Jump to content
Sign in to follow this  

07 CRF450R Bog

Recommended Posts

Typical question here: I have an 07 CRF450R That I just installed a DrD full Ti system and a jd jetting kit into today. These are the only engine mods I have. Bike runs good everywhere except for an off-idle bog when I crack the throttle open hard. I don't believe its an AP issue or anything, because the bike ran perfect before I threw on the pipe and jetting kit.

I have the Red needle in currently at the 4th position fron the bottom.

#185 Main.

Fuel screw at approx 2 turns out.

Stock slow jet, which is #43 I believe.

I adjusted the fuel screw a bit from 1 3/4 to 2 turns out and it helped, but only to a certain extent. I'm assuming I'm running rich off the bottom, and running a good a/f ratio on top. Do I need to drop a position on my needle, or a bigger slow jet? I'm new to jetting, if you can't tell! I'm trying to educate myself more on jetting while I wait for a response from you guys.

I ride at about 2600 +/-500ft elevation.

Help would be appreciated!!

Thanks!

Edit: More info, I just checked the plug: Its a light gray.

Edited by IronSteed450

Share this post


Link to post
Share on other sites

If it's bogging right off throttle/idle "only" and "not" through the entire first 1/4 throttle then it's probable the leak jet, NOT THE PILOT (slow jet, same things). If the bog is through the entire first 1/4 throttle then I would look at the pilot jet.

Read this to test. https://thumpertalk.com/forum/showthread.php?t=327405

I have a 07 CRF250R, had the same issue. I mean the exact same issue. Didn't do the mods you've talked about however, had the same bog. Went from a stock 70 leak jet to a 40 leak jet, played with the AP screw a little. BLAM!! Bog it now gone!!! (Thank you William1!)

Anyway, not 100% sure if it's the same fix for your 450 because I'm still learning about about these 4S carbs myself but, from what I've read and what I've expereiances,.... it's the leak jet and AP screw. It's an 07 so you should need the AP mod.

As far as these issues just starting now after the mods you've done, that normal after any mod (like you've talked about) to a point.

Hope this helps, bro!!

Share this post


Link to post
Share on other sites

Thanks for your help Motodogg01. I picked up a #45 pilot today that I'm going to try. If that doesn't help, I will give what you said a shot. I also got a work back from James Dean today so I'll give it a shot tomorrow and let you guys know how it goes!

Share this post


Link to post
Share on other sites

Cool! Remember, you might have to "fine tune" the AP screw to get the bog totally out.

You might want to read this thread. It's the thread I started when I was looking for help with my 07. William1 give some great "step-by-step" instructions for tuning a FCR carbs.

https://thumpertalk.com/forum/showthread.php?t=872855&highlight=off+idle+bog

Share this post


Link to post
Share on other sites

You should be using a 162 main jet at that altitude.

You can pinch the leak jet closed and it will run better. Put the end that goes down into the bowl in a vise and pinch it shut. You'll have great throttle response.

Share this post


Link to post
Share on other sites
You should be using a 162 main jet at that altitude.

You can pinch the leak jet closed and it will run better. Put the end that goes down into the bowl in a vise and pinch it shut. You'll have great throttle response.

I don't know if I really feel comfortable doing that. It is really really dry and acrid here, which causes a little bit more of a lean condition, according to the Honda manual. I actually swapped the 185 main out for a 190 because that's what the JD Jetting kit calls for, and I threw in the 45 slow jet last night, and it cleared up about 95% of the bog that I had on the bottom. A little fine tuning of the air screw and I should be golden.

Share this post


Link to post
Share on other sites

Eddie is the source for completely blocking off the leak jet. I was a little skeptical but have tried it on numerous bikes with great results.

After reading your post again, I saw that it's a 250 rather than a 450. The JD instructions are pretty darn accurate.

Share this post


Link to post
Share on other sites
Eddie is the source for completely blocking off the leak jet. I was a little skeptical but have tried it on numerous bikes with great results.

After reading your post again, I saw that it's a 250 rather than a 450. The JD instructions are pretty darn accurate.

Interesting. What does pinching the leak jet off do exactly? Its a 450, actually.

Share this post


Link to post
Share on other sites

I installed a new plug along with the 45 slow jet last night and rode it for about 10 minutes this morning. Here's what the plug looks like:

DSC00215.jpg

Share this post


Link to post
Share on other sites
Interesting. What does pinching the leak jet off do exactly? Its a 450, actually.

The leak jet is a bleed off jet back into the bowl for the AP.

For example: (These are hypothetical numbers just to illustrate this scenario) If you're running a #70 leak jet then you're allowing 1 oz. of fuel to be squirted into the carb via the AP and 2 oz. of fuel to be bled back off through the leak jet back in to the bowl. If you're running a #40 leak jet then you're allowing 2 oz. of fuel to be squirted into the carb via the AP and 1 oz. of fuel to be bled back off through the leak jet back in to the bowl.

The smaller the leak jet the richer the squirt!! Hence, your pilot was probably "OK" and the issue was the leak jet and AP. I tried to re jet the pilot on mine too. I never could get the bog to stay out on a consistent basis.

