Engine problem???


24 replies to this topic
  • andymanmoel

Posted February 23, 2008 - 12:48 PM

#1

Hello,
Just give my 05 WR 450 its post winter bush greasing, and installed a K+N filter. I already have the JD jet kit with 168 main and needle 3 from the top and it ran good. I was a bit concerned with the spark plug looking a bit sooty so I dropped the needle 1 notch and tried to run it. It started up good, ran for about 10 seconds then cut out, I started it again and there was a big backfire and it cut out again. Now I cant start it for love or money!!!! It was a bit hard to turn over after the backfire but now it turns freely.
There is no effort from the engine to start, it just turns over.
Any ideas????
Andrew

  • 2grimjim

Posted February 24, 2008 - 07:36 AM

#2

First of all, throw the K&N filter as far as you can and never use one again in your bike.

Pun in a NEW sparkplug.

Sometimes WR/YZ4xx owners experience the 'no compression syndrome' when trying to start their machine aftes it's been sitting for a a month or more. There's been a lot of discussion as to the culprit of this problem but in most cases it seems to be a transient phenomena associated with extended periods of storage. Add a small ammount of oil through the sparkplug hole before trying to start it again.

  • andymanmoel

Posted February 24, 2008 - 08:01 AM

#3

Tried the new plug and oil in the bore and still wont start! It seems ok on compression but it wont run!!!!
What is wrong with the K+N filter?
Andrew

  • 2grimjim

Posted February 24, 2008 - 08:42 AM

#4

A long shot here........... The '03 WR450's had issues with the woodruf key for the flywheel shearing (because of incorrect torque spec frpm the factory), BUT that was only an issue on the '03's. That's not to say that the bike you have has not done this. If at some time in the past someone had the flywheel off and it was not torqued properly, you may have sheared the key when it backfired hard (bump/push starting can cause this too).

Aside from this you need to go through the basics for the no-start:

How old is the fuel? If it is more than a month old drain it and replace it.

Make sure the fuel is getting to the carby. Take off the bowl plug and open the petcock......no fuel means a stuck needle/seat. You may have gummed fuel blocking the pilot circuit as well.

You are getting spark aren't you?

Unfortunately, compression isn't so easy to check on your machine. The automatic compression release will not allow accurate compression checks to be made (normally a compression of >90psi is needed to make a machine run).
Short of disabling the autocomp release you need to check the top end with a Leakdown tester.

If you have fuel, CORRECTLY TIMED spark, and compression it should run.

A while back I worked at a local M/C shop and had regular experiences with owners installing K&N filters on their 4 wheelers. They would bring in their machines for the same problem, no-start or hard-start. In every case where a maching had starting problems and a K&N filter the problem was the same....zero valve clearance on the intake valves. After scolding the customer for using a K&N air filter (and replacing it with a stock filter) and repairing their machine the starting problem never reappeared.

K&N's DO NOT FILTER THE AIR WORTH A DAMN! They will eventually pass enough dirt to tear up the valves.

  • dirtysouth

Posted February 24, 2008 - 11:07 AM

#5

A long shot here........... The '03 WR450's had issues with the woodruf key for the flywheel shearing (because of incorrect torque spec frpm the factory), BUT that was only an issue on the '03's. That's not to say that the bike you have has not done this. If at some time in the past someone had the flywheel off and it was not torqued properly, you may have sheared the key when it backfired hard (bump/push starting can cause this too).

Aside from this you need to go through the basics for the no-start:

How old is the fuel? If it is more than a month old drain it and replace it.

Make sure the fuel is getting to the carby. Take off the bowl plug and open the petcock......no fuel means a stuck needle/seat. You may have gummed fuel blocking the pilot circuit as well.



You are getting spark aren't you?

Unfortunately, compression isn't so easy to check on your machine. The automatic compression release will not allow accurate compression checks to be made (normally a compression of >90psi is needed to make a machine run).
Short of disabling the autocomp release you need to check the top end with a Leakdown tester.

If you have fuel, CORRECTLY TIMED spark, and compression it should run.

A while back I worked at a local M/C shop and had regular experiences with owners installing K&N filters on their 4 wheelers. They would bring in their machines for the same problem, no-start or hard-start. In every case where a maching had starting problems and a K&N filter the problem was the same....zero valve clearance on the intake valves. After scolding the customer for using a K&N air filter (and replacing it with a stock filter) and repairing their machine the starting problem never reappeared.

K&N's DO NOT FILTER THE AIR WORTH A DAMN! They will eventually pass enough dirt to tear up the valves.


