Reliability of engines

JaxInsany said:

Greetings all, my quest for the best 4 stroke engine (keeping price in mind) continues! I have already ruled out the HF 212cc as MUCH too large and question the internals of the HF 79cc. Does anyone know if the Lifan 99cc:
http://www.homedepot.com/p/t/203281...nf-_-pip_203281925__W176393372#specifications

is more reliable/a better buy than the Harbor frieght 79cc? I want an engine that will last a long a** time with good power if I'm going to spend a sizable chunk of cash on it. Thanks!

Click to expand...

If reliability is your goal, get a Honda.
There's a reason everyone clones them.

I have a 98cc Lifan which I believe is the same as the engine you've posted the link to. Reliable? Yes, very much so. Power wise, I think you may be better off with a 79cc predator. I would expect nearly the same reliability out of both engines, but the 98/99cc Lifan is going to max out at around 5200 rpms, where the 79cc will spin 6k easily once the governor is removed. However, if you do wish to get the Lifan, there are some very simple mods that will raise the rpms, such as shimming the valve springs or removing the compression release. The compression release on the Lifan is a copy of the Briggs EZ-start, a permanent bump on the cam which keeps the intake valve open through 95% of the compression stroke. But I would probably start with shimming the valve springs, as it's not necessary to remove the compression release if all you're after is more rpms. The 79cc engine can spin all the way up to 7k without mods, and higher with stiffer valve springs, but continuously over-revving any engine can be very bad. The Lifan will probably not go over 6k-6500 even with the springs shimmed. You can get the spring shims from affordable go karts for $1.95 apiece, and if you call them, they'll stick them in an envelope for $1, otherwise it's gonna be $9-10 for the shipping. But yes, the Lifan engine has been reliable for me from day one. I recommend an aftermarket carb such as the mikuni pz19. I ran the stock carb for awhile, but it seems to run better with the mikuni. You'll need a custom intake manifold for an aftermarket carb though, unless you get a Honda carb, same bolt pattern so it will bolt right on and it is tuneable. The stock carb is not. I'm rambling, so if you want to ask more questions, feel free to pm me

Here's some comparisons to consider:

97.7cc Lifan 2.5HP 19 lbs $119
79cc Pred 3.0HP 22 lbs $99
49cc HS142 2.5HP 7 lbs $169

Although the most expensive, look at the power to weight ratio of the HS142. I have a 79 sitting on my bench that I removed due to it's weight (among other issues) and I've just ordered a 97.7 for a mini-bike rebuild (more to follow on the 97.7).

As an old fat fart, I'm sold on light weight aluminum frames with the light weight and great performance of the HS 142.

Just some thoughts to throw at ya!

Jax:

You should know that the Home Depot info is all messed up. The picture is correct, if you order that engine you get the 79cc OHV Lifan 152F-3 engine.

The old 98cc flat head is long gone.

Now for some facts.
The compression release is the standard centrifugal activated Exhaust bump. It completely disengages around 250 rpm on all of the engines I have worked on.

Opening up the exhaust on that engine by adding a motorcycle style exhaust really helps performance. The box exhaust that comes on the engine is very restrictive.

The OEM carburetor is tiny, about 10mm in the venturi. We have had great performance by switching to the carburetor for an XR75 Honda - clone carbs are 20 bucks on E-bay & it solves the throttle cable question at the same time. The 19mm round slide really lets that engine breathe.

There is no need to do any valve spring work. we spin those engines past 6,000 rpm all thetime without issue. Several people I know are running that engine daily. I see the one belt primary bike all over town on a regular basis. He is running about 15:1 overall drive ratio too.

Should be a trouble free engine for you. Here are some pics of them installed:
http://motorbicycling.com/showthread.php?t=54897

BarryT said:

Here's some comparisons to consider:

97.7cc Lifan 2.5HP 19 lbs $119
79cc Pred 3.0HP 22 lbs $99
49cc HS142 2.5HP 7 lbs $169

Although the most expensive, look at the power to weight ratio of the HS142. I have a 79 sitting on my bench that I removed due to it's weight (among other issues) and I've just ordered a 97.7 for a mini-bike rebuild (more to follow on the 97.7).

As an old fat fart, I'm sold on light weight aluminum frames with the light weight and great performance of the HS 142.

Click to expand...

7 lbs?? Where did you get that from?

The HS motor was cloned from a Honda GXH 50 weighs 12 lbs.
The HS also makes less than 2 HP

http://m.engines.honda.com/models/model-detail/GXH50

Dry Weight 12.1 lb (5.5 kg)

Engine Type Air-cooled 4-stroke OHV
Bore x Stroke 41.8 X 36 mm
Displacement 49.4 cm3
Net Power Output* 2.1 HP (1.6 kW) @ 7,000 rpm
Net Torque 2.0 lb-ft (2.7 Nm) @ 4,500 rpm

Click to expand...

