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What would be a good way to move your powerband around?

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I know.  Crazy right?  Why would anyone want to soften the hit, down low.  Well, I was just thinking about it and I wanted to hear what you folks thought.  Here’s the deal.

 

My crf150f, which has a 230f top end (among just about everything else) runs pretty good.  It’s a fun bike.  I did some changes and the throttle is extremely sensitive down low.  It’s so sensitive that it’s hard to ride a flat turn.  I have to really pay attention to my throttle control to be smooth.  It’s pipey!  I prefer to ride higher in the powerband rpm’s. 

 

Now that I have power to spare down low, I wondered what I could do to move some of that power up into the mid or high RPM’s. 

 

I guess changing sprockets could do this.  A shorter pipe might also do it, but I don’t have the welding skills to do that.

 

A different Cam?  I’m running an Engine’s Only Stage 2 cam. 

 

What do you guys think?  I just thought it would be fun to hear what suggestions our community had.

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Bigger cam.  As much duration as you can run given your compression ratio.  Ask Frank Nye or Mike Coe what they think.

 

A decrease in initial timing and a less aggressive curve would also help but I don't think there's an economical solution out there.

 

How about a bigger carb and/or bigger intake port?  Retard the cam timing?

 

Tone - Just realized it was you.  How have you been?

Edited by VortecCPI

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Hey VortecCPI,

 

How's things.  Yes, every once in a while I like to sneak in and poke around.  I enjoy to throw out questions on things and see what comes up.  And as I expected, you came through with flying colors.  A larger carb.  I didn't think of that, but I believe that would do it.  Ah.  I love it.  

 

Yes, I might be back for a bit.  I was out due to shoulder surgery (old baseball injury) and the rehab was almost a year!  Crazy right?  Anyway, I just started riding again so I'm pretty excited to get back into it.  "It" being modding the bike and actually riding it too.  :)

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Good to see you back.  I could still kick myself for not snatching up that EO system you had years ago.  I've been in continuous contact with Frank and I'm still waiting to get my hands on one of his new stepped and stainless steel systems.

 

Riding has been light here so far but I've cut some new trails for test & tune and tested a few new things in the mean time.

 

What cab are you running on your bike right now?  I happen to have an XR's Only 32 mm Mikuni.

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Go for an EO stage three cam, while your having Frank install it, have him port it for you. (You'll have the head off and disassembled anyway)

Install a larger diameter header pipe.

(XR's Only)

2004XR250r 30mm carb would be next IMO.

be sure to match the 230 Intake manifold to the carb and the Intake port.

If I'm not mistaken, you have a std compression and size OEM. 230 piston correct?

If so, you really won't have to worry about having to much low end power, if you do all of the above mods, because you won't!

Try it, you may like it????

But if it was me, add some compression while it's apart.

You'll be smiling from ear to ear if you do all of the above, guaranteed or your money back, LOL

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Some other ideas just to throw them out there with those above.

Flywheel weight is sure to smooth things out.

One tooth larger on front sprocket or two teeth smaller on the rear will slow things down. Smaller front will allow you to move the wheel back and lengthen the wheel base a bit.

Change the cam timing around. Frank at Engines Only has a slotted cam sprocket. You really need to talk with him about how it can help you tune.
If you have an EO cam you may have a slotted sprocket already.

Also look at your suspension. Is everthing working right? Swingarm and linkage lubed and tight? Shock in need of rebuild or revalve or spring choice? Slow down the rebound a bit to keep the rear settled on long corners. Not enough rebound and it load and unload on the shock.

Rear tire choice? Air pressure? How old is your rubber? Old tires are stiff and don't work as well as they once did.

Edited by 4strokeridertt

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Aw shucks.  You guys are swell.  J  I ask and everyone delivers.  Awesome. 

