Author Topic: LT 500 Rebuild (Read 3297 times)

Chuck D · « **on:** January 15, 2013, 02:59:31 pm »

So I just picked up a clapped out 89 quadzilla that runs but runs like sh*t. I was told it has a 560 big bore and noticed it has a Poul turner pipe. I paid $200 for it. I'm a certified technician and have been for 10 years. Just from my a quick look over it has broken shift shaft spring, clapped out fat boy silencer, base gasket leak, counter shaft leak, shift shaft seal leak and the water pump bearings and seals are out, exhaust leak by the cylinder and silencer joint. So I'm gonna rebuild top and bottom end. What are some tricks to make this thing scream and hold up for reliability? Should I replace the rod and bearings even if they are smooth and have no play? Is a welded crank a good move or not needed? Also I noticed that the font of the frame below the arms, the rails are smashed and bent to sh*t. Like he hit every single boulder he came across. As is they are not adding any support. Can I cut those off and grind smooth before powder coat? Or will I run into frame issues? Do I need a new frame? Thanks in advance for any advice and experienced knowledge.

nASSty Zilla · « **Reply #1 on:** January 15, 2013, 03:58:46 pm »

200 bucks seems like a steal! I just went through the rebuild process, it's fun haha! 560 is a pretty big bore! idk if Wiseco makes a piston that big for a 500??? so you might just want to get a brand new top end with a fresh sleeve there would be less heating issues that way. I myself would replace the rod and bearing because these bikes have a bad history with those. As for the crank I had mine welded...but I'm sure there are some guys that'll say it is not needed. For the frame if I were you I'd find someone to repair before the powder coat and just play it safe. Good luck on your build man!!!

Chuck D · « **Reply #2 on:** January 15, 2013, 04:58:03 pm »

The lower frame rails are not fixable. They are smash flat against the frame. I can cut it off and grind smooth or replace the frame. Or just leave it but its ugly and it would bother me. I'm looking for some info on carb bore size and squish band for race fuel. What is standerd bore and stroke? What should I aim for in my engine build?

Nopick · « **Reply #3 on:** January 15, 2013, 05:42:31 pm »

If you are talking about the crush tube below the main frame rail, I had one replaced during my rebuild.

Picture link in my signature.

Quadster · « **Reply #4 on:** January 15, 2013, 06:02:56 pm »

Its probably .060 over so... 500 +60 = 560.

nASSty Zilla · « **Reply #5 on:** January 15, 2013, 06:12:25 pm »

Standard bore and stroke are both 86mm, and a good carb to run is a 39PWK(thats what i run) a lot of guys bore them out to a 41. As for the engine build it depends on how much power you want and the type of riding you plan on doing. I went for a dune bike, I like to race up the hills so I'm ported, run a fuel customs intake, Delta V-vorce3 reed cage, CT racing outlaw pipe, 39 PWK keihin carb, and bored 3.5 over which makes my bike a 541cc. For fueling i go 50/50 with pump and 110oct race fuel and my oil is mixed at 32-1 I like to use Golden Spectrum. It's a dune bike not a drag.

Chuck D · « **Reply #6 on:** January 15, 2013, 06:19:52 pm »

I don't see how a tenth of an inch bigger bore would increase 60cc's . But anyway where did you get the frame fixed at? Mine is a lot worse than that but I would like to find a place that could fix it. How much something like that cost?

Nopick · « **Reply #7 on:** January 15, 2013, 08:29:17 pm »

A guy I know that welds for a living did it for me. Any shop that does fab work should be able to fix er up.

El Diablo · « **Reply #8 on:** January 15, 2013, 08:50:37 pm »

