I just finished getting my bike to a 290cc big bore.  Currently I'm running the stock gears in the bike.  I am finding it a huge pain to ride on tight and rough trails with my bike because I'm just exhausting my hand from clutching in and out constantly so I don't stall my bike.  I have to give it spurts of power as I go through these trails otherwise I'm going too slow and I will stall my bike.

How much better can I make it with just changing to sprockets?

try flywheel weights instead i dont think sprockets will do a whole lot for that you could allways try retarding the timing to wr

10 oz fw weight on mine helped a lot, don't even have a big bore yet! Going from 13/49 to 13/51 before the next ride. Less than 5% difference but every little bit helps. Tell us more about your 290, who's kit, jetting needed, overall impressions, such as how and where the power is better and or worse, would you do it again, etc.

+1 on the flywheel weights

Weights and try a 13/52 sprocket combo.

E30 guy, on 09 April 2012 - 07:47 PM, said:

As it is, if it's sounding like it's bogging down to a stall and i give the throttle a crack it wakes right up, I don't recall noticing this before.  I did the big bore over the winter so kinda hard to be certain how much of a difference it made since I don't ride in the winter.  I got the 290cc from lukes racing.  I cant really comment on top end power since I feel like my wheel is burning out as I ride down logging roads in 4th (5th was way to scary at this place where I was at last).  I got very comfortable with my 250cc so I decided to go 290cc because I had to get a rebuild and why the hell not.  It was a cheap investment at that point.

I'll look into flywheel weights then, thanks all!

Edited by ninjai, 09 April 2012 - 08:47 PM.

Sorry for double post, but to install the flywheel weight, can I just take the cover off and slip out the old weight and put the new one in, or do I need to pull the flywheel with a flywheel puller? If so, what do I need to know in terms of markings and such?

Steahly, the one I use, simply replaces the stock flywheel nut with their weight. Also utilizes small allen bolts along the perimeter for additional clamping force. Well designed product and very helpful people too.

E30 guy, on 10 April 2012 - 08:35 PM, said:

That's the one I was looking at.  So I would need a flywheel puller then, since I have to replace it.

ninjai, on 09 April 2012 - 05:53 PM, said:

What sprocket combo do you currently have and what year yzf do you have?  The BB 290 should give you a big boost in bottom end, so it should actually run in the lower rpm's much better than before.  How is the jetting?  Does the bike run smooth at a relatively low rpm?  If not, it may be a jetting change you need to make.  With a BB290 I would stick with taller gearing, maybe a 13/48 or 13/49.  Alot of people like a 13/51 in the woods, but thats on a stock YZF250, you have so much bottom end power that it probably wouldnt work well for you.

All I ever did with 13-51 was piss off my riding buddies... because I could crawl... over anything. I went back to the stock (13-48) after the Big Bore kit and realized how much I missed the speed when the trail opens up.

Experiment with cheap steel sprockets and see what you like

If you were closer I would be able to hook you up with a 50T and 51T.

Edited by SleepyHeadYZF, 12 April 2012 - 01:57 PM.

SleepyHeadYZF, on 12 April 2012 - 01:55 PM, said:

This is exactly it.  Most people I ride with love the trails... and have trail bikes.  When I hit an open stretch, or the sand hill at this place I ride at sometimes, I LOVE the speed and acceleration my bike can produce!  I think I will pick up some other sprockets.  I run steel ones now anyways because of cost and wear and tear being not as bad as aluminum

I have a stock 09 and actually run the 13/48. I have to ride it a bit more like a 125 but it is fun and I don't run out of gears. It also seams smoother in general. Less engine breaking too. Most people go the other way but this works well for me. I am thinking about a big bore kit but not sure which one I want yet. Good luck.

REKLUSE

A couple of months ago i was in the same situation like you. I bought a 13T front sprocket and said to myself - Now what!? 48, 49,50,51 no idea. I bought it with 48 but didn't like it very much. So i went with the 49. Went on some local trails and the bike performed amazingly. Don't know how it would be with 50 but for now i am ok. Keep in mind that i am with athena. Cheers!

nk_dimitrov, on 17 April 2012 - 05:47 AM, said:

Really? One tooth makes that much of a difference!? Well, I actually just finished purchasing a 51 tooth.  We'll see how that is.  Hopefully it's not too crazy low, and I can still get some speed when I want it.  I just recently started riding at blue mountain in Maple Ridge, BC and man is that area a bitch, especially with 13/48 sprockets!

Edit:

LukeYZ426F, on 16 April 2012 - 08:10 PM, said:

I actually thought of this recently.  I remember seeing a yz250f with a recluse before I bought mine and I thought it was stupid (I prefer to drive manual vehicles over automatics and this made it sound like an automatic) but now I realize how awesome that would actually be... the thing with the recluse clutches that confuses me is that I have no idea what I need.  They have so many bits and pieces under weird names I don't know how much it would cost me to just install one.

Edited by ninjai, 17 April 2012 - 10:44 AM.

go buy the rekluse EXP2.0 for 399 and thats it. thats all you need. maybe some new oil for your bike. boom. SHABAM! rekluse

Ninjai,

Wondering if you have tried the new gearing yet?

I have the same issue. I ride a stock 03 YZ250F. Mostly with my kids (CR70f & CR100f) on low speed tight, rocky woods roads trails in Newfoundland.  

I'm thinking about new sprockets and flywheel weights as well

Cheers!

I tried a 13/51 yesterday and loved it. Perfect gearing for 2nd-3rd gear riding (Southeastern Woods)

Sorry for the delay in response... You will not need a flywheel puller as you will not be removing the flywheel itself. The flywheel nut is all you are replacing, so you will need a way to hold the engine from rotating. Fifth gear engaged and rear brake on  hard worked for me. Depending on how much weight you choose, a small spacer for the cover might be included. As I said, they're great people and very informative too, just call or email them with any questions.