2006 WR450F blown silcener apart

[hthomson1]

I have a 2005/2006 WR450f which I have owned from new. In total the bike has only covered just over 2000km.

I originally used the bike for enduro's which resulted in the usual abuse and when I identified that a hole had been blown in the side of the silencer, I did't think much about it. Recently I decided to convert the bike to supermoto and as part of the conversion I had a new full system fitted as well as rejetted and dyno'd.

I just recevieved the bike back today and took it for a run for about 30 mins. Half way through the run the exhaust became very loud and on returning home I found that the silencer had been blown apart.

Has anyone come across a similar problem as I'm at a loss as to the cause.

[n16ht5]

seen an 09 YZ450F do that.. otherwise no. too much backpressure is usually the cause.

[MANIAC998]

Pics? Without seeing the damage, I'm thinking that the silencer needed a re-packing job. The seismic waves traveling thru the exhaust have a lot of energy, and will destroy anything in it's path if the silencer packing doesn't dampen the wave's amplitude. But that's just my guess without seeing some pics.

Maniac

[new2it400]

MANIAC KNOWS HIS SHIT MATE TRUST ME!!!!

Edited June 17, 2012 by new2it400

[hthomson]

The exhaust was brand new and had just been dyno'd so I think its unlikely it was an issue with the packing

[Rocky739]

Yea, maybe some language difference but to us blown apart means the exuast is in tiny bits and needs to be swept up, thrown away and replaced, and a hole would indicate the tire... had been rubbing for a very long time and again ready to be chucked out with the empty beer cans.. If you simply mean its loud from the packing inside being shot then you simply need to re-pack (I recommend silent sport brand) with fresh packing.. Fiberglass OE packing lasts about five minutes so new doesn't mean anything..

[hthomson1]

How strange... blown apart means the same to me.. hence the reason why I used the term!!

Please refrain from replying unless you have previous experience of this type of problem happening to a WR450. With the greatest of respect I'm not interested in hearing from people who think the tyre has been rubbing or the exhaust is a bit loud...

[Mtn-Track]

If you do a lot of deceleration against the engine and load up the pipe & muffler with unburned fuel, then it can light-off in the pipe and/or muffler. I've seen that blow a muffler apart before and even split a head pipe...

On my '08 450 I made the mistake of heading out for a ride with the cold-start botton pulled and in less than a minute the extra fuel in the pipe got it poping and so hot (almost transparent hot) it melted my airbox all over everything. If it had started to pop real hard then it could have easily blown the exhaust system apart.

Edited June 18, 2012 by Mtn-Track

[MaxPower]

How strange... blown apart means the same to me.. hence the reason why I used the term!!

Please refrain from replying unless you have previous experience of this type of problem happening to a WR450. With the greatest of respect I'm not interested in hearing from people who think the tyre has been rubbing or the exhaust is a bit loud...

Since you seem to be the only person to ever "Blow their silencer" I can only assume it never happened and you would like to feel important by creating something that happened to you to gain attention or it really did happen but only because you replacked your silencer with the insides of a old Citroen back seat.

Or maybe you did everything correctly but rode your WR around at 14,000 rpm in first gear and caused your problem.

Perhaps you can show a little patients for members here trying to help you with your problem. I have read many intelligent post by Maniac however I have yet to read one from you. So until we can catch up to your level of brilliance it would be very much appreciated if you can not lay the smack down on the minions here wanting to assist you with your issues.

[hthomson1]

To MaxPower, please refrain from commenting within this topic I do not have the time or patience to deal with people who have to much time on their hands and obviously does not have the knowledge or experience to add value to the discussion.

Mtn - Track

Many thanks for your response.. at last someone with some valuable information.

I believe you are accurately describing the problem I encountered as there was a signifcant amount of popping taking place as I was going down a very large hill with the throttle fully closed and as such I can only conclude that the detonations resulted in the exhaust evetually blowing up.

As you indicate in your case the problem was due to you running the bike with the cold start opened and this was'nt the case in my circumstance, do you think the problem maybe due to my bike running lean and as such I should be looking at the jetting or an air leak in the carb or exhaust header?

