1980 yz125g head vs 1980 it175g head

gavan
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Can anyone advise the difference between 1980 yz125g head vs 1980 it175g heads.

If it will fit then i think i can reshape if need be. 

It looks like the same and have asked questions around, if you have a 1980 it175 head or cylinder perhaps you can measure it up and I can compare to my 1980yz125 measurements.

 

Hope to hear back soon as i have a head for sale that I am looking at:-)

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mxrose3
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10/15/2024 7:06pm Edited Date/Time 10/15/2024 7:15pm

it may look the same and have the same head bolt pattern, but the diameter of the combustion chamber is 66mm on the IT175, vs 56mm on the YZ125G.   I believe the dome is larger on the IT as well.   The IT175G was basically a bored out YZ125 by 10mm.   It shared the same crank stroke of 50mm though.

Head gasket is wider too.   I wouldn't do it, unless you know a welder and a machinist who could fill the space with weld, and machine it to the right width / specs / dome shape.

Also, this topic should be in 'Old School Moto'.    Good luck.

gavan
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10/15/2024 10:24pm

Thanks for the detailed info, i will let it go :-)

Still looking for DG head and performance pipe options, even considering modifying one of my later model pipes to try and see how they go from measurements they are very close but slightly larger diameter and gradually increase in diam instead of const on header so maybe be good.

gavan
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10/16/2024 4:29am

Pity those parts arnt readily available these days

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The Shop

GrapeApe
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10/16/2024 4:37am Edited Date/Time 10/16/2024 4:38am

Looks like a different bolt pattern (YZ on top)

YZIT 0.png?VersionId=tGJ8RqNyd1WDMqBq0KFW5rj
PTshox
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10/16/2024 7:52am

Call Harry Klemm. He will know what to do.... Pretty sure he worked at DG. 

 

928-763-7600

Email: Groupklemm@aol.com

4597 Calle Del Media Ft. Mohave, AZ. 86426

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mxrose3
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10/16/2024 9:02am
GrapeApe wrote:
Looks like a different bolt pattern (YZ on top)

Looks like a different bolt pattern (YZ on top)

YZIT 0.png?VersionId=tGJ8RqNyd1WDMqBq0KFW5rj

The top one in your pic is a 1979 125 head.   They changed to the 5 bolt pattern in 1980.

GrapeApe
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10/16/2024 9:16am
GrapeApe wrote:
Looks like a different bolt pattern (YZ on top)

Looks like a different bolt pattern (YZ on top)

YZIT 0.png?VersionId=tGJ8RqNyd1WDMqBq0KFW5rj
mxrose3 wrote:

The top one in your pic is a 1979 125 head.   They changed to the 5 bolt pattern in 1980.

Sorry you're right, the "YZ125g" diagram I was looking at was actually labeled "YZ125e-f" in the corner.

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mxrose3
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10/16/2024 9:20am
GrapeApe wrote:
Looks like a different bolt pattern (YZ on top)

Looks like a different bolt pattern (YZ on top)

YZIT 0.png?VersionId=tGJ8RqNyd1WDMqBq0KFW5rj
mxrose3 wrote:

The top one in your pic is a 1979 125 head.   They changed to the 5 bolt pattern in 1980.

GrapeApe wrote:

Sorry you're right, the "YZ125g" diagram I was looking at was actually labeled "YZ125e-f" in the corner.

all good.   Thats a time when bikes were changing at a blistering pace! :-)

1
gavan
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10/16/2024 3:43pm
PTshox wrote:

Call Harry Klemm. He will know what to do.... Pretty sure he worked at DG. 

 

928-763-7600

Email: Groupklemm@aol.com

4597 Calle Del Media Ft. Mohave, AZ. 86426

Thanks for the tip, i will contact him.

TDC
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10/16/2024 6:23pm

175cc, the sweet spot for keeping 125 flick-ability. 200's have a heavier feel. From what I've read, that is.

