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Honda XR250R shut off at high speed

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Hey everyone,

New member and totally new rider in general here. I bought my first bike a month ago, a 1986 XR250R. The previous owner says that he had just rebuilt the top end, and to my knowledge he was telling the truth. The carb is very clean and set to spec, it starts in a kick or two, cold or hot. 

My problem began today. I had been riding out in the woods on easy slow terrain for the first few weeks on my bike, but today took it out on a road to get home quicker. I rode for a few miles at 50-55 mph, which is the fastest I'd taken the bike so far. When I entered a town I pulled in my clutch to shift down, accidentally still had the throttle engaged a bit so it revved loud and then shut off completely. I rolled the bike to a stop nearby and could not get it to start again. Tried to let it cool off, kicked through with decompression pulled and fuel off just in case. Couldn't get it to start. Had to get hauled home, which sucked. 

 

Does anyone have any ideas of what might be going on? I'm at a loss and pretty bummed. Just want to ride the bike. Thanks! 

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Do you still feel compression when kicking the engine over?

Would the engine cycle with the kickstarter immediately after it shut down? If so, you can probably assume it wasn't a seizure.

For troubleshooting sake, you have to assume that it shutting down from the over rev was a coincidence, as in, something else happened at the same time.

Check to see if you're getting spark.

Any wiring mods that's been done to it over the years that have to do with the ignition system?

Fuel starvation can cause it to die suddenly too. Like from a gas cap that isn't venting the tank properly. But after the bike sits awhile and the tank equalizes, the engine will restart.

Change the spark plug, to rule that out. Clean around the base of the plug good before you remove it.

Make sure the fuel level in the tank isn't below the main pick up. If it is, you need to set the petcock to the reserve position to get fuel to the carb.

Start there.

 

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On 9/11/2017 at 5:33 PM, Trailryder42 said:

Do you still feel compression when kicking the engine over?

Would the engine cycle with the kickstarter immediately after it shut down? If so, you can probably assume it wasn't a seizure.

For troubleshooting sake, you have to assume that it shutting down from the over rev was a coincidence, as in, something else happened at the same time.

Check to see if you're getting spark.

Any wiring mods that's been done to it over the years that have to do with the ignition system?

Fuel starvation can cause it to die suddenly too. Like from a gas cap that isn't venting the tank properly. But after the bike sits awhile and the tank equalizes, the engine will restart.

Change the spark plug, to rule that out. Clean around the base of the plug good before you remove it.

Make sure the fuel level in the tank isn't below the main pick up. If it is, you need to set the petcock to the reserve position to get fuel to the carb.

Start there.

 

Thanks for the great input! My friends had surmised that maybe I had a bad plug too. Unfortunately this bike didn't come with an 18 mm Honda tool to take the plug in and out, so I was only able to remove it with this generic tool I bought off of motosport... so now I'm forced to wait another couple days for the thinner Honda tool that will be able to fit properly to reinstall a spark plug..

i attached a pic of what the old plug looked like compared to a new one. The old was was still able to get a spark (but yellow)... does this spark mean that it may not have been the plug?

Also, as for your other suggestions, the gas tank was full, and the cap should be venting just fine to my knowledge. I'll let you know if the plug replacement does the trick, I'm really hoping it does! Thanks. 

IMG_2142.JPG

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your old plug looks toasted  if your getting a yellow or pink spark it indicates the spark is week. if the new plug shows the same colour spark not blue then id say the coil or some part of the ignition is faulty. a week spark can and will fail under compression.

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9 hours ago, vicxr400 said:

your old plug looks toasted  if your getting a yellow or pink spark it indicates the spark is week. if the new plug shows the same colour spark not blue then id say the coil or some part of the ignition is faulty. a week spark can and will fail under compression.

Thankfully the new spark plug is sparking blue when I test it. Is it possible that a bad spark plug actually could cause a bike to just shut off while riding? 

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if you have a close look at your old plug take note of the electrode coming out of the porcelain under the earth tang  its very badly worn and uneven.

the carbon build up can cause the spark to dissipate creating a break down. and that's only the external that you can see.

spark plugs are an under appreciated bit of kit and like most parts generally the more expensive the better quality. also a part that gets overlooked until it gives trouble

for the small cost of a new plug I suggest that it should be replaced at least twice a year depending on the time spent riding, fuel condition and the quality of the plug also every time you do a service ie. oil change air filter clean. take the plug out and give it a clean with a wire brush and a piece of piano wire to clean down around the electrode check the gap and a small amount of some heat proof anti seize on the thread. all part of general maintenance. there is a real good chance that that bad dirty plug is your problem I hope you get it sorted and the plug was your prob   cheap fix if it is. 

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8 hours ago, vicxr400 said:

if you have a close look at your old plug take note of the electrode coming out of the porcelain under the earth tang  its very badly worn and uneven.

the carbon build up can cause the spark to dissipate creating a break down. and that's only the external that you can see.

spark plugs are an under appreciated bit of kit and like most parts generally the more expensive the better quality. also a part that gets overlooked until it gives trouble

for the small cost of a new plug I suggest that it should be replaced at least twice a year depending on the time spent riding, fuel condition and the quality of the plug also every time you do a service ie. oil change air filter clean. take the plug out and give it a clean with a wire brush and a piece of piano wire to clean down around the electrode check the gap and a small amount of some heat proof anti seize on the thread. all part of general maintenance. there is a real good chance that that bad dirty plug is your problem I hope you get it sorted and the plug was your prob   cheap fix if it is. 

Well, after purchasing 2 different tools that were supposed to fit into this bike to remove and install a spark plug, I still haven't gotten one that fits. I did manage to install the new plug and screw it in to where it sits pretty firmly though.

 

The bike still does not want to start. It sputters to life for a second or two when I kick it, headlight comes on, and then it quickly dies. It's like it wants to start but just can't quite get rolling.. Does anyone have any recommendations as to what I should look at next? 

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did you pull the plug after trying to start to see if the plug was wet with fuel or dry??  almost sounds flooded if it is flooded the plug will be wet when you take it out after trying to start. tap the plug (electrode down) in the palm of your hand if you get fuel coming out of the plug its well and flooded.  excessive fuel can cause your symptoms if you find excessive fuel to be the problem check your engine oil to be sure the excess fuel hasn't contaminated your oil it will smell of fuel if it has.

have you checked the valve clearances?? also hows your compression? being cdi ignition when was the last time it was washed or dunked in water? could be dirty wiring connectors. have you been using the choke to try to start?

http://www.ebay.com.au/itm/Honda-XR600-XR200-XR250-spark-plug-wrench-tool-brand-new-honda-xr-models-/172762183855?epid=1230538715&hash=item28396db8af:g:OLgAAOSwbsBXmr3J

about the only plug spanner that will fit.

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Hi. Remove the pipe from

the fuel tap and check fuel is actually passing into the carb i got caught out by that one . 

 

Hope it helps 

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Finally got the bike running great again. I ended up taking it to a friend who's a technician and he was able to get it going. He pulled and cleaned the carb, couldn't find anything in particular that was wrong with it and put it back in. Once he put it back in it ran perfectly. He made sure the valves were adjusted properly and everything was set to spec. We think that I might have just done a less than perfect job putting it back in when I took it out myself. New plug definitely made a noticeable improvement in performance. Novice mistake :devil:.. Time to ride. Thanks for the great advice! 

Edited by BlackVault

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