# HOME DEPOT LIFAN ENGINES

Discussion in 'Firewall Forward / Props / Fuel system' started by Armilite, Aug 10, 2019.

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1. Aug 10, 2019

### Armilite

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2. Aug 10, 2019

### Spencer Fisher

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24 hp and 100 lbs? :/

3. Aug 11, 2019

### Armilite

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I believe you're looking at Shipping Weight and like the Harbor Freight 670cc V Twin, and the Honda/Clone Singles, once you strip off all Non Essential stuff, replace some parts with Billet Aluminium lighter parts and swap some parts with High-Performance parts for using them at Higher rpm, it would make a viable Engine, as would their Singles.

4. Aug 11, 2019

### GeneG

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Harbor Freight goes offer a horizontal shaft engine also to keep from the oil conversion problem. As for the internal parts, I believe that the camshaft gear is the only part needing addressed. Certainly going with forged pistons is a looser. Increasing compression, porting, camshaft changes and carburation may help.

5. Aug 11, 2019

### Aerowerx

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I see these threads on using these small engines and always wonder if it would work to link 2 of them together. Maybe with a belt drive or chain drive system. This could be included as part of the PSRU.

6. Aug 12, 2019

### Armilite

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Why would you want to add the extra Weight & Complexity to your Aircraft, when you just need to learn How to Build the Engine right for your HP needed. 99.9% of the Legal Part 103's only need 25hp - 35hp. The Bigger the Plane the more hp needed. If the GX390 Based Singles can be Big Bored +12mm to 100mm, and so far 86.5mm is the largest Stroker Crank I have seen. These V Twins can also be Big Bored probably +12mm. IF, you didn't use the Sleeve and Nikasiled the Cylinder you might pick up 4-5mm more.

2 Strokes with a Muffler at 6500rpm!
hp wanted times 10.5cc.
Example: Want 25hp x 10.5cc = 262.5cc Minimum needed.
Example: Rotax 277UL(268.4cc) was rated 26hp@6250rpm, but actually Dynoed 25.4hp@6000rpm. On Scat Hover Craft they were rated 28hp@6400rpm. 277UL with an R&D Aero Tuned Pipe Dynoed 30.5hp@6250rpm!

2 Strokes with a Tuned Pipe, using 11.5cr, proper Carb and used at 6500rpm!
hp wanted times 7cc.
Example: Want 25hp x 7cc = 175cc Minimum needed.
==================================================

4 Strokes used at 5000-5500rpm!
hp wanted times probably 13cc
Example: Want 35hp x 13cc = 455cc Engine needed.

460cc Clone Single making 37.37hp@5000rpm.

7. Aug 12, 2019

### Armilite

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On All of these Singles and the V Twins you need too:

1. Disable Low Oil Sensor and Governor!
2. Install a Billet Aluminum Rod.
3. To Save Weight, and to use at Higher than 5000rpm, you need the Billet Aluminum Flywheel.
4. You need to Install a High Rev kit (HD Push Rods, HD Valve Springs & Valve keepers & Locks).
5. For more HP you need a Bigger Carb.
6. For more HP you need a less Restrictive K&N Type Air Filter.
7. For more Hp you need a Tuned Header Exhaust.
8. For Durability, you need Needle Bearing Rocker Arms.
9. For Durability, and more Hp, you need a Better CAM.

For even more Hp!
1. Use a Higher CR.
2. Use a Bigger CAM.
3. Use Higher Rpm.
4. Use Bigger Valves.

8. Aug 12, 2019

### pictsidhe

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That would really need a rigid coupling between cranks. otherwise, you need heavy-ish flywheels on both and a soft redrive, which is more engineering. It's much easier to have one prop per engine. A direct drive shrouded prop set up on the smaller engines looks intersting. You get to spin them at 4-5k but still have decent propulsive efficiency.
The weakest point on these engines is often the rods. If you want more than a little extra power, you need to address cooling somehow.

