2 stroke texture finish question

[clay]

I’m building a KX125 / KDX200 hybrid after years of 4 strokes and have a textured finish question. Would there be any advantage from applying texture to the flywheel itself or even to the crankcase? Wondering if this would help slightly in preventing “loading up” during a slow, tight section. I’ve always assumed this is from fuel sticking to the crankcase walls and puddling in the crankcase during lower rpm operation. I can see the flywheel potentially helping this but probably not the crankcase itself. I do realize jetting will take care of the majority of this but wonder if anybody thinks this has potential. I’m not necessarily after more power - just a “cleaner” running engine. Engine is completely apart now for replate, bearings, piston, rod, etc. Thanks, Clay

[englertracing]

https://www.snowest.com/2009/03/cranksh ... -twostroke

Well, this guy thinks it helps 24%
I think 0.24%-2.4% might be more correct.

Have you considered texturing the transfer ports?

[clay]

24% improvement huh . I thought about transfer ports but figured doing the crankshaft and maybe the crankcase walls would have no effect on flow. That way it would be almost no chance of a negative outcome at least. Like I said before I’m not really thinking any extra power just hoping for a cleaner running engine in an extended tight woods section. Clay

[pamotorman]

24% improvement huh . I thought about transfer ports but figured doing the crankshaft and maybe the crankcase walls would have no effect on flow. That way it would be almost no chance of a negative outcome at least. Like I said before I’m not really thinking any extra power just hoping for a cleaner running engine in an extended tight woods section. Clay

i divided the intake trac in half from the carb slide to the center of the "V" reed and as long as you stayed under half throttle you increased the velocity in the intake trac and the 2 stroke ran like a 4 stoke in the tight stuff. my son who also is named clay and i used to run 4 hour hare scrambles. that crank deal as been around since the 80s. i even won in the over 45 class.

[groberts101]

I highly doubt you could hurt the mixture homigneity with such tricks.

These are awesome. No gimmicks.. no dyno required.. they just flat out work with slide style carbs.

https://thunderproducts.com/product/u-f ... optimizer/

[clay]

Thanks for the other ideas! I like the divided intake tract idea. I’ll definately give that a shot. I’ll see if they make the slide “insert” for lack of a better term for the Airstriker carb. 2 good ideas that will be easy to effectively test. Whatever I end up doing to the crank / crankcase there won’t be any A - B - A testing so who knows what the gains will be.
I rode a lot when I was younger and got back into it about 5 years ago. Be 48 this year. Tried 2 Enduros. Had a YZ450F on the first one. Big mistake. Brought my YZ250F to the second one. Ended up tearing my right ACL. 6 months later back on the bike - left ACL on my birthday. After that I slowed down and got in the gym. Basically lack of strength / endurance was a big part of my problem in both cases. That plus a lot of work on technique and balance have helped tremendously. I think it definately keeps you young! Clay

[pcnsd]

I highly doubt you could hurt the mixture homigneity with such tricks.

These are awesome. No gimmicks.. no dyno required.. they just flat out work with slide style carbs.

https://thunderproducts.com/product/u-f ... optimizer/

I will respectfully disagree. Although they may work in some applications, it was not the case for me. It was impossible to establish a idle mixture that was stable in the ambient temperature range I ride in. (55-105F). It required using a different idle jet with nearly every ride that ranged from soldered shut to a #25. The part itself required significant hand fitting to allow the slide to fully close. It worked best at colder temperatures and so it may work for those in the snowmobile community, but I would advise just updating to a appropriate flatslide if you are looking to increase carb airflow.

[groberts101]

I highly doubt you could hurt the mixture homigneity with such tricks.

These are awesome. No gimmicks.. no dyno required.. they just flat out work with slide style carbs.

https://thunderproducts.com/product/u-f ... optimizer/

I will respectfully disagree. Although they may work in some applications, it was not the case for me. It was impossible to establish a idle mixture that was stable in the ambient temperature range I ride in. (55-105F). It required using a different idle jet with nearly every ride that ranged from soldered shut to a #25. The part itself required significant hand fitting to allow the slide to fully close. It worked best at colder temperatures and so it may work for those in the snowmobile community, but I would advise just updating to a appropriate flatslide if you are looking to increase carb airflow.

Hmmm.. not sure why myself and others had such different experiences with them. As for the temp related variable.. I grass dragged my sled for several years with them installed in the dead heat of summer as well. But I will say that it was a liquid cooled engine too so maybe that is the difference in results. Although I still find it odd as several of my friends also used them in various dirt bikes which I helped port and tune. They seemed to help a great deal coming out of tight corners and were much more responsive to fueling changes.

