Rotax 277 piston port to reed valve conversion

[Desertduler]

This is such a well explained theory of operation, very well said!

Thanks

 

[Desertduler]

With much testing I have settled on these two different reed valve stuffers for different power delivery. Here is a reed valve block without any reeds installed to show how the reed valve stuffers fit into the reed valve block.The one that fills the reed valve block and directs the flow narrower induces air intake velocity and the engine makes more low end power and the other open one makes more top end, I can change the power delivery to a degree with the choice of these stuffers depending on the track layout in order to achieve the best results.

 

[yanbolduc]

Very good infos. Did you try different reeds also

 

[Desertduler]

Very good infos. Did you try different reeds also

Yes I have and currently to date the best ones I have tried are the Boyesen carbon fiber dual stage pro series reeds.

 

[Desertduler]

I just received a crankshaft that I bought off of ebay today for this engine that is in great shape! I am stocking up spare parts for this engine as I have plans down the road for other conversions,ebay for me has been a great resource for obsolete parts that I have needed,if you wait long enough you can find what you need most of the time.

 

[Desertduler]

Kudos to member ''yanbolduc'' as he has converted his 277 Rotax engine in his snowmobile from piston porting to reed valve induction like I have done on my kart, He has sent me pictures of his conversion and he has done a wonderful job, I admire someone that dares to take the bull by the horns and take on and complete a task that they have never done, I call it "Balz and Guts"

 

[rushking19]

That's sounds awesome

 

[landuse]

Kudos to member ''yanbolduc'' as he has converted his 277 Rotax engine in his snowmobile from piston porting to reed valve induction like I have done on my kart, He has sent me pictures of his conversion and he has done a wonderful job, I admire someone that dares to take the bull by the horns and take on and complete a task that they have never done, I call it "Balz and Guts"

Nice work yanbolduc!

 

[Armilite]

Hello

I don't get here often, but I have just READ this whole Rotax 277 Reed Valve thread. Desertduler your Awesome! Thanks for posting such Clear Info, and Photo's.

I'm more into Ultralight Airplanes, and Sleds myself, to Big, and Fat, to fit most Go Carts.

A few observations. A good Cylinder/Case Porter I respect, once told me for my Ultralight Engines, used at max 6500rpms, if designed, and built right, it takes 7cc to make 1hp at 6500rpms. So 268.7cc/7cc = 38.4hp is possible at 6500rpms.

Specifications (277UL) - With just R&Ds after market Tuned Pipe it made 30.4hp at 6250rpms on the Dyno. Scat Hover Craft also used them, and they rated them 28hp at 6400rpms.

Data from ROTAX 277 UL Data Sheet[1]
General characteristics

Type: two-stroke air-cooled aeroengine
Bore: 72 mm (2.83 in)
Stroke: 66 mm (2.60 in)
Displacement: 268.7 cc (16.40 cu in)
Dry weight: 29.5 kg (65 lb) (complete including reduction drive and exhaust system)

Components

Valvetrain: piston ports
Fuel system: pneumatic pump pressurized
Fuel type: premium unleaded autofuel
Oil system: premixed in the fuel at 50:1
Cooling system: fan or free air

Performance

Power output: 19 kW (26 hp) at 6250 rpm
Compression ratio: Theoretical 11.8, effective 6.7
Power-to-weight ratio: 0.64 kW/kg (0.40 hp/lb)

============================================
With a Reed Valve, Cylinder/Case Porting, better Tuned Pipe, turning it even higher rpms than Stock, I would bet your making more like 45-50hp!
==================================================================
A Yamaha 292cc Single, with a Reed Valve, was the highest HP Single Sled Engine ever made. With one of Aaen's Tuned pipes, it made 70hp at 9000rpms on the Dyno, with another designed for oval racing it made 50hp at 7000rpms on the Dyno.
=================================================================
For the guy wanting to use a Rotax 377, it's 36hp at 7000rpms with a 9.6cr. The 377UL with a 9.6cr was 35hp at 6500rpms with a single 36mm Carb. Over Sea's, they made a 380HO 48hp at 700rpms with a 11.2cr. 380HOs with and aftermarket Tuned Pipe have been Dynoed making 57hp at 7000rpms, 63hp at 7300rpms.
================================================================
Skidoo also made a 340, Type 336, Single, 36hp, and a 292, 31hp, and it used 10.5cr. I haven't verified what the 340 used for CR. I also have verified at what rpms they both were rated at.
================================================================
Has anyone here Big Bored a 277?

Has any one Documented with photo's a Bosch Points to CDI conversion on a 277?

Thanks
Rich

---------- Post added at 08:50 AM ---------- Previous post was at 08:44 AM ----------

Go Kart Speed Calc
http://www.csgnetwork.com/kartpotentialspeedcalc.html

There are torque / hp Calc on the net.

