[thruster2002]

Ok I just upgraded (I hope) from my 05 crf250 to the 07 crf250. I raced it last weekend and noticed straight away that it is bogging heaps more then the 05 ever did though I did have a dep silencer and header on the 05. I have read some of the threads on here and sounds like the JD Jetting kit is a must also the Quickshot 2 but what exhaust systems are you guys running or are you keeping them stock? also any other tips would be great.

[redrider911]

Even stock, it should not bog. If you are sure its a bog and not the power flatting out, recheck your float level and jetting.
As far as pipes, can't help you for an 08.
Quick shot.....I didn't notice a big enough difference to spend that amount of $$$, others like it. If you have money burning a hole, then buy it.

[Monkeywrench]

Thruster: congrats on your new bike, bog or not. These things have gotten so pricey these days that to be able to just own one is becoming a challenge worth celebrating in itself.

I saw someone just the other day with an '07 250R which had the White Brothers X2 (??) single pipe(!!!) and a completely different header. VERY loud. Not sure he had a bog, but it didn't seem like it.

Although not an '07 250R owner, I did hear of the bog issue. Was inches from purchasing an '07 250R, but discovered an (un)used '06 450R actually for a good chunk less $$ and went that route instead. But looking back at the bogging I had with my '04 250X (was very bad) there may be some things (low down on the cost scale) which you can do to at least see if you're making the bog worse, or if it's getting better.

One popular thought (at least around my neck of the woods) is that the '07 is "over carbureated". Meaning too big a bore. Now, I'm no expert on airflow or even jetting, but I know you tend to slow down airflow (or at least the venturi effect it produces when you increase bore size, which is an air stream's ability to draft a liquid up through an orifice located below the air stream -- which would be your main jet). If this is the case with the '07, then sleeving the carb may be the answer, which would decrease the bore size, thereby increasing airspeed. I think ~ has commented on such an insert being made available through Ron Hamp Cycles.

The other thing you could try is more trial-and-error based. I believe the theory behind the Boyesen pump cover is that it holds "more" gas than the stock cover. And refills faster, as well (??). That being said, even if you're snapping the throttle repeatedly with the stock cover, you shouldn't (theoretically) have a bog so long as you give the pump enough time to refill, and the pump timing adjustment is dead-on. I would start there. Maybe even advance the pump timing so that the fuel stream is just nipping the throttle slide at the bottom, as it raises up during your throttle twist. This way you at least rule out the timing adjustment being the problem.

Also richening up your pilot screw, or even the pilot jet itself can help. Last but not least, maybe expiriment with the next smallest leak jet, in the float bowl. This will add pressure to the accelerator pump circut, as a smaller leak jet causes less fuel to be returned to the bowl during throttle whacks, and more fuel to be delivered to the a/p nozzle. Think of it as a leak in a garden hose. A bigger leak means less water is delivered to the nozzle. A smaller leak means more water goes to the nozzle. Similar with the leak jet in the A/P circut.

So (just me again since I like to tweak) before spending a dime on anything else I'd mess ith each of these one at a time and see what the changes are, if any. The only reason being I'm not sure just yet if anyone has nailed it down to a routine process of how to fix your bogging '07 250R. (Or maybe they have by now!). But I would start with those changes -- I agree with redrider... even stock it should not bog. It's a race bike, not a trail bike. Bog means a fuel delivery timing issue, or maybe volume issue, or maybe both. Now, if this delivery issue stems from the carb bore being too big, then I'd say sleeving the carb should help. But as I understand it, the whole function of the accelerator pump is to supplement for the lack of venturi effect, when the rpm's are too low to draw gas up through the main jet. So look into the accel. pump circut - play with the timing, try a different leak jet, play with the fuel screw. I think (maybe just me again) the problem lies somewhere in the blending of these things along with the a/p. When that vital part of the carb is not earning its keep, it's almost not even fun to ride.

Good luck to you - I hope this helps.
Nothing worse than grabbing a fistful of throttle only to hear crickets and tumbleweeds back for an answer. (Hello power? Are you there??)
-matt

[Zish]

have a 07 crf 250x that had some wicked bad bog.
get the JD jet kit before yopu do anything else.
In 07 you don't have to do the acc. pump mod.
was a big difference in my bike.

[thruster2002]

thanks for the tips, I read 5 minutes after my first post that the quick shot wasn't needed. Have changed the main jet to a 175 that came in the spares kit but havn't been riding yet as the waves have been pumping here, but will be out racing in our last club run for the year this sunday.

[Monkeywrench]

A 175 sounds pretty rich.
Mid 160's should suffice if you can get ahold of one.

With the 175 you may notice a pretty 'rich' odor, as well as begin fouling the plug, over time...

just a couple thoughts, but DO play by all means.
It's not bogging right now because it's too rich, that's for sure!
-matt

[thruster2002]

I have gone the 175 main jet because it say's in the honda manual that if you ride in sand with long straights and up hill sections then go the next larger.

[Monkeywrench]

I have gone the 175 main jet because it say's in the honda manual that if you ride in sand with long straights and up hill sections then go the next larger.

So by going to the next larger, you mean you are already in the 170's?
Not sure if the 175 will fix your bog. Have you noticed a difference?

[thruster2002]

The bike came brand new from my local honda dealer here in Western Australia with a 172 main as stock and a 170 and 175 in the spares kit so did my old 2005 crf250.
Anyway the 175 has done nothing to help the bog problem, I might try going one tooth bigger on the back as iam sure this will help

[Monkeywrench]

Oh, ok.
Yup, I have heard about that. The '07 model.
Over carbureation is the issue I believe.
You might try knocking down the carb's intake bore with a sleeve available from Ron Hamp.
~ has done some looking into that, or has heard of that being done I believe. He might be able to steer you closer.
good luck,
-matt

[thruster2002]

I think its fixed. I ended up putting on a Dep header pipe off my old 05 crf250. This header is longer then the stock header and fits straight on keeping the 07 twins. I only rode it today for the first time and it was on a rough sand MX track but it felt heaps better, cant wait for the next race day.
One thing I have noticed the 07 turns way better then the 05 and I thought the 05 was good.

[Monkeywrench]

Good deal!