Weed eater engine conversion

Motor choice

Mark,

I have some experience with the 50 CC Honda. It was initially sold to me by my Honda distributor as being omni oiling when in fact it is not. I have one sitting here on the bench and it requires a UJ etc. I have had great experience with Robin. Their 1.6 is omni oiling. Hence no UJ is required. It has tremendous durability. I know nothing about Honda 35 CC motors. I think that the biggest problem with the small motor concept is that they still cost a lot of money but you can't water ski with one after spending that much money. The big advantage is light weight with reliable dependability.

I am currently building a 9 HP longshaft that has a 1.5 / 1 reduction. There are a lot of impoundments that limit HP and people still want push with out weight. It is probably going to weigh about 80 lbs.

 

Hi Mark -

I may have misspoke - your competitor did not see a difference between the Robin and the mini Honda four stroke he curently uses. Both performed the same. I would think this would make the Robin a better choice as 2 stroke motors are cheaper than 4 strokes, lighter, and are easier to maintain.

I am worried about my mud motor with the Honda motor. It is specificallly not recomended for ice augers due to the oiling system employed by this motor and the fat that it does not work well in cold weather. Well, the only time I use this motor is when it is really cold and ice prevents me from using my bigger boat and regular boat motor du to the ramps being iced in. Time will tell.

Nice to hear from you Mark. Keep plugging away.

Mark

 

Robin 4 stroke

Mark,

You probably presumed that the Robin that I use is a 2 stroke because they make so many million of them and that is what most people are familiar with as a result. The one that I use is a 8,000 rpm 4 stroke. It is also omni oiling. They make both a vertical and horizontal model. The longshaft use we are talking about is sufficiently horizontal to work with out a UJ. They are also broadly distributed in northern North America and Northern Europe - Russia.I have communicated with people in northern central Russia that use them.

It is coming right along.

Mark C.

 

Really

I learn somethign new everyday. I did not know of any Robin mini 4 stroke motors.

After making several 2 stroke longtails, I most definately prefer the 4 stroke due to it being quieter, better on the gas mileage, and reliable. I've got to tell you that the Honda GX35 is a very nice motor. I am still concerned about the oiling (misting or whatever Honda calls it) when used in cold weather and at the angles I am using this motor in the longtail application. I ahve run it for 2 seasons now with no problems - hope that continues.

Mark

 

Could you describe your concerns a little more in detail?I am unfamiliar with the GX Hondas.

 

My concern is the oil spraying system employed by Honda for these mini 4 stroke engines. This concern comes from Honda's own information about using these engines in cold weather (they don't reccommend it) This is why you don't see any ice augers built around the Honda mini 4 stroke motors.

I'm not saying it is a valid concern, just something I have in the back of my mind since my mini mud motor is used frequently in temps below zero.

Mark

 

Is there any kind of engine pre-warmer you could use? Once the engine has run for a bit, it should maintain above freezing temps on its own.

 

Perhaps a battery powered bench warmer would work?

 

Clearly you need the right oil for the temperature you are working at ...maybe honda did not envisage use at so low a tem ..best look in your car manual for a similar temp range

 

Ok

Bringing along a battery and a heater defeats the purpose of having a lightweight set up to put on my duckboat.

Different weight oils could be possible but Honda does not list what those options are - they just state (or at least they used to) that these motors are not to be used in cold environments. Can't recall the specifics and it is not something that is causing me much duress, it is just something I am monitoring and paying attention to.

Mark

 

Just wrap a rag around the front of the cylinder. Its air cooled minus what ever is too cold.

 

Maybe you should read the Honda mini 4 stroke engine precautions. It is the oil misting system that does not work in the cold weather. A rag will not help. Wish it were that simple.

I've had these discussion with the motor manufacturer. I really don't have to worry much with the way and angle I am using this motor. Should it be used at extreme angles (ie 90 degrees), I would then be more concerned. Thus the reason there are no ice auger using this moto.

Mark

 

Looking for performance experiences

Hey all. I built a sweet little longtail, ala Pistonbrokes 6.5. Because I used the chain/gear setup, I am able to change out gears to experiment with different ratios. My unit is powered by a B&S 4 HP. The prop is either 8.5 x 8 or 8 x 8.5. The max rpm is 3400. I started out with 2:1 reduction and got 6.5mph WOT. I then switched gears to 1.5:1, and had a top end speed of 8.5.

I plugged these stats into a prop calculator on the web and determined that I'm experiencing .495 slippage. That sure seems like an awful lot to me. The one thing I'm also surprised at, is that even at 1.5:1, my engine is still maxing out at the no load 3400 rpm limit. I have a 1:1 gear that I'm also going to try, just to see if it will still max out at 3400. I figure my WOT speed will be in the 12-13 mph range, and my idle speed will probable be damn near 10!!! I saw John O'neals longtails were direct drive, but I couldn't find out anywhere what his max rpms were on those.

Would any of you like to share your performance experiences? I just wish I had a wider range of rpms to work with as even at idle at 1.5:1, I'm already at 5.5mph!!! This can be a bit much when trying to navigate against a current, in the dark, amoungst willow choked shorelines and islands when waterfowl hunting. Wish I could figure out how to make a hi/lo range transmission!!!!!

Oh, I started out with a clutch and removed it. I found I only had about 1000 rpm to work with from the time the clutch engaged and WOT.

Looking forward to your comments/questions!

 

Forgot to add above that I live at 4100', so I have a substantial power loss...more like a 3hp instead of the mfgr rating of 4.

 

A bigger slower reving prop will have less slip ...a normal outboard prop does 2000 rpm so your ratio is wrong you need over 2 to 1 I used 2.3 :1 I think. Next you need the motor doing 3600 rpm at WOT driving the prop so adjust the pitch to get this ...bend the blades..you can adjust the clutch so that it lets you crank the engine easy for starting but comes in as soon as it starts ..weaker spring inside

Also you forget what is called displacement speed ..the max speed you can go without putting in loads of power .......sq root of length in ft x 1.5 ..for a 12ft boat its about 5 mph.....photos please ....in thailand they do about 5 or 6 to 1 reduction on the small motors ...