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1992 WR500, new to big bore 2 strokes

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I just picked up a wr500 last night in a trade, and is in startlingly good condition, considering i traded a shotgun for the bike! It was a bad ass gun, but i feel i got the deal of a lifetime. I've always been mystified by the legendary 500 2 stroke, but now I've finally got my own. Now for the questions: is there a special trick to starting these beasts? It seems like maybe there should be higher compression when I'm trying to kick it because it feels very similar to my rm250 as far as resistance when kicking. I can pull start it, and it runs like it's pissed off lol scary fast. Also, I've read different things about rigging lights up to make it street legal. My hope is to make this a road worthy machine, so what would go into making a light setup for it? It of curiosity, about where would the wr500 stack up next to a cr500 or kx500? I honestly had never heard of the wr500 until yesterday about 2 hours before i owned this one. Thank you guys for your patience!

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Ease in kickstarting might be caused by low compression. Purchase a compression tester, and check it out. As for how it would compare to the mighty CR500 or KX500, is that it probably doesn't compare all that well. But all of them have more than enough horsepower to win races, so it all comes down to the rider.

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I've got all the tools at work, but i don't think I'll need them now. I replaced the spark plug just for kicks and now it fires up first or second kick. I expected it to be tougher to start but I'm not complaining :D next on the list is a carb rebuild, the float bowl is overflowing after i shut the bike off. I'm not a great off road rider nor do i claim to be, so this bike is way more than enough for me on the trails or track. But my goal is to make it a dual sport/supermoto as I've never seen a big two stroke anywhere around where i live on the street.

Edited by dguysk01

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The YZ490s and the WR500s were very competitive bikes when stacked up against the same year offerings from the other factories.  The early YZ490s were know to be very hard to jet and vibrated pretty bad, but there are dozens of threads of how to address those short comings.

 

I would love to find a WR500 to add to my collection, but they are about as common as hens teeth anymore.

 

Probably the single biggest short fall of the Yamaha big bores was that they really cut back on the R&D after about 1985 or so.  But they still make monster power when properly jetted.

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Sweet. That will be a good ready later

Current ride: 1986 TRX250R with lots of mods.

Have owned: 1981 ATC250R with lots of mods, 1983 200X, 1986 250SX, 1991 KDX200

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Thank you, harryhandshake! That article is great! I've read a ton of threads of people bashing on the yz490 about how bad they ping and that the head has to be modified to correct that. My question now is if there is a way around having to perform internal modifications? I am an automotive technician, and to my understanding this "ping" is what is referred to as spark knock in my profession. Could higher octane fuel/richer oil ratio help? I run 93 octane with valvoline synthetic oil at 32:1. The bike runs like a raped ape, even if it is a bit tougher to start now when it's hot. But i noticed that when cruising at a steady rpm or decelerating it wants you to rap the throttle or else it will ping here and there. The bike basically just wants to accelerate lol i just don't want to pull the engine out and rebuild it when it runs so good.

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i dont have any real experience with yz490. the ping you refer to is probly just another name for detonation. whether your bike is experiencing that or not is hard to say. but since its aircooled it might make tingy sounds in its normal operation. if theres any significant amount of deto going on that could cause engine damage then im sure you would see evidence on the piston top and head. if piston and head looks fine then you have nothing to worry about. plenty of piston photos on google of what deto looks like.

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I had a 1993 wr500 , awesome machine spent a lot of time on the engine and achieved 69 hp out of it on 116 octane fuel, it destroyed back tyres, chains and sprockets on a regular basis, ha ha 

It also freaked out 450 riders . good luck trying to ride it on the road. 

Best advice i can give is to fit a digital ignition and muck around with jetting this will make it easy to start hot or cold.

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Thank you, harryhandshake! That article is great! I've read a ton of threads of people bashing on the yz490 about how bad they ping and that the head has to be modified to correct that. My question now is if there is a way around having to perform internal modifications? I am an automotive technician, and to my understanding this "ping" is what is referred to as spark knock in my profession. Could higher octane fuel/richer oil ratio help? I run 93 octane with valvoline synthetic oil at 32:1. The bike runs like a raped ape, even if it is a bit tougher to start now when it's hot. But i noticed that when cruising at a steady rpm or decelerating it wants you to rap the throttle or else it will ping here and there. The bike basically just wants to accelerate lol i just don't want to pull the engine out and rebuild it when it runs so good.

