35HP CRF230F...Simple ...By MOMUS?

[mixxer]

My newfound butt nugget cling-on , Momus ,has told me that he actually doesn't know how to start a thread of his own...

So , being the nice guy that I am, I decided to help him out and start his very first thread just for him... Like a Big Boy?...

And the good news is that, thank God, he is here to finally show everyone in this forum how to actually build some power from these bikes!!

35Hp for everyone!! (countershaft ? or rear wheel??)

Without further ado, I start Momus's first thread with a quote from him... And he will take it over from there with detailed information and excellent photography... Grab some popcorn and put on your thinking caps everyone!! Here he is ?????????(the crowd goes crazy, even men are crying and throwing their panties!!)

 

 

"In the CRF230 I have a top end going on early SL100 cases for a MX bike that will run in a Pre1975 class. Judging by what can be done with the XR100's with fair reliabilty using top shelf bits - billet pistons with very thin rings, roller cam, bore coatings, proper valves, lightweight con rod etc 35 hp peak with a wide curve should be achievable despite the small ish valves these are limited to."

[adnohguy]

[Doogee57]

   Oooo, Oooo, Oooo, who's gonna bring the ginormous half gallon cup of Coke?

[mixxer]

Where is old Momus boy at now??

I introduced him... Gave him the stage....and handed him the microphone....

And now he's hiding ,what's up with that??? 

Seems kinda like he only wants to ride on my back in my threads to get the attention he so desperately craves...??

 

[mixxer]

Hold the phone!!

Breaking news from Momus R&D...

Perhaps the 35Hp is just a mild version of what our 230's are capable of achieving... I think Momus is developing a 50Hp version based on this intel I was able to intercept... Straight from the Momus Mouth:

 

"Getting top end is the issue, not a strong mid, is the way I see it.   Well developed MX 250 4 valve race engines are using 2 intake valves about the same size or larger than, the biggest single valve commonly fitted in the SL/XR/CRF's,  to get their tractable, reliable 50 hp."

[mixxer]

I'm not exactly sure where Momus R&D is located....

But I do see definite similarities in engineering style and power reporting to a couple other TT members...

Oldie230- already over 30Hp with the Chinese roller cam shop....

GreenHuman- the equivalent of The Island of Dr Moreau as far as engines go (don't buy a cam from this dude, he doesn't know the real specs of his own cams)

I wonder if these guys all are related in some way??

[SteveThe Snakes]

Earth to world I think we have a problem with getting 35 RWHP out of a CRF230. We will also have a problem getting 50 RWHP out of a 250cc motocross bike. ?

I sure wish a few of the boys would pony up on getting their bikes on a dyno. Might be surprised when they end up with 20 RWHP.  
 

https://www.cycleworld.com/2018-250f-motocross-bikes-on-dyno/

 

[Oregon lightweight moto]

18 minutes ago, SteveThe Snakes said:

Earth to world I think we have a problem with getting 35 RWHP out of a CRF230. We will also have a problem getting 50 RWHP out of a 250cc motocross bike. ?

I sure wish a few of the boys would pony up on getting their bikes on a dyno. Might be surprised when they end up with 20 RWHP.  
 

https://www.cycleworld.com/2018-250f-motocross-bikes-on-dyno/

 

You must not believe in magic. 

[SteveThe Snakes]

1 hour ago, Bigfatredpig said:

You must not believe in magic. 

Oops did I pinch the fairy dust on that one. ?

[Oregon lightweight moto]

So this gentleman momus is trolling and doesn’t know what he speaks of correct? 

I found that website where you can make any fake dyno graph you want. 

you should have seen my Xr650l dyno graph, 102 pounds of torque and 189 rh horsepower on a single cylinder. She revs to 22 thousand rpm with a points ignition system off a 1955 cbr. 

I did read an excellent article on points ignition and why the manufactures switched to a Cdi ignition system because of his nutty claims. 
 

Edited January 18, 2021 by Bigfatredpig

[adnohguy]

1 hour ago, Bigfatredpig said:

So this gentleman momus is trolling and doesn’t know what he speaks of correct? 

I found that website where you can make any fake dyno graph you want. 

you should have seen my Xr650l dyno graph, 102 pounds of torque and 189 rh horsepower on a single cylinder. 

I did read an excellent article on points ignition and why the manufactures switched to a Cdi ignition system because of his nutty claims. 
 

Yes but you also mention that it all happens at 16-19k rpm with points ignition. ??

[Oregon lightweight moto]

2 minutes ago, adnohguy said:

Yes but you also mention that it all happens at 16-19k rpm with points ignition. ??