I realise you cannot provide a definitive answer, however, I would appreciate your insight.

[miweber929]

I have nothing to add but couldn't refrain from commenting on this thread.

Enjoy reading my response.

[DrFeelGood]

Really?!? You have a total of three posts here and you think that being rude is going to help your cause.

I'll bet google searches REALLY piss you off. "What?!?! 345,234,221 results returned?!?! &%$#@!! I do not have the time or patience to deal with your pathetic answers!!"

I do have some valuable insight but I'll refrain from posting it as I might be scolded if he doesn't like the answer.

Edited June 19, 2012 by DrFeelGood

[Mtn-Track]

I believe you are accurately describing the problem I encountered as there was a signifcant amount of popping taking place as I was going down a very large hill with the throttle fully closed and as such I can only conclude that the detonations resulted in the exhaust evetually blowing up.

As you indicate in your case the problem was due to you running the bike with the cold start opened and this was'nt the case in my circumstance, do you think the problem maybe due to my bike running lean and as such I should be looking at the jetting or an air leak in the carb or exhaust header?

I realise you cannot provide a definitive answer, however, I would appreciate your insight.

I think it's a 'rich' condition that's causing it by coasting against the engine with the throttle closed. Open the throttle and that adds enough oxygen to possibly cause detonation of the rich mixture in the pipe/muffler. My issue was an example of how the process can be accelerated, not a sugestion that you ran with the cold-start pulled. I think I have the leanest main jet in a WR450 with a 152, so I doubt it's a lean issue. That being said, too lean under power can burn-out an exhaust system, but blowing one apart I would think is 'rich' detonation...

[YAMAHASAVAGE]

Sounds like a bad Flux Capacitor.

[allterra]

I have had and seen baffles, mufflers, silencers and spark arresters blown off, out, split, punctured and melted.

You have not given near enough information. I.E. What kind of "new full exhaust". You "dyno'd" it Did they not check your flow and gasses to tell you if you had it set lean or rich @ given rpms?. If so than that would be important info. Where the "silencer had been blown apart" and in what manor? Is it internal or external on a seam, near a screw or mount? Are there any other deformations? What rpms were you at when it happened? Was it a sudden change in volume/pitch or was it gradual? These are just a few of the question that come to mind at the moment.

[hthomson1]

OK, it has taken a long time to make progress, however, the following is a brief update.

The exhaust was a DEP S7.

Carb settings were Pilot 45, Starter 65, Main 165, ODBEK S setting 3.

The exhaust had a hole in the side 10cm wide and 30cm long. It was returned to DEP and they concluded they had never seen such damage and identified the problem as the bike running exceptionally lean.

First problem I identified was the valves were tight which I addressed, however, although the bike was running better it was still backfiring which in turn was resolved by increasing the pilot to 48.

Bike was now starting better but running rough from 1/4 throttle. Lots of playing about with needles and jets before finally arriving at the following jetting

Pilot 50, starter 65, main 170, PAJ 100, no change to needle.

Bike and the response was very much improved, however, still bogging down and backfiring after it had been run for 20 - 30 mins on the road.

I have now stripped the exhaust and sealed the gasget at the head and also at the silencer. I'll see if this addresses the problem. If not it may be the carb o-ring seal next on the list.

I have also ordered a JD it to see it that eliminates the remaining problems.

It been a long and frustrating road, however, it's moving in the right direction.

Will provide another update when I have it running faultlessly.

[DrFeelGood]

If not it may be the carb o-ring seal next on the list.

While the bike is running, squirt some carb cleaner ( or anything flammable) around the carb seal to the head and listen for a change in rpm. If it changes, you've got a leak.

[hthomson1]

Good tip, I will try that today.

I took the bikefor a 30 minute run last night and there was a significant improvment to the point where I would have said the problems were fixed, all up until the last stretch of road which is a couple of miles long when I opened the bike up a bit and all of a sudden the misfire was back, also exhaust tone changes and the bike sounds louder.

My gut feeling is I have an air leak at the manifold and today I'm going to place a few washers on the exhaust manifold bolts as it may be the case that the bolts are hitting the bottom of their threads before the gasget is fully compressed.

worth a try...