YZ 125 (alu frame) pipe to frame clearance

Just wondering how it's supposed to be. Mine is a 2015 with an HGS and in a really decent condition (no dents in the pipe so I guess it shouldn't be bent) but the frame to pipe clearance by the water pump is surprisingly low. The coolant hose running from the pump up to the radiator is practically squeezed in between. Still has a round shape but does not move freely. IMO, nothing should be pressed against the exhaust.

The cylinder to exhaust mating flange of the pipe (hope it's the right term) is coming towards the cylinder at an angle. The exhaust port centerline should in theory be aligned with the pipe opening centerline, but it isn't.
Mounts are not bent or anything though, I'm positive.

Is this normal? Or is my pipe bent? Can I fix it? Does it affect performance?

If the radiator hose is touching I'd be worried.
Usually my hidden bends are in the narrowest point of pipe right where it comes out of motor.

Sent from my SAMSUNG-SM-J320AZ using ThumperTalk mobile app

There is usually a fair amount of play in pipe mounting; at least there is on the YZ250.

Try loosening all the pipe & silencer mounts and wiggling things around, looking for the most relaxed & natural fit. Hopefully this will buy you a little clearance in those tight areas.

Good luck, and keep us updated with you find. :thumbsup:

Pipe could be bent, they are pretty soft. If it was crashed on a soft surface it could bend and not leave a dent. It can be wrestled with a long bar or pipe and manipulated pretty easily.

On my 2010 YZ125 with all OEM parts,

the water pump hose has a molded on rubber protective 'sleeve' of about 32mm in outer diameter where 

it passes next to the expansion chamber, mine barely touches it but doesn't bend the coolant line in any way.

 

Perhaps the HGS pipe has a larger diameter body than the stocker ?

Edited by mlatour
3 hours ago, CaptDan said:

There is usually a fair amount of play in pipe mounting; at least there is on the YZ250.

Try loosening all the pipe & silencer mounts and wiggling things around, looking for the most relaxed & natural fit. Hopefully this will buy you a little clearance in those tight areas.

Good luck, and keep us updated with you find. :thumbsup:

Thanks for your input!
Actually I only noticed it when doing a top end so I already tried that while fitting the pipe back on. No position makes it any better. 

 

1 hour ago, mlatour said:

On my 2010 YZ125 with all OEM parts,

the water pump hose has a molded on rubber protective 'sleeve' of about 32mm in outer diameter where 

it passes next to the expansion chamber, mine barely touches it but doesn't bend the coolant line in any way.

 

Perhaps the HGS pipe has a larger diameter body than the stocker ?

Yep, it's touching the sleeve. Can't tell the possible diameter difference since I don't have an OEM pipe to compare it to. It would seem to me like a completely unaccepteble design flaw if this is how it's supposed to be.

Pics coming up in a few mins.

This is how it looks like. Pretty squeezed if you ask me. Bad flange alignment too.

The hose is absolutely fine though, I inspected it thoroughly. It must have been like that for some time also, because it has more than 10 hours of ride time since last crash.

IMG_20170805_195444.jpg

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Edited by Narciss

If you loosen all the exhaust system mounting bolts & brackets (all the way to the silencer)

can the pipe be pushed on straight onto the cylinder's flange until it's flush all around ?

 

That's my usual procedure to ensure everything is aligned:

first mount the pipe flush on the flange, next install the springs, then tighten the mounting bolts afterwards.

Edited by mlatour
10 minutes ago, mlatour said:

If you loosen all the exhaust system mounting bolts & brackets (all the way to the silencer)

can the pipe be pushed on straight onto the cylinder's flange until it's flush all around ?

 

That's my usual procedure to ensure everything is aligned:

first mount the pipe flush on the flange, next install the springs, then tighten the mounting bolts afterwards.

It comes closer, but not much really.

You can bend it to fit how you want if need be.

1 hour ago, Kinger317 said:

You can bend it to fit how you want if need be.

Probably my best bet. Going to try tomorrow hopefully, will report. Thanks (y)

Probably my best bet. Going to try tomorrow hopefully, will report. Thanks (y)

Get a magic marker, Mark the head pipe where the gap is widest with the cylinder. Take pipe off, wedge/hold/clamp/get a heavy person to sit on the expansion chamber to hold it. Stick shovel handle or equivalent in header opening and pry in direction opposite the magic marker mark (looks like that would be down and left if you were sitting on bike with pipe on). Test fit, pry more, test fit etc.
12 hours ago, Kinger317 said:


Get a magic marker, Mark the head pipe where the gap is widest with the cylinder. Take pipe off, wedge/hold/clamp/get a heavy person to sit on the expansion chamber to hold it. Stick shovel handle or equivalent in header opening and pry in direction opposite the magic marker mark (looks like that would be down and left if you were sitting on bike with pipe on). Test fit, pry more, test fit etc.