You are correct I fixed it 

[Momus]

Historically, what later proves to be a completely wrong theory ("The Sun orbits the Earth."), neatly explains observable phenomenon and accurately predicts outcomes, e.g. eclipses.
More recently, the best brains of the twentieth century tirelessly sought more data to determine if the expanding universe had enough momentum to overcome gravity and expand forever, or if the expansion would slow, halt and reverse, eventually producing a Big Implosion.
What was discovered instead is that many observable astronomical phenomenon ("Not only is the universe expanding, it is accelerating!") are explainable only by the presence of an overwhelming percentage in the universe of Dark Matter, undetectable by direct observation and hence also only theoretical at present.

What does this have to do with 35 or 40 countershaft horsepower CR230F's?

&%$#@! if I know.

My project is based on an SL90/100/125 single, destined for a vintage class,  that may or may not use some CRF230 parts.

Polite enquiries- ie non derisive, may persuade me to share my early planning for the design of the modifications.

This is another high involvement, time and funds costly, lengthy, non commercial project for me.

Edited January 18, 2021 by Momus

[mg600]

I like a good joke and taking the piss out of others and even myself. But this topic/ thread is pretty low and not what I come to the crf230 forum for. And I doubt many others do either. 
Lots of great info and learning to be had here, and some winding up of other members aswell?, but not this. Move on people

[Armbarn sailor]

250mx bikes are hitting 50 horse on factory engines. I’ve been told there isn’t a bike in the top ten under 50hp. The 230 is a turd, just like all of the “f” series bikes previously called “xr”. They are seriously limited in ability to run stronger but nobody with common sense would buy them so they can spend serious money trying to hit 30hp on a very weak chassis. This thread is stupid for a lot of reasons. One guy is put on blast for hyping a build on an antique design, the others think they actually know how to do it. Am I right? Seems for the price of a new crf230 anyone could buy an older 125 or 250 yz and just smoke the hell out of all of you? Stock.

[jjmaine]

[mixxer]

4 hours ago, hondaman331 said:

250mx bikes are hitting 50 horse on factory engines. I’ve been told there isn’t a bike in the top ten under 50hp. The 230 is a turd, just like all of the “f” series bikes previously called “xr”. They are seriously limited in ability to run stronger but nobody with common sense would buy them so they can spend serious money trying to hit 30hp on a very weak chassis. This thread is stupid for a lot of reasons. One guy is put on blast for hyping a build on an antique design, the others think they actually know how to do it. Am I right? Seems for the price of a new crf230 anyone could buy an older 125 or 250 yz and just smoke the hell out of all of you? Stock.

Wow! Thank the heavens you showed up to misinterpret everything... 

The only thing people are doing with 230's in this forum is trail riding / street and trail riding/ or at the most doing some vet hare scrambles...

Nobody is thinking they are going motocross racing on one , but thanks for all the "insider" info....

Next up, they actually aren't seriously limited in potential of running stronger, but again, nobody is building one to start campaigning in any MX format.... Most people here have plenty of other bikes and this one is just a fun play bike that they enjoy modding up a bit for the pure fun of it....

The one douchebag put on blast is for claiming his xr100 based engines are pushing 30hp and his shift point before the curve rolls over peak is 16,000 RPM (points ignition, of course) on his upper 20hp motocross xr100 based engines....

So that brought up him saying that the CRF230 head should support 50hp range based on his "calculations" and the fact that all the 250mx bikes are stone reliable and running 50+ hp....

So now that you personally have the inside dope that the factory 250's (completely rebuilt after every event, btw) are all over 50hp....

I'm just waiting for someone who thinks they are even more connected to the inner sanctum of holy hp gods to pop up and say that the 250'sare all over 60Hp and the pros ride them on the street from event to event and they never rebuild these simple and utterly reliable builds until end of season... 

[Armbarn sailor]

3 minutes ago, mixxer said:

Wow! Thank the heavens you showed up to misinterpret everything... 

The only thing people are doing with 230's in this forum is trail riding / street and trail riding/ or at the most doing some vet hare scrambles...

Nobody is thinking they are going motocross racing on one , but thanks for all the "insider" info....

Next up, they actually aren't seriously limited in potential of running stronger, but again, nobody is building one to start campaigning in any MX format.... Most people here have plenty of other bikes and this one is just a fun play bike that they enjoy modding up a bit for the pure fun of it....

The one douchebag put on blast is for claiming his xr100 based engines are pushing 30hp and his shift point before the curve rolls over peak is 16,000 RPM (points ignition, of course) on his upper 20hp motocross xr100 based engines....

So that brought up him saying that the CRF230 head should support 50hp range based on his "calculations" and the fact that all the 250mx bikes are stone reliable and running 50+ hp....

So now that you personally have the inside dope that the factory 250's (completely rebuilt after every event, btw) are all over 50hp....

I'm just waiting for someone who thinks they are even more connected to the inner sanctum of holy hp gods to pop up and say that the 250'sare all over 60Hp and the pros ride them on the street from event to event and they never rebuild these simple and utterly reliable builds until end of season... 

