Jump to content
Sign in to follow this  

2007 kx250f *New* *Need help!*

Recommended Posts

Okay I am new to TT and I just bought a 2007 kx250f it does not run and backfires really bad when trying to start. The guy I bought it from said he got it to start but it ran for about 10secs popping and back firing really bad. He said he cleaned the carb and it was no better. If anyone has any idea or questions please replay. :lol:

Thanks.

Share this post


Link to post
Share on other sites

Sounds like an air leak.

Make sure the exhaust header pipe seals properly against the cylinder head. There is a copper crush gasket between them that might need tightening/replacement.

Check that the hotstart closes completely.

If that does not help, remove valve cover and check timing.

Share this post


Link to post
Share on other sites

okay I will check the exahst and I have pulled the head off and I believe it is lined up TDC I think the value need to be shimmed? any advise? or responses

Share this post


Link to post
Share on other sites

Thinking about it is not enough. You must measure the valve clearance with feeler gauges.

Share this post


Link to post
Share on other sites
okay I will check the exahst and I have pulled the head off and I believe it is lined up TDC I think the value need to be shimmed? any advise? or responses

I think you mean the valve cover. If you removed the head you went too far. If you are looking at the cam timing as an issue you need to be 100% sure it is correct. I believe you need a repair manual to show proper pictures of this as I don't think the owners manual will show it.

To check the valve clearance you will need feeler gauges in the range of .001 to .010 thousands of an inch. Your problem is most likely the hot start or the valves. The hot start is a common problem with the carbed bikes. To check it: pull the lever, if it does not move at least a quarter inch toward the bars or moves toward the bars and does not return you found your problem. Fixing it is a bigger problem. Let us know if you need help.

Share this post


Link to post
Share on other sites

Now, I know that I may catch flack and probably make you feel like I am an ass.. I am an ass how ever I'm not trying to disrpect you.. How ever there is a search button on this forum and there is a sticky post with linked threads on how to check valves on the top of this forum..

See the thing is if you don't know what you're doing and have to ask on this forum what you should do then you probably should not have bought a bike that doesn't run.. It's one of those things.. I can understand more that if you bought the bike new and it's now not running and seaking advice.. but buying a bike that isn't running when you don't know how why howlong ect the issue was going makes it hard to diagnose the issue.. that and not even knowing the basic checks just seems senseless to me.. You may end up spending alot more to just get it running not to mention countless hours of work. when you could have just spent a little more and got a running bike..

It might be worth your effort on either A. taking the bike to a dealer ship and paying to get it running.. or B. if you know someone who knows what they are doing with these bikes and taking it to them to see if they can help you or just figure out whats wrong with the bike and going from there..

Like I said I'm not trying to disrespect you. I'm just trying to point out the obvios.. Good luck I hope you get it running and it's a simple fix..

So..

1. make sure the cam timing is correct.

2. check valve clearance.

3. make sure there is no major air leaks either by a degraded air boots, or stuck hot start

4. make sure the fuel screw is still in the carb [i've seen them fall out before]

5. clogged pilot jet [might want to check first or better to just replace this first since its the easiest to do]

6. check the ignition coil stick for cracks or full on break

7. bad gas? replace gas with fresh new gas

8. clogged broken exhaust [the packing screen will break and the packing can clog the exhaust to the point it no longer can run]

To that if you feel I'm and ass.. The truth is I am.. how ever I am sorry but I am what I am..

Share this post


Link to post
Share on other sites

Primal is right.

But here is a pic of the cam timing anyway.

kxfcamtiming.jpg

Share this post


Link to post
Share on other sites

I have checked to make sure the dot marks are even with the case like in the picture above. Thank you I am not a complete idiot to Primal. I have rebuild and worked on 2 stokes and this is my first time working on a 4 stroke. I am positive it is TDC. I have already used a filler gauge and and measured the valve clearance and the intakes are .011 in. and ex. are .009in. I have researched before coming to post here and I was jw if anyone on here could give some advise sorry if seem like an idiot. I do not have a maually but have used the link at the top for specs on the clearances.

