Everything2Stroke Forum banner

1 - 20 of 24 Posts

·
Registered
Joined
·
11 Posts
Discussion Starter #1 (Edited)
Lt 500 Jetting

I recently bought a Quadzilla and had it rebuilt. I went with the 517 Wiseco kit in the rebuild. Well it had no airbox with the Uni filter directly on the carb and it would break up on the top end so I thought that was the cause and put the stock airbox setup on it. It still breaks up so Im guessing its the jetting at this point. It has the stock Mikuni carb from what I was told by previous owner, FMF exhaust, and I put new Vforce 3 reeds on it. I took the carb apart and the large jet says 380 and the smaller one says 52. (Sorry Im new to carbs, other bikes are fuel injected). Well what do you guys think I should run in the carb with the mods I have? Thanks for the help. The bike is a monster down low and I can only imagine how fast it will be with the correct tune. Posted a pic of the jets and carb.
 

Attachments

·
Registered
Joined
·
572 Posts
Couple things you're probably not going to want to hear but if you want to do it right then it is what it is. First off you need to leak test the engine, you will never be able to jet it properly with air leaks and I can just about guarantee you have one or two somewhere. I know where these things leak and still find leaks after I rebuild one most times.

Second, you need a new slide. That one is well past worn out, you'll never get the jetting right with that either. Don't buy it from Suzuki, you will pay twice as much as buying from Sudco. Take a look at the carb rebuild thread I wrote that is stickied at the top of this page, I believe I have the part number for the correct slide in there.

Your jetting should be close, if it's idling ok leave the pilot jet alone and do a plug chop with it winding out pull in the clutch, kill the motor and coast to a stop then check the plug. Sounds like it might be a little rich.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #3
Ok I installed the new slide, did the leak test and there were no leaks. I have V3 reeds, FMF exhaust, Uni open filter on the carb. I tried the 400 main and 40 pilot but it was still rich when I did the plug chop. So then I went to the 380 main and the 35 pilot and its still rich. What other changes should I make, what are other ways to fine tune the carb? I read on here about setting the needle but I'm not familiar with this, could someone elaborate? It idles perfect and the bottom end is strong but breaks up on the top side when wot. Thanks for all the help so far guys.
 

·
Registered
Joined
·
572 Posts
Before you go any further make sure the exhaust valve is working, if it's not closing the engine will never wind out. Start the engine and lean down to where you can look in the inspection window on the right side of the cylinder. Stab the throttle and make sure the valve is closing. You should see it turn about 90 degrees. If you were idling fine with the 40 pilot go back to it, you don't want to lean it out at idle.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #5 (Edited)
Ok thanks. I'll give that a try. So when I hit the throttle I can see it move? I always wondered what that window was for but didn't give it much thought. And is the pilot jet only for idle?
 

·
Registered
Joined
·
572 Posts
Yes and yes. Air filter connected directly to the carb isn't a good thing. I would go back to the airbox setup you had. If not then you need to attach a 3-4" piece of pvc between the carb and the air filter to get that tunnel affect for your air flow. The 380/52 that was originally in your carb should be close, maybe a little higher on the main. If you were idling ok with the 52 I'd put that back in, it has nothing to do with the top end. Pilot is idle to maybe 1/4 throttle, needle/needle position is 1/4 to 3/4 throttle and main is 3/4 throttle to wide open with a little overlap between.

Right now you need to check that exhaust valve. Your engine will never wind out if the exhaust valve isn't closing and you will keep chasing your tail. If it's not closing you will need to fix it, hopefully someone just screwed up the adjustment. The adjuster is on the other side of the engine. Remove the two phillip head screws that hold the locking plate on and remove the adjustment cap. If you flip the cap over you will see a slot where a spring inside the motor rides. Put the cap back on making sure the end of the spring fits inside the slot. Now turn the cap 1 full turn counter clockwise and lock it down with the plate and 2 screws then fire it up and see if it is working.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #7
Ok I'll give that a try today. I still have the stock airbox in place and can reattach it. Im going to spray it down with some liquid wrench first and let it sit because Im not sure if the bolts are seized up and probably would be tough to loosen. Thanks again man. Hopefully this will get it going right.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #8
I finally got around to taking the cap off of the power valve adjustment and the spring was a mangled piece of s##t (I attached a pic). Is there anywhere I can get just the spring or is there anything I can do as an alternative? And also, if the spring is not working would that cause the power valve to remain open or would it remain closed. PV Spring.jpg
 

·
Registered
Joined
·
45 Posts
The spring is available separately from suzuki. My power valve was not working on a zilla I bought and it made a very noticeable difference in power when I got it working properly
 

·
Registered
Joined
·
572 Posts
That's what I thought it was. Someone didn't know what they were doing and tried adjusting it. You got lucky though, that's an easy fix, here is the part number for the spring 09444-15006 call and order one, they're only about $4. Once you get it adjust it like I said and remember 1 turn COUNTERCLOCKWISE, lol. You better be holding on when you wind it out after that.

If I were you I'd put that 400 main back in with the 50 or 52 pilot you had in it and go from there after you get the exhaust valve fixed. Better to be a little rich than a little lean. Not sure if you realize it or not but you don't need to remove the carb to change the jets, you can just loosen up the clamps and turn it enough to get the bowl off. 380/50 is probably pretty close with the stock airbox and no air leaks.

BTW, that exhaust valve had to be taken apart (or should have been) to bore the cylinder so whoever did that for you either screwed up that spring or put it back together like that. Either way I'd find a new mechanic.

Edit to add: Took my carb apart this weekend to clean it out before I put the quad away for the season and realized I gave you bad info on the pilot jet size. I was thinking of the Keihin PWK that I ran a 50 in, the Mikuni I'm currently running a 30 so you should probably be down around there somewhere. My bad.
 

·
Registered
Joined
·
572 Posts
Doesn't sound right, replacing that spring should have made a HUGE difference. I've been through this with several people and you're the first to tell me that getting the valve to work didn't make a big difference on the top end. Did you make sure it's closing when you rev it up and then opening back up as you let off the throttle? If it's moving it's full rotation you should be able to see that little lever through the sight glass turn about 90 degrees then fall back. You need to watch leaning it out too far, especially on a new top end.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #15
Yeah I watched the arm move up toward the front. And to make sure it was closed I took the exhaust off and stuck my hand inside where I could feel the valve close. I took out the spring and I put a flat piece of metal in instead of the spring where I could lock it closed and its still doing it. If I have it closed shut, it should open up on top end correct? With it closed all the time it would just affect the bottom end right? And yeah I don't want to lean it out anymore, I'd rather it be a little rich than too lean (380 main 30 pilot). I guess I just have to keep going with the process of elimination... CDI, coil, and maybe the stator?
 

·
Registered
Joined
·
572 Posts
Yeah I watched the arm move up toward the front. And to make sure it was closed I took the exhaust off and stuck my hand inside where I could feel the valve close. I took out the spring and I put a flat piece of metal in instead of the spring where I could lock it closed and its still doing it. If I have it closed shut, it should open up on top end correct? With it closed all the time it would just affect the bottom end right? And yeah I don't want to lean it out anymore, I'd rather it be a little rich than too lean (380 main 30 pilot). I guess I just have to keep going with the process of elimination... CDI, coil, and maybe the stator?
Yes, if you lock it closed it will only affect the bottom end, it will act like most other two strokes and not have the torque at low rpm's that it does. I have one more question before moving on to other possible causes. I am assuming by using a flat piece of metal to lock it closed you fit it between the slot on the cap and the slot on the valve correct? If that is the case which way did you turn the cap to lock it closed?
 

·
Registered
Joined
·
11 Posts
Discussion Starter #17
Yeah exactly, I fit it between the slot on the valve and the slot on the cap, and I turned it clockwise. I did it with the exhaust off so I can feel whether or not it was closed and then I put the exhaust back on and tried it again and it was the same. Thanks too Jerkin, for all the help. Is there a way to check the CDI without buying a new one, not looking to spend $200 if its not the problem you know. I've tried running with the airbox, filter directly on the carb and even tried a short pull with no filter at all and still the same result. Thought it may have been my carb so I tried the Keihin carb from my brother's banshee and it still did the same.
 

·
Registered
Joined
·
572 Posts
That was right then, hard to believe that didn't make a difference, something else must be screwed up. Almost has to be something electrical then. Did you take the stator cover off and check the timing? The lines need to be lined up perfectly. Another thing you could check that won't cost anything is the pickup coil. You should have about 0.025" clearance between it and the small rectangular piece on the outside of flywheel when it comes around, probably wouldn't hurt to clean that piece up with a scotch brite pad either.

I remember hearing about a bad flywheel screwing up a guys top end too but it was on the old (now defunct) site and I don't remember who it was. He went crazy trying to figure it out too and if I remember correctly they had it on Hall's dyno and Jerry suggested swapping the flywheel and that fixed it. They never did figure out what was wrong with the old one.

BTW, this is a zilla, there is no $200 cdi, try $600 for a new one, lol. There is no way to test a cdi either so you really don't know what you're getting from ebay. You can test the coil with an ohmmeter though. Might try to pull all the wires from the stator up under the tank where they connect into the harness and clean those. Check your grounds too.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #19
Whoa! $600 lol. Lets hope that's not the issue then lol. I'll check the stator when I get off work, I was a little intimidated to take that off and check it, I've been trying to work around it lol. Will the cdi from a LT 250R work? My buddy has one of those I could try on my zilla.

That was right then, hard to believe that didn't make a difference, something else must be screwed up. Almost has to be something electrical then. Did you take the stator cover off and check the timing? The lines need to be lined up perfectly. Another thing you could check that won't cost anything is the pickup coil. You should have about 0.025" clearance between it and the small rectangular piece on the outside of flywheel when it comes around, probably wouldn't hurt to clean that piece up with a scotch brite pad either.

I remember hearing about a bad flywheel screwing up a guys top end too but it was on the old (now defunct) site and I don't remember who it was. He went crazy trying to figure it out too and if I remember correctly they had it on Hall's dyno and Jerry suggested swapping the flywheel and that fixed it. They never did figure out what was wrong with the old one.

BTW, this is a zilla, there is no $200 cdi, try $600 for a new one, lol. There is no way to test a cdi either so you really don't know what you're getting from ebay. You can test the coil with an ohmmeter though. Might try to pull all the wires from the stator up under the tank where they connect into the harness and clean those. Check your grounds too.
 

·
Registered
Joined
·
572 Posts
Stator isn't a big deal, you should probably order a flywheel puller off ebay though, they're good to have even if you don't need to pull the flywheel right now and they're only around $12. If you're buddy has one you can just borrow his, most of the two strokes use the same puller. You don't need to pull the flywheel to check the timing or the gap between the pickup coil and flywheel though.

As long as your buddy's lt250 is an 87+ it will interchange. That would be great if you could borrow it and rule out the cdi, you can check everything else electrical with an ohmmeter.
 
1 - 20 of 24 Posts
Top