Problems starting...

[Shelton48]

Hi,

I have a 2004 KX250F. I have owned it for about a year and a half. It does not like to start! The bike has always ran great. - (When and if you get it started.) It was always hard to start, and began loosing compression after about 6 months. I replaced the top end on it. Then I couldn't get it to start at all. I took it to the local shop (this was all last year) and they found that it had a bent valve. They replaced the valves, adjusted them to spec, and said it was good to go. (Should have known something was up, when I picked it up and it took about 10-12 kicks to start.) Anyway - I rode it last season and had to kick it 10-20 times everytime! (Cold, hot, choke, gas, no gas, hot start - doesn't seem to phase it.) I pulled it out of the garage to get ready for this season. It still does not want to start! So here is where I am at...

When I got it started - (25 or 30 kicks) it ran great like always!

Tore it down to check timing and valves - Timing was good, and valves were a little tight, so I shimmed them.

Still didn't start easily - (About 30 kicks) - But ran even better!

Not happy with how it starts - Tore the carb down. - Found that the jetting was not stock. I figure whoever owned it before had aftermarket exhaust, and put the stock back on to sell it. It had a 175 main with a 45 pilot. (Stock calls for a 178 main with a 40 pilot.) So... I put the jetting to stock. I replaced the main, pilot, and the jet needle clip. - WON'T START AT ALL!

Obviously not happy with that - I was told that a bigger pilot jet would help it start. I tore it down again and put in a 42 pilot jet - STILL WON'T START AT ALL!!!

That is where I am... sorry this post is so long, but the main thing I always read it that the person didn't give enough info!

Any help or ideas would be great!!! Thank you.

[the white stallion]

If you say your valves are in spec it could be your fuel screw. Close it all the way and reset it to 1 1/ 2 turns and try that working out to 2 1/2 turns.

[Shelton48]

Tried to adjust the fuel screw, and nothing yet. Thanks for your help. Any more suggestions?

[JamesG1019]

Any more suggestions?

Go to the KX250F forum "stickies" and look at the thread called "Jetting "201" Pro Circuit or Team Green by Pr1malR8gw"

[Shelton48]

Thanks once again... That took a while to read, and I feel like a jetting pro now (LoL). Still no luck though. It just won't start at all! I have changed the jetting 4 times now. I have also torn it down, and checked the timing and valves 2 more times TODAY. Thinking about selling it (LoL).

[kwalhood]

Shelton48 it sounds like we are in the same boat. I have a '06 KX250F that I put in the shop 2 weeks ago because I couldn't get it to start no matter how many kicks or how many times being pulled behind a 4-wheeler.My income tax check came in so I said the hell with it.So after I washed my hands of this problem the mechanic calls and says that he was going to replace the valves along with the crank bearings,seals,and a couple of other things than I should be good to go.All together $1100 I said go for it.This past friday he calls me and says the bike runs like a bat out of hell,excellent,top notch,but the only way he can start it is for someone to pull him.He said no matter what he can't kick start it for the life of him.Only if being pulled.When he told me this I kinda laughed and said yeah I know.That is why I brought the bike to you in the first place.Except he got one up on me by being able to pull start it when I couldn't.Anyways needless to say the bike is still in the shop and I'll let you know what it is if you don't find out first.One weird thing is when kicking it .It feels like it should have more compression,but the cylinder and rings are brand new.I would think that if it was a compression issue that if it did start then it would run like crap and not as good as the mechanic stated.

[pumasforpets]

Is there potential for there to be something wrong with the auto decomp mechanism?

Funny, but both guys having starting problems are from Texas. That makes me think it's an air/fuel issue.

[JamesG1019]

I had that same problem with my 05, (it would push start, but not kickstart), after spending like $250 the shop told me it had something to do with the kickstart. I remember him saying something about a "return" thingy had broken in there.