If you want more power than bling affect, adapt the air boots for a STIC Super X 38mm PWK carb. These are small bore magic. Provides big-bore low end with its improved sensitivity to the weaker vacuum signal at low RPM and extended top end peak hp. It will easily be quicker and pull an IT 250. My 200SX out pulled a fresh rebuilt '98 KX250 and the owner confirmed it with a few laps on the 2hun at the track.

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10/16/2024 6:34pm
TDC wrote:
175cc, the sweet spot for keeping 125 flick-ability. 200's have a heavier feel. From what I've read, that is.If you want more power than bling affect...

175cc, the sweet spot for keeping 125 flick-ability. 200's have a heavier feel. From what I've read, that is.

If you want more power than bling affect, adapt the air boots for a STIC Super X 38mm PWK carb. These are small bore magic. Provides big-bore low end with its improved sensitivity to the weaker vacuum signal at low RPM and extended top end peak hp. It will easily be quicker and pull an IT 250. My 200SX out pulled a fresh rebuilt '98 KX250 and the owner confirmed it with a few laps on the 2hun at the track.

I had both, the IT200 was a much better bike than the IT175, it felt more flickable, the IT175 felt top heavy.

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TDC
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10/16/2024 6:45pm
TDC wrote:
175cc, the sweet spot for keeping 125 flick-ability. 200's have a heavier feel. From what I've read, that is.If you want more power than bling affect...

175cc, the sweet spot for keeping 125 flick-ability. 200's have a heavier feel. From what I've read, that is.

If you want more power than bling affect, adapt the air boots for a STIC Super X 38mm PWK carb. These are small bore magic. Provides big-bore low end with its improved sensitivity to the weaker vacuum signal at low RPM and extended top end peak hp. It will easily be quicker and pull an IT 250. My 200SX out pulled a fresh rebuilt '98 KX250 and the owner confirmed it with a few laps on the 2hun at the track.

I had both, the IT200 was a much better bike than the IT175, it felt more flickable, the IT175 felt top heavy.

Wouldn't top heavy be outside the difference of bore and 20-ish CC gyro and piston weight change? 

But hey you've ridden both.  

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10/16/2024 7:28pm
TDC wrote:
175cc, the sweet spot for keeping 125 flick-ability. 200's have a heavier feel. From what I've read, that is.If you want more power than bling affect...

175cc, the sweet spot for keeping 125 flick-ability. 200's have a heavier feel. From what I've read, that is.

If you want more power than bling affect, adapt the air boots for a STIC Super X 38mm PWK carb. These are small bore magic. Provides big-bore low end with its improved sensitivity to the weaker vacuum signal at low RPM and extended top end peak hp. It will easily be quicker and pull an IT 250. My 200SX out pulled a fresh rebuilt '98 KX250 and the owner confirmed it with a few laps on the 2hun at the track.

I had both, the IT200 was a much better bike than the IT175, it felt more flickable, the IT175 felt top heavy.

TDC wrote:

Wouldn't top heavy be outside the difference of bore and 20-ish CC gyro and piston weight change? 

But hey you've ridden both.  

The IT175's shock was almost horizontal under the seat

459817220 tp-3754360455

the IT200s shock was lower

maxresdefault-2823750937

I don't know if this was the cause, but the IT200 did fell more flickable to me.

PFitzG38
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10/17/2024 10:30am
mxrose3 wrote:
it may look the same and have the same head bolt pattern, but the diameter of the combustion chamber is 66mm on the IT175, vs 56mm...

it may look the same and have the same head bolt pattern, but the diameter of the combustion chamber is 66mm on the IT175, vs 56mm on the YZ125G.   I believe the dome is larger on the IT as well.   The IT175G was basically a bored out YZ125 by 10mm.   It shared the same crank stroke of 50mm though.

Head gasket is wider too.   I wouldn't do it, unless you know a welder and a machinist who could fill the space with weld, and machine it to the right width / specs / dome shape.

Also, this topic should be in 'Old School Moto'.    Good luck.

It will totally work. You just need to find a 2T tuner who can reshape the squish band. I’ve heard they measure it with drops of water mixed with a water tension releaser. My bro used to watch Steve Dobernick of SD Racing do it.

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