ROTAX 185 cc, 2-cycle 9HP Engine from Wajax "Pacific Pumper Mark 3" Fire-Fighting Rig

[Boomstick]

Actually, now that you say that makes me think that it's either low compression (which WOULD make it rider friendly!), or it only makes 9hp at a set speed down low... like 4000RPM's (a number I'm pulling out of my own rear end).

If it does rev higher, who knows, it may not have hit it's powerband at the speed it originally ran at. If you could wind it to 8000, it might either be an absolute monster (15-16hp that comes on really, REALLY quickly), or it would fall flat on it's face.

My primary concern was that on a minibike, it would have been a complete dog until the split second it hit it's powerband... then HANG ON!!!

 

[chazdaddy]

check out this vid: Lazair engine

sounds pretty stout to me, I am thinking kart engine...

here's another vid: Tuning the Lazair Rotax 185 motors

did you see this "If your 185 has a woodruff key slot on the crankshaft it is not advised to run anything heavier than the biplane style props. Consequently, Rotax upgraded the Rotax 185 with stronger cranks which could accept much larger props. Many people now have the strong crank shafts installed in their Rotax."

 

[chazdaddy]

found this: engine data doesn't look very scary, verified my theory

I saw parts prices too, very expensive: piston $180, crankshaft $1000, reminds me of my Rotax

 

[MoTo-BunnY]

Thanks for all the great info! This is a very intriguing engine for us as we have never messed with 2-stroke engines before and this one seems amazingly well made. Parts availability and cost seems to be a major negative, but we will see if we even need anything.

The only thing keeping us from giving it a test run is the carb. It was really chalky on the outside and looks like it had been stored for quite a while with no air filter or covering on it. I took it off last night and put it in the ultrasonic cleaner for a few cycles with some simple green and it cleaned up real good. I also got the information off of it, the carb is a Tillotson HL63E with a manufacture code of 11/63.

I'm not sure if this was a replacement someone put on the engine later or if the engine is actually that old? I looked up the carb online and just found that it was used in these water pumps as well as a few 1959 models of McCulloch chain saws.

I would like to maybe rebuild the carb, just to be sure it is good working condition but I can't seem to find a rebuild kit anywhere for it. I can find ones for similar models but not an exact match, unfortunately. I might just put it on the engine as is, get some 2-cycle oil and (try) to start it up. :thumbsup:

Here are some pictures of the cleaned up carb:

 

[MoTo-BunnY]

I just watched this video of a Rotax 185 running-it sounds crazy, I love it! Mine has that same muffler set up, too (different than the type of muffler they use for the ultralights).


Rotax 185 start - YouTube

 

[MoTo-BunnY]

Actually, now that you say that makes me think that it's either low compression (which WOULD make it rider friendly!), or it only makes 9hp at a set speed down low... like 4000RPM's (a number I'm pulling out of my own rear end).

If it does rev higher, who knows, it may not have hit it's powerband at the speed it originally ran at. If you could wind it to 8000, it might either be an absolute monster (15-16hp that comes on really, REALLY quickly), or it would fall flat on it's face.

My primary concern was that on a minibike, it would have been a complete dog until the split second it hit it's powerband... then HANG ON!!!

We are thinking about using it on a mini drag bike and possibly with one of those new Downs Brothers manual clutches so it might be a real good match for that application?

 

[Neck]

I really don't think that engine was ported with peak horse power in mind. Does the spec tell what rpm 9 HP. was made?
This is a 175 go kart engine from the 60's, it has 11:1 compression and is rated at 16 HP. @ 7000/7500 rpm.

 

[chazdaddy]

see post #23 above

Power output-continuous
5.2 hp @ 3000 rpm
7.6 hp @ 4000 rpm
9.2 hp @ 5000 rpm

so you gear it about like a stock 5hp Briggs FH :shrug:

 

[MoTo-BunnY]

After watching that video, it sure sounds like it can turn more than 5000rpm so I don't know where the peak or max HP would be. I also can't find any info about compression ratio.

Sure there are higher HP engines to be had but I already have this one-that Maico does look killer though! It just seems like this Rotax is an interesting engine especially as a 2-stroke, and I thought I would play around with it?