No Woodruf on 05's....For the problem though...check to see that your intake boot (carb to head) is seated properly. Had the exact same issue with mine after doing all of my jetting. I didn't realize that there was a key/slot for the boot to mount to the intake runner which positions it and lets it slide down enough to seat. So after jetting and all I fired it up and off I went. Then in the woods I started having chugging issues then when I hit the road she just stalled out. Started and idled for a few then after a couple of wheel turns died never to start again. Went back to the truck and pulled the tank, checked the battery, fuel lines, wires, plug and put it all back together...still nothing..I was about to load it up and go to the house when I noticed that the carb and boot had slipped from the intake runner on the head. Put it back on (correctly) and never had trouble like that since.:smirk: Good luck dude.

  • andymanmoel

Posted February 25, 2008 - 12:47 PM

#6

Thanks for the replies!!!
I have put the stock needle back in, stock main and pilot, Checked the valves and they are ok. Checked the timing and they are ok, Fuel is 2 weeks old so ok there. I have a good spark. I am getting fuel to the carb and when I try to start it it will run for about 10 sec then cut out, kick it over about 20 times and it backfires, 2 more kicks and it runs again for another 10 seconds. It was running fine 2 weeks ago and I only changed the jetting due to getting the K+N on a friends recomendation. I have no idea now it is back standard why it wont run. Seems to be starving it of fuel yet the plug when removed is wet.
I am nearly ready to throw it in the river!
Help please!!!!!
Andrew

  • evilinsano

Posted February 25, 2008 - 07:19 PM

#7

When you say the valves are OK what did you check? Just the clearance? My WR400 will sometimes not hit that "hard spot" at TDC. I just replaced the cylinder and piston because it had a hole in the piston and only gotted it started once since the rebuild. I am worried about the lack of compression between some kicks. I am suspecting something with the valves but I am not sure. I am not sure if you are having a similar issue but I wonder if its worth taking the heads off and leak testing the head. Not sure why I didn't do it while it was off but I guess I never suspected anything with the head. I guess part of it was being cheap and just wanting to get it back together to ride.

  • matt4x4

Posted February 26, 2008 - 04:45 AM

#8

Ok, since all you did was remove the carb to change jets and the needle and this problem appeared, I have to say that your issue is a simple one, so take a step back and think about what could possibly be wrong here.

No, it's not valves since the machine ran fine right before the carb came out

No, it's not a hole in the piston since the machine ran fine before the carb came out.

Let's get back to simple basics here and look at the possibilities:

When the carb is installed in the bike, it sits upright, when the carb is removed from the bike, it can be in any position depending on how it's being held.

While the carb was in the bike, more than likely, there was dirt in the bowl - I haven't seen a single carb that didn't have some form of contamination in it after 1 year of running - since you had the carb out, it is highly likely that the dirt moved to another spot in the carb due to turning it every which way.

My suggestion here is to take the carb out, disassemble it COMPLETELY (meaning the accel. pump etc as well) and clean it with carb cleaner, blow out all passages with compressed air, reassemble it and reinstall it, I have a feeling it will run just fine after that.

Oh, BTW - backfire usually means it's lean - which equals too little fuel or too much air which can easily mean a clogged pilot circuit.

  • andymanmoel

Posted February 26, 2008 - 12:55 PM

#9

Just took your advice and done a total strip down and clean of the carb. Re installed and tried to run it, it started fine then stopped. Few more kicks and life again then stoped. No backfiring now but each time it seems to run a bit longer. Suspecting that there is a bit of carb cleaner still in there somewhere. It is 20:45 here in the UK and the missus wont let me keep running it now!
When I tried to start it after the carb re build I still had the K+N in and it would not run. Returned to standard set up and it fired straight away! K+N is destined for the bin!!!!!

  • Thebosss83

Posted February 26, 2008 - 01:21 PM

#10

I had a similar issue once when preparing to ride on a cold morning in the parking lot. I went to kick the bike and there was ZERO compression, put it this way, I could push the starter all the way down with my hands!!. All you could hear was a clicking sound as I turned the bike over. The bike had run fine the day before, oil level was fine, carb was fine, etc. I checked to see if it was the compression release valve (02 wr426) and that sounded like it was seating fine. I kicked it like 20 times, I did everything I could think of.... I pulled the seat/tank/plug kicked it w/ the plug out etc. Finally after holding up the rest of the crew for 15 minutes, I finally got compression and it started on the next kick?!?!

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  • matt4x4

Posted February 27, 2008 - 06:53 AM

#11

So when I recommended you tear it down, did you take EVERYTHING apart and blow compressed air through EVERY orifice? It looks like you are progressing with it, before yanking it out again, it may just have to be started a few times before your accel pump refills completely etc etc, so give it a couple of more tries, if it continues to die, take the carb out again and completely tear it down, use generous amounts of carb cleaner, let it sit inside the carb and it's orifices, it sometimes takes a bit to dissolve varnish completely, also take all the jets (minus rubber parts) and soak them in carb cleaner, then use an old toothbrush to clean inside the jets.