Share this post


Link to post
Share on other sites

I also thought that it could have been a carb. problem so I will take that off clean it and check the jets. I also noticed when you pull the throttle the return is slow like kx450f63 mentioned I really appreciate the help guys.

Share this post


Link to post
Share on other sites

for the throttle u can take off the boot, unscrew the 2 screws and take off the throttle cables. take off the throttle and clean the inside of the tube and bars and lube your cables and when you put it back on make sure the throttle isnt all the way against the bars so it isnt bound up against the bars when it turns. and id clean your jets and drain the gas. fresh gas and check your boot and clean or get a new air filter.

Share this post


Link to post
Share on other sites

i dont know if the 07's do it but the 04-05's have a problem where the cam gear slips on the cam as it is only pressed on.... when the dots on the cam gears are lined up with the head where are the lobes? even post a pic.... there is a hole in the gear and a hole in both lobes that should all line up when you sight down them... just another thing to try :lol:

Share this post


Link to post
Share on other sites
i dont know if the 07's do it but the 04-05's have a problem where the cam gear slips on the cam as it is only pressed on.... when the dots on the cam gears are lined up with the head where are the lobes? even post a pic.... there is a hole in the gear and a hole in both lobes that should all line up when you sight down them... just another thing to try :lol:

The cam lobes face away from one another the way there are suppose to when you are at TDC. I have followed this guide http://www.kxriders.com/forums/index.php?action=dlattach;topic=4819.0;attach=4174 The exhaust valve were to spec at .009in. but the intakes were way off. So I took both cams out and removed the intake tappets and shims and they were very oddly worn. Well put it this way when I went to mic. them I could not get an accurate reading. I could post a pic if anyone would like to see.

Share this post


Link to post
Share on other sites
The cam lobes face away from one another the way there are suppose to when you are at TDC. I have followed this guide http://www.kxriders.com/forums/index.php?action=dlattach;topic=4819.0;attach=4174 The exhaust valve were to spec at .009in. but the intakes were way off. So I took both cams out and removed the intake tappets and shims and they were very oddly worn. Well put it this way when I went to mic. them I could not get an accurate reading. I could post a pic if anyone would like to see.

pics help

Share this post


Link to post
Share on other sites
have you replaced your old pilot with a new, shiny 42?

I cleaned my carb out and the pilot jet looked nice and shiny. I will unload a pic of those shims tonight.

Share this post


Link to post
Share on other sites
I cleaned my carb out and the pilot jet looked nice and shiny. I will unload a pic of those shims tonight.

Well, thanks for not exactly going off on my response. as I was trying to say I'm not trying to disrespect you..

how ever the outside of the pilot jet doesn't matter its the inside.. and cleaning it out with just contact cleaner ect wont fix it.. if it has buildup.. Since they are 5 bucks as most it's worth just replacing it..

Share this post


Link to post
Share on other sites

This seems like an easy fix to me, and he could learn a lot from it, just keep updating us with new information as you do the checklist.

Share this post


Link to post
Share on other sites
Well, thanks for not exactly going off on my response. as I was trying to say I'm not trying to disrespect you..

how ever the outside of the pilot jet doesn't matter its the inside.. and cleaning it out with just contact cleaner ect wont fix it.. if it has buildup.. Since they are 5 bucks as most it's worth just replacing it..

I took the carb apart and blew it out with the compresser. So there is no build up now. I am in the process of ordering the correct shims and when they come in I will put it all back together and yet yall know how it goes. i appreiate all the help and advice guys! :lol:

Share this post


Link to post
Share on other sites
I took the carb apart and blew it out with the compresser. So there is no build up now. I am in the process of ordering the correct shims and when they come in I will put it all back together and yet yall know how it goes. i appreiate all the help and advice guys! :lol:

I don't think you're understanding what we are saying....

The pilot jets have a tendency to build up a layer of tarnish you can not blow it out.. it needs to be reamed out..

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  

×