VTR 250 Misfire

[BenG]

OK, on the way to work this morning my VTR developed a misifre above about 6000rpm.

If was fine, then suddenly she just wouldn't rev any more.

Has anyone had a similar problem? What should I be looking for?

Cheers.

[Cbr Junkie]

Does it rev fully through the rev range in neutral?

[BenG]

Didn't really have chance to check it... I pulled into the station and jumped on a train cos I was late for work and didn't fancy tackling the freeway traffic on a bike that wasn't running right... I'll check that tonight...

[shaynoinsano]

Check all the silly things 1'st..
When was the last time you put fuel in the big girl? Might have poor fuel in it, carbs might need a clean,
How's the battery?

[BenG]

Fuel has been in there for about a week, done 150km on it so far, so I doubt its that. Battery not sure, I'll need to test it. I've only had the bike a month so I'm not really sure about all that, but it was (supposedly) serviced a couple of months ago...

[Cbr Junkie]

Try reving it in neutral and let me know what happens

[filbert]

150kms could be just about ready to switch over to reserve depending how hard you ride or if you didn't fill the tank all the way up and if you left the choke on it would use more, i used to hit reserve at 170 on mine when it was full to the brim if i was highway riding but i'm also pretty heavy lol and i rode her hard.

[shaynoinsano]

Isn't that the only way to ride a 250?
Haha

[BenG]

Last time I filled her up at 130kms and she only took just over 4 litres... I've been doing a bit more highway riding this time around but I'd hope to get a bit more than that still because I haven't been flogging it... After work I'll try switching to reserve and see how she goes...

[Cbr Junkie]

Doubt the state of the fuel is going to go stopping you from reaching the end of the rev range if it combusts at low revs it will combust at high revs unless your ignition system is playing up!

[Cbr Junkie]

One way to check the ignition is to borrow a timing light run it off each spark plug lead and you should be able to see with the light on if the spark is breaking up at high revs!

[BenG]

Doubt the state of the fuel is going to go stopping you from reaching the end of the rev range if it combusts at low revs it will combust at high revs unless your ignition system is playing up!

Thats what I thought... It feels and sounds like an ignition problem, but I'll try any simple fix to see if it helps!

[BenG]

One way to check the ignition is to borrow a timing light run it off each spark plug lead and you should be able to see with the light on if the spark is breaking up at high revs!

I've got a timing light at home, I'll give that a go too...

[Thirsty]

Spark plugs?

[BenG]

Ok, update...

Rode her home, still doing the same thing... Seems to be load related as it revs easier in lower gears. In neutral she'll go all the way to the redline.

Every now and again whilst riding it would fire for a second or two, and then stop again... Seems to be on one cylinder most of the time above 5000rpm.

Switched to the reserve just in case it was that, no difference.

I won't have time for a proper play with her until Sunday, but in the meantime any more suggestions are welcome.

[Cbr Junkie]

If it fires all the way through the rev range then id say the fuel is fine i would be looking at the coil packs as they can break down under high load but also check leads and plugs, and you can check the leads with a timing light like i said.

Best way to load it up would be on a stand in top gear or the highest gear it will go in without stalling and rev from idle and watch for the spark to break up to find out which cylinder it is!

Ps, Also might pay to strap the bike down or have someone hold it while reving on a stand!

[Cbr Junkie]

So is it fixed?

[BenG]

Been busy all day today, gonna have a look tomorrow...

[BenG]

Bit of an update: Took each lead off in turn and started her up, with one she ran and revved, on the other she coughed and spluttered, so that narrows it down a bit... Timing light shows both leads have spark, so I'm thinking its plug at the minute... Just gotta hunt down a plug wrench I can actually get onto those plugs, as my current one won't...

[Huggy]

What fuel did u put in it? 91, 95 or 98?

i've found that with 91 i had a really sluggish feel, felt like it was only firing on one cyclinder, acceleration was severely reduced...

i thought i must have had a problem with ignition or whatever, but after a few tanks of 95 and 98 it came good.

sounds like you've narrowed it down tho