When blowing air through the orifices, do it in both directions to make sure anything that may be stuck is going to come out - if you do not have a compressor, get a can of compressed air from the computer store or office supply store - they don't do nearly as much, but better than nothing.

Also clean the hot start and choke while they're out.

  • bg10459

Posted February 27, 2008 - 07:13 AM

#12

Maybe a clogged gas tank vent?

  • andymanmoel

Posted February 27, 2008 - 10:28 AM

#13

Thought I had solved it but when I went to start it today it ran then backfired and cut out again. I have totally striped the carb to every last bolt and screw I could find, Blew compressed air through every hole I could find and it still wont run! Does anyone think it could be an electrical fault? It seems to just stop with a backfire then the compression in the engine is too great for the starter motor. I am really at my wits end with it now!!!!!

  • matt4x4

Posted February 27, 2008 - 11:49 AM

#14

What kind of Hot start do you have on the bike, a remote or the red knob on the carb - it sounds like a lean condition (the backfire) which can be caused by the hotstart sticking open.
Did you plug your TPS back in on the carb? Did you have the TPS off the carb originally? (TPS is the throttle position sensor located near the top, it's black, has wires coming off it).
Are all your breather hoses clear coming off the carb/case?

If it is electrical (which it may well be) the first thing I would do is to disconnect/reconnect every connector you can possibly find - sometimes it's just dust breaking a connection somewhere.

OH, BTW - Did you ever try a new sparkplug????
Mine died once, never to start again, i replaced the plug and all was well.
If you've got a crack in the plug it may still fire cold or give you spark during the test, but then the almost instant heat in the plug can cause it to misfire almost immediately.

  • dirtysouth

Posted February 27, 2008 - 01:05 PM

#15

What kind of Hot start do you have on the bike, a remote or the red knob on the carb - it sounds like a lean condition (the backfire) which can be caused by the hotstart sticking open.
Did you plug your TPS back in on the carb? Did you have the TPS off the carb originally? (TPS is the throttle position sensor located near the top, it's black, has wires coming off it).
Are all your breather hoses clear coming off the carb/case?

If it is electrical (which it may well be) the first thing I would do is to disconnect/reconnect every connector you can possibly find - sometimes it's just dust breaking a connection somewhere.

OH, BTW - Did you ever try a new sparkplug????
Mine died once, never to start again, i replaced the plug and all was well.
If you've got a crack in the plug it may still fire cold or give you spark during the test, but then the almost instant heat in the plug can cause it to misfire almost immediately.



After all that I have read I have to agree with the latter section of matt4x4's post. Be sure and check your gap on the plug too to be sure that it is within tolerance. We have dropped plugs before and closed the gap up enough to cause similar issues. You may wanna blast out the boot as well and dab the end of the plug with a touch of silicone...good luck. Also, to be a little redundant, make sure that the boot fits the intake runner as it should. Make sure that the tab on the intake runner slides into the slot on the boot.

  • andymanmoel

Posted February 28, 2008 - 09:35 AM

#16

Thanks for your replies!! I have had a ring round a few bike dealers today and they come up with the following:
1 Auto decompressor is sticking open
2 Stator is knackered!
What is your thoughts on this?

  • matt4x4

Posted February 28, 2008 - 11:38 AM

#17

I also read that yesterday that the same symptoms can be due to a bad stator, however, in the same sentence it was mentioned that it was a rare occurrence.

I don't have auto decomp on my bike, but it shouldn't be too hard to determine if the valve is sticking open.

  • andymanmoel

Posted February 29, 2008 - 12:31 PM

#18

First of all thanks to everyone!
After checking the timing, valve clearance, new petrol, new spark plug, checking all the wiring cleaning out the carb and checking the auto de compressor I have finally come to the conclusion that it is time to admit defeat and take it to the dealer! I will keep you informed of what they say!
Andrew

  • TRUE_2_YAMAHA_001

Posted March 02, 2008 - 09:29 PM

#19

Start back at square 1.
put the stock jet and needle back in it with a fresh plug and work from there.

I am running a 166 with a #2 needle on the middle setting and it is dynomite, but i have done some other stuff so it could be different in your bike.

  • andymanmoel

Posted March 03, 2008 - 11:57 AM

#20

Already done! Ihonestly think it is not a fuel issue! Will have to wait till wednesday till the dealer can have a look at it!!!




 
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