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Options For More CC's

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I went with the BBR 67mm piston for 233cc's and I had plans to add a 6mm stroker for the ultimate goal of about 250cc's.  I have a few questions in my quest to get more CC's. I have a ST2.0 and ST2.5 cam and also head porting. I will soon add the PWK 28mm carb that I feel is the missing piece from my current engine combo.  I was thinking that around 250cc's would be optimal with a ST2.5 cam, porting, and a 28mm PWK. 

 

Are there options to get a crank stroked to 6mm?  I asked my local machine guy to help that is a great machinist but has no experience with a 230. Someone posted about adding a offset crank pin, who does this?  This route would be the easiest and most cost effective option since I have an oversized piston already installed.  There must be other options for stroking a 230 crankshaft?

 

At this point it seems counter productive to add a sleeve and a 69mm piston, but if I did have to go this route to get to 250cc's where can I find a sleeve and 69mm piston?  My local machinist can add the sleeve and bore the case so that part is easy, just not sure where to find a sleeve, piston,mrings, head gasket.

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The stroker has to give it more, technically speaking, however, I think what your looking for will be found in the carb. My stroker gave me more power without the rpm's. But not much, It was faster, but the difference was lifting the front with less effort, less finding yourself needing to gear down , holding pressure with the throttle. However, my stock bike with the stock carb with a UFO under the slide, came up equal in power to my highly built 230. This tells me that the stock carb is the weak link. It's all about the fuel perfume spraying rather that dribbling. You will have to get used to the different "roll" on of power because of the required throttle change.

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10 minutes ago, 1gr8bldr said:

The stroker has to give it more, technically speaking, however, I think what your looking for will be found in the carb. My stroker gave me more power without the rpm's. But not much, It was faster, but the difference was lifting the front with less effort, less finding yourself needing to gear down , holding pressure with the throttle. However, my stock bike with the stock carb with a UFO under the slide, came up equal in power to my highly built 230. This tells me that the stock carb is the weak link. It's all about the fuel perfume spraying rather that dribbling. You will have to get used to the different "roll" on of power because of the required throttle change.

Very interesting.  Night-and-Day difference between my stock engine and my engine with Web 40mc/402 cam and Wiseco piston.  I still find it incredibly interesting that there are some ho-hum results with builds far beyond mine.  I am very happy and very surprised by the results.  I guess it all depends upon expectations and riding context.  Since I mostly ride slow short tight areas and I only weigh 150 pounds my engine is great.

100% agreed on stock carb holding the engine back given all of BTR's feedback in here.

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25 minutes ago, VortecCPI said:

Very interesting.  Night-and-Day difference between my stock engine and my engine with Web 40mc/402 cam and Wiseco piston.  I still find it incredibly interesting that there are some ho-hum results with builds far beyond mine.  I am very happy and very surprised by the results.  I guess it all depends upon expectations and riding context.  Since I mostly ride slow short tight areas and I only weigh 150 pounds my engine is great.

100% agreed on stock carb holding the engine back given all of BTR's feedback in here.

I wish I had some way to measure performance other than just by the seat feel. Like when I was playing with the cam advance and retard. I know that one spot should clearly be the best performing, yet I could not feel the difference. But I know it was there. I just never found it. If there was another way, other than dyno, Each mod, could be maximized. As it is, I feel like a blind man. However, I could feel the stroker, and I could feel the UFO in the carb. 

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The CRF230's are almost a square bore and stroke. They have tons of torque. I decided to do a bore only from Engines only they have a nice 11.5 to 1 kit that gives you almost 250cc's.  http://xr100.com/crf230.htm

That combined with a open air box good pipe and a PWK carb should give some great performance. I even run the Web 89a cam with excellent results from off idle torque to peak rpm. 

I really wouldn't change a thing as I would loose something to gain something. The only drag is you have to split the cases and have them bored to fit the sleeve. 

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30 minutes ago, stevethe said:

The CRF230's are almost a square bore and stroke. They have tons of torque. I decided to do a bore only from Engines only they have a nice 11.5 to 1 kit that gives you almost 250cc's.  http://xr100.com/crf230.htm

That combined with a open air box good pipe and a PWK carb should give some great performance. I even run the Web 89a cam with excellent results from off idle torque to peak rpm. 