I'm going to put the carb back on and try to run it if it doesn't run then I might just move on as I can't seem to find a carb kit for it and we have like 30 or so Briggs and Tecumseh engines so I can just mess around with those, instead. :shrug:

 

[roccosbike]

View image in gallery​

View image in gallery​

this engine 318CC makes 18HP and there is a bigger version sporting 340CC,they all share the same block.

 

[MoTo-BunnY]

View image in gallery​

this engine 318CC makes 18HP and there is a bigger version sporting 340CC,they all share the same block.

What kind of carburetor are you using? Kinda looks like a Tecumseh?

That looks like a really fun ride!

 

[Neck]

Your not limited to a pumper carb you know, you can also use a float style, or even a slide style. The pumper is just better when the engine will be running out of the ideal position. In a Mini, pretty much any style of carb that's properly sized will work.

 

[MoTo-BunnY]

Your not limited to a pumper carb you know, you can also use a float style, or even a slide style. The pumper is just better when the engine will be running out of the ideal position. In a Mini, pretty much any style of carb that's properly sized will work.

But there is this small vacuum port thingy on the manifold of the carb that meshes with a port on the engine. Isn't that how the fuel delivery is assisted? There were a couple posts here on OldMiniBikes mentioning this carb and similar, where I discovered that. :shrug:

See the small hole down on the bottom of the flange? (the big one isn't all the way through) It lines up to a hole on the engine carb flange for vacuum that assists fuel delivery or whatever. I COULD use a different carb (I did notice the holes are Tecumseh spacing) I suppose but I think I would have to block off that engine vacuum port or something?

 

[Neck]

That port is for crank case pulses which is what makes the diaphragm in your current carb work. That wont be necessary for any float style carb, and a gasket will block it off should you decide to go that route. Also, mounted in a Mini frame, you could use a gravity fuel feed by mounting the tank over the carb in some manner.

 

[MoTo-BunnY]

That port is for crank case pulses which is what makes the diaphragm in your current carb work. That wont be necessary for any float style carb, and a gasket will block it off should you decide to go that route. Also, mounted in a Mini frame, you could use a gravity fuel feed by mounting the tank over the carb in some manner.

Wow, OK. . .thanks for that info! I was worried that vacuum port would leak or something I guess, and also not sure if there were any huge differences between 2 and 4 stroke carbs? Running this Rotax is sounding more and more doable, as I have several extra Tecumseh carbs and they do mesh up to the Rotax carb mount.

I am going to give it a whirl in the next couple of days (once I finish a project on my van I am trying to wrap up) and see what happens. I'll try the stock carb first and if no-go, I can try a known good working Tec 5HP carb.

Two (basic) questions though, is this push-pull thingy on the front a compression release? It seems like it but the knob broke when I tried to push or pull it (the cable seems all stuck)

Also, there is this little yellow lever thingy I'm not sure what it is for....it goes in and out and makes a "chunk" sound when you move it but not sure what it is for?

I am assuming the red button is the shut off for the Bosch magneto but I sure wish I could find ANY kind of literature for this dang thing (I just have a kinda bad scan parts manual) . . ..even a basic operators manual would answer these embarrassingly basic questions.... :001_tongue:

 

[bikebudy]

Rotax uses a internal impulse system to run the fuel pump diaphragm in the carb, taking away the need for a separate fuel pump.

Now on the larger engines they use an external impulse from the crank case to run a external fuel pump.

All you would have to do is drill a hole in the crank case, install a nipple and add the external fuel pump. Then you can place the fuel tank anywhere you like. Most external fuel pumps are no more than a foot away from the engine / carb. Due to pressure loss over distance.

In a snowmobile, the carb often had a return line which pushed fuel and air back to the tank. The air pressurized the tank a bit to help with distance and the fuel delivery of the fuel pump.
With external fuel pump system you can run any carb that matches up well with engine size.

I think on all mikuni carb boxes it says not for air plane use. Reason is mikuni does not run on its side or upside down, Or any float carb for that matter.

That's why Tillotson and Walbro was a carb of choice. As well as 2 stroke engines will run in any position you put them in, like a chain saw will. As long as it has the right needle and impulse pivot arm that is.