 

Carb?  Currently, I’ve moved back to the stock carb.  I thought about doing the XR250 carb; I just haven’t yet.  I had the EO 28mm flat slide carb on there, and it worked really well, but I was doing too many mods at the time and I couldn’t tell what was doing what.  To eliminate the confusion, I removed it so I could pay attention to each mod, one at a time. 

 

Once I took it off, however, someone wanted it and I sold it.  Oops.  Probably shouldn’t have, but I did.  I may have to look into a different carb again.

 

Stage III cam?  That does sound like the correct option, but I wasn’t sure if I wanted to go that big just yet.  I just installed a hi-comp piston (this Sunday was the 1st ride after the break-in period ride) and the engine is much stronger.  I have to ride it a little more to become more familiar with what I have.

 

Porting?  My head has already been ported.  Frank actually was impressed by the port job when he saw it, years ago.  A friend did it for me.  When the engine was a 170cc EO engine, with the porting, it pushed the power band from the lows into the highs.  It was awesome.  Now its on the new engine and the powerband is in the mids.  It’s good.  I just wanted to brainstorm on how to move it (the powerband) and if its possible .

 

Flywheel weight?  Humm.  That would do it.  I haven’t thought of that.  Hummmm.

 

Slotted cam sprocket?  I do have an EO stage II cam.  I have to admit, however, I don’t know if mines slotted.

 

Suspension?  Oh boy.  I did make a lot of changes to my suspension!  I was bored and just changed my setting.  I forgot about that.  I’ll  have to address that.

 

Tire? Well, new tires are a joy.  I just bought a new Dunlop the other day.  I’m looking forward to putting that on.  It’s just about time for new rubber.

 

Thanks for the suggestions everyone.  I’m looking forward to doing a few new mods.

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1/4 turn throttle verses a 1 full turn throttle.

You would have to point your elbow on the throttle side forward to gas it!

Lol

By the way, don't the pro riders just pull in the clutch a little when they don't need as much power transmitted to the ground rather than letting off the throttle?

Seems like I have heard that before somewhere?

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Hey Tone! 

 

It's me, Fishfreq, aka Albert. I think your powerband issue is in your right wrist! 

 

I don't know if you found your solution for the 'abrupt' throttle response on your crf but I think I know exactly what you're talking about - my crf150f does the same thing, albeit at a much smaller scale than your mod 230 mill, and it's kinda like the throttle return SPRING is too strong, am I right? It's like it's hard to modulate the initial 1/8 throttle turn? 

 

Here's a simple idea! Try one of those throttle twist grip assemblies with interchangeable cams. There are a few out there, one by Motion Pro that says their 'Progressive cam designs can make the throttle feel soft at smaller openings'.

 

http://www.motionpro.com/motorcycle/tools/featured/revolver/

 

Just a thought.... 

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It is difficult to remotely diagnose problems but I've had similar problems with XR200/218s and my 250X when trail riding technical in the lower gears.  (two very different carbs; the XRs use a PD and the X a FCR)

I found that  a worn needle jet will cause a part throttle richness during the transition to the needle that makes for a ragged throttle response when opening from a  trailing throttle. So my fix on the XRs have been a new needle jet set (includes a needle jet)

 

Too rich a main exaggerates the condition, as does too big a pilot, or too rich a needle clip position, or too rich a mixture screw setting, or combinations. 

So you can experiment leaning some of those circuits to see if it makes a difference, maybe even a leaner slide cut away. 

 

A slower turn throttle, or a variable rate throttle,  can help but at the speeds you are running I don't think that would be much help. 

 

The XR250Rs use a multi taper needle that may also help, they will fit the other PD carbs.

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Feeding the power with the clutch really helps me smooth out any "hyper" bikes I've ridden out of slow, technical turns. It eliminates abrupt engine hit and increases control for me. My finger is nearly always covering the clutch lever and using it just a little helps mellow throttle feed as well as instantly increasing drive if required. Sometimes both corrections are needed quickly leaving a corner/obstacle. For me, this works really well.

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