9. Aug 12, 2019

### GeneG

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And for those who want to run at less than 5000 RPM, you may skip the hot rod parts, disable the low oil sensor and governor and go flying.
Camshafts can be ground to produce different results. I did mention a new cam, but on the line of the high torque RV cams for cars. I did mention compression increase and carbs plus porting.
Not installing the high rate valve springs reduces the need for the expensive rockers, springs etc. These operate many hours without them.
I agree with the flywheel if you use a starter.

Last edited: Aug 12, 2019
10. Aug 12, 2019

### Armilite

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1. Most of the Governors are set at 3800rpm, some brands it's set at 4000rpm.

2. You Replace the Stock parts with HD Racing parts to either Save Weight or their better Parts then Stock for more Endurance, (Longer Life). Hence Billet Rod and Billet Flywheel.

3. The #1 Weakest Point on most all 4 Strokes is the Valve Train. Hence, WHY you want the needle Bearing Rocker Arms, HD Push Rods, HD Valve Locks and HD Keepers. These Industrial Engines were not Designed to run even 4000rpm Continuously turning a Prop for Hours!!! Stock Valve Springs are very Marginal even for 3600-4000rpm at 16-18lbs. Many of these Industrial Honda/Clone Engine Companies offer a Hi-Rev kit for their Engine, usually for Max 4900rpm. Why 4900rpm, account the Stock Cast Iron Flywheels have been known to disintegrate over 5000rpm! They also Weigh a lot 12-15lbs. There is also a Heavy Cast Iron Balance Shaft 4-6lbs that can be taken out. I wouldn't run an Engine without a Flywheel, and most People want some form of Electric today.

4. 2nd Weak Point of these Industrial 4 Stroke Engines is the Stock CAM which is CAST, not a Billet CAM. I would use the HD Billet Lifters also. CAM's are made with Lift & Duration & different Lobe Centers. These Stock CAM's are terrible, not even really Optimized for Industrial use, Crap for Airplane use. These Engines are not put in RV's, you want a Marine CAM. What are many Hours to you, 300, 400, 500, 750, 1000, 1500, 2000, etc?

Good Video on CAM's for these Industrial Engines. He has some other good video's.

5. If you want to use a lower rpm, you can, but you won't make as much HP! It all boils down to HP vs Weight vs Lifespan(TBO). Let's use a Honda GX670 Spec's. The Rotax 912 80hp 4 Stroke is rated at 5500rpm!
https://www.engine-specs.net/honda/gx670.html

Max. horsepower 24 HP (17.7 kW HP) at 3,600 rpm
Max. torque (crank PTO) 50.8 N·m (5.18 kg·m, 37.5 ft·lb) at 2,500 rpm
Compression ratio: 8.3:1
Bore x Stroke (77mm x 72mm) or (3.0 in x 2.8 in)
Displacement 670 cc (40.9 cu-in) 670.8cc exactly.

Using the Peak Flow/HP Calc. 670cc At 24hp@3600rpm it comes in between 84-86% Volumetric Efficiency Stock! Does the Stock Engine make exactly 24hp, I doubt it. Most Companies round up. This Calc only uses whole Numbers. https://www.mk5cortinaestate.co.uk/calculator3.php

670cc at 84% at 4000rpm = 27hp
670cc at 86% at 4000rpm = 27hp

Now, how much HP are you going to Gain by just using a Bigger Carb, a Better K&N Type Air Filter, a Better Tuned Header Exhaust System, a +400rpm? An Increase of 5% = 1.35hp, a 10% = 2.7hp, a 15% = 4.05hp, etc. I can't tell you, account Nobody that I have found has ever Dynoed one with just them Base Improvements. I can tell you, those People who that have done those Base Mods and with a better CAM and raised the CR to 11.0cr and turned them 5000-5500rpm they are seeing a 120-130% Volumetric Efficiency.

670cc at 100% at 4000rpm = 32hp
670cc at 110% at 4000rpm = 35hp
670cc at 120% at 4000rpm = 38hp
670cc at 130% at 4000rpm = 41hp

A 460cc Single. Max 37.37hp@5000rpm. Even with a Higher Lift 307 CAM, it's not a good CAM.
You can see where it Averaged over +2hp up to 3600rpm and then started losing hp. Still made 33.99hp@4000rpm. I believe Stock CAMs are .226 Lift & .226 Dur. You want a Higher Lift and Higher Duration with a Wide 110 Lobe for plane use. This Engine would probably be used in the Minimum range 2600rpm (19.2hp) to 3800rpm(32.46hp) range for continuous use. 5000rpm at 75% = 3750rpm.

