Author Topic: 87 lt500r start up idle issue....... (Read 2885 times)

dennisgreener · « **on:** May 22, 2016, 10:32:23 pm »

Hey all, new to this forum and to the zilla world. Just bought my first lt500r (have wanted one for years). I found an awesome 87 and just about everything on it is new but still in original form. Here is my problem........the guy I got it from was running it on AVGAS mixed 30:1 and it pulled like crazy right when u would lay in to it but then act like it was flooding itself. I will tell you before I go further that I am somewhat new with carburetors...... (I'm big in the LS engine world. Haha) so I decided, since I had heard mixed reviews about AVGAS, that I would switch it back to 93 pump mixed with amsoil dominator. I loosened connections on carb (which is a 39mm keihin) and rolled it so I could look at main jet. I saw that it's a 175 jet and I figured it should run "okay" at least for a starting point with this so I reinstalled and rolled it back and tightened connections. Completely drained tank and changed fuels. Then it wouldn't start at all. Before it would start and idle perfect everytime. Messed with adjustment screws and still nothing. Then I loosened all air intake connections made sure they were sealed and tightened back up. Fired right up after that. But now right when it lights off I have to shut it off immediately because it tries to wrap all the way out like the idle won't quit going up. I have messed with the adjustment screws till I had tried everything there. Throttle cable seems to be working perfect but it just won't start and not try to go to redline. Thank you in advance!!!!!

Mods are FMF gold series pipe, DG silencer, keihin pwk 39mm carb, new top and bottom end (he said no bore, just a hone) Duncan racing air filter w/cover and no lid on air box. Pretty much just a bolt on stock bike and I just want to enjoy it for now. Not worried about crazy performance. Thanks!!!!!

MotorGeek - Jerry Hall · « **Reply #1 on:** May 22, 2016, 11:11:46 pm »

Sounds like the slide is not closing all of the way. The cable is probably not fully seated in the fitting in the top of the carb. or thumb throttle. The choke cannot function when the slide is open a little making kick starting next to impossible when the engine is cold.

When kick starting, if the throttle is open more than about 3/8"and the engine is not flooded, the air velocity over the needle jet is too slow to pull fuel from the needle jet.

dennisgreener · « **Reply #2 on:** May 22, 2016, 11:15:44 pm »

It fires right up now. Even cold. But it just won't quit rising in rpms. It wouldn't start before because of a leak in the air intake I suppose but now it will start on every kick. Just then immediately keeps going higher and higher till I shut it off. Throttle cable appears to be working properly.

Q2W · « **Reply #3 on:** May 23, 2016, 08:33:43 am »

sounds like you may have more air leaks. You'll need to seal it up. Leakdown test!

Dutch_Rutter · « **Reply #4 on:** May 23, 2016, 12:21:46 pm »

^ X2

Make sure to check your base gasket and head gasket for leaks as well. especially if the PO didn't get the head seated right with the top end work, or he did not have the base gasket replaced. Good luck

dennisgreener · « **Reply #5 on:** May 23, 2016, 03:34:21 pm »

I will check all that tonight but I know that's not the problem as the bike started and idled perfect when I bought it a couple weeks ago. It ran perfect except for the top end was way too rich on the AVGAS. It has only started doing this since I messed with the carb. I'm just new to carburetors because I work with only fuel injection stuff. I just don't know what inside the carb could cause this issue.

dennisgreener · « **Reply #6 on:** May 23, 2016, 06:11:49 pm »

I believe I found the problem........I pulled the carb completely off to inspect and everything appear to be fine. As I was reinstalling I noticed the "intake manifold" or whatever you call it, where is slips over the carb has a slit in it where it has ****. Anyone know the best solution? Is there an aftermarket piece that can take its place or just spend $80 bucks on another one like this? Lol. Thanks in advance

Rogue1970 · « **Reply #7 on:** May 23, 2016, 07:27:10 pm »

Welcome to the forum. Yes, there are aftermarket billet custom built intakes, but they are hard to find, expensive and probably not the direction you should go in right now.