Did it this morning and it went quite well. Didn't think the pipes are this soft. I bent it too much the second time so I had to go back.. just used a rubber hammer and gave the end flange a few firm taps in the desired direction. Still isn't perfect, so I'll have to add a tap or two the next time I remove the pipe. Until then.. thanks for all the help, awesome community! :D

Results and prying setup photos attached

Edit: I also marked the pipe at three convenient locations to measure my progress. Turned out really helpful.

The pipe on the photo is an older FMF Fatty, just for demonstration.

Edit2: Photo of current pipe to frame clearance added. No words needed.

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Edited by Narciss

Narciss, out of curiosity,

how different are the engine power characteristics with the HGS pipe versus the stocker ?

Edited by mlatour
19 minutes ago, mlatour said:

Narciss, out of curiosity,

how different are the engine power characteristics with the HGS pipe versus the stocker ?

Don't really have anything to compare it to as it came with the bike when I bought it. 

FMF pipes are readily available around here, but none of our top 125 guys really use them. All are running HGS. Seems to be the trend all around Europe.

My subjective experience vs the FMF fatty on an '02 YZ 125 is that the FMF has more torque down low and is a bit flatter on the very top. Mid is okay. On the other hand, HGS just pulls and pulls, there is no sudden surge of power, instead it's more gradual and more predictable I guess. Responsive as HECK with the VForce 3 reeds throughout the whole range. What really astonishes me is the over rev, not just the RPM, the power goes on forever. Could be more of a intermediate/pro skill pipe, I'd have it over FMF any day, nonetheless.

Thanks for the comparison, I'm running the stock exhaust on mine,

since this season I've finally started to wind up the RPMs like a 125 should be ridden and realizing the pipe's limitations on over rev but,

wouldn't want to trade away the very decent low-to-mid of the stocker for a few hundred more RPMs on top.

 

I'd wait until the stock pipe got damaged before replacing it but since I ride soft/sandy conditions there's not a single dent in it after countless tumbles,

plus I already have a 2nd stocker as a spare... my jetting is also well sorted out so hesitant to introduce a new variable.

After a bit of research on the web, comments found about the 05+ YZ125 HGS pipe either mention it's a mid-range pipe

or "delivers good power from the bottom all to way to the top with improved over rev". 

 

In the USA, Bud Racing pipe website states : 'Developped by Bud racing and made by HGS' ,

by the small thumbnail the pipe even has the two name brands stamped on it. 

 

 

Edited by mlatour

My best "solution" to a slightly

tweaked pipe is to leave it on the

bike, bolts slightly loose, and 

figure out the angles to give

it a good jolt. 

Find a big tree or something, 

and use Tie Downs wrapped 

around  the pipe in diferent area's ,

and ram it backwards into place

The pipe was on the bike when

it got bent, so its just reversing

the hit, and the tie downs dont

leave marks or dents

12 hours ago, mlatour said:

Thanks for the comparison, I'm running the stock exhaust on mine,

since this season I've finally started to wind up the RPMs like a 125 should be ridden and realizing the pipe's limitations on over rev but,

wouldn't want to trade away the very decent low-to-mid of the stocker for a few hundred more RPMs on top.

 

I'd wait until the stock pipe got damaged before replacing it but since I ride soft/sandy conditions there's not a single dent in it after countless tumbles,

plus I already have a 2nd stocker as a spare... my jetting is also well sorted out so hesitant to introduce a new variable.

Hey man, it's what suits YOU best. I'm 22 and 160 pounds, most people say just get a 250f and be done with it but since I'm at the very beginning in motocross, 125 power is plenty enough for me. Also, I like how it forces you to carry momentum through corners and thus drives your progress at a steeper rate.

So I guess whether you'd be better off with an aftermarket pipe or not is up to what you'd like your riding experience to be, compared to now. Or any point in the future, when you start considering upgrades as your skill improves.

If it's not enough anymore, a new pipe is the place to start. :)

Good job, surprising how easy they are to manipulate in that way. Dents are another story! I like your straps and pallet set up :-) looks better than a heavy person!

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