[the white stallion]

99Percent of the time hard starting or pull starts is a timing/valve issue. Not to insult anyone but most of the time if double trippled checked the timing is found to be off. Make sure you are using the right timing mark, cam lobes pointed away from each other and punch marks level across the head. The last part can be miss conceiving so you count your cam chain pins from left mark on exhaust cam gear to right mark on intake cam gear.You should have 28 cam chain pins from mark to mark. Lack of compression or to much normally indicates something is off. Now to throw in another eqaution one of the cam gears could of spun or the cam chain is so shot that it's throwing you off. If none of the above is found to be true....... Take the rag out of your airbox and turn the fuel on.This normally works as a last resort.lol

[Shelton48]

Shelton48 it sounds like we are in the same boat. I have a '06 KX250F that I put in the shop 2 weeks ago because I couldn't get it to start no matter how many kicks or how many times being pulled behind a 4-wheeler.My income tax check came in so I said the hell with it.So after I washed my hands of this problem the mechanic calls and says that he was going to replace the valves along with the crank bearings,seals,and a couple of other things than I should be good to go.All together $1100 I said go for it.This past friday he calls me and says the bike runs like a bat out of hell,excellent,top notch,but the only way he can start it is for someone to pull him.He said no matter what he can't kick start it for the life of him.Only if being pulled.When he told me this I kinda laughed and said yeah I know.That is why I brought the bike to you in the first place.Except he got one up on me by being able to pull start it when I couldn't.Anyways needless to say the bike is still in the shop and I'll let you know what it is if you don't find out first.One weird thing is when kicking it .It feels like it should have more compression,but the cylinder and rings are brand new.I would think that if it was a compression issue that if it did start then it would run like crap and not as good as the mechanic stated.

That is nuts! What shop is your bike at? LoL Please let me know if you find anything out. My bike also has a new top end, valves, etc. I added it up last night, and I have exactly 6 hrs on it from last year when I had the valves replaced. I wouldn't think anything else in the top end could be messed up so I am REALLY hoping for a carb problem still!

[Shelton48]

99Percent of the time hard starting or pull starts is a timing/valve issue. Not to insult anyone but most of the time if double trippled checked the timing is found to be off. Make sure you are using the right timing mark, cam lobes pointed away from each other and punch marks level across the head. The last part can be miss conceiving so you count your cam chain pins from left mark on exhaust cam gear to right mark on intake cam gear.You should have 28 cam chain pins from mark to mark. Lack of compression or to much normally indicates something is off. Now to throw in another eqaution one of the cam gears could of spun or the cam chain is so shot that it's throwing you off. If none of the above is found to be true....... Take the rag out of your airbox and turn the fuel on.This normally works as a last resort.lol

Dang it... I keep checking and checking and checking. LoL I really hope it is something that I overlooked! If not, something else is wrong. I have done the timing just like you are saying - which is just like the manual says. What do you mean by the cam gear could have spun? If you mean jump a tooth... it is still where it is soposed to be. If you mean something diff, let me know what to check for. Thanks again for the help! I'm going to go pull that rag out of the air box now...(Hehe)

[Shelton48]

Forgot one more thing... I will look up stuff about the auto decompression. I am not familiar with what you are talking about, but I'll see what I can figure out and check that it is not the problem. Thanks.

[pumasforpets]

Forgot one more thing... I will look up stuff about the auto decompression. I am not familiar with what you are talking about, but I'll see what I can figure out and check that it is not the problem. Thanks.

On starting, the auto decomp is held toward the center of the cam by a spring. This changes the valve timing so that the head is decompressed at TDC to allow for easier starting (recall that before decompression mechanisms were developed, one had to bump the engine past TDC in order to start it without being thrown over the handlebars). This is why a 4 stroke starts easier with a slow, smooth kick. I can actually start my bike by hand. When the engine starts, the cam spins faster and throws the decomp outwards which brings the timing back to normal.

If for some reason your auto decomp was seized in the inward position, you would never get proper compression. Even the other poster who said his only bump starts might have a sticking decomp that will only swing out with higher than normal rotation.

Just a thought. I could be completely wrong

[kwalhood]

Shelton48 please forgive me if it sounds like I'm trying to take over your thread,but since there is a lot of useful input coming up on this subject I wanted to give a little more info. about my problem and see what other info. will come up in hopes of pinpointing the problem.

A couple of weeks before this problem I was riding at the track and was in like 3rd or 4th gear when all of a sudden my bike started bogging down as if it was running out of gas.When I would shift down each gear and give it some gas it would start to pick back up and then start to bog again.When I got to 1st gear it ran OK for 10 sec. or so and then it just died as if it ran out of gas.I torn it down 2-3 times checked,double checked and triple checked everything.Still no start.So this is where I am today with the mechanic even scratching his head.When I had it down I did check the auto decomp.and it did feel as if there was no more resistance other than that of the spring.I gotta steer away from it being an air/fuel problem due to the fact that it ran fine before it died.I went through the carb.and cleaned it.No jets appeared to be clogged,but cleaned them since I already had it apart.Any other possible solutions?