You should just order up a OEM replacement boot "intake pipe". I'm not sure if we still get a discount at HondaEastToledo. Lately, I've been using Partzilla.

Here is a link:

http://www.partzilla.com/parts/detail/suzuki/SP-13110-43B00.html

If you can get better prices thru a local dealer, then that would be good.

A friend of mine had the same thing happen and he only noticed it when R&Ring the carb.

Good Luck.

P.S. You should perform a leak down test once you get this new part installed. There are a few spots on this quad that seem to always leak a little. Without the leak down, you can burn down your engine.

dennisgreener · « **Reply #8 on:** May 24, 2016, 09:12:26 am »

Finally got her to idle!!!!!! While I'm waiting on a new intake pipe I figured I would use some "seal all" and see if I could at least know that was the issue. So I patched it up last night and started it up this morning. Second kick light right up!!!!! Let it warm up a bit and then took it out just to see if switching to pump gas helped the top end any from the AVgas and it didnt. Now just to jet it down.........I'm in central Missouri and it is pretty humid and muggy here. Right now this keihin 39mm pwk has a 175 main in it. I think I'm going to order a few jets around the 160 range and see what they do. Low end feels great. Top end is just dead from too much fuel.

dennisgreener · « **Reply #9 on:** May 24, 2016, 09:57:40 am »

Anyone have a rough idea on the pwk carb main jet for my 87 500? I have read that avgas and pump gas use somewhat of the same jets. Or does avgas take bigger jets? I'm going to just play around with it and see what happens because I have 3 bigger jets on hand all the way to 190. If not then the new smaller jets will be in this week.

MotorGeek - Jerry Hall · « **Reply #10 on:** May 24, 2016, 05:17:28 pm »

The heating value (caloric value) of Av gas is a little higher than pump gas especially if the pump gas has ethanol or MTBE. Av gas usually requires smaller jets than pump gas .

ZillaFreak · « **Reply #11 on:** May 25, 2016, 06:46:11 am »

Why did you switch away from AVgas?
What mixes reviews did you hear?

MotorGeek - Jerry Hall · « **Reply #12 on:** May 25, 2016, 07:28:40 am »

Quote from: ZillaFreak on May 25, 2016, 06:46:11 am

Why did you switch away from AVgas?
What mixes reviews did you hear?

I did not change my views on AV gas, I still recommend it for most recreational and racing applications.

dennisgreener · « **Reply #13 on:** May 25, 2016, 07:32:02 am »

Well, like I said, it was running like sit on the top end and I have read that avgas is great for low end but can mess up the top end. I've still got 10 gallons of a gas sitting here but I figured I would switch back to b pump gas to attempt to get everything to run normal and then work from that point. So far with no luck.

Q2W · « **Reply #14 on:** May 25, 2016, 08:39:20 am »

Quote from: dennisgreener on May 25, 2016, 07:32:02 am

I have read that avgas is great for low end but can mess up the top end.

That's bizarre. It just needs to be jetted correctly.

dennisgreener · « **Reply #15 on:** May 25, 2016, 08:46:41 am »

Once I get it running okay on pump I will start playing w/the avgas

ZillaFreak · « **Reply #16 on:** May 25, 2016, 08:55:29 am »

You are wasting your time switching to pump then back to AVgas for many reasons.
1) Pump gas is like 93 AKI. 100LL (AVgas) is around 100AKI. So if your engine is setup up for running 100AKI fuel, running pump gas will not be good.
2) As Jerry stated, you will have to rejet.
3) Who ever told you AVgas is bad for your 2-stroke most likely has never ran it before.

Pick a fuel, pick a premix ratio and stick with it. Don't keep switching.

Also Jerry, my post about switching away wasn't directed to you.

dennisgreener · « **Reply #17 on:** May 25, 2016, 09:00:24 am »

Don't really know what constitutes a motor that "is built to run avgas" it's a stock bore lt500r w/new top and bottom w/an fmf pipe, dg silencer and a keihin 39mm pwk. Pump should be fine.