I really wouldn't change a thing as I would loose something to gain something. The only drag is you have to split the cases and have them bored to fit the sleeve. 

My guess is a 247cc 11.5:1 engine with Web 89a cam and PWK carb and exhaust is a very good engine.  Before going the "easy" route I spoke with Frank quite a bit about going 247cc 11.5:1 with his #2 cam.  I really just wanted to see what ~$300 would get me first.  It got me a lot.

Do you have any head work done Steve?

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12 minutes ago, VortecCPI said:

My guess is a 247cc 11.5:1 engine with Web 89a cam and PWK carb and exhaust is a very good engine.  Before going the "easy" route I spoke with Frank quite a bit about going 247cc 11.5:1 with his #2 cam.  I really just wanted to see what ~$300 would get me first.  It got me a lot.

Do you have any head work done Steve?

Sorry yeah porting is a must otherwise it is a obstruction in your performance. 

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1 minute ago, stevethe said:

Sorry yeah porting is a must otherwise it is a obstruction in your performance. 

I figured you did.  I'll bet that engine works great from idle to redline.  Any issues with heat or detonation?  Ever try a carb other than the PWK?

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10 minutes ago, VortecCPI said:

I figured you did.  I'll bet that engine works great from idle to redline.  Any issues with heat or detonation?  Ever try a carb other than the PWK?

No pinging on premium pump fuel. No I never tried a different carb on this bike. But baja Larry had a BBR framed CRF230 with a XR250 carb that I tried. The PWK carb is superior at perfuming fuel into the motor. 

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I have rode Steves BBR 250cc bore only. His bike big time haul ass with power everywhere,including tractor stump pulling power. Now I know the next Question How Does It Compare To Your Stroker. Cant tell exactly because I rode it before I got a stock framed 230. His bike uses super low gearing  (OK what is it Steve). Mine runs 14 or15 / 45. Mine pulls street bike gear like a 13/50.Also very Hi speed  6th gear with grunt in first gear to spare. Here is Good news and maybe bad news. We are waiting this week to hear if Terry will ever again make stroker cranks. If not Mike will make his maybe offer others.

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3 minutes ago, stevethe said:

No pinging on premium pump fuel. No I never tried a different carb on this bike. But baja Larry had a BBR framed CRF230 with a XR250 carb that I tried. The PWK carb is superior at perfuming fuel into the motor. 

While you have to kind of respect the history and simplicity of the Keihin PD series of carbs they are archaic in design like the old Holleys.  I have no first-hand experience with Keihin PWK (yet) but all I have read tells me they are far superior.  Larry in particular has made that pretty clear with his testing on both stock and modified engines.

As always, thanks for sharing Steve.

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All Thank yous on PWK go to Steve as he give me info on carb. I wont forget that he left out one detail that made me pull carb 40 times. We where in my garage other day.With the other stock carb 230s. Starting idling hitting the throttle the sound tone type hit.The Pwk carb bike sounds like my 450 guys said. Touch the throttle WABA rap. Hit the throttle stock carb WOOF WOOF  LAZY  JAAAAA!

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12 minutes ago, bajatrailrider said:

All Thank yous on PWK go to Steve as he give me info on carb. I wont forget that he left out one detail that made me pull carb 40 times. We where in my garage other day.With the other stock carb 230s. Starting idling hitting the throttle the sound tone type hit.The Pwk carb bike sounds like my 450 guys said. Touch the throttle WABA rap. Hit the throttle stock carb WOOF WOOF  LAZY  JAAAAA!

Are we allowed to know about that detail or is it one of Steve's little super-secret things he does not share to keep his edge?

If only we could get an air screw on the right-hand side...

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15 minutes ago, bajatrailrider said:

All Thank yous on PWK go to Steve as he give me info on carb. I wont forget that he left out one detail that made me pull carb 40 times. We where in my garage other day.With the other stock carb 230s. Starting idling hitting the throttle the sound tone type hit.The Pwk carb bike sounds like my 450 guys said. Touch the throttle WABA rap. Hit the throttle stock carb WOOF WOOF  LAZY  JAAAAA!