FFV8 said:

Jax:

You should know that the Home Depot info is all messed up. The picture is correct, if you order that engine you get the 79cc OHV Lifan 152F-3 engine.

The old 98cc flat head is long gone.

Now for some facts.
The compression release is the standard centrifugal activated Exhaust bump. It completely disengages around 250 rpm on all of the engines I have worked on.

Opening up the exhaust on that engine by adding a motorcycle style exhaust really helps performance. The box exhaust that comes on the engine is very restrictive.

The OEM carburetor is tiny, about 10mm in the venturi. We have had great performance by switching to the carburetor for an XR75 Honda - clone carbs are 20 bucks on E-bay & it solves the throttle cable question at the same time. The 19mm round slide really lets that engine breathe.

There is no need to do any valve spring work. we spin those engines past 6,000 rpm all thetime without issue. Several people I know are running that engine daily. I see the one belt primary bike all over town on a regular basis. He is running about 15:1 overall drive ratio too.

Should be a trouble free engine for you. Here are some pics of them installed:
http://motorbicycling.com/showthread.php?t=54897

Click to expand...

Just to clarify, the info I gave is still accurate for the 98cc flathead. There are still a few around. OMB warehouse sells them brand new as replacement engines.

Here is a link to the engine from OMB. It's labeled as a Baja 97cc (the doodlebug is made by Baja), but it's the same engine) http://www.ombwarehouse.com/987899001-Baja-OEM-2.8HP-Engine.html. $140, and free shipping on orders over $75. Might pick me one up soon as a replacement.

<removed out of protest to certain "staff" practices in this forum.>

My interest is really up now. Home Depot delivers what they're calling a 97.7cc to me this coming Monday. If it is in fact a '79, they for SURE will hear from me (loudly!)
I also stand corrected on the weight of the HS142 that I got from Bicycle-Engines.com, it's 7 kilos, not pounds (15.4 pounds) sorry for the bad gouge..
Barry

Barry;

I don't think I would be upset at getting the better engine in this case.

I have both the 98cc flathead, and the 79cc OHV. The flathead has less than 6:1 compression, and limited possibilities for performance enhancement.

The OHV engine performs well out of the box - making as much power as flathead did with less displacement.

The only reason to want the older engine would be a appearance issue - or you want to burn kerosene for fuel, because the 5.6:1 compression will actually work with that.

The reason the flathead has such low compression is because of the compression release. Remove it, and it will make more power. How much? Dunno, but with the comp release keeping the intake valve open through 95% of the intake stroke, it's got to be robbing some power. Not to mention the highly inconsistent idle. My next pay, I'm ordering a replacement crankcase gasket so I can crack this mother and file that comp release off the cam. Partly because I want to know how much more power it can make, and partly because I'm having issues with my clutch due to the inconsistency of the idle. I tuned my clutch for about 2500 rpms engagement, but when the idle decides to go higher, it tries to engage the clutch at a standstill, and this makes the clutch hot, and then it slips. Removing the comp release should fix the idle, which should take care of the clutch problem. And yes, I do like the appearance of the flathead. I built my bike to resemble a classic motorcycle, which it could very easily be considered due to displacement, weight, power and most of all appearance. Not gonna get that with an ohv engine. So there are pros and cons to both versions of this engine. Shimming the valve springs should also net another 1000 rpms, so it wouldn't take much to get decent performance out of this engine. For looks and a few mods for mild performance increase, the flathead is a decent engine. But to each their own.

The_Aleman said:

The real Honda isn't necessarily better at all. It will only have slightly more power, have much more expensive OEM replacement parts, and have a higher up-front cost. Some of the Honda engines aren't even made in Japan anymore, and I have seen many complaints regarding those non-Japan Hondas, as well with an increasing number of all Honda utility engines these days.

There's some Honda engines that really aren't very good to begin with, like the OHC GC series; no one's bothered to clone one yet (thank goodness for that, too!).

Also, an example: My brother built his bike with a GXH50 (still made in Japan) and had to rebuild the engine after ~1500 miles. My bike has a clone of that engine (HS142F), over 5x the miles, and hasn't needed a rebuild. He constantly has starting problems with his Honda - as do more "real" Hondas than you'd believe these days - while those with the clones tend to have less problems.

Just because an engine is a "clone" doesn't make it inferior to what it was cloned from.

