What's the purpose of a subframe?

JW381
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JW381
Edited Date/Time 2/13/2016 7:06am
My buddy is fixing up a beater 86 YZ125. I was over helping last night (drinking beer), and noticed it didn't have a subframe. Its kinda cool looking at the old bikes and comparing to new technology. It also has a shock midstroke booster connected to the rear brake pedal.

Was just curious what the advantage to a subframe is. Weight?
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RPM68
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RPM68 2/12/2016 11:09am
2/12/2016 11:09am
SO YOU DONT NEED A NEW FRAME WHEN YOU POGO STICK YOUR SHIT.
RoflCopter726 2/12/2016 11:10am
2/12/2016 11:10am
RPM68 wrote:
SO YOU DONT NEED A NEW FRAME WHEN YOU POGO STICK YOUR SHIT.
Have you been hanging out with Tyler lately?
Robgvx
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Robgvx 2/12/2016 11:12am
2/12/2016 11:12am
Easier access to the shock. Easier to replace if you bend it.
One Last Comeback 2/12/2016 11:13am
2/12/2016 11:13am
So you can remove the airbox and rear fender and access the shock etc. by taking off three bolts.
I always thought it was for speed of repairs.

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Olson
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Olson 2/12/2016 11:22am
2/12/2016 11:22am
It's for superman seat grabs.
Uncle Tony
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Uncle Tony 2/12/2016 11:22am
2/12/2016 11:22am
That wire connected to,the brake pedal is B.A.S.S. brake activated suspension system, when you apply the rear brake that softens the compression damping Yamaha offed it after 87, sub frames started coming into play in the early 80's only advantage was ease of maintaince but had the benefit of being replaced in a crash
RPM68
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RPM68 2/12/2016 11:29am
2/12/2016 11:29am
RPM68 wrote:
SO YOU DONT NEED A NEW FRAME WHEN YOU POGO STICK YOUR SHIT.
RoflCopter726 wrote:
Have you been hanging out with Tyler lately?
LOL I forgot to turn off the caps lock apparently...
GrapeApe
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GrapeApe 2/12/2016 11:31am
2/12/2016 11:31am
RPM68 wrote:
SO YOU DONT NEED A NEW FRAME WHEN YOU POGO STICK YOUR SHIT.
RoflCopter726 wrote:
Have you been hanging out with Tyler lately?
RPM68 wrote:
LOL I forgot to turn off the caps lock apparently...
It did seem odd to get so fired up at a rather innocuous question. Lol
Olson
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Olson 2/12/2016 11:32am
2/12/2016 11:32am
RPM68 wrote:
LOL I forgot to turn off the caps lock apparently...
Is it a Tixas thing?
disbanded
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disbanded 2/12/2016 11:33am
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It gives you more area to place air in the frame
Olson
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Olson 2/12/2016 11:35am
2/12/2016 11:35am
disbanded wrote:
It gives you more area to place air in the frame
Volume*
Tumblin
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Tumblin 2/12/2016 11:47am
2/12/2016 11:47am
Go ahead and pull that sub frame off and then go seat bounce your favorite step up.....you'll know.
RPM68
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RPM68 2/12/2016 11:56am
2/12/2016 11:56am
RPM68 wrote:
LOL I forgot to turn off the caps lock apparently...
Olson wrote:
Is it a Tixas thing?
I may or mat not have posted this during work hours...lol
Track and Trail 2/12/2016 1:14pm
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It allows almost endless underwater operation, but only if you have the nuclear version.
JW381
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JW381 2/12/2016 1:33pm
2/12/2016 1:33pm
Lol thanks for the varied replies.

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JW381
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JW381 2/12/2016 1:34pm
2/12/2016 1:34pm Edited Date/Time 2/12/2016 1:34pm
Uncle Tony wrote:
That wire connected to,the brake pedal is B.A.S.S. brake activated suspension system, when you apply the rear brake that softens the compression damping Yamaha offed it...
That wire connected to,the brake pedal is B.A.S.S. brake activated suspension system, when you apply the rear brake that softens the compression damping Yamaha offed it after 87, sub frames started coming into play in the early 80's only advantage was ease of maintaince but had the benefit of being replaced in a crash
Softens or stiffens? My buddy was under the impression it stiffened the midstroke.
ando
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ando 2/12/2016 1:39pm
2/12/2016 1:39pm
I assume you mean removable subframe, not just subframe? Every (?) bike has a subframe, it holds up the seat and rear fender.
Uncle Tony
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Uncle Tony 2/12/2016 1:39pm
2/12/2016 1:39pm
No it softens, the idea was when you approach a corner and apply the rear brake it softens to absorb braking bumps, most riders back in the day just disconnected it or you can just put a lot of slack to disable it
JW381
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JW381 2/12/2016 1:49pm
2/12/2016 1:49pm
ando wrote:
I assume you mean removable subframe, not just subframe? Every (?) bike has a subframe, it holds up the seat and rear fender.
Right, thanks. Good point.
JW381
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JW381 2/12/2016 1:50pm
2/12/2016 1:50pm
Uncle Tony wrote:
No it softens, the idea was when you approach a corner and apply the rear brake it softens to absorb braking bumps, most riders back in...
No it softens, the idea was when you approach a corner and apply the rear brake it softens to absorb braking bumps, most riders back in the day just disconnected it or you can just put a lot of slack to disable it
Got it, cool. Yeah this one was disconnected.