Camshaft, 307 Series
307 SERIES Serious camshaft for serious motors and big tracks.
Approx .307 lift and 260 duration.

11. Aug 12, 2019

### Armilite

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Stamped Stock Rocker vs Roller Tip Rocker vs HD Billet Needle Bearing Rocker. So if you want to Bank your Life, your Engine, on a $2 Rocker Arm, so be it! Notice they make Rockers in both Stock 1.2 and 1.3 Ratios. 12. Aug 12, 2019 ### Armilite ### Armilite #### Well-Known Member Joined: Sep 6, 2011 Messages: 3,016 Likes Received: 239 Location: AMES, IA USA 13. Aug 12, 2019 ### Armilite ### Armilite #### Well-Known Member Joined: Sep 6, 2011 Messages: 3,016 Likes Received: 239 Location: AMES, IA USA GX390 Head. Could you go with Bigger Valves, Yes. Could you Polish your own Ports, Yes. Our Pro Velocity cylinder head kits are fully machined, including milled cylinder deck surface, multi-angle valve job, ported and polished runners, flow tested on a Superflow flow bench to ensure port flow and velocity meets requirements, nitrided stainless steel valves with hardened tips (no lash caps required), split style automotive type valve locks and billet aluminum valve spring retainers. https://www.bullfrogperformanceproducts.com/product-p/100.2044.htm 14. Aug 12, 2019 ### GeneG ### GeneG #### Well-Known Member Joined: Jul 6, 2019 Messages: 46 Likes Received: 2 Location: Arkansas 15. Aug 12, 2019 ### Armilite ### Armilite #### Well-Known Member Joined: Sep 6, 2011 Messages: 3,016 Likes Received: 239 Location: AMES, IA USA 1. Most of the Governors are set at 3800rpm, some brands it's set at 4000rpm. What are many Hours to you, 300, 400, 500, 750, 1000, 1500, 2000, etc? I agree with disabling the governor and running about 4500 RPM. ===> Max rpm is for only 2-3min, so you can go up to 5500rpm if Design right. <=== 1500 to 2000 Hours. ===> The 084 Military Generator 4 Stroke Engines, basically a Small O-200 Type Engine used on Kitplanes, if taken care of was Lucky to make 1000-1200hrs. I'd hate to see what they Cost us New. Hirths have a 1000hr TBO, Simonini has a 600hr TBO, and Rotax has a 300hr TBO on their 2 Strokes. I think it can be done if you use the best parts and do some upgrades. I'd be real Happy to get these Rotax 2 strokes up to 1000hrs as well as these Small Industrial 4 Stroke Engines. When you can buy a Duramax 440cc 18hp Single for$299 and put less than $400 in Upgrades/Mods into it and get 35+hp out of it. I would be happy at 1000-1200hrs. <=== Now, how much HP are you going to Gain by just using a Bigger Carb, a Better K&N Type Air Filter, a Better Tuned Header Exhaust System, a +400rpm? An Increase of 5% = 1.35hp, a 10% = 2.7hp, a 15% = 4.05hp, etc. I can't tell you, account Nobody that I have found has ever Dynoed one with just them Base Improvements. I can tell you, those People who that have done those Base Mods and with a better CAM and raised the CR to 11.0cr and turned them 5000-5500rpm they are seeing a 120-130% Volumetric Efficiency. What fuel are you using? ===> Depends on CR being used, but minimum 91+. 93 is the Highest around me at the Pump. Airports around me usually only carry 100LL any more. In a 50 Mile radius of me, only 1 in 21 Airports even carries Mogas. That's also what I Averaged going out to 200 mile radius. If you Fly out of an Acreage only, or haul Gas, you can Buy what you want to use. 100LL here is$4.80 and Mogas at the airport is $4.20. Some places around me, 100LL is as low as$4.00.

