Jump to content
Sign in to follow this  

My god offal bog is back!

Recommended Posts

I have been successful in the past, but now am ready to throw in the towel.

Here is what I have done:

JD jet kit to his recommendations in an email:

Try running the following-

#42 pilot jet

1 3/4 turns out on the fuel screw

Red marked needle in the #5 from top clip position

#170 main jet

Thicker O-ring on the pump linkage

Leak jet float bowl

I have done all this and it still has a bog. Even with the leak jet float bowl.

Stock KTM AP.

I have set valves before, but will do it again tomorrow just to be sure.

I also just put in a new spark plug.

Verified the two intake ports are aligned with the airfilter boot port holes.

I have set the mixture screw from 1-1/2 to 2-1/2 turns out.

I also played with the AP screw, and finally set it back to stock.

None of this helped.

Here is the rub, it works great when warm, but when hot (3 rides up and down the street), it starts to bog. It runs decent before that.

Am I into an electrical problem now?

Share this post


Link to post
Share on other sites
Just a few questions: What bike? What size leak jet is in the float bowl. RB

2007 450 EXC.

Float bowl is straight from JD, so whatever leak jet he puts in there.

Share this post


Link to post
Share on other sites

Let us know if it changes after you adjust the valves.

Could be the intakes have tighten up enough to let combustion gas into the intake track. This will lean out the fuel charge before it gets to the cylinder. You will usually see black in the intake track if you remove the carb. and look into where the valves are.

Be sure to use the 1/6 method for setting your valves.

Share this post


Link to post
Share on other sites

I got this email back from JD jetting:

Lewis,

When the motor gets hot, the jetting gets richer. If you start to snap the throttle open repeatedly it will become overly rich and stall/bog from running rich, cooling the cylinder head with raw fuel. Do not snap the throttle repeatedly when parked, only evaluate while riding to check response.

Did you make the following evaluation?...

What position did the fuel screw slow the motor down at?

=========

Check the fuel screw setting by riding the bike to get it fully hot, then at idle, turn the fuel screw inwards until the idle slows from running lean. Take note of this position, then turn the fuel screw outwards 1 1/4 turns from this position, which will increase the idle speed and give a good overall setting in most cases.

See the effect that the fuel screw has on idle speeds and air/fuel mixture at-

http://www.pbase.com/jdjetting1/image/82894252

The Red marked needle in clip position #4 should also be a good setting with the float bowl (considering the elevation), and fine-tuning on the fuel screw.

Are you still using the stock accelerator pump diaphragm?

You may want to check the pump squirt to see that it pushes fuel 4-5ft from the bike in a quick spray, just to be sure nothing is clogged.

Thanks,

James

Share this post


Link to post
Share on other sites

it is highly possibly you are having an electrical problem. i had a cdi box go bad on a kawi years ago and it was similar, ok cold, ok warm, sputter and boggy when hot. it could be stator or cdi. if you have a buddy with a similar year make model you might try swapping the cdi out

  • Like 1

Share this post


Link to post
Share on other sites

I was messing with it standing still, which would seem to explain why it ran fine at first, and when I stopped and wacked the throttle, it got worse. I will set the fuel screw again and see how it goes tomorrow at Rowher.

Share this post


Link to post
Share on other sites

So how do you adjust the AP squirt timing?

I know you want it to just miss the slide, but how do you check this?

Do you look through the airbox using a mirror and a flashlight, or do you need to remove the carb and hope there is enough fuel left in the bowl to see a squirt?

Specific instructions would be much appreciated, like remove the carb, but leave the throttle cables hooked up, turn the throttle and check.

Share this post


Link to post
Share on other sites
another thing is if the top end is just worn out it will also bog and quick full throttle openings, but run OK if you roll the throttle on.

I have 155 hours on the motor now and hope that is not the problem.

Share this post


Link to post
Share on other sites
So how do you adjust the AP squirt timing?

I know you want it to just miss the slide, but how do you check this?

Do you look through the airbox using a mirror and a flashlight, or do you need to remove the carb and hope there is enough fuel left in the bowl to see a squirt?

Specific instructions would be much appreciated, like remove the carb, but leave the throttle cables hooked up, turn the throttle and check.

I remove the carb. to check it. Be sure the bowl is full. I just turn the throttle cam by hand, but you could leave the cables connected and watch from the air filter side of the carb. Be aware of where you are squirting. It should shoot at least 6 feet out of the carb.

Here is a picture from JD's site. CLICK HERE.

Have you adjusted your valves yet?

