Well now that i got my zilla running great my buddy's zilla started acting up. It wants to scream when you start it like its running lean or has an air leak. We checked and replaced just about all the gaskets and seals and it still does it. We checked for cracks to see if it was cracked like mine was and it wasnt that either. I even loaned hime my carb to see if that was the problem but it still did it. We even checked the ignition timing to see if that got knocked off some how but that is fine also. this is a real brain teaser and cant figure it out. Any of you guys have this problem before and fixed it? We have checked everything and nothing seems to be wrong with it. I realy need some other options. I cant think of anything else. Thanks in advance.

 

Have you checked the carb boot? Mine was cracked from using a gear clamp on it instead of the proper clamp and was sucking air from that crack in the rubber!!!

87 zilla
87 quadsport

 

The one he had on it had a few hair line cracks in it so we bought a new one and it still didnt fix the problem. Thanks for the help though.

 

Ive heard that its possible to suck in air throught the main bearing seals through the gearbox etc. this is another possibility. The best thing to do is to get a leak down test done. This will test for a leak in the cylinder. This wil tell u whether you have a leak or not. Try that and tell us the result [img]i/expressions/face-icon-small-smile.gif[/img]

 

Sounds like the crank seals are bad. The only fix is to replace them, which means complete teardown. Quadzillas are notorious for the crank bearings 'wobbling' out the cases, so check that when you put new bearings in they dont just drop in. They should be a snug fit!
Anyway, if the bearing saddle is loose, the crank will move excessively and screw up the seal. Once the seal leaks, it sucks air and causes it to rev to the moon, and this also means it is too lean.
addict

 

Replacing the main seals does not require a complete tear down. On some motors you have to split the halves and install the seals from the inside. That is not the case on the LT500R.

The first thing you should do is remove the flywheel cover and try to move the flywheel up and down. If it moves at all, the bearings are bad which allows the seals to leak. Replacing the main bearings, of course, requires a complete tear down.

If the bearings seem good, the only way to know for sure if the seals are leaking is through a leak down test as previously mentioned. To save yourself some money, remove the exhaust, carb, intake boot, and reed cage before bringing the quad into a shop to have this test performed. If instead you want to replace the seals and find out if that fixed the problem, let me know and I will explain the process. Unless you, or somebody that can help you, has a good amount of mechanical ability, I would not recommend doing this job yourself. Special tools and techniques are required and, no matter what, you should have a shop manual.

 

we checked the bearings and they are tight. There is no slop what so ever. The seals should be fine cause 9 times out of ten if the seals are bad there will be an oil residue under the flywheel and there isnt so i think that they are fine. I realy doubt that they would be bad cause when he had the shop rebuild it this spring it had new crank bearings and seals put in. Is there any other suggestions before we change the seals when they should be fine? Thanks for all the help so far guys.

 

I realize that it is hard to trust the suggestions of someone on a forum but you will be doing yourself a favor if you believe what I am saying. YOU DO HAVE AN AIRLEAK SOMEWHERE (assumming that you have given me all pertinent information)! If the sparkplug is tight, the carb-to-intake clamp is tight, the intake boot is not cracked, the boot-to-reed cage and reed cage-to-cylinder is tight, then that leaves the main bearing seals, the gasket between the halves, and the base gasket as the only possibilities for leaks.

First of all, I should point out that, even with a new gasket, the reed cage area can still leak. To be safe, I like to use a thin layer of Yamabond 4 on the mating surfaces in that area. Also, make sure the bolts are tightened evenly and not over tightened. Otherwise, the flimsy intake boot can deflect and create a vacuum leak.

Secondly, the base gasket directly underneath the reed cage has a tendency to leak on the big LT. Some people recommend using a spray-on gasket adheasive on both sides of the gasket in that area before installation. Do not spray the entire gasket because the cylinder will never want to come off again!

Thirdly, the liquid gasket between the engine halves could be leaking. I have never heard of this happening because it is fairly easy to apply this stuff and, if applied correctly, does not develop a leak later on down the road. If the person that put the two halve together was an idiot, however, anything is possible.

As much as you seem to hate to hear this, the most likely culprit is one or both of the main seals. The fact that the seals are fairly new DOES NOT MATTER! Brand new, freshly installed seals can leak. A thorough shop will always do a leak-down test on an engine that has had the seals replaced, before fully assembling the engine. These seals damage easily during installation. Even if the damage was small enough that the engine ran fine at first, after some usase the problem can get worse. Like anything else, some seals can come bad from the factory also.

You mention not seeing residue under the flywheel and again I say IT DOES NOT MATTER! First of all, there are TWO SEALS. I actually have a harder time installing the seal on the other side on my 'Zilla so that one is more prone to damage during installation. If the right side seal goes out but the bearing are good, taking off the flywheel cover will give you ZERO information as to the cause of your problem. Secondly, it sounds like you didn't even remove the flywheel but mearly looked under it. You have to remove the flywheel to see the seal and the area immediately around it. It may take a long time for any oil to seep down to the bottom of the flywheel housing and the machine may very likely die long before that ever happens.

 

Btodd

Yes i actually removed the flywheel. I actually am an experienced mechanic and know what i am doing. What i was hoping for by posting this topic in the forum was for some weird thing that zillas do that others dont since i have found after owning my own zilla that they do lots of weird stuff compared to the average 2 stroke. The guy that owns the zilla doesnt have alot of money and wants the seals to be the last thing we check. I just did some tinkering on it yestarday and waiting for a head gasket to see if i got it fixed. If it still does it after this the only other thing to do is replace the seals. And my buddy may not like it but i am a beleiver in changing bearings and seals together. Cause i mean since its apart yah might as well do the whole works. Well thanks for the advice everyone.

 

Listen carefully this time. YOU DO NOT HAVE TO TOTALLY DISASSEMBLE THE ENGINE TO REPLACE THE MAIN SEALS ON THE LT500R! You don't even have to remove the engine from the frame. The flywheel side is the easiest. To avoid scratching the seal to case mating surface, you should use a seal remover. They are simply a hook or claw at the end of a screw-driver type handle. They are cheap so I recommend that you buy one. Use medium strength thread-lock on the new seal outer edges and a small amount of grease on the inner edges of it before installation. Be very carefull since, like I said previously, they damage easily (especially the inner "lips&quot.

To replace the right side seal, You will have to remove the right side engine cover. Then remove the entire clutch and the gears on the crank (make sure the timing marks are all lined up when you reinstall). You can now remove the right seal with a seal remover (It is held in with a holder that will need to be removed also).

If the main bearings were recently replaced as you say, and there appears to be no slop in them, do not waste your time and money putting new ones in. You would then have to remove the engine as well as alot more parts. The cases will have to be split and all seals will have to be replaced. Plus, every time you press out the main bearings and press in the new ones, you are weakening the case inserts. These inserts are prone to failure on the Quadzilla anyway so why speed up that process. When they wear out you have to send both case halves to a shop for them to install new inserts (another costly and time consuming venture).

If you had to replace the main bearings then yes, you would want to replace the seals. However, vise-versa makes no sense to do.


Like I said before, if you take the exhaust, carb, and intake off that quad and bring it to a dealer for a leak-down test, the cost should be minimal. The test should not take more that 20 minutes and then you could reinstall the parts later. There is absolutely no reason not to have this done! The nickel and diming you are doing now to try to find the problem yourself will probably cost the same amount if not more. The biggest benefit will be to end the frustration of not knowing! Also, evertime you restart that quad to check if the problem is still there, you are further damaging the cylinder and bore from the lean condition. There is no real load on the engine at that time so the damage isn't as servere but it is still occuring.

Lastly, I say again, DO NOT WORK ON THAT QUAD WITHOUT THE PROPER MANUAL! I guarantee you that I know LOADS more about the LT500 engine than you do and even I wouldn't operate on it without a service manual. You have to know: torques; backwards threads; timing marks; parts positioning; when to use locktight and what type; etc..