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New 254 installed... initial impressions

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I got the motor back from Terry last week and got it (mostly) broke in over the weekend.  I still need to get the jetting sorted out as it's a bit lean right now and it has a mid-RPM stumble but it's not too bad.  Judging by the plug, I'm guessing it's a half size off so it's close but still needs some work.  Even with that however, it runs VERY strong.  Even keeping the throttle to 80% or so results in wheel spin all the way up the band in 4th.  It may do it in 5th as well but I'm waiting until I have some more time on it and get the jetting sorted out before really getting on it.  This bike is really a completely different animal at this point and requires much more right hand finesse in the marbles.  Of additional note is that I'm currently running a 50/50 mix of premium pump and 110 octane LL.  The intent is to run 100% premium though.  I'm running a mix just for the first 2-3 tanks.

Since this motor was being built to fulfill an "Adventure-lite" role, the plan was to build up the mid to top end of the band while keeping all of the tractor-like power at the bottom end.  I finished the main break-in yesterday but that was on the street so it was a little difficult to compare the new motor to the stock one.  But when I took it out today for an easy 20 minute ride through some desert two-track, I could really feel the difference.  At first I thought Terry must have messed up the cam specs because there was an OBVIOUS increase at the bottom end.  But once the bike gets up to about 3k-4k RPM, it feels like someone flips a switch and it just starts pulling like mad.  There may be some early ride excitement in there but it feels really good.  I need to find a local with a stock bike and ride them back to back.  Falcon 1 has been pestering me to come down and ride with him so that will give me the opportunity to compare his 254 build to mine.

The next step is to get the jetting sorted out and then deal with gearing.  Current gearing is stock (13/50).  I suspect that I can pull a 15/44 on this without any trouble and swap to a 14/44 for the dirt.  I'm still playing with that though so we'll see what happens.  I'll likely get the soft luggage put on there first (and maybe a small windscreen) and see how it handles the additional wind resistance before doing anything.

Specs:
- 254cc
- Wossner piston/gasket/bore; CR at 10.6-10.75
- Custom cam (ball-barked as a ST 3.0-3.5 or so compared to the other common grinds out there)
- Fully ported head
- Hardened rockers, oversized valves and aftermarket springs
- HD clutch
- Stock carb (yeah, yeah, I know.  I may upgrade to the PWK later down the road)
- Modified FMF Powerbomb with modded OEM muffler
- OEM CDI box
 

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Sounds like an awesome setup...

Any more mods would just be external and not need to go back into the engine for anything....

Stock carb can be opened up a significant amount to make the bore match the slide at wide open..  have die grinder, will travel.. lol...

I really wish you could try a full performance exhaust system... The OEM mufflers, no matter how modified, are not meant to enhance vacuum signal to the exhaust port.. they are meant to dampen all wave activity...Good and bad.. and what they limit only gets worse as your engine gets bigger and more performance oriented...

I haven't looked into details of a 254... I didn't want to bother with an overbore to get near sleeve limit and only gain 10cc...

If no stroker is involved, I'm guessing you need a bigger sleeve... Do the cases need to be bored to accept the sleeve??

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I love your build as you know stock carb makes it tame.Big hold back. My 254 with stock carb test then to PKW test. Stock carb to never be used again.

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5 hours ago, mixxer said:

Sounds like an awesome setup...

Any more mods would just be external and not need to go back into the engine for anything....

Stock carb can be opened up a significant amount to make the bore match the slide at wide open..  have die grinder, will travel.. lol...

I really wish you could try a full performance exhaust system... The OEM mufflers, no matter how modified, are not meant to enhance vacuum signal to the exhaust port.. they are meant to dampen all wave activity...Good and bad.. and what they limit only gets worse as your engine gets bigger and more performance oriented...

I haven't looked into details of a 254... I didn't want to bother with an overbore to get near sleeve limit and only gain 10cc...

If no stroker is involved, I'm guessing you need a bigger sleeve... Do the cases need to be bored to accept the sleeve??