Carbs only need to meet the required airflow, much bigger reduces lower speed performance.
====> To a point you are Correct, but many of these 2 & 4 Strokes are under Carbed. Many have to Restrictive Air Filters and Restrictive Exhaust.

A 2 Stoke Gulps Air, since Intake Port is only open about 50% of the Time. So Racers usually Double the Carb cfm needed when Sizing a Carb. My 1972 Skidoo Standard 335 (20hp@5500rpm) Single came with 9.0cr and a 32mm Carb, the same motor but called a 340 TNT (26hp@6500rpm) came with 10.5cr and a 38mm Carb.

These Small GX200 to GX390+ Industrial Engines all have Small 18mm to 24mm Carbs, and Racers put on 32-38mm. The Rotax 185UL also has a Small Carb. Even the 277UL has a 36mm Carb, and on a Dyno Sheet, you can see it's starving for Air! It Averages 2.8hp per +250rpm till 5500rpm, then it starts dropping in hp! It actually Dynoed 25.4hp@6000rpm. A 36mm Carb Flows 86.2cfm, a 38mm Flows 96cfm. It could be the Rotax Exhaust is too Restrictive also. Porting would also Help for +10-15%. With an R&D Aero Tuned Pipe, the 277UL made 30.5hp@6250rpm. Scat Hovercraft used them also and was rated 24hp@6400rpm. I have never seen what Exhaust they used on them. So the Exhaust used can make a difference. If you use the simple rule of thumb told to me by a Porting Specialist, at 6500rpm using 11.5cr and a Good Tuned Pipe, 268cc/7cc = 38.2hp is possible. MY Skidoo 670 Dynoed 115.7hp@7750rpm which comes in at 93%. A 277(268cc) at 93% = 38hp.

277UL(268cc) at 6000rpm needs 37cfm x 2 = 74cfm.
277UL(268cc) at 6250rpm needs 38cfm x 2 = 76cfm.
277UL(268cc) at 6500rpm needs 40cfm x 2 = 80cfm.

377UL(368cc) at 6500rpm needs 53cfm x 2 = 106cfm. It only used a single 36mm Carb. A 38-40mm would be a better choice.

I personally would keep compression below 9.5.
====> Hirth & Simonini has adopted 9.5cr for almost all of their Engines. My Rule of thumb is +1.0cr = 2hp, so +.5cr = 1hp. As long as you know what your Motor needs for Octane you can use any CR, but for Plane use, 11.8cr is the highest I would ever go. Some 532UL used 12.5cr. The 670HO used 12.5cr, Standard 670 used 11.5cr. Racers go up to 16:1 running Race Gas. The Rotax 277UL uses 11.8cr and runs well on 91 Octane. But is on the Edge, so you want to always use fresh 91+ Gas! <===

A 460cc Single. Max 37.37hp@5000rpm. Even with a Higher Lift 307 CAM, it's not a good CAM. You can see where it Averaged over +2hp up to 3600rpm and then started losing hp. Still made 33.99hp@4000rpm. I believe Stock CAMs are .226 Lift & .226 Dur. You want a Higher Lift and Higher Duration with a Wide 110 Lobe for plane use. This Engine would probably be used in the Minimum range 2600rpm (19.2hp) to 3800rpm(32.46hp) range for continuous use. 5000rpm at 75% = 3750rpm.

Sounds about right except I would reduce the lobe separation to 106 to 108 to tame the idle.
====> Ultralights & Small Airplanes that use Small Engines don't Idle very long. You want a Wider Lobe for Airplane use where you want the Power Band in the upper rpm range. For Ultralights 18hp to 35hp, Small Kitplanes 20hp to 50hp. <===

I am interested on keeping the costs to a minimum and not scare away the non engine builders.
===> Most People on here are not Engine builders and we all want it as cheap as we can get. Durability and Safety and HP Costs. <===

BTW --- How much does a bare 460 weigh?
====> Some people have said 55-60lbs, but they never say, is that with the Stock Cast Iron Flywheel (12-15lbs)or the Billet Aluminum one, and does it have the Cast Iron Balance Shaft (4-6lbs) or not. Nobody, that I have seen has done a Full Aviation Version lighten up as much as possible and posted the info. Most Part 103 Airframes can handle 70-80lbs for an Engine setup. A Simonini Victor 1 Single is 70lbs and comes in 44hp/48hp/54hp. A Hirth F-33(28hp) is 45lbs and a Hirth F-23(50hp) is 78lbs with Electric Start. There are things you can do to make them lighter, but that takes Time & Money also.