No, race bikes get rebuilt often. I race my bike and trail ride as well. Maybe I should settle down a bit, my first bike was an xr75, 1975 or 76, still have it and quite honestly was the most fun bike ever and still may be.... but it’s not fast and I wouldn’t buy another one for any sort of engine potential. It’s a limited trail bike. And it’s way to small, as are the 230fs. I look at it like this, the xr line is for trails at a campground or something where a healthy dose of having fun is found. I used to take mine up to the lake and blast some trails. If you are any more serious then that on them they are pretty dumb. I guess I’m having a hard time understanding why said guy on blast is wasting his time with a small 2 valve over flywheeled 4 stroke and then apparently pissing people off with unrealistic expectations? Or why it would make anyone mad? Sort of like the town fool, I would think, and people may give him a Pat on the back or something for not overdosing on crayon consumption. The head of a 4 stroke makes the most of the bore and stroke, I’d imagine there is an aftermarket head out there that may give a bit more juice to the 230, but why? Ride it stock and change the oil every 5 years wether it needs it or not. If there was a zombie apocalypse I would own 3, but until then I just figure you drink Busch light and cruise a 230 around the campground, and honestly it sounds really fun.

[mixxer]

They are just plain fun and reliable bikes ... And fun to hop up a bit an have fun on....

There is a decided lack of decent forums and information exchange on the XR/CRF 100's for the american audience, while they are popular engines used in lots of bike formats in japan...

I have built 3 different 100's... 2 for my kids and now one for me for the farm and camp and trail use...

I took it upon myself, after getting some half baked info on buying an aftermarket head, to detail a thread on the build for everyone's benefit...

I had to work on the ports ....and work quite a bit to get compression up with that large valve / large combustion chamber... ended up at 130cc and 11.3:1 compression with a 26mm accelerator pump carb... It runs fantastic... decidedly better than the last 2 (120cc/130cc) I built for kids....

I said I would be happy to put it up against other 100 builds of any sort , even though this was a budget minded fun project it still hauls the mail!

Then captain douchebag had to come in and blow up the thread with his fleet of upper 25+hp and 16k shift point xr100's .... And on and on it goes... Dude wont host his own thread, just piggyback and blow up threads I have started....

[Momus]

37 minutes ago, mixxer said:

They are just plain fun and reliable bikes ... And fun to hop up a bit an have fun on....

There is a decided lack of decent forums and information exchange on the XR/CRF 100's for the american audience, while they are popular engines used in lots of bike formats in japan...

I have built 3 different 100's... 2 for my kids and now one for me for the farm and camp and trail use...

I took it upon myself, after getting some half baked info on buying an aftermarket head, to detail a thread on the build for everyone's benefit...

I had to work on the ports ....and work quite a bit to get compression up with that large valve / large combustion chamber... ended up at 130cc and 11.3:1 compression with a 26mm accelerator pump carb... It runs fantastic... decidedly better than the last 2 (120cc/130cc) I built for kids....

I said I would be happy to put it up against other 100 builds of any sort , even though this was a budget minded fun project it still hauls the mail!

Then captain douchebag had to come in and blow up the thread with his fleet of upper 25+hp and 16k shift point xr100's .... And on and on it goes... Dude wont host his own thread, just piggyback and blow up threads I have started....

Settle mixxer you don't have to qualify and justify yourself... so defensive.

Dude is right though about the general  impression of 230's being a wife's bikes with an engine basically disregarded by the aftermarket.

They're serviced with some notably inferior cams and valve gear by a couple of US vendors and some carry over pistons- but that's it.

Quote

Hondaman 331 said:

I guess I’m having a hard time understanding why said guy on blast is wasting his time with a small 2 valve over flywheeled 4 stroke and then apparently pissing people off with unrealistic expectations?

There are still highly competitive, vintage championship series, however minor, that XR75's  with XR100 engines can be raced in all over the place and a following reasonable justification for serious engine development. Some of the Japanese engineers responsible for this stuff are/were ex Honda A grade professionals. You don't get an engine, the CB50 vertical with 4 hp that became the XR75 4 speed, then evolved into the XR100 to up well over 20 hp and 15000 rpm with 125 cc (green line), as a reliable, bolt in kit unless you know what your doing.  With further work, and higher rpm there is more power and more displacement. 

Takegawa, whose graph is provided has been making race parts for the Japanese market for well over 50 years- my first contact with them was a 5 speed cr box for a Honda SL70- in the 1970's.

The bike in the photo is an XR75 and is as fast or faster in a straight line as a modern 6 speed 85 and some 100's. 

Not to mention the grandaddy of these small Honda's the ubiquitous horizontal cylinder under-bone step thru engine. The amount of tuning gear for them swamps what is available for the XR50/75/80/100 family and with their better cylinder heads good power. Standard length stroke, big bore horizontals set up right run to 17000 rpm.

Point of building an engine for a full size National Championship vintage MX class- Pre 1975 is to run a 4 stroke SL100 based machine (the grand daddy of the 230) with a developed 230 style engine against 2 strokes.

Edited January 18, 2021 by Momus