ESE's works engine tuner

[Michael Moore]

http://hotrodsproducts.com/ProductSearch.aspx

You can put in a conrod length (and +/- amount) and it will serve up all that are found, but then you have to look at each one to determine the BE/SE diameters, pin sizes, etc.

cheers,
Michael

[katinas]

https://www.royalrods.com.tw/yamaha-...d/RY-2107.html 116x21x32
They are very informative
And Yamaha RD 400 115mm but big and small ends maybe not as big as you need

Very interesting to follow how manufactures testing with conrod lenght on MX 125 through years
Honda CR 125 100 104 mm
Yamaha YZ 125 105 102 mm
Kawasaki KX 125 106 109 104 mm
Suzuki RM 125 105 102 110 mm
KTM SX 125 110 mm

Assumed with road racing reed engines rod dimensions, looks like for reed valve 125, for good balance, 110 mm rod is maximum.

Remember street Jawa 350, 2 cylinder engine with relatively very long rods - 145 mm, with 65 mm stroke and 58 mm bore.

[TZ350]

RD 400 115mm but big and small ends maybe not as big as you need

An RD400 rod is what I use. I have been spinning mine to 14,000 rpm. 48mm stroke, original 115mm Yamaha Mitaka 2T2 rod with an RGV250 flat caged B/E brg.

[Michael Moore]

The 2T MX bikes are pretty standardized at 125mm OC, but if you go back to the 99 KTM 250SX with 67.5x69.5 instead of the modern 66.5x72 numbers you can get a 132mm rod.

I find it interesting that if roughly square B&S seems to be ideal (at least that is what I've gathered from comments) then KTM and Yamaha should have stayed with those dimensions as used in their prior to 2000 MX 250s. But the undersquare dimensions seem to have been standard for 20 years now. I presume there's a reason why, perhaps they are a bit more responsive for dirt use compared to RR hp from square dimensions?

cheers,
Michael

[katinas]

https://www.tkart.it/en/magazine/und...hifter-iame/#2
Some photos with cylinder head.
https://www.tkart.it/en/magazine/und...-of-changes/#2

I took this pictures today at a tool store, nothing special, four transfers piston ported ECHO chainsaw 50 cc max 12500 rpm 3.5 hp
engine, but one interesting thing. B windows arranged upward, like as usual C.


http://www.arcticinsider.com/Article...C2-8000-Engine A transfer windows shape, add photo.

[mantonakakis]

Thanks Husa, I'd just started looking for 'Farmaken'. I'll keep it in mind.

This might be my first post on this site, but I have been reading this thread for a few years now, and I am almost caught up!
Thanks again to Husa, as I am hoping to build or procure an ATAC valve soon too for a current project. Some moped guys have used this valve with some success, I think:
https://www.matco-norca.com/product..../product_id/61
It seems like it could be shortened, and it should be possible to braze it to the header.
And thank you to everyone else (Frits, Wobbly, TZ, everyone!) for all of the knowledge (often learned the hard way) shared here.

[Lightbulb]

Turbo charges or super charges have been banned already in most of the model engine classes these days. They also introduce limits for plenum volumes under the venturi point to the valve as well.
Some great drawings that were shown. It is great to see what people have done quite a few years ago.
Neil

[husaberg]

The 2T MX bikes are pretty standardized at 125mm OC, but if you go back to the 99 KTM 250SX with 67.5x69.5 instead of the modern 66.5x72 numbers you can get a 132mm rod.

I find it interesting that if roughly square B&S seems to be ideal (at least that is what I've gathered from comments) then KTM and Yamaha should have stayed with those dimensions as used in their prior to 2000 MX 250s. But the undersquare dimensions seem to have been standard for 20 years now. I presume there's a reason why, perhaps they are a bit more responsive for dirt use compared to RR hp from square dimensions?

cheers,
Michael

My musing is the square is the best comromise for a high revving and highest possible output two stroke
Undersqaure is the best compromise best for a mildly tuned MX 250.
The rod length is also likely a design compromise to keep the height down and or give a bettr ring life as the ring pack can be lower for a given height.

https://www.royalrods.com.tw/yamaha-...d/RY-2107.html 116x21x32
They are very informative
And Yamaha RD 400 115mm but big and small ends maybe not as big as you need

Very interesting to follow how manufactures testing with conrod lenght on MX 125 through years
Honda CR 125 100 104 m[m
Yamaha YZ 125 105 102 mm
Kawasaki KX 125 106 109 104 mm
Suzuki RM 125 105 102 110 mm
KTM SX 125 110 mm

Assumed with road racing reed engines rod dimensions, looks like for reed valve 125, for good balance, 110 mm rod is maximum.