[groberts101]

Duplicate post

[jsgarage]

Quote-
24% improvement huh . I thought about transfer ports but figured doing the crankshaft and maybe the crankcase walls would have no effect on flow. That way it would be almost no chance of a negative outcome at least. Like I said before I’m not really thinking any extra power just hoping for a cleaner running engine in an extended tight woods section.
Clay
________________________________________________________________________________________________

The Scott 'Flying Squirrel', a pre-WW2 hi-po (for the time) two cylinder 2 stroke water cooled motorcycle, used bolt-on transfer ports, which I always thought was a neat innovation that saved retooling the whole engine to add them. And Bultaco 250 Pursangs of the '60s had enough meat in the aluminum cylinder walls for a few tuners to hog out a third transfer port in the back while only shaving down the outside of the iron cylinder sleeve a bit. TT specialist Sonny Kenyon in N. CA used a perforated cylinder wall at the top of his Bul's 'transfer port' which he called a 'spray-port'. Worked well enough to beat early Yamaha 250s. I had one; very peaky but fun! 'Course, my opinion might be suspect; I commuted 30 miles a day for 10 years on a modified Kawasaki 500 triple, the very definition of 'peaky'!....

[pcnsd]

Quote-
24% improvement huh . I thought about transfer ports but figured doing the crankshaft and maybe the crankcase walls would have no effect on flow. That way it would be almost no chance of a negative outcome at least. Like I said before I’m not really thinking any extra power just hoping for a cleaner running engine in an extended tight woods section.
Clay
________________________________________________________________________________________________

The Scott 'Flying Squirrel', a pre-WW2 hi-po (for the time) two cylinder 2 stroke water cooled motorcycle, used bolt-on transfer ports, which I always thought was a neat innovation that saved retooling the whole engine to add them. And Bultaco 250 Pursangs of the '60s had enough meat in the aluminum cylinder walls for a few tuners to hog out a third transfer port in the back while only shaving down the outside of the iron cylinder sleeve a bit. TT specialist Sonny Kenyon in N. CA used a perforated cylinder wall at the top of his Bul's 'transfer port' which he called a 'spray-port'. Worked well enough to beat early Yamaha 250s. I had one; very peaky but fun! 'Course, my opinion might be suspect; I commuted 30 miles a day for 10 years on a modified Kawasaki 500 triple, the very definition of 'peaky'!....

My third near death experience was on a Kawasaki Mach 1. Thanks for reminding me.

[adam728]

The Parris Racing turbo crank made the rounds on another forum a few years back. HUGE claims. And not much to back it up. User that claimed to be the owner was part of the conversation, and was not at all knowledgeable nor confident inspiring.


KDX hybrid. I still want to build one someday. I've had 3 last-gen KDX's, and at one point about 11 years ago nabbed a 99 KX125 to build the bike, but never found time. I still miss that KDX, had Freddete port it, rework the head, and bore the carb, plus the usual stuff. Still buttery smooth power, and revved MUCH higher. Was a great power plant.

KX_KDX.jpg

Moved on to different stuff for now.

dwnszd.jpg

[pamotorman]

Quote-
24% improvement huh . I thought about transfer ports but figured doing the crankshaft and maybe the crankcase walls would have no effect on flow. That way it would be almost no chance of a negative outcome at least. Like I said before I’m not really thinking any extra power just hoping for a cleaner running engine in an extended tight woods section.
Clay
________________________________________________________________________________________________

The Scott 'Flying Squirrel', a pre-WW2 hi-po (for the time) two cylinder 2 stroke water cooled motorcycle, used bolt-on transfer ports, which I always thought was a neat innovation that saved retooling the whole engine to add them. And Bultaco 250 Pursangs of the '60s had enough meat in the aluminum cylinder walls for a few tuners to hog out a third transfer port in the back while only shaving down the outside of the iron cylinder sleeve a bit. TT specialist Sonny Kenyon in N. CA used a perforated cylinder wall at the top of his Bul's 'transfer port' which he called a 'spray-port'. Worked well enough to beat early Yamaha 250s. I had one; very peaky but fun! 'Course, my opinion might be suspect; I commuted 30 miles a day for 10 years on a modified Kawasaki 500 triple, the very definition of 'peaky'!....

My third near death experience was on a Kawasaki Mach 1. Thanks for reminding me.

i added piston fed boost ports to my ossa dirt bikes for more power but this did not help stopping when the brakes were wet.

[clay]

https://www.flickr.com/gp/140010520@N08/3F8F15

Current state of the project for anybody interested. Hope to get engine cases and swingarm modified tonight for mock up of engine. DMV inspector is coming tomorrow and hopefully I can get a title so I can get a tag. Just after a tag for the mile or 2 I ride highway to connect trails. Clay

If the picture doesn’t show up I’ll work on it.

[af2]

Clay, Nice project!!!!
The 3 best things I have done when racing Outlaw carts and building them for customers was.
#1 set squish at 50% of bore at 3* pointing to dome. stay at .010" per inch of bore for clearance.
#2 widen the exhaust port at the top WITHOUT raising it as far as you can (close to the transfer ports)and relieve the bridge a couple thousandths.
#3 get a hold of an expansion chamber that will keep the mid range where you want.

As far as texturing I see no need just like the turbo crank I see 0 improvement. Raising the crank case compression has always been the way to go. The Honda CR500 had the sheet metal attached to the crank for that reason.

When chiseling the head on the lathe to deal with the squish and re forming the chamber to decrease the CR sand it smooth for easy clean up on next re ring.

I have found with pump gas and 50:1 Castor 927 keep the Cranking compression at 175 lbs.