start Dan. That is what I found on the plug I tried, worked as good as stock but not better.
There is no guarentee that one that works in my engine really well will do the same in yours though. Due to manufacturing differences ( Chin using a bigger hammer than Ching) and Differences such as different exhaust and air cleaners.
 
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