 

1 minute ago, VortecCPI said:

Are we allowed to know about that detail or is it one of Steve's little super-secret things he does not share to keep his edge?

If only we could get an air screw on the right-hand side...

He didn't buy the right Sudco needle jet and there was his problem. 

You should be able to set the air screw and forget about it. 

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JAAAAAAA    TRUE needle jet has to be changed only use sudco needle jet. That is the one detail he left out. His super secret details to give him the edge over you. He will not share with his own brother the last 40 years.

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8 minutes ago, bajatrailrider said:

JAAAAAAA    TRUE needle jet has to be changed only use sudco needle jet. That is the one detail he left out. His super secret details to give him the edge over you. He will not share with his own brother the last 40 years.

I have a brother and I get it!

If Terry is going to be "away" for a while I wonder if i can get Bruce Triplett to make adapters for us.  He is basically a Millwright and has a pretty solid machine shop.  I assume the adapters are just an interference fit?  I have an XRs Only XR250 32mm TM kit I can use for dimensional data.

The only thing really holding me back at this point are the adapters.  Thanks to you and Steve we have all the really hard work done for us.

What are you guys doing with the intake manifold?  Are you just opening up the ID to match the PWK?  Any weird steps or flow restrictions in the manifold when using a PWK?  Anything in there to ruin good laminar airflow?

Edited by VortecCPI

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22 minutes ago, VortecCPI said:

I have a brother and I get it!

If Terry is going to be "away" for a while I wonder if i can get Bruce Triplett to make adapters for us.  He is basically a Millwright and has a pretty solid machine shop.  I assume the adapters are just an interference fit?  I have an XRs Only XR250 32mm TM kit I can use for dimensional data.

The only thing really holding me back at this point are the adapters.  Thanks to you and Steve we have all the really hard work done for us.

What are you guys doing with the intake manifold?  Are you just opening up the ID to match the PWK?  Any weird steps or flow restrictions in the manifold when using a PWK?  Anything in there to ruin good laminar airflow?

There is nothing to do on mild build 230 match carb intake. As intake manifold bigger then carb outlet.

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I went with the BBR 67mm piston for 233cc's and I had plans to add a 6mm stroker for the ultimate goal of about 250cc's.  I have a few questions in my quest to get more CC's. I have a ST2.0 and ST2.5 cam and also head porting. I will soon add the PWK 28mm carb that I feel is the missing piece from my current engine combo.  I was thinking that around 250cc's would be optimal with a ST2.5 cam, porting, and a 28mm PWK. 
 
Are there options to get a crank stroked to 6mm?  I asked my local machine guy to help that is a great machinist but has no experience with a 230. Someone posted about adding a offset crank pin, who does this?  This route would be the easiest and most cost effective option since I have an oversized piston already installed.  There must be other options for stroking a 230 crankshaft?
 
At this point it seems counter productive to add a sleeve and a 69mm piston, but if I did have to go this route to get to 250cc's where can I find a sleeve and 69mm piston?  My local machinist can add the sleeve and bore the case so that part is easy, just not sure where to find a sleeve, piston,mrings, head gasket.



EO xr100.com and/or Terry Miller

Offset pins are used and Readily available outside the USA but your connecting rod will be too long by the same amount your increasing the stroke.
EO has cranks stroked by Terry in the past, not sure if they still do?

Call Frank and ask him what he recommends...

Stock rod not good on strokers because the more the pin is moved out, the more oil pressure and oil volume is lost.

Wossner rod is best choice to avoid this problem.

But:

No matter what rod is used, they have to be knotched in two places to clear interference with 3rd gear main shaft.

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The CRF230's are almost a square bore and stroke. They have tons of torque. I decided to do a bore only from Engines only they have a nice 11.5 to 1 kit that gives you almost 250cc's.  http://xr100.com/crf230.htm
That combined with a open air box good pipe and a PWK carb should give some great performance. I even run the Web 89a cam with excellent results from off idle torque to peak rpm. 
I really wouldn't change a thing as I would loose something to gain something. The only drag is you have to split the cases and have them bored to fit the sleeve. 


Sorry, have to disagree, don't knock it till you at least try it.
THERE IS SO MUCH MORE THAT YOUR MISSING OUT ON.
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