Good find for $200. Let's see if we can help you out with some of your questions. Since you have to pull the engine out for frame repair & rebuild, pull the cylinder off & mic the bore. One thing i've learned when buying an old project is not to take the sellers word as gold. If the bore is over 88.5 mm, you might want to consider a new sleeve unless you want to start getting into custom parts. Since you might be looking into a new sleeve job, I would recomend getting the rear ears on the cylinder reinforced before the new sleeve is installed Any of the builders here on the site would be able to help you out with this procedure. Also send them the cylinder head so that the squish can be adjusted correctly.
This brings us to the bottom end. Check for up & down bearing movement from the connecting rod & crankshaft. From what you described, I would do a complete tear down. Have the case halves machined for bearing inserts. I would recomend sending the complete transmission out to get rebuilt. My personal preference is to have W-C-R in Gorgia do the pro mod package to the trans. This includes back cutting & deburring the gears, cryogenic treatment for strength, & micro polishing. Then put everything back together with brand new gaskets & seals.
As far as the carb goes, you can't go wrong with a Mikuni. The stock 38mm carb can also be bored out to 41+mm. The PWK is a good carb but can only be taper bored rather than through bored. You may also want to look into the Mikuni VM-44 carb. However going to this carb will require carb intake boot & air filter intake funnel modifications.
For the lower rail on your frame, unless you are building a dedicated light weight drag bike, I would cut it out & replace the mangled piece. Also, if you think you may be doing anything other than drag racing or mild duning, we would recomend getting your frame gusseted before you send it out to get powder coated. When you get it back from the powder coater, be sure to sand down to bare metal the areas where the engine & coil mount to ensure a good electrical ground.
The Paul Turner pipe is a good all around pipe but there are way better ones out there. Take your time & ask questions to the members here about their pipes & decide what workes for you.
One last thing. POST UP PICTURES!!! WE LIKE PICTURES!!!

LT500Kid · « **Reply #9 on:** January 15, 2013, 08:57:01 pm »

good job diablo but dont forget the 99 rm top bearing and billet thrust washers

STARPUSS · « **Reply #10 on:** January 15, 2013, 09:13:42 pm »

$200.00 Not Bad , After you stick 2300 or so into her it will still be a good deal!

Post some Pic's!

Chuck D · « **Reply #11 on:** January 15, 2013, 09:16:18 pm »

I'm looking for something in between a full drag motor and trail motor. I plan on running it mainly at the dunes shooting hills. Might put a 4" extended swingarm on it. But I will be riding it in the mountains every now and then. So with that said I want as much top end i can get without it being a pain to ride on the trails. What should my squish angle be for the head? I will run straight 110 race fuel. I can bore my carb, how much should I go or is there a better rout? Thanks again. Thanks el diablo, I have a machine shop that does work for me with my snowmobile builds. They bore my carbs and machine my heads to the specs I give them. I will probably go with the 41mm carb bore. But what about my head? As far as the bore that's the first thing I plan on doing is finding out where it's at. Machine inserts for the main bearings? Is there a known problem with the bearing to case fit? And is it really necessary to do all that to the transmission? Sounds like overkill to me? Also top bearing and thrust washers? Is that to prevent piston movement? Sorry for all the questions I have experience with modding snowmobile motors. Just trying to figure out the weaknesses of the motor so I can decide for myself what is necessary. Thanks again for the info. I am a sponge, let me soak it up

Chuck D · « **Reply #12 on:** January 15, 2013, 09:39:22 pm »

Also what about more timming? How far can you go? And I will post some pics next week

Stpltn250r · « **Reply #13 on:** January 15, 2013, 10:09:55 pm »

Dont go over stock timing. There is a thread on here with info about head geometry. I would just go with a stock mikuni or buy one that is already bored out. I would say if your going for a full rebuild. Best to go ahead and get everything done on the inside of the cases done first so you dont have to split them for a while. So tranny back cut and crank rebuilt and welded. Have the cylinder checked out. You can always stay with the 540 and have the cylinder sent for porting and send it out to millennium technologies and have it over bored an plated so it will last alot longer. And not need to be bored for some time to come. I think 196/128 seems to be a good dune port job but the shape of the ports and width is to be determined by the one who is doing the porting. Best to have whoever is doing the porting to go ahead and do the head also. Make sure the piston is cut to clear the transfer and intake ports at TDC.

The thrust washers need to be replace because the stock ones are made of steel and WILL break and when the do they will wreak havoc on the cylinder and head. There aluminum washers being made but you will need to run an OEM small end bearing from an RM250. 99 year model.

Everyone is going to have there own opinion on what you need done. But I think if you want longevity than you will need to spend some bucks.

Tranny is one of the things that should not be looked over. Seeing that so much goes into it, to get it serviced. Why not bite the bullet and get it knocked out on the top of the list?

The bearing pockets are known for going out or coming out of spec for one because the head geometry is off and guys run pumps gas and dont know how to properly tune a carb. ie DETONATION. That will a crank bearing pocket. So spend the money to get those fixed. Think the rate for that is 325 including the price for the bearings.

Pipe would also be goo to get the bike running the best.

Dont forget reeds. Guys say the V2's are the best for the zillas but seeing as they are becoming even rarer and rarer. Just buy some V3's or the newer V4's. Think there are some guys out there modifying V2 cages from other bikes to run on a zilla intake. So that is an option.

BUT you could always just get the head fixed. Replace the broken parts which can be fixed without spliting cases. Get a carb and pipe for it and see what happens.

Place I found with bored carbs
http://www.thecrankshopvt.com/product_info.php?cPath=21_26&products_id=765&osCsid=57ah1kie9oe7ken9qv2u6e88r3

This is all my non expert opinion. Just my

Q2W · « **Reply #14 on:** January 16, 2013, 08:21:44 am »

Great buy for 200! My buddy had a zilla that had the front lower rails smashed and he took it to a guy that builds choppers and he cut them off and replaced them with chromoly. Did a great job. Do like all these guys suggested, the Zilla has a few factory flaws but once you get them lined out, it's just as if not more reliable than the new 450s. Not to mention faster. I completely rebuilt my 88 Zilla about 8 years ago now and it's NEVER left me stranded or broke. (other than dropping a few nuts and bolts in the sand. DON'T USE SS NUTS & BOLTS! Or aluminum axle nuts.) Starts 1-3 kicks every time.

Quadster was just making a joke. We see lots of people trying to sell these bikes and they all seem to think .04, .06, .08, etc = CC. Like .08 some how = 80cc.

Good Luck, and post pics!

Chuck D · « **Reply #15 on:** January 27, 2013, 05:50:22 pm »

So I finally had time today to pull the motor and check the squish and cylinder bore size. Found a big surprise when I took the head off. Somthing went threw the motor. I can't believe it still would fire up and run. I knew the compression was low just by the feel when kicking it over but I did not expect this. When I removed the cylinder I was surprised to find that there was no noticeable damage on the bottom end. It was like whatever went threw the motor did not go in threw the bottom end. The bottom of the piston had no marks from impact. The crank and rod didn't show any sighns of impact either. The top ring was broken where the ring end gap is on the exhaust side. I think the piston ring end gap pin fell out of the piston. I have herd of this before on snowmobiles. But yea the cylinder is the standard 86mm bore. I also noticed that there wasn't any piston thrust washers. There is no way they broke of because there would be damage under the piston. It's like someone replaced the piston and didn't put them back on. Here are some pics I took along the way. I'm not to upset because I am only into it $200

Chuck D · « **Reply #16 on:** January 27, 2013, 05:52:34 pm »

Chuck D · « **Reply #17 on:** January 27, 2013, 06:45:32 pm »

GrkGuy · « **Reply #18 on:** January 27, 2013, 09:28:02 pm »

well looks like you might get lucky with the head, when they fix the squish it should take all the marks out of it

Rider414 · « **Reply #19 on:** January 28, 2013, 12:37:22 pm »

Damn $200.00 bucks.........wish I could find a deal like that. I need another money pit..........

Chuck D · « **Reply #20 on:** January 28, 2013, 04:03:43 pm »

Lol, yea will see how much money I'm into after all said and done. I'm afraid I'm gonna be at least $2000 into it. Already dropped $500 on a newly powder coated frame , flywheel puller and service Manuel. Shipping cost more than the frame.

Chuck D · « **Reply #21 on:** February 01, 2013, 03:15:02 pm »

What's wrong with K+S complete gasket kit?

Dezsled · « **Reply #22 on:** February 01, 2013, 03:20:35 pm »

There's a pic of how far off the clutch cover gasket is, it's no bueno for sure.

Chuck D · « **Reply #23 on:** February 01, 2013, 03:30:57 pm »

What is the best option for a complete gasket, seal, and O ring kit.

Rider414 · « **Reply #24 on:** February 01, 2013, 03:51:55 pm »

Hit up HondaEast for some OEM gaskets. Jason is a member on here.

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Author Topic: LT 500 Rebuild (Read 3297 times)

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