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FMF Gnarly: Bent Head Pipe Fix

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I've got a 07' YZ250 that has an FMF Gnarly on it (its new to me) and I noticed that the previous owner must have taken a pretty good spill and on the U-bend on the left side of the bike, it looks like it has been pushed back a little. You can only tell when you look where the pipe meets the head.

Would it be possibly to get the bike/pipe hot and with a cheater bar and a block of wood, bend it back to somewhat straight?

Recommendations? :thumbsup:

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Fill it with water and freeze it. Several recommendations from other users on 4-stroke head pipes and have heard that it works on expansion chambers. Worth a shot. Don't cap or seal the pipe, the water will skin with ice and gently push the dent out. It might take a couple of passes to get it all of the way out.

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I heard about that but I'm so skeptical it would work, let us know how the freezing thing goes.

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Fill it with water and freeze it. Several recommendations from other users on 4-stroke head pipes and have heard that it works on expansion chambers. Worth a shot. Don't cap or seal the pipe, the water will skin with ice and gently push the dent out. It might take a couple of passes to get it all of the way out.

wow, never heard of this, does this really work? have u done it?

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I froze a hgs pipe off a TM250 a few years back, its bust a couple of welds & wrote off the pipe,

Options are limited for a gnarley, tough pipe to bend and straighten, lots of heat and get med-evil with it.. bang bang..

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To fix pipes, I choose heat over cold- fire over freezing. My method that has worked well has been to pressurize the pipe- plug and add air via a homemade plug/valve devise and add pressure- heat the dent and watch it come back out. Freezing seems to be less precise and manageable.

As for the OP, bent necks are tricky since you need to bend back the entire pipe- not just pop a dent. That said, I've done it with ok success for a friend- using heat, a vice, a come along, hammer and some luck/strength. Op may consider a donor pipe that has a destroyed mid section and swap/chop weld in a new neck.

When all else fails, might have to eBay another. I'd much rather fix dents than a bent neck on a pipe.

Best of luck!

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By the way- don't Over bend it- you need to keep a good seal at the head. This is tough to bent even heated because of the close multiple welds...

Edited by nch209
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I rather try the airpressure with heating method. I have to bend back my stock pipe too. Once I did it successfully I report back.

deff do this its quick and easy. some people use assetaline when they do this

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I have used the heat-air method serveral times, works great on dented or crushed pipes. If your pipe is slightly or mildly bent, your results may not be as good.

If you are getting a good seal on the exhaust port and there is no real kink I would leave it alone. Most likely there will be no gain on performance. A while ago dirt rider did a test on dented pipes with a dyno and the power differences were very minimal with small dents/bends.

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I've got a 07' YZ250 that has an FMF Gnarly on it (its new to me) and I noticed that the previous owner must have taken a pretty good spill and on the U-bend on the left side of the bike, it looks like it has been pushed back a little. You can only tell when you look where the pipe meets the head.

Would it be possibly to get the bike/pipe hot and with a cheater bar and a block of wood, bend it back to somewhat straight?

Recommendations? :thumbsup:

Yeh l think you got it right with the cheater bar/block of wood deal,air or freezing won't work on a neck bend

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Thats the method i used, worked well just make sure you pay attention to how it fits on the cylinder(equal gap all the way around) and do little tweaks at a time. i didn't have a vise so i just layed the pipe on the floor and stood on it while tweaking it

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I've straightened mine by clamping a chunck of solid stock in a vice, slide the pipe over the solid stock, and heat where you think its bent. Then pull it straight and be really careful not to bend too far. It's pretty easy to do just have to eye it up and be delicate. The air and heat method is also the best for dents. I popped a huge mid section dent in a matter of minutes. Also cant stress enough SAFETY WIRE! I use one of the little mapp/oxy torches from home depot. The O2 runs out pretty fast but it works really well.

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Also cant stress enough SAFETY WIRE! I use one of the little mapp/oxy torches from home depot. The O2 runs out pretty fast but it works really well.

What is the SAFETY WIRE in regards to? Are you using it for stainless welding/brazing?

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What is the SAFETY WIRE in regards to? Are you using it for stainless welding/brazing?

In reference to blowing out dents, its to keep the plugs from flying across the room or hit you or someone else

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In reference to blowing out dents, its to keep the plugs from flying across the room or hit you or someone else

across the room? I launched one over two houses. Never to be seen again. And i had it tied on. I guess the line wasn't strong enough...

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across the room? I launched one over two houses. Never to be seen again. And i had it tied on. I guess the line wasn't strong enough...

LOL, i've found around 30lbs of airpressure works good by the time i heated and removed the dent the pressure was almost 60lbs so if having a higher starting i can believe it. Atleast nobody got killed

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