If it were me and if it was my engine and I had no need or worry of it staying original.
I would drill the crank case add the nipple. Install a external fuel pump and install a Mikuni carb. Mainly for starting , reliability and response.


( Yes , it is compression release ) and may be stuck

You may find a carb kit here

mcculloch mac 200 , 250 chainsaw tillotson hl63e carburetor

 

[MoTo-BunnY]

GOOD NEWS! I have finally found an operation / parts / service manual! The downside is that it is for the most recent version of the water pump that is now made by Waterax (Rotax sold them the rights years ago) and has electronic ignition and other things my engine doesn't. HOWEVER, the manual seems to be pretty good in showing some of the older Rotax components, too. I would still love to find any original Rotax literature for this engine but this will do for now. :smile:

Here is where I found the manual:

http://waterax.com/eng/downloads/servicemanuals/Mark-3_Service_Manual.pdf

Rotax uses a internal impulse system to run the fuel pump diaphragm in the carb, taking away the need for a separate fuel pump.

Now on the larger engines they use an external impulse from the crank case to run a external fuel pump.

All you would have to do is drill a hole in the crank case, install a nipple and add the external fuel pump. Then you can place the fuel tank anywhere you like. Most external fuel pumps are no more than a foot away from the engine / carb. Due to pressure loss over distance.

In a snowmobile, the carb often had a return line which pushed fuel and air back to the tank. The air pressurized the tank a bit to help with distance and the fuel delivery of the fuel pump.
With external fuel pump system you can run any carb that matches up well with engine size.

I think on all mikuni carb boxes it says not for air plane use. Reason is mikuni does not run on its side or upside down, Or any float carb for that matter.

That's why Tillotson and Walbro was a carb of choice. As well as 2 stroke engines will run in any position you put them in, like a chain saw will. As long as it has the right needle and impulse pivot arm that is.



If it were me and if it was my engine and I had no need or worry of it staying original.
I would drill the crank case add the nipple. Install a external fuel pump and install a Mikuni carb. Mainly for starting , reliability and response.

Thanks so much for all the info! (and awesome photo explanations!) I wondered if that was a compression release, as I had seen similar on old motorcycles.

I had no idea about all this vacuum assist carb stuff, very good to know.

So, with your idea of plumbing the case and going to an external fuel pump, is that THE best way to go? (assuming this carb doesn't work right) or kinda the only way? I mean, could I use a Tecumseh float carb OK, for instance-at least just to test run it? (using just a gravity feed, since I don't need the engine to run upside down and what not)

If I decide to use this engine for a drag mini project though, then the Mikuni would definitely be the way to go given how much good I have heard about them.

I must say, this is an interesting engine and I will have to keep an eye out for other Rotax stuff at the swap meets. Too bad I don't still live in snow country and could find their various snow mobile engines but I bet there are more of these water pump engines around here (given all the forests here and the equipment to fight forest fires you find at the swap meets)

 

[bikebudy]

Tecumseh float carb should work fine, as a gravity feed carb.

Otherwise, you would still need a external fuel pump if the tank were lower than the carb.

Also don't think a 2 stroke don't have power

These are 2 stroke

http://www.youtube.com/watch?v=nrldkXg7-Jo


I would love to see that pump end pulled off the engine and see the crank shaft end?

 

[Neck]

Uh, the speedway bike is not a two stroke, but many an hour I have pondered a drag bike with one of those Jawa short stroke 500 engines on it!

 

[bikebudy]

I stand corrected ! I always thought they were.

ed; A little ground to stand on, lol

I used a pic from the wrong era. 55-70's

Some 2 strokes were used in speedway racing. LOL

The Hummer was a motorcycle model manufactured by Harley-Davidson from 1955 to 1959. However, the name 'Hummer' is now used generically to refer to all American-made single-cylinder two-stroke Harley-Davidson motorcycles manufactured from 1948 to 1966. These motorcycles were based on the DKW RT125 [DKW was the world's largest motorcycle manufacturer in the 1930s], the drawings for which were taken from east Germany as war reparations after World War II. RT125 drawings were also given to Britain and the Soviet Union as war reparations, resulting in the BSA Bantam and the MMZ M-1A Moskva, later known as the Minsk.