Need Mods to Improve Power/Efficiency of Honda GX35 + Electric Starter & EFI Install

[shellboi]

I'm an engineering student working on a vehicle project involving a Honda GX35 engine, and I’m looking for ways to improve its power and efficiency (efficiency takes priority). I also need to install an electric starter and convert it to an electronic fuel injection (EFI) system as a requirement.


My Goals:
Increase power and/or efficiency – Looking for performance mods (intake, exhaust, tuning, etc.).
Install an electric starter – Any kits or DIY solutions for this?
Convert to EFI – Are there small EFI kits that work with the GX35? Any recommendations on sensors, injectors, or controllers?


If anyone has experience with these kinds of mods, I’d love some guidance on what parts to use, what challenges to expect, and any resources that could help. Thanks!

 

[Gordy]

Everything you want to do is pretty doable, except maybe the EFI.

The best way to improve efficiency of an engine is to improve how the gasses flow. Smoothing the port castings, polishing exhaust port, free flowing pipe, matching the intake to the exhaust, stuff like that. Just think if how water would flow through it, and what might cause ripples. You will need to pull the head off and completely disassemble it.

The electrical start, a simple solution is just a belt drive. Do you have to retain pull start function?

And fir the EFI... You might have to design and make something. I don't think anyone makes anything small enough for that. It would have to be really simple. Probably something similar to the EFI in early 90s Chevy trucks.

 

[DieselTech]

I'm an engineering student working on a vehicle project involving a Honda GX35 engine, and I’m looking for ways to improve its power and efficiency (efficiency takes priority). I also need to install an electric starter and convert it to an electronic fuel injection (EFI) system as a requirement.


My Goals:
Increase power and/or efficiency – Looking for performance mods (intake, exhaust, tuning, etc.).
Install an electric starter – Any kits or DIY solutions for this?
Convert to EFI – Are there small EFI kits that work with the GX35? Any recommendations on sensors, injectors, or controllers?


If anyone has experience with these kinds of mods, I’d love some guidance on what parts to use, what challenges to expect, and any resources that could help. Thanks!

There used to be a EFI kit you could buy for the Honda gx35, but I see it was discontinued now.

 

[cloakedvillain]

Have you seen those smart carbs? I recommend emailing them about your particular application.

Here are some leads, I have not looked too deeply into any of these.

EFI for small engines - rusefi.com

View: https://m.youtube.com/watch?v=OmAfNGKYG2A&pp=ygUKI2Nsb2NrdWlubw%3D%3D

NanoEFI

Fuel Injection for Single-Cylinder Engines

www.nanoefi.com

View: https://m.youtube.com/watch?v=RKe1_gTOsms

HAE small engine injection kit

HAE small engine injection kit

www.modelenginemaker.com

Small engines EFI kits

www.snowblowerforum.com

Electronic Fuel Injection Systems - Walbro

www.walbro.com

Small engine fuel injection conversion, carburetor to EFI

List of engines from popular RC manufacturers that can be converted to EFI engine systems to use as power plants for UAVs.

www.loweheiser.com

As for the starter this thread looks promising: Thread 'Electric starter' https://motoredbikes.com/threads/electric-starter.11310/

There is this type that bolts to the pto where the clutch normally mounts:
View: https://youtu.be/gYtocYVfOfA?si=KebvZOz1nvQAIb2M

I can't remember if it uses a sprag clutch/ freewheels but if it doesnt freewheel, but if you can get at the distinct windings you can build a circuit to use it as a starter and generator. Look into series motors and dynamic braking.

 

[Sidewinder Jerry]

Is this a project you're doing on your own or is it a school project? Your post is somewhat vague concerning this. What is the engine going to be used for?

The Honda GX 35 is a very high-quality Japanese engine, unlike the Chinese clones. Trying to mod it for more power you run the risk of structural damage to the engine.

I use a 4-stroke Robin Subaru EH035 engine. To get maximum power and efficiency here's what I did to my engine:

I removed the spark catch screen in the exhaust.

I changed the non-adjustable diaphragm carburetor to an adjustable diaphragm carburetor. It has high/low air/fuel mixture screws and an idle screw. I used my tachometer to set the tuning adjustments to my carburetor.

I do scheduled routine maintenance. Every 10 hours of use I clean the air filter. I change the oil every 25 hours and check the valve lash clearance. I use a high-mileage synthetic oil and only use ethanol-free gas. This is where an hour counter comes in handy on the tachometer.

The most important information one can have about an engine is the factory stats. My engine, the RS 35, stats are: 3000 rpm idle; 5000 rpm max torque 1.2 foot/lbs; 7000 rpm max horsepower 1.6 hp; max rpm 8000. Centrifugal clutch engagement is 4500 rpm. My engine is 15 years old and still going strong after 5000 hours of use. That's more than I can say for myself, lol.

Another key to the engine's longevity is the drive system. The first bike the Staton Inc. kit was on was a LandRider. The bike shifted 7 human/engine-driven gears automatically. The kit is now on a Schwinn Sidewinder. I manually shift gears on it. I use a triple chainring shift kit and setup a color-coded, left hand shifting system for both derailleurs. It uses 9 sequential non-redundant gears. At full throttle I use gear selection to maintain an rpm range of 6000~7000 rpm. Because of the drive systems I've used the centrifugal clutch is also 15 years old. With the color-coded shifting system, cross-chaining has been eliminated on the bicycle chain. The current Shimano HG71 bicycle chain is 4 years old.

Now are you ready for the real feat to all of this? The bike weighs 100 lbs; I weigh 250 lbs; the detachable pull-behind trailer can hold 200 lbs. I live in the mountains where 30% grade hills are common. I've pulled a full load up these hills at 8 mph. I've ridden by small mopeds being pushed/throttle-assisted up some of these hills.

 

[Will'smotobikes19]

As for the starter this thread looks promising: Thread 'Electric starter' https://motoredbikes.com/threads/electric-starter.11310/

There is this type that bolts to the pto where the clutch normally mounts:
View: https://youtu.be/gYtocYVfOfA?si=KebvZOz1nvQAIb2M

I can't remember if it uses a sprag clutch/ freewheels but if it doesnt freewheel, but if you can get at the distinct windings you can build a circuit to use it as a starter and generator. Look into series motors and dynamic braking.

Ya I recognize that starter they are used on 43cc and 49cc mitsu clones. I had one with a starter on it ended up selling the motor. I would think a custom longer shaft or crank would be needed. Also you'd have to figure out how to mount it. On them the pullstart and electric start are combined as one unit, never seen one on the clutch side of a cag.

 

[Will'smotobikes19]

Electric Starter Gas Scooter Part 43cc 49cc 2 Stroke Electric Start Coil Magneto | eBay

This is a brand new parts used in most of 2 strokes . Contact for other parts .

www.ebay.com

Here's one for a reasonable price.

 

[Will'smotobikes19]

Amazon.com

 

[Sidewinder Jerry]

Looking more and more like a One & Done

 

[Will'smotobikes19]

Looking more and more like a One & Done

Ya he was last seen an hour after he joined.