[pumasforpets]

I'm no mechanic, but I do have alot of experience troubleshooting. So forgive the stupid questions, but it might help eliminate potential issues.

When you take the fuel hose off the carb and open the petcock, does fuel pour out at the rate you would expect?

With the fuel open and the hose on the carb, when you lay the bike over on its side, does fuel poor out the overflow hoses under the bike?

Have you ensured a secure connection between the air to carb and carb to engine boots?

Have you completely eliminated the possibility of an obstruction in the air box? (for instance you took the carb off for a while and a rodent built a nest in the boot between the filter and carb...it happens)

Have you checked the float bowl pin for corrosion? My buddy's bike wouldn't start last season and we found that the pin on the float bowl that slides had corrosion on it and wouldn't allow the float to move properly. Used some WD40 and a rough cloth to fix it. http://aventura.bloguedesporto.com/11881/Preparacao-Carburador-KEIHIN-FCR/ scroll down the page to picture 12 to see the pin I'm talking about.

Is your cam chain tensioner set up and torqued correctly?

Is there anything obstructing airflow into the air box such as the inlets on the side of the bike being plugged or otherwise covered?

Is the head gasket/exhaust gasket in good shape?

Are you getting good spark?

Is your hot start in good shape? If the O-rings are in poor shape, it may be letting too much air into the carb.

That's all I got for now

[jtaps]

This is just a suggestion, maybe get another cdi box ( the black box by the steering column) and swap it out. Know anyone with the same bike, you could just borrow it. That would rule that out...

[kwalhood]

O.K. found out what the problem was.The mechanic told me that there was too much of a gap between the flywheel and the pick up.He said that he adjusted it and it fired up on the first kick!I don't understand how it moved but at least it is finally fixed .Thank you everyone for your input and Shelton48 I wish you the best of luck in fixing your bike.

[the white stallion]

This is a good thread on starting problems other than timing.

https://www.thumpertalk.com/forum/showthread.php?t=872960

[Shelton48]

LOOKS LIKE A GOOD DAY FOR EVERYONE! Congrats kwalhood - I am happy for you. So it has been rainy here in Texas, and I let the bike sit for a few days. This morning before work I decided to take a look at it. Very frustrated - I decided to push start it to see what would happen. (I don't like to push start because it seems like if it won't kick start that something is wrong.) After about 6 pushes it started - and ran like crap. I went ahead and putted around the yard for a sec. I pulled over to mess with the idol and it died! Now here is the best part...... It started right back up (by kicking)! I putted around for a min. and all of a sudden it seemed to kind of clear out and sound better. After a few blips of the throttle it was back to its old self - running great! I HAVE NO IDEA WHAT WAS WRONG! My dad who works on cars not bikes, said the only thing he could think of was a major air bubble or bug in the carb that worked itself out. Too weird. I truly don't know what the problem was! After playing with it - (starting it hot, cold, warm, etc.) it still seems touchy. It sometimes started within 3-4 kicks and sometimes within 9-10. Even a few 15-20's in there. The first race of the season is this weekend and I am so excited that it runs, I am going to quit tuning it for now. After the weekend I hope to make it start easier, but I am just excited that I really think it is a carb problem and not something too serious.

THANKS FOR EVERYONE'S ADVICE, CONCERN, AND HELP!!! This website is great. And even though I don't feel that this solved anything or made any sense at all - I feel a lot smarter about everything discussed above.

THANKS AGAIN!

[D-K]

You guys do not mention if there is dirt or not in the float bowl, maybe time to start filtering the fuel?

Another thing is all the hoses coming out of the carb, they need to be clean. Mud in the end of them can cause issues.

Once (after winter storage) my buddys old -07 didn´t run any good, it was hard to start, it ran rough and backfired and so on. The carb had been dry all winter, and it was stored indoors in room temp.

When it had run for a couple of minutes it just went away like a miracle.

My guess is something was dancing around in the carb, maybe a spec of dirt in the needle float or something. It was really strange, it went from running pisspoor to great in 2 seconds...

There is a new beer out, I´m gonna have another one and ponder over life and KXF problems this friday night: