Cylinder head cross-reference and modifications!

Ramblerman · 06-20-2011, 03:40 PM

Hi. As some of you know, I purchased my bike with a blown engine (broken valve head bounced around in cylinder). The cylinder head was toast and a new one costs over $500 which is rediculous! :jawdrop: Used GZ-250 heads are nearly impossible to find!

I found that a mid 1980's Suzuki Quadrunner LT250 ATV with the four-valve head had ALMOST EXACTLY THE SAME cylinder head (I believe there is a 2-valve version also, so be careful). The rest of the engine appears to basically be identical too, BTW.

My bike now runs great with this head and I have just put my first 30 miles on it! I wanted to let everyone know (and put in writing) what minor modifications were involved in making this head compatible with the GZ-250 engine:

1. The carb to head gasket/intake neck needs to be transferred from the GZ head.
2. The exhaust studs/bolts on QuadRunner head are 8MM, not 6MM like the GZ, so you will need to drill out the holes in the exhaust flanges on the GZ exhaust pipes - This is easy to do!
3. The QR camshaft is identical to the GZ camshaft as far as the lobes and timing, HOWEVER, the end of the cam that is near the outside of the engine where the gear attaches is LARGER. You will NEED to use the camshaft from the QuadRunner engine.
4. Likewise, you wil NEED the cam cover (top of engine) from the QR engine to mate up to the cylinder head and cam!
5. You do not need to do anything different with valve adjustments, except to know that the locking nut is 9MM instead of 8MM! It uses the same valve adjustment covers on both engines!

All of these modifications are what I had to do to make my bike run properly. It does not necessarily mean you will have to all of these same things, although this should be a rough guideline for anyone thinking about using this particular cylinder head!!

-Daniel

sc_frontier · 10-18-2011, 02:04 PM

Wow, thanks for this useful post!

Ramblerman · 10-20-2011, 06:02 PM

You are welcome!

When I was looking for this type of information, I could not easily find it. So, I just wanted to post it here so that, in the future, GZ250 owners with a similar situation would be able to find it!

-Daniel

mrlmd1 · 10-21-2011, 04:27 PM

Ramblerman- does that Delorean still run? Do you drive it?

06-20-2011, 03:40 PM	#1
Ramblerman Junior Member Join Date: Apr 2011 Location: Arizona Posts: 18	Cylinder head cross-reference and modifications! Hi. As some of you know, I purchased my bike with a blown engine (broken valve head bounced around in cylinder). The cylinder head was toast and a new one costs over $500 which is rediculous! :jawdrop: Used GZ-250 heads are nearly impossible to find! I found that a mid 1980's Suzuki Quadrunner LT250 ATV with the four-valve head had ALMOST EXACTLY THE SAME cylinder head (I believe there is a 2-valve version also, so be careful). The rest of the engine appears to basically be identical too, BTW. My bike now runs great with this head and I have just put my first 30 miles on it! I wanted to let everyone know (and put in writing) what minor modifications were involved in making this head compatible with the GZ-250 engine: 1. The carb to head gasket/intake neck needs to be transferred from the GZ head. 2. The exhaust studs/bolts on QuadRunner head are 8MM, not 6MM like the GZ, so you will need to drill out the holes in the exhaust flanges on the GZ exhaust pipes - This is easy to do! 3. The QR camshaft is identical to the GZ camshaft as far as the lobes and timing, HOWEVER, the end of the cam that is near the outside of the engine where the gear attaches is LARGER. You will NEED to use the camshaft from the QuadRunner engine. 4. Likewise, you wil NEED the cam cover (top of engine) from the QR engine to mate up to the cylinder head and cam! 5. You do not need to do anything different with valve adjustments, except to know that the locking nut is 9MM instead of 8MM! It uses the same valve adjustment covers on both engines! All of these modifications are what I had to do to make my bike run properly. It does not necessarily mean you will have to all of these same things, although this should be a rough guideline for anyone thinking about using this particular cylinder head!! -Daniel Login or Register to Remove Ads
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10-18-2011, 02:04 PM	#2
sc_frontier Member Join Date: Dec 2010 Location: Sherman, Texas Posts: 65	Re: Cylinder head cross-reference and modifications! Wow, thanks for this useful post! __________________ SC
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10-20-2011, 06:02 PM	#3
Ramblerman Junior Member Join Date: Apr 2011 Location: Arizona Posts: 18	Re: Cylinder head cross-reference and modifications! You are welcome! When I was looking for this type of information, I could not easily find it. So, I just wanted to post it here so that, in the future, GZ250 owners with a similar situation would be able to find it! -Daniel Login or Register to Remove Ads
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10-21-2011, 04:27 PM	#4
mrlmd1 Senior Member Join Date: Jan 2008 Location: Crawfordville, Florida Posts: 2,853	Re: Cylinder head cross-reference and modifications! Ramblerman- does that Delorean still run? Do you drive it?
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