For the 240 big bore (only 233cc) no case bore but max on stock sleeve.

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No, I meant the question of what does a 254 setup entail......

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No, I meant the question of what does a 254 setup entail......

 

67 mm bore with 6mm stroke

So:

67 X 72 = 253.95 cc

 

No case boring required but sleeve still has a more than safe thickness Margin.

Terry adjusts the rod length for a very close to "0" deck height and supplies a solid copper head gasket for proper squish.

So with that said, Wossner piston, proper squish, 6mm stroke, and non dished/cupped stainless valves = equals a healthy compression ratio.

 

If this engine is built as I described above, (I have no idea if it is) then,

IMO:

91 pump is not a safety margin choice that I would recommend.

 

Not sure what that cam is "3-3.5" ? But if it is the one I'm thinking it is, it's a good runner!

Just a shame it's still got a stock carb. (Bottle neck)

 

And: IMO

Up to this 254cc engine size, but no larger, as long as it has an over size header on it, a stock muffler will work ok, but the restrictor needs to be removed and the FMF header has to have the outlet that slides into the OEM muffler increased/replaced with the same size tubing as the rest of the header.

 

IMG_2391.JPG

 

After a larger carb then a different muffler would be best (larger diameter tubing between header and muffler)

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1 hour ago, Baja Rambler said:

The venturi on the pwk is art.  The venturi on the PD is something else and cluttered.

 

PDvsPWKcarb0966.jpg

I rode a similar equipped bbr framed 230/250cc bike as mine with a XR250 carb. Mine having the PWK and it is a night and day difference in response and performance through the power band. 

With a built bike your really loosing a lot. 

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You guys sound like a bunch of old hens. :D

A PWK was always planned for the future.  With everything else going on right now, I'm not terribly worried about it but it is on the list to get taken care of.  Regarding the exhaust, see this thread for what I've done to it:

The entire point, as mixxer mentioned, was to get the engine itself done.  Everything else from here is bolt-ons.  Yes, there is more to do.  I'm aware of that. :)

3 hours ago, adnohguy said:

 

67 mm bore with 6mm stroke

So:

67 X 72 = 253.95 cc

 

No case boring required but sleeve still has a more than safe thickness Margin.

Terry adjusts the rod length for a very close to "0" deck height and supplies a solid copper head gasket for proper squish.

So with that said, Wossner piston, proper squish, 6mm stroke, and non dished/cupped stainless valves = equals a healthy compression ratio.

It is built as described with the exception of the valves.  I can't guarantee that as the valves are oversized so I'm not sure what he spec'd.  Regarding octane, 91 is "premium" here at our altitude.  Terry set the compression ratio to allow me to get away with it, even on hot days (we'll see if that pans out).  If I'm in a situation where I'm dealing with bad gas, I intend to carry octane boost on hand.

3 hours ago, adnohguy said:

Not sure what that cam is "3-3.5" ? But if it is the one I'm thinking it is, it's a good runner!

I don't have the complete specs but maybe Terry can chime in with them.  Lift was described as .380 intake, .360 exhaust.  The 3.0-3.5ish description was based on a comment Terry made in this thread:

 

Edited by baglock1
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2 hours ago, Baja Rambler said:

The venturi on the pwk is art.  The venturi on the PD is something else and cluttered.

 

PDvsPWKcarb0966.jpg

While archaic and utilitarian in design and nature the Keihin PD series of carbs has served Honda very well.  It is a reliable and simple design that is very tolerant to changes in elevation and temperature and the oval slide design promotes high velocity at small throttle openings.  All good things for a Lo-Po engine but not so good for a Hi-Po engine.

All that being said I sure wish I had the time to try one of Terry's PWKs on my mild 230 build.  I have zero doubts it is better by every measure due to feedback from so many riders.  Except maybe for the fact the idle mixture screw is no longer accessible when mounted on a CRF230.

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I'm going to relocate the idle screw to the outside and put it on my stock motor as the first mod and maybe a cam.