ZillaFreak · « **Reply #18 on:** May 25, 2016, 09:21:27 am »

Set up for avgas (higher octane) is compression ratio, static and dynamic compression, timing, dome design, many things.

dennisgreener · « **Reply #19 on:** May 25, 2016, 09:51:46 am »

Yeah, this motor should definitely be on pump gas then. Stock head, stock compression.

Rogue1970 · « **Reply #20 on:** May 25, 2016, 03:22:39 pm »

I dug this up from some saved notes:

Poor Fuel/Premix - 91 pump fuel now has 5%+ of Ethanol and that attracts water is not consistent. The OEM head/squish band on the LT500 is prone to detonation.
FIX: Race fuel is recommended w/Good Oil (Castor 927).
FIX: Have the head squish band cut by Tudor, Hall Precision Racing, or other LT500 builders.

Today's pump fuel is crap and increasing % of Ethanol is making it worse. There are some LT500 owners that have kept their machines together on nothing but pump gas.

Since around 2005 or so, my Zilla has always had a blend of pump/race fuel to bring up the octane, trying to prevent detonation that will destroy your crank bearings. I have always run the Mikuni carb, so I can't comment on the PWK. If you search around you will find many people have switched to a modified Mikuni to help eliminate this one area when trying to get their Zillas running better.

Also, you might want to check and see if the rebuild included OEM thrust washers. The OEM ones are known for breaking and tearing up your engine. Replacing them with a set of aluminum washers w/ a RM250 bearing can save your engine.

Again, spend some time reading thru the information on this forum and you'll find lots of tips to help you with your Zilla. Here is a post I put a few years ago going over some of the basic mods every Zilla (and 250) owner should perform:

http://www.suzukiquadracerhq.com/2-stroke-tech-talk/building-a-reliable-zilla/msg2110

dennisgreener · « **Reply #21 on:** May 25, 2016, 04:43:53 pm »

Thanks for the info, I know when he did the motor he did the bigger head studs and fixed the crank issues known with the 87's. Waiting on a new intake pipe to come in right now before I can test much more. I was able to patch the old one together long enough to know that it is still running like sit on the top end even on pump. Runs perfect at idle and down low. Also, looked deeper today and saw that it has the aftermarket tansarini motor reed cage or however you spell it. Runs absolutely amazing right when u lay in to it down low and then horrible after that. It's hard for me to believe, from reading everyone else's posts, that it would be running too rich on a 175 main jet but Im going to take it out once the new intake pipe gets here and run it wide open for a minute then shut it off to check the plug then. I just for ****, rebuilt the carb so I know it's all new and I found its running a 58 pilot jet which seems normal. Needle was on 2nd clip up so I switched it to the middle as most people say that works better for them. I think it will just be trial and error.

El Diablo · « **Reply #22 on:** May 25, 2016, 09:37:59 pm »

I know it's a subject of debate, but I would sell that PWK39 to some unsuspecting guy and buy a Mikuni 38. Then send it out to get bored out to a 41.

dennisgreener · « **Reply #23 on:** May 25, 2016, 09:45:37 pm »

Lol, thinking about it. But for now, I think I may be on to something with my issue. I really didn't know anything prior to this about a "power valve" but after this evening I have really learned what they do and how to adjust them. Hopefully tomorrow when I get to take it out that ends up being the problem. I have been informed that if you really don't have a powerband at all then it needs to be turned counterclockwise in 1/4 turn incremints. I will see what happens tomorrow evening.

Q2W · « **Reply #24 on:** May 26, 2016, 12:52:28 pm »

First off, i'd check to see if the PV moves freely or is even hooked up. Then, i'd just set it back to stock. Never heard of the 1/4 turn thingy. take off the cap to relieve tension on the spring. Put it back on and turn 1 full turn CCW and it's set.

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Author Topic: 87 lt500r start up idle issue....... (Read 2885 times)

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