Remember street Jawa 350, 2 cylinder engine with relatively very long rods - 145 mm, with 65 mm stroke and 58 mm bore.

KTM200 has a nice long rod in 22mm crankpin
118mm


03.6248 ProX Con.Rod Kit KTM200SX-EXC ’98-16 20.00 28.00 118.00 15.90 15.90 151.40 94.00 22.00 55.00 22 x 37 x 1.0

[lohring]

Turbo charges or super charges have been banned already in most of the model engine classes these days. They also introduce limits for plenum volumes under the venturi point to the valve as well.
Some great drawings that were shown. It is great to see what people have done quite a few years ago.
Neil

That's not completely true. Our GX twin boat racing class allows a two cylinder engine with a total of 64 cc. Unlike the G classes where only tuned pipes are allowed, there is no mention of super or turbo charging. A little turbo like the Garrett GT0632SZ Would be fun to experiment with.

Lohring Miller

[41juergen]

My musing is the square is the best comromise for a high revving and highest possible output two stroke
Undersqaure is the best compromise best for a mildly tuned MX 250.
The rod length is also likely a design compromise to keep the height down and or give a bettr ring life as the ring pack can be lower for a given height.


KTM200 has a nice long rod in 22mm crankpin
118mm


03.6248 ProX Con.Rod Kit KTM200SX-EXC ’98-16 20.00 28.00 118.00 15.90 15.90 151.40 94.00 22.00 55.00 22 x 37 x 1.0

Thank's for the help, unfortunately none would fit easy. So if the big end diameter is too small can I bore that up or is that hardened?

[Lightbulb]

Lohring, one thing that does work, is to have a fan like feature on the PTO drive , like on the outbord model engines. There is a 400 rpm gain over one that does not drive a PTO or a std PTO with the single or 2 slots.
Neil

[ceci]

Seeing it reminded me of Roland Holzmer's project, but he doesn't use the crank case to pump.
My question is: does a supercharged two stroke engine need the crank case?
Look for the answer here:

http://oa.upm.es/136/1/01199904.pdf

I'm not sure since everyone supports the M6 minarelli project with turbo that uses the crank case and not Roland Holzmer'

[ceci]

Seeing it reminded me of Roland Holzmer's project, but he doesn't use the crank case to pump.
My question is: does a supercharged two stroke engine need the crank case?
Look for the answer here:

http://oa.upm.es/136/1/01199904.pdf

I'm not sure since everyone supports the M6 minarelli project with turbo that uses the crank case and not Roland Holzmer'

Another question, the crankcase will not be a brake engine

[husaberg]

Thank's a lot for the feedback Wob. Have done a set of RGV250 barrels and they go into the engine soon.

Just one other question: I'm looking for a 115mm conrod with the following dimensions:
small end: diameter 21 mm, width min 16 mm
big end: diameter 31mm, width min 16mm
At least prox don't have an appropirate one, even with a wider width of the small or big end...

Thank's for the help, unfortunately none would fit easy. So if the big end diameter is too small can I bore that up or is that hardened?

Sorry i missed the original question. I just seen RGV so was thinking 22mm pin.
why are you looging for a conrod with those outside dimensions?
exctlu what crankpin dia and small end are you loking for. or is it 31mm crankpin??

i know MZ125 have crazy long lengths with 31 big ends
Big-end Width (mm): 16.9

Small-end Width (mm): 16.9

Big-end Bore (mm): 31

Small-end Bore (mm): 19

Center-to-center (mm): 125

Pin Diameter (mm): 25

Pin Length (mm): 49

Big-end Bearing (mm): 25*31*17

Small-end Bearing (mm): 15*19*20

Washer Thickness (mm): N/A

---

Or the NSR150
NSR150 110lc-c 21se 16.85 31mm KW6.

[TZ350]

My question is: does a supercharged two stroke engine need the crank case?

No. Commer Diesel come to mind.