I don't know if I really feel comfortable doing that. It is really really dry and acrid here, which causes a little bit more of a lean condition, according to the Honda manual. I actually swapped the 185 main out for a 190 because that's what the JD Jetting kit calls for, and I threw in the 45 slow jet last night, and it cleared up about 95% of the bog that I had on the bottom. A little fine tuning of the air screw and I should be golden.

FYI. Four strokes don't have a "air screw" they have a "fuel screw". On a two-stroke when you screw out the "air screw" you allow more air in which leans the mixture. On a four-stroke when you screw out the "fuel screw" you allow more fuel in which richen the mixture. Just FYI, bro.

Hope that helps, bro!!

Share this post


Link to post
Share on other sites

That makes sense, thanks for taking the time to explain it. Did you pinch your leak jet off as well? And if so, did you have to make jetting changes elsewhere because of it?

As for the fuel screw mix up, gotcha 👍 I'm still learning about 4 strokes, been a 2 stroke guy for the past 8 years! Thanks bro!

*Update* I checked my AP timing, seems to be pretty good. It doesn't hit the slide, but it seems it could be timed a tad bit faster.

Edited by IronSteed450

Share this post


Link to post
Share on other sites

Totally understand about learning about these 4S's. I too was a 2S guy for the past thirty years. Stick around here, you'll learn alot.

As far as that leak jet mod, no I didn't need it. Moving from a stock #70 (I think it was) to a #40 combined with some AP timing was good enough for mine. I'm not a 100% sure of this but, I believe I've read within several other threads that this typical mod these 450's. Not sure of the year of bike ranges though. You might have to do a search to get that answer.

*Update* I checked my AP timing, seems to be pretty good. It doesn't hit the slide, but it seems it could be timed a tad bit faster.

If you're talking about what I think you're talking about this will also be effected by the leak jet. The smaller the leak jet the more pressure the squirt will have, hence be "faster".

Don't get me wrong. You want to be running the largest leak jet you can with out bogging. That's why you install a smaller leak jet like a #45 (or pinch it off), then start fine tuning the AP, then move to a little bigger leak jet like a #55, then fine tune the AP. You do this until the bog comes back and can't be tuned out via the AP then go back one step.

FYI. There are hundreds of threads on jetting/AP tuning for these 450's. If you use the search button from above you will be able to narrow down the threads and get some good info!!

Hope that helps, bro!!

Share this post


Link to post
Share on other sites

If you're talking about what I think you're talking about this will also be effected by the leak jet. The smaller the leak jet the more pressure the squirt will have, hence be "faster".

Don't get me wrong. You want to be running the largest leak jet you can with out bogging. That's why you install a smaller leak jet like a #45 (or pinch it off), then start fine tuning the AP, then move to a little bigger leak jet like a #55, then fine tune the AP. You do this until the bog comes back and can't be tuned out via the AP then go back one step.

Smaller bore under the same pressure= more velocity... I understand 👍

What do you think about an adjustable leak jet?

Edited by IronSteed450

Share this post


Link to post
Share on other sites

I had one one my 04, don't have one on the 07 yet but, I will put one on there. From what I've seen out of my 04 250, love~em. I mean, once you get really close to where you need to be on jetting, then a adjustable leak jet can really help "keep" your tunning perfect. I can tell a difference if we're out riding on a Saturday when its 90 degrees with clear sky's and then go riding the very next day when it's raining and 20 degrees cooler. The adjustable leak jet "helps keep" your tunning perfect. There kind of high dollar for what they are but, sometimes you have to pay extra for not just the performance but the convenience of "Jetting on the fly".

Share this post


Link to post
Share on other sites

First off the stock pilot is a 42 and main is 168.

You are WAY fat on the main. Go back to stock.

Once you get back to stock, then try adjusting the fuel screw. If that doesnt help, then try a different leak jet.

Share this post


Link to post
Share on other sites

Why would the JD jet kit call for a 190 main at my elevation if its too fat? Just curious. It runs pretty good at WOT. I swapped for the #45 pilot and threw in the 190 main and it helped out alot. Seems to run well, but I'm going to go ride it hard tomorrow and do a plug check. If it looks too fat ill go down on the main. And the stock 07 main jet is actually a 178.

Share this post


Link to post
Share on other sites

Update: I went out and rode yesterday for about 4 hours or so. The bike ran well with no hiccups or bogs of any kind. I believe the change to a 45 pilot, and a little tuning of the AP made the bog go away. I just pulled the plug, it looks like this:

DSC00222.jpg

Anyone have any thoughts?

Edited by IronSteed450

Share this post


Link to post
Share on other sites

That looks a little rich to me. Not bad, but a little rich.

From what I've read on the Internet it seems to be rich at the main. But, don't hold me to that. You can find charts that talk about different throttle portions effecting different parts to the porcelain. From what I've read the lower/deep inside portion is WOT, and middle is 1/2 throttle, top is idle to 1/4.

I've never read spark plugs to that degree I read about on the Internet. I saw your plug and started looking for charts, found those things I just talked about. I don't know. Maybe JJRace is on to something?$%?#

Might take a look at this.

http://www.4strokes.com/tech/sparkplg.asp

Edited by motodogg01

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...