277UL

Engine without carburetor, fuel pump exhaust,
gear drive B 19.3 kg (45.5lb)
carburetor with socket .9 kg (2.0lb)
exhaust system 4.0 kg (8.8lb)
intake silencer with filter .84 kg (1.9lb)
electric starter 3.5 kg (7.7lb)
gearbox (B), dry 4.5 kg (12.1lb)

so about 78lbs, without Starter 70.3lbs. A Tuned Pipe is usually 3-4lbs lighter, say 66.3lbs. A Belt Drive is usually lighter than the Gear Drives 2-3lbs, say 63lbs. Take out the Cast Iron Sleeve and use Nikasil, Drill Holes in Crank Wheels, use a Titanium Rod, Light Weight Pistons, Grind Off any excess metal, and you might save another 5-8+lbs. A Free Air is Lighter than a Fanner.
<===

16. Aug 12, 2019

### Aerowerx

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Armilite, pictsidhe:

So the answer to my (rhetorical) question is that it is not practical. And would end up heavier than a single engine of twice the HP.

17. Aug 12, 2019

### GeneG

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Volumetric efficiency cannot exceed 100% It is the total swept volume of the cylinder(s) times rotation for normally aspirated engines.

A 44 cu inch 4 stroke engine turning 5000 RPM would flow 44*5000/2 = 110,000 cu inch at 100% volumetric efficiency. You only intake once every 2 revs.

Now we divide by 1728 to convert to CFM for the carb. 110,000/1728 = 64.66 CFM. Usually you add 15 - 20% to make sure the restriction is elsewhere.

True racing engines come near to 93% volumetric efficiency, however normal run of the mill stuff rarely exceeds 85%.

Comparing 2 stroke stuff to 4 stroke really doesn't work well.

I certainly will not be removing any counterbalance shaft on my engine. They vibrate enough as is.

Tuned pipes are great for 2 strokes, but less effective on 4 strokes by a wide margin.

The weight I asked for was for a bare single not a twin. It appears that you could replace a 1/2 VW with one.

Do you know off hand of anyone experimenting with a fluid damper on these small engines?

Thanks.

18. Aug 12, 2019

### GeneG

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It appears that it would be the same horsepower for a 50% weight penalty, however, the engine would not require much in the way of expensive parts, and would be under less stress increasing time to failure.
The twin also has full pressure filtered lubrication which I regard as important.

19. Aug 12, 2019

### Armilite

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Correct! Correct! Most of these 4 Stroke Industrial Engines can easily make 3x there stated Hp. Many of these 2 Strokes only use a Muffler, so with a Tuned Pipe can make 12+hp more at same rpm. If Rotax made a 40hp 277UL, they would have never Sold a 35hp 377UL, or a 40hp 447UL all for more CASH! The 380HO Stock was 48hp@7000rpm, 57.26hp@7000rpm with a better-Tuned Pipe and was never Sold in the Continental USA. The 503 hasn't been Sold in the US since 2003, but it's still made in Russia under the RMZ Brand, so is the 250F Single, 377F, 440F, 550F. A new 503F over there was around $1,500 usd, the 250F is around$850 usd.

RMZ/Rotax Engines. 250F (72mm x 61mm) 248.4cc, 22hp@6500rpm with a Muffler, Case, has Provision 8 Holes! Put a 550F Cylinder on it and you have a (76mm x 61mm) 276.8cc Single. The 277UL was 268.8cc. Skidoo made a 250 Type 253 here just like this. They only had Pro3 Holes on our Cases.

20. Aug 12, 2019

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