There are Smart phone Speed Aps, Speed test

---------- Post added at 08:52 AM ---------- Previous post was at 08:50 AM ----------

HP / Touque

http://www.1728.org/mtrtrq.htm

---------- Post added at 09:01 AM ---------- Previous post was at 08:52 AM ----------

26hp at 6250rpms makes 29.6214 Torque - Rotax UL Pipe

28hp at 6400rpms makes 31.1524 Torque - Scat Pipe

30.4hp at 6250rpms makes 34.6343 Torque - R&D Pipe

Skidoo 670 built for plane use 92hp at 6500rpms 100.783 - Modified 618UL Pipe

http://ncalculators.com/electrical/horsepower-to-torque-calculator.htm

---------- Post added at 09:04 AM ---------- Previous post was at 09:01 AM ----------

http://www.diygokarts.com/speed-calculator.html

---------- Post added at 09:06 AM ---------- Previous post was at 09:04 AM ----------

https://www.gokartsupply.com/ratios.htm

---------- Post added at 09:18 AM ---------- Previous post was at 09:06 AM ----------

Some different Rotax Dyno prints by R&D from the 90's.
http://www.rotaxservices.com/dyno.html

Rich

 

[Desertduler]

Thank you Armilite for the compliment! There is not a lot of call on this site for these types of engines or modifications, most people on here are interested in small utility splash lubricated four stroke engines from Harbor Freight.

 

[rushking19]

Lol yeah that's why I love the engine I have on my go Kart because it's different from most peoples on this form

 

[Desertduler]

Now that it is winter time in my location it is time to tear this engine down and see how well that it has survived the punishment that I gave it this past summer.

 

[chancer]

Just Curious... before you tear it apart, What type of wear or damage to expect to see after this summers "punishment"?

I would bet it still looks new.

 

[Desertduler]

Just Curious... before you tear it apart, What type of wear or damage to expect to see after this summers "punishment"?

I would bet it still looks new.

What I will be looking for is wear and the overall condition of the engine after I have ran this engine hard all summer after its reed valve conversion, the cylinder that I have had on this engine is one that works best around 7500-7800 rpm with two piston rings, my kart was faster overall with this cylinder than the higher rpm level cylinders I tried.
This engine was ran hard on the lakebed with many long straightaways and it was subjected to high ambient air temperatures also.

 

[Desertduler]

A look at the piston in the exhaust port is a good place to start to check the condition of a two stroke engine, here is how I have the spark plug ground electrode indexed in the combustion chamber this is so that the incoming air fuel mixture rolls in between the electrodes and there is a greater chance of the air fuel mixture being lit off at the correct time that the plug fires than if it is shielded by the ground electrode facing the opposite way, this is called spark plug indexing, here one can see the piston wash pattern on the crown of the piston and the the piston at B.D.C. in the cylinder and one can see the rear boost port that I have cut in this cylinder, the cylinder looks to be in great shape.

 

[Desertduler]

Here is the cylinder removed and the exhaust and intake side of the piston, the piston looks good enough to use for another season as it still has most all of its oil retention grooves on the piston skirts, the Noram Enforcer clutch has worked flawlessly and is one tough unit.

 

[chancer]

A look at the piston in the exhaust port is a good place to start to check the condition of a two stroke engine, here is how I have the spark plug ground electrode indexed in the combustion chamber this is so that the incoming air fuel mixture rolls in between the electrodes and there is a greater chance of the air fuel mixture being lit off at the correct time that the plug fires than if it is shielded by the ground electrode facing the opposite way, this is called spark plug indexing, here one can see the piston wash pattern on the crown of the piston and the the piston at B.D.C. in the cylinder and one can see the rear boost port that I have cut in this cylinder, the cylinder looks to be in great shape.

If I may add to this... Here is link to a how to on Spark plug indexing. It is a cheap way to grab a tiny advantage for almost no cost. Worth 5 minutes of time, If you have the head off an engine already.
http://www.affordablegokarts.com/index-spark-plug.php

 

[Desertduler]

If I may add to this... Here is link to a how to on Spark plug indexing. It is a cheap way to grab a tiny advantage for almost no cost. Worth 5 minutes of time, If you have the head off an engine already.
http://www.affordablegokarts.com/index-spark-plug.php

Yup, exactly, sometime I will have to tell the story on how I made 8000.00 plus on a spark plug indexing tune up job.

 

[kawicat]

Yup, exactly, sometime I will have to tell the story on how I made 8000.00 plus on a spark plug indexing tune up job.

this almost sounds like one of those ads you see on the side of webpages...

but my question is how in the world did you get so lucky??

 

[Desertduler]

this almost sounds like one of those ads you see on the side of webpages...

but my question is how in the world did you get so lucky??

I used to do quite a bit of side work on peoples things and I had a guy ask me if I could make his boat run better so I told him yes his boat had twin small block 350 Chevrolet engines in it so I bought four sets of spark plugs for his engines and out of 32 plugs I was able to index 16 of them correctly in the engines combustion chambers and I recurved the centrifugal advance in both HEI distributors in his engines and he paid me with penny stocks a bunch of them, at first I was not going to take them as payment but he was a trusted friend of an acquaintance of mine so I took them as payment, I have a friend that is a stock broker and I gave them to him to see what they were worth so after a day or so he called me and said that some of them were worth some good money and some were not worth anything at the time so I asked him if I should just hang on to them and see if they would be worth more in time and he replied " The hogs get slaughtered in this game" so I told him to sell them for me and he did and when he gave me the check for the sold stocks I about sh-t! I was floored to say the least! I had to pay income tax on my earnings but that was well worth my time and effort and the guy was tickled with his boat and that is how I made over 8000.00 on a tune up.