250-500cc wr300 top end

done about 80 hours or so on my 2010wr300(no hour meter, 3000-3500km-speedo stopped workin but got new one under warranty!). bike still running sweet but figure its time for top end rebuild. got the whole genuine kit from hall's ready and waiting but want some opinionson whether should do now or wait till drop in power/excess smoke etc. what risks do you run letting it go longer(cylinder scoring/seizure/broken piston skirt?) mainly 3rd gear type riding, hot aussie weather, rocks, hills, single trails but not too much wide open stuff. im about 220lbs fully kitted if that affects engine wear any. meticulous with air filter changes, run fully synthetic oil & 98 octane fuel. gets well used but not abused. mate destroyed his ktm 300(probably because it was orange -Kant Take Much)but was during finke desert race(very high speed) and dont wanna do the same-was very expensive and i have kids so im poor. also any need to remove head when doing piston/rings? gonna have a shot at doin it myself-got workshop manual. thanks in advance.

I just did the top end for the first time on my 09 wr300. I'm not a real hard revver, but i have used it for 7-8 days of racing plus lots and lots of aggressive riding (i have another bike for technical goat trails). I waited 200 hrs ish, and compression was still good and the bike ran strong. For people that don't rev the living crap out of bikes, I don't see any need to do it earlier than 200 hrs unless you just want the peace of mind. I've done the same schedule for years on my ktms as well.

Issues you can have (non-comprehensive list) in letting it go too long, if it wears enough to start rattling around, you can shatter the piston. I've never heard of that happening in a modern bike on the original top end tho. I let my ktm 300 go about 500 or more hours, and that was too long, plus i was running it a bit lean off idle because I was a slow spode at the time. The rings had worn to a sharp taper and that combined with the carbon blowing back from the lean jetting caused enough wear in the cylinder that I had to have it replated. The bike was still running fine when i tore it down however.

So, take that for what it's worth. If you have the time and inclination and it'll make you feel better, do it now, but I think 200 hrs on a 300 (any 300) is pretty safe for almost anyone.

I didn't bother cleaning the pv on mine. I normally don't anyway because the amsoil interceptor oil burns so clean, but i have never seen such a clean pv as on my 200 hr wr300. It looked new. Must be running it without coolant burns off all the carbon.

cheers for the reply mate. 200hrs seems like a very long time(talking like 6000-8000k's for me), 500 on your kato seems insane! people keep telling me 50hrs max but sounds like spare part dealers talk to me-maybe a 125 but not a slower revving big bore surely. mates with berg 300s reckon they wont touch theirs till 100 hours and i tend to agree(one of em rides real hard/quick too-ex motocrosser!). think its these four stroke lovers who are worried about droppin valves or bustin cam chains but still maintain their bikes will go longer between rebuilds than mine tryin to spook me & justify their engine choice. by the way the gas gas dealer near me reckons an 05/06ish ec300 went near on 30,000k's on original everything(plug inclusive-said it was a mess inside though but that aint bad!)

Shawbagga, you have have all the parts ready to go, do a comp check now at 80hrs (get an hr meter too) and then check it at 100 - it will give you a guage on how much compression you are dropping.

I'm a bit inclined with Motosapiens in that 150~200hrs operational hours is about right DEPENDING on how you ride and where you ride, how well the bike is jetted etc etc...simple rule of thumb, you rev the tits off it every time you ride or you slack cleaning the filter then change them at 100hrs.

I would just do a comp check with the guage and also by right foot on the kickstarter..when the bastard stops being a bastard to start then the comp is low

Just remember.....it's s two stroke!!!

ohmygewd whats a compression gauge worth & what sort of compression should it have, any ideas? yeah was planning on getting an hour meter when i rebuilt it so could check hours on next top end. always clean filter & dont flog it too much but it gets a workout! jetting/carby feels good/crisp and is stock unrestricted(from dealer-im unsure of settings). ive never had any dramas starting it once i got used to the kickstart(normal kickstarters just feel plain wrong now!) and still feels like it got good compresssion, but. any suggestions for carb/jetting settings youd recommend for FNQ weather/conditions(hot, humid not much above sea level) & better fuel economy(is this possible or are ya robbing peter to pay paul-better economy/performance at the expense of reliability?) short of getting the keihin carb? or ya reckon if it aint broke dont fix it?!
at the end of the day tho id rather sacrifice a bit of performance/fuel economy and run her rich/oily(40:1 but still dont blow much smoke) for peace of mind that my engine aint gonna go bang 80k's from me car! what ya mean by "just remember...its 2 stroke"? chz mate

hey motosapiens what piston kit & gaskets did you use? i got the genuine husky A size(smallest) piston & 0.5mm gasket. for first rebuild A size should be right hey? does base gasket size(0.3,0.4,0.5,0.8mm) make much difference power delivery wise-more torque or power one way or the other? i didnt even know there were different sizes available in the base gaskets-Halls just sent 0.5mm-middle of the road i guess. told em it was engines first top end so got smallest piston, tell me this is right-pain in the arse to send back to the US! anyone help a simple aussie out?