Click to expand...

I fully agree with your rebuttal.
I am referring ONLY to the early Honda engines that INSPIRED all the clones, NOT the current crop made to compete with the clones...
With a motorcycle carb, the early Honda's are hard to beat for reliable daily use.
My second choice would be a briggs flathead. Simple, easy to find, and the advent of Jr. Drag racing has exploded the aftermarket so you can easily build a rocket with as much hp as you can afford.

FFV8 said:

Barry;

I don't think I would be upset at getting the better engine in this case.

I have both the 98cc flathead, and the 79cc OHV. The flathead has less than 6:1 compression, and limited possibilities for performance enhancement.

The OHV engine performs well out of the box - making as much power as flathead did with less displacement...

Click to expand...

Not dissimilar to the 2 vs 4 debate - there's pros & cons to any engine design, power to weight preformance simply isn't a flathead attribute;

Advantages;

The main advantages of a sidevalve engine are simplicity, reliability, cheapness, compactness, responsive low-speed power, and insensitivity to low-octane fuel. The absence of a complicated ohv valvetrain allows a compact engine that is cheaper to manufacture, as the cylinder head may be little more than a simple metal casting...

Disadvantages;

The main disadvantages of a sidevalve engine are poor gas flow, poor combustion chamber shape, and low compression ratio, all of which result in a low power output. The sidevalve configuration makes intake and exhaust gases follow a circuitous route, with low volumetric efficiency, or "poor breathing"...

http://en.wikipedia.org/wiki/Flathead_engine

Click to expand...

...even the seemingly reduced price of the commonplace flathead utility motors isn't necessarily an advantage, given the potential complexity & cost of redrives needed for our application - I'd suggest researching carefully all the options available in engine and redrive design before making any decision, I do like flatheads... but if preformance & cost are both primary concerns, there's other motors that may suit those goals better in the long run

Valve spring shims, $1.95 each. Replacement crankcase gasket, $17 shipped. Removing the compression release, free as long as you don't botch it. At $140, the replacement flathead is more expensive than the 79cc predator, but for the look it's worth it to some. If you want an engine with unnecessary hp increases (it's a bicycle), go for something with ohv I guess.

The 79cc predator is on sale for $99, and agk has stiffer valve springs for it for about $4 apiece, making it cheaper all around. Guess the main advantage of the flathead is looks, but I'm ok with that. The 98cc flathead is very reliable, and I'm not looking for a ton of performance, just a little extra.

greaser_monkey_87 said:

The reason the flathead has such low compression is because of the compression release. Remove it, and it will make more power. How much? Dunno, but with the comp release keeping the intake valve open through 95% of the intake stroke, it's got to be robbing some power. Not to mention the highly inconsistent idle. My next pay, I'm ordering a replacement crankcase gasket so I can crack this mother and file that comp release off the cam. Partly because I want to know how much more power it can make, and partly because I'm having issues with my clutch due to the inconsistency of the idle. I tuned my clutch for about 2500 rpms engagement, but when the idle decides to go higher, it tries to engage the clutch at a standstill, and this makes the clutch hot, and then it slips. Removing the comp release should fix the idle, which should take care of the clutch problem. And yes, I do like the appearance of the flathead. I built my bike to resemble a classic motorcycle, which it could very easily be considered due to displacement, weight, power and most of all appearance. Not gonna get that with an ohv engine. So there are pros and cons to both versions of this engine. Shimming the valve springs should also net another 1000 rpms, so it wouldn't take much to get decent performance out of this engine. For looks and a few mods for mild performance increase, the flathead is a decent engine. But to each their own.

Click to expand...

You do realize that the compression release is only in effect at under 300 rpm, no one idles their engines that low and expects any power out if them.

<removed out of protest to certain "staff" practices in this forum.>

To put this thread back on track, the 152F engine has been OHV for at least a year now:



That tag says 07/13 for a MFG date, as well as 79cc.

I have had the engine for more than 9 months, so any flat head 2.5hp Lifan engines out there are old stock that is still flushing from low volume re-sellers.

The OP asked about longevity. So far running a stock rod & valve springs, the engines are holding up well, even with running 6200 rpm.

.

The compression release in the Lifan flathead is a copy of the Briggs ez-spin (thought it was called ez-start, but I was wrong), being discussed in this thread: http://www.oldminibikes.com/forum/briggs-stratton-engines/61954-briggs-ez-spin.html you can see from the video and photo that the compression release is a PERMANENT bump on the cam lobe. The only difference is Briggs put it on the exhaust lobe, while Lifan put it on the intake lobe. This is not the same as an ohv comp release which opens and closes.