The guy he bought it off had also put a self tapping screw thru the powervalve arm inside the powervalve case to keep it open. Blink
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hillbilly 2/12/2016 1:55pm
2/12/2016 1:55pm
Uncle Tony wrote:
That wire connected to,the brake pedal is B.A.S.S. brake activated suspension system, when you apply the rear brake that softens the compression damping Yamaha offed it...
That wire connected to,the brake pedal is B.A.S.S. brake activated suspension system, when you apply the rear brake that softens the compression damping Yamaha offed it after 87, sub frames started coming into play in the early 80's only advantage was ease of maintaince but had the benefit of being replaced in a crash
JW381 wrote:
Softens or stiffens? My buddy was under the impression it stiffened the midstroke.
If it did anything . It opened the orifice at the resivor for the displaced oil from the shaft entering the shock body so it flowed easier.

I dont think they had adjustments on them then like now.

It was a gimmick,those shocks were junk,the bodies deformed with heat and wear was so bad the oil was full of aluminum just from roilling the bike out the truck bed.

I have a ohlins and white power that was on my 84 490
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GrapeApe 2/12/2016 1:56pm
2/12/2016 1:56pm Edited Date/Time 2/12/2016 1:57pm
Uncle Tony wrote:
No it softens, the idea was when you approach a corner and apply the rear brake it softens to absorb braking bumps, most riders back in...
No it softens, the idea was when you approach a corner and apply the rear brake it softens to absorb braking bumps, most riders back in the day just disconnected it or you can just put a lot of slack to disable it
JW381 wrote:
Got it, cool. Yeah this one was disconnected. The guy he bought it off had also put a self tapping screw thru the powervalve arm inside...
Got it, cool. Yeah this one was disconnected.

The guy he bought it off had also put a self tapping screw thru the powervalve arm inside the powervalve case to keep it open. Blink
Holy shit I bet that thing had powerband for days . . .
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Uncle Tony 2/12/2016 2:01pm
2/12/2016 2:01pm
hillbilly wrote:
If it did anything . It opened the orifice at the resivor for the displaced oil from the shaft entering the shock body so it flowed...
If it did anything . It opened the orifice at the resivor for the displaced oil from the shaft entering the shock body so it flowed easier.

I dont think they had adjustments on them then like now.

It was a gimmick,those shocks were junk,the bodies deformed with heat and wear was so bad the oil was full of aluminum just from roilling the bike out the truck bed.

I have a ohlins and white power that was on my 84 490
I raced yamahas back in the 80's the funny thing was when you got the wrench report it suggested you replace the shock with an ohlins (Yamaha did own ohlins at that time)
JW381
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JW381 2/12/2016 2:12pm
2/12/2016 2:12pm
Uncle Tony wrote:
That wire connected to,the brake pedal is B.A.S.S. brake activated suspension system, when you apply the rear brake that softens the compression damping Yamaha offed it...
That wire connected to,the brake pedal is B.A.S.S. brake activated suspension system, when you apply the rear brake that softens the compression damping Yamaha offed it after 87, sub frames started coming into play in the early 80's only advantage was ease of maintaince but had the benefit of being replaced in a crash
JW381 wrote:
Softens or stiffens? My buddy was under the impression it stiffened the midstroke.
hillbilly wrote:
If it did anything . It opened the orifice at the resivor for the displaced oil from the shaft entering the shock body so it flowed...
If it did anything . It opened the orifice at the resivor for the displaced oil from the shaft entering the shock body so it flowed easier.

I dont think they had adjustments on them then like now.

It was a gimmick,those shocks were junk,the bodies deformed with heat and wear was so bad the oil was full of aluminum just from roilling the bike out the truck bed.

I have a ohlins and white power that was on my 84 490
You sure know your shit before the moonshine starts flowing! My dad had an 82 and 83 490. He loved them, only rode them at the dunes. Wanted an 84 very badly.
JW381
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JW381 2/12/2016 2:13pm
2/12/2016 2:13pm
Uncle Tony wrote:
No it softens, the idea was when you approach a corner and apply the rear brake it softens to absorb braking bumps, most riders back in...
No it softens, the idea was when you approach a corner and apply the rear brake it softens to absorb braking bumps, most riders back in the day just disconnected it or you can just put a lot of slack to disable it
JW381 wrote:
Got it, cool. Yeah this one was disconnected. The guy he bought it off had also put a self tapping screw thru the powervalve arm inside...
Got it, cool. Yeah this one was disconnected.

The guy he bought it off had also put a self tapping screw thru the powervalve arm inside the powervalve case to keep it open. Blink
GrapeApe wrote:
Holy shit I bet that thing had powerband for days . . .
Yeah he said he just assumed that old 125s were completely gutless on bottom then ripped up top. Then he pulled the PV cover off lol
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Uncle Tony 2/12/2016 2:20pm
2/12/2016 2:20pm
That's funny with the screw in the power valve carting guys do that, the 82 and 83 were not that good the 84 was the best open bike that year, I have an 88 YZ490 that I still love to race in vintage races and sometimes the modern class then it's cool to jump on my 125 afterwards

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