The knocking (pinging) that everyone refers to happens when the engine is under load (ie hard acceleration, riding in sand or mud), they very seldom ping when under light load.  What you are probably hearing/feeling is the normal sensation of a big bore smoker "surging" under very light or no load on the engine.  It is completely normal.  If you are hearing the pinging when under load (it will sound as if a bearing or nut or something is rattling around in the cylinder), then you definitely need to address that as you can damage your engine if you continue to run it.  Try jetting first (use the highest grade non-ethanol fuel you can get at the pumps), and if you cannot get it jetted correctly, then look at doing the head mod.  Again, the head mod is not that difficult to do and any reputable machine shop should be able to do it for you.

 

I last had an '89 YZ490 that I had running great on 93 octane pump gas.  I did the head mod which is really very easy to do if you have access to a machine shop and a high school shop class level of knowledge.

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im not in the car industry but i think ping/spark knock/detonation may be all the same thing. just different term depending what you prefer to call it.

 

 

if your not familiar with dirtbikes they do make strange noises compared to a car. since not every 2t engine has the same design, they generally make different sounds depending on the specific engine. my ktm seems to make alittle noise from the clutch area even when new. it changes as the clutch is puled in and out.  this is pretty normal. honda seems to be alittle more quiet.  then youve got the sound from the intake and exh side plus theres spur gears spinning. so alot of people not familiar with 2t engines freak out at these new noises when generally theyre normal sounds. then add in loose pipe springs and chain slap and theres all kinds of noises going at the same time.

 

usedyz426f  you say to do the head mod but thats about as vague a statement as a person can get. can you provide specific info about the issue with the head and how to correct it ?   i mention this only because you refer to a '89 model and the OP has a '92. perhaps if there was a head issue maybe yamaha corrected it on the later bikes ?  according to the mag article posted there was no problems with he head making noise on '93 bikes

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The head mod helps all of the YZ490/WR500 motors.  There are literally dozens of threads on this site that go into detail what needs to be shaved off to correct the squish band and combustion cylinder shape.  I would guess that at least half of the YZ490/WR500 heads out there in the world have had the mod done, that is why I said to start with jetting and go from there.

 

In the 12+ year run that Yamaha had with the YZ490/WR500 engines, they made only minimal changes to the head and only one major revision to the jug (center exhaust port vs angled exhaust port).  Really, about the time Yamaha changed the frames to accommodate the center exhaust port (in 1986 I believe), they basically stopped development on the head/cylinder.  Other than minor changes in ports, they are all the same.  You can swap the complete topend from any 1986-1992, or 1982-1985 models without modifications.

 

This is about the simplest diagram I have found for the head mod:

 

Head_Mod.jpg

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If i were to do a top end rebuild and have the ports worked, would the whole engine have to come out? Or is there clearance in the chassis to get the jug out? The reason i ask is because my little brother hoped on it and took it for a high speed run without warming it up and out died on him, and now it has no compression. I can spin it over by hand :( looks like now is the time to do that head mod, if it hasn't already been fixed by the manufacturer for my model year

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I just got the head off the bike, and it appears as though the head modification has already been performed. The exhaust side of the piston has melted down, along with the rings. It almost looks to me like i have a jetting problem. Or maybe this bike needs higher than 93 octane... any this? Thank guys so much for your thoughts and advice so far, I'm glad i joined this forum!

IMG_20140518_171153_154.jpg

IMG_20140518_171203_491.jpg

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appears to be a 89mm wiseco if im reading the numbers correct. i think thats the biggest oversize they make. so if the walls are pooched then you might need a new sleeve. im assuming you can put in a new sleeve. i havent been around a aircooled bike in 20yrs so im not sure

 

personally i would ditch that autozone valvoline stuff. cant go wrong with 927 or supertechniplate. r50 aint a bad choice either and will do well in cold weather unlike the others that have castor. if you dont plan to ride in winter then by all means throw some castor at it

 

use the best fuel you can afford. i havent used pump gas in years but i realize race gas can burn a hole in the wallet if you ride alot. you shouldnt have a problem with 93 if the engine is setup good. sorry i cant be of more help with exact specifics because i havent owned a 490

Edited by harryhandshake
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Thank you for the info, i am worried about having to sleeve it. The numbers on the piston are: 8191I on the intake side, and 546M09900 on the center. Idk if you can tell by that, but i don't have my micrometer handy do i can't measure it. The cylinder is toast, very scored. I'll post a few pics of the damage

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you sure it says  546M09900 and not 546M08900 ?  8900 indictes the size. hell maybe theres a 99mm piston but i doubt it. wiseco dont show nothin like that on their site

Edited by harryhandshake

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