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1 hour ago, VortecCPI said:

While archaic and utilitarian in design and nature the Keihin PD series of carbs has served Honda very well.  It is a reliable and simple design that is very tolerant to changes in elevation and temperature and the oval slide design promotes high velocity at small throttle openings.  All good things for a Lo-Po engine but not so good for a Hi-Po engine.

All that being said I sure wish I had the time to try one of Terry's PWKs on my mild 230 build.  I have zero doubts it is better by every measure due to feedback from so many riders.  Except maybe for the fact the idle mixture screw is no longer accessible when mounted on a CRF230.

Idle screw. Set it and forget it. 

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9 hours ago, bajatrailrider said:

I love your build as you know stock carb makes it tame.Big hold back. My 254 with stock carb test then to PKW test. Stock carb to never be used again.

Look, Needle, this PWK has the tent pole already on it!

http://www.ebay.com/itm/carb-carburetor-30PWK-30mm-PWK-fit-Honda-yamaha-ktm-suzuki-BMW-BSA-OKO-w-stack-/222239599003?hash=item33be83299b:g:ks4AAOSwMgdXzBrF&vxp=mtr

 

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11 minutes ago, Baja Rambler said:

Oh my the Taiwanese special even has a chrome dome on her.

I ordered a tapered bore PWK factory Honda carb from the Phillipines and was not happy with it. I sent it to Mexico. 

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You guys sound like a bunch of old hens.

A PWK was always planned for the future.  With everything else going on right now, I'm not terribly worried about it but it is on the list to get taken care of.  Regarding the exhaust, see this thread for what I've done to it:
[/url] The entire point, as mixxer mentioned, was to get the engine itself done.  Everything else from here is bolt-ons.  Yes, there is more to do.  I'm aware of that.
I don't have the complete specs but maybe Terry can chime in with them.  Lift was described as .380 intake, .360 exhaust.  The 3.0-3.5ish description was based on a comment Terry made in this thread:
 


While I was posting about your build, I was thinking about all the other readers that might be interested in learning about how to increase there own bikes performance.
Keep in mind that I was not pointing fingers or criticizing your build.
I Haven't had a chance to talk to Terry lately but in the past, with out him disclosing any names or who this particular engine build was for, I remember that this engine (turns out to be yours) was "generally" discussed between us.

So the specs you posted about your cam that your using is the one that I was thinking about when I posted my thoughts about your build.
It's a good one, it's not a Catalog Cam, it's a way more powerful cam than ANY Catalog Cam and it requires "at least a shorter intake valve guide" for the stem seal to clear the spring retainer binding at full lift.
It makes good torque from Idle on up as long as the compression is up where I suspect yours is.
(More compression is good)

IMO:
It takes a cam,such as yours, to adequately feed a 6mm stroker.

Since you stated your engine has an oversized intake valve, and Terry built it for you, you have at least one valve that increases compression. ( but I suspect that used his exhaust valve also)
Your cylinder head/cam setup would work really well up to and including 269cc so if you decide to use a 69mm piston someday, your good to go.

Since you have disclosed that you future plans are to upgrade to a PWK carb, that will will be a whole new level of "large smiles" and performance.

With your future exhaust system upgrade, with the right choice, you will be able to "tell the difference in power" using the "seat of the pants Dyno" but not as much as the carb alone.

Keep in mind, that with your cam, and a 6mm stroke, an " over the counter" exhaust system that is sold by every one for a stocker, or even a warmed up stocker, will not work as well as one would expect it too. I found that out the hard way.....and it cost a lot of $ to find this out.

By all means Good Luck, your now inducted into the 1% club. Huge smiles are awaiting you so enjoy.

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9 hours ago, adnohguy said:

Oh I didn't take it that way Guy so no worries there. I just didn't want you guys thinking that all the comments on this forum about carb and exhaust on strokers was lost on me. I do pay attention to the lessons you guys have learned and passed on to the rest of us. I just have my own way (and timeline) of applying them. :)

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