Good range is around 150-200psi (even up to 250psi), there are a few factors but since yours is stock then that range could be 150 to 210psi...below 150psi and the rings are on there way out.
A car compression tester from autobahn, supercheap, repco, ebay etc is all you need and to do the test is:
1) Take spark plug off and connect compression guage to spark plug socket.
1) Open the throttle fully
2) Use kick starter to rotate motor until the compression needle stops ( you can do this a few times as a good guage will stop at the highest reading).

You can also measure the ring gap (take the head off) and see if they are within spec...l don't know what brand piston comes with the WR300 but if it's Wossner, then you get go two ring changes before replacing the piston (thats on my WR360).

Base gasket will effect the amount of compression but can influence port timing as well. 0.5mm is perfect - if you have a 0.3mm, try your compression guage and see what you get..and the 'A' piston is correct.

As for FNQ (Far North Queensland), same logic to jetting applies (hit the search button on the 2 stroke forum..plenty of info)... the long and the short is get to know your low, mid and full throttle feels like, a have a familiar track to test (not up and down the street) and if the bike stutters/bog going from 1/4 throttle to 1/2 then you have jetting issues...if you have excessive oil from the exhaust then it's jetting - just don't fall for the 'Its the fuel mixature' business.

If it aint broke don't fix....it's correct but preventative maintenance and a good log book does wonders for a bike e.g. Did compression test on dd/mm/yy recorded 180psi with xxhrs or xxx km's.

There are a few FNQ boys here..sound them out - lol l'm for Vic so that 32C at 90% humid fark that that's beer time

no idea. i didn't really stress about it because the engine already has more power than I need everywhere. I did measure the old base-gasket at .5mm and got the same size to replace it.

Dont forget to ground the plug cap to a cylinder head nut so you dont fry your electricals.

cheers for answers gentlemens

Hello guys! I have a WR 300 2010. My bike has dome around 85 hours now. I use it mainly for Enduro and sometimes gravelroads, but during the last two winters i only been iceracing it. On the ice it,s a lot of wot and i used the high comp head for iceracing. I still haven,t changed the piston and the bike has perfect compression and the piston looks great, so i don,t think there is any reason to change piston before 150 hours if you use it for Enduro and keep the sercice intervals and use good oil. I always run 3% or 2,5% for enduro in summertime. Now i have honda CR 500 that i have ported and done a lot to, so there will only be Enduro/ gravelroads for the 300 in the future.

Johnny

cr500 eh, nice ride mate. wouldnt mind a spin on that! how many sets of rings/small end bearings have you done in that time johnny? i had a look through the exhaust outlet at the piston & noticed some blow by(black carbon) below the rings-this means rings are worn yes? i also noticed some slight scratching on the piston-this is bad yes? i havnt had time to take it apart yet but when i do ill just replace piston anyway as theyre fairly cheap really(good engine insurance i guess). whatdya reckon mate? anyone? the cylinders are pretty hardy im told so hopefully i havnt scored that too much you think!?

Hello Shawbagga. I haven,t changed anything on my 300, except the head. Everything looks so good that i find no reason to change anything yet. There is always a small amount of carbon on the exhaust side, but as long it,s no build up carbon deposits you don,t have to worry too much. the piston is of course getting coloured in that area. The small scratches on your piston you don,t have to worry about as long as they aren,t really deep. You have probably got some dirt in there sometime, but that will not be anything you have to care about. If you want to be sure and feel extra safe, change piston when you already have disassembled everything. i can clearly see the honing marks still in my cylinder, so the quality is good on the jug and also the vertex pistons. Good luck, my friend!

Johnny

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thanks cobber, yeah black build up marks on exhaust outlet side makes sense. as you are probably aware by now i am a gun mechanic(which button is the sarcasm one?) :0)

haha! Ok, gun mechanic! If you feel in the bore with your fingernale and it doesn,t hook up, don,t worry. If there has been some debree in the bore it,s gone now anyway. Change your piston and you can sleep well;=)! Are you running with the standard Mikuni carb?

yeah mate standard mikuni & standard settings(whatever they are i havnt touched it!). they swapped the slide/throttle stop thing at the dealership when i got it-the standard ones restrictive for on road legalities apparently. it came with spare jets/needle etc, unsure whether the dealer changed anything there but doubt it. dont know nothin about jetting & it seems to run ok, doesnