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Author Topic: ZILLA OEM ENGINE FLAWS & WHAT TO LOOK FOR WHEN BUYING  (Read 1473 times)

Offline All American

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ZILLA OEM ENGINE FLAWS & WHAT TO LOOK FOR WHEN BUYING
« on: November 28, 2016, 07:03:31 am »
The title pretty much says it.  What are the flaws with a stock zilla motor, what are the corrections for them...prices???  and what to look for when buying a zilla.  "School" us please
1-1985 SUZUKI LT250R
1-2013 HONDA TRX450ER

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Offline ZillaFreak

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Re: ZILLA OEM ENGINE FLAWS & WHAT TO LOOK FOR WHEN BUYING
« Reply #1 on: November 28, 2016, 08:27:28 am »
87 was known for Head Gasket blown. Fixes were run a copper gasket. Increase studs to M10. I just used the paper gaskets and tighten it down more than specs. Also, no matter what you use, check bolt tightness regularly.
The cylinder ears were known to crack. Fix is to weld them and reinforce them.
Detonation. The stock dome size and shape can detonate when running pump gas. Best fix is to get it reshaped and possibly run higher octane fuel.
Another thing is vibration. Many say the head stay can cause issues when the engine is vibrating badly. This is what can lead to the cylinder ears cracking, and possibly other things. Many just don't run the head stay.

Offline Q2W

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Re: ZILLA OEM ENGINE FLAWS & WHAT TO LOOK FOR WHEN BUYING
« Reply #2 on: November 28, 2016, 10:02:13 am »
O geez.  Where to start. lol.

Case inserts.  The OEM case inserts do not expand at the right rate causing the main bearings to fail and suck air in the motor.  I've seen a few fixes for this.  Brass inserts were one but i believe they weren't the best fix?  Seems like builders were using a different metal that worked better. 

Flywheel rivets fail.   Better get that hub welded.  Suzuki tried to fix it in the later year zillas by using a larger hub.  I believe they still fail.  I prefer using the smaller hub ones since they are much lighter.  As soon as you start adding HP to the zilla, the flywheel WILL fail if you skip welding it.  Seen it on a couple of my buddies zillas.

Ill more people chime in about the rest.

Offline ATVMXR

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Re: ZILLA OEM ENGINE FLAWS & WHAT TO LOOK FOR WHEN BUYING
« Reply #3 on: November 28, 2016, 10:29:07 am »
O geez.  Where to start. lol.


yeah, no ****.  zilla motor can be made reliable, but it needs to really be gone through - more so than any other motor I know of

head, needs squish redone
jug, needs ears reinforced.  and it needs to be ported
wrist pin, need to get rid of the thrust washers
case inserts
welded flywheel
back cut 2,3rd gear transmission. there is something else that needs to be done to keep it from down shifting into neutral from 3rd. 
have to keep an eye on the water pump impeller to make sure the bolt doesnt back out and tear up the case.  (I keep a spare clutch cover just for this)
eventually it will break the fingers off the stock clutch basket.  the aftermarket baskets have issues shearing the bolts off that hold the basket to the gear
V2 reeds and there is some trimming that needs to be done along the reed block and intake.
carb has to be redone
mod the petcock to flow from both reserve and on
after you do all the this, the stock airbox/filter wont move enough air and you have to come up with a intake system


92/87 Hybrid
88 Zilla
bunch of other race quads

Offline All American

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Re: ZILLA OEM ENGINE FLAWS & WHAT TO LOOK FOR WHEN BUYING
« Reply #4 on: December 04, 2016, 02:04:56 am »
I'm very limited to aftermarket parts and long travel suspension options when it comes to my 85' 250.  What is the aftermarket like for Zilla engine parts & also long travel suspension parts?  And does SBLT500R offer anything for the Zillas?  His work is nice!  I have soooo many questions.  I'm trying to learn more about the Zillas so I can make a purchase that makes sense for me.  Were all Zilla motors the same beside the hub?  Are the early Zillas limited when compared to the later models?  I know with the 250, the 87' & 88' + have more aftermarket selections. 
1-1985 SUZUKI LT250R
1-2013 HONDA TRX450ER

Offline Canada

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Re: ZILLA OEM ENGINE FLAWS & WHAT TO LOOK FOR WHEN BUYING
« Reply #5 on: December 09, 2016, 08:19:58 pm »
When it comes to buying a Quadzilla, all I can say is just go for it!

I am super happy with mine I bought a 88 just to avoid some of the bigger issues.

That said it is a great engine and I like it best of my 3 two stroke quads, Mine was already mostly restored but mostly back to original more or less, and I again went over some of the listed flaws, but it is at least worth it.

Current Rides
2014 KFX-450R big 2
1986 TRX-310ESR
2004 TRX-450R hybrid
1996 Banshee 421 Serval MX
1988 Quadzilla fully restored
2006 CR-265R motion BB
2001 CR-500R
2005 DS-650X
2005 Argo Avenger

Offline Canada

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Re: ZILLA OEM ENGINE FLAWS & WHAT TO LOOK FOR WHEN BUYING
« Reply #6 on: December 09, 2016, 08:35:14 pm »
Oh ATVMXR, how do you do the mod on the fuel valve so it flows on both circits, I bought a new one but it still only works in reserve.

I did search all over but cant find it +k2
Current Rides
2014 KFX-450R big 2
1986 TRX-310ESR
2004 TRX-450R hybrid
1996 Banshee 421 Serval MX
1988 Quadzilla fully restored
2006 CR-265R motion BB
2001 CR-500R
2005 DS-650X
2005 Argo Avenger

Offline Q2W

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Re: ZILLA OEM ENGINE FLAWS & WHAT TO LOOK FOR WHEN BUYING
« Reply #7 on: December 12, 2016, 07:30:31 am »
Oh ATVMXR, how do you do the mod on the fuel valve so it flows on both circits, I bought a new one but it still only works in reserve.

I did search all over but cant find it +k2

You have to hog out the channel so that you're able to turn the lever to the fuel mark.

I did the mod on an old one and used a drill bit that was the same size as the channel.  Using a hand drill, i milled it out. literally took about 5 minutes.

Offline Canada

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Re: ZILLA OEM ENGINE FLAWS & WHAT TO LOOK FOR WHEN BUYING
« Reply #8 on: December 13, 2016, 12:31:49 pm »
Thanks a bunch Q2W  +k2
Current Rides
2014 KFX-450R big 2
1986 TRX-310ESR
2004 TRX-450R hybrid
1996 Banshee 421 Serval MX
1988 Quadzilla fully restored
2006 CR-265R motion BB
2001 CR-500R
2005 DS-650X
2005 Argo Avenger

Offline Rainman56

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Re: ZILLA OEM ENGINE FLAWS & WHAT TO LOOK FOR WHEN BUYING
« Reply #9 on: December 13, 2016, 06:43:55 pm »
When it comes to buying a Quadzilla, all I can say is just go for it!

I am super happy with mine I bought a 88 just to avoid some of the bigger issues.

That said it is a great engine and I like it best of my 3 two stroke quads, Mine was already mostly restored but mostly back to original more or less, and I again went over some of the listed flaws, but it is at least worth it.




Personally I love the power of the 500 but hated the Zilla chassis.Too bulky for me,much prefer a hybrid but everyone is different.I sold my Zilla for that reason...As far a trouble areas I agree with what others have said and they seem to need more work than most to stay reliable...That said when running well they are a blast.:)
Can,t fix stupid.:)

 

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