You should do a compression test on it also. Should be around 115 PSI.

Share this post


Link to post
Share on other sites

The stock accelerator pump diaphram typically allows to much fuel to be pumped. I believe a stock crf 450 diaphram will help with your problem. If you do a search you should be able to find what year crf diaphram will work. The crf has a lolonger post that will shorten your squirt time which helped me out alot. You want preasure not volume on that bike. And i found it much easier to have the carb out of the bike with a friend holding a flashlight so you can see the squirt duration and volume. Hope that helps

Share this post


Link to post
Share on other sites

wear glasses cuz the squirt may get you in the face. There is enuf gas in there to give seceral squirts so you can see what is going on. The other thing Ive had happen is the squirt nozzle gets plugged with dried gas residue, the squirt is weak and erratic. Hard to clean out. I used a very fine SS wire held by needle node pliers to stab the hole in the nozzle and work it in there. Took a few tries to hit it and then a few times of clean and squirt til it was clean.

  • Like 1

Share this post


Link to post
Share on other sites

I adjusted the valves, they were out a bit and checked the fuel squirt through the airbox. I saw nothing. Then I fully warmed it up and turned the fuel screw down to see when it lowers the idle, it was all the way closed before it caused a rpm drop. I cleaned all the jets and it still is having problems. I guess I will take it apart again and double check the pilot circuit.

Share this post


Link to post
Share on other sites

Took the carb apart again and cleaned out all the passages with gum-out and then blew them out. All the AP lines including the nozzle are free. Put it back together and with the choke on, it snaps too. Once the choke is off, bog city. It sounds like it is gasping for breath and then, wam, power. It almost sounds like the 60 leak jet is too big. Any thoughts?

Share this post


Link to post
Share on other sites
Took the carb apart again and cleaned out all the passages with gum-out and then blew them out. All the AP lines including the nozzle are free. Put it back together and with the choke on, it snaps too. Once the choke is off, bog city. It sounds like it is gasping for breath and then, wam, power. It almost sounds like the 60 leak jet is too big. Any thoughts?

I hate to rehash things but what you just described is classic plugged Pilot jet symptoms. I know you said you cleaned the jets but are you sure you pulled the pilot and then inspected it after the cleaning? the hole need to look round and clean. Blow through it to make sure it is open. Good luck. RB

Share this post


Link to post
Share on other sites
Took the carb apart again and cleaned out all the passages with gum-out and then blew them out. All the AP lines including the nozzle are free. Put it back together and with the choke on, it snaps too. Once the choke is off, bog city. It sounds like it is gasping for breath and then, wam, power. It almost sounds like the 60 leak jet is too big. Any thoughts?

So how was the squirt?

Was it a solid stream? Did it miss the slide? How long does it last?

Are you riding it when you test it or is it on a stand?

I didn't realize you had a leak jet. Watch this video about leak jets. This is an adjustable leak jet but you will get the idea.

Share this post


Link to post
Share on other sites
I hate to rehash things but what you just described is classic plugged Pilot jet symptoms. I know you said you cleaned the jets but are you sure you pulled the pilot and then inspected it after the cleaning? the hole need to look round and clean. Blow through it to make sure it is open. Good luck. RB

I cleaned that pilot 4 times, but after reading your post, I put in another 42 pilot I had lying around, and it is 80% better. Not perfect, but doable, thanks. Oddly enough, I tried to buy 2 new 42 pilots, but got some that were too small to screw in. They were Keihin N424-74C series pilots. Not good, but they were cheap. I just ordered the correct ones and if the problem continues, I will put one in. Thanks again.

Edited by ULEWZ

Share this post


Link to post
Share on other sites
I cleaned that pilot 4 times, but after reading your post, I put in another 42 pilot I had lying around, and it is 80% better. Not perfect, but doable, thanks. Oddly enough, I tried to buy 2 new 42 pilots, but got some that were too small to screw in. They were Keihin N424-74C series pilots. Not good, but they were cheap. I just ordered the correct ones and if the problem continues, I will put one in. Thanks again.

Great! Glad you got close to getting to the bottom of the problem. If the old 42 you had made it 80% better then you know what the main problem is. You might try the next size larger pilot and see if that get you closer to 100%. You are at least headed in the right direction. Good luck. RB

  • Like 1

Share this post


Link to post
Share on other sites

Holy crap, the bike it back to normal. I was wheelie-ing at will. I am very happy. The funny thing is, the bike is harder to ride with this much snap, but I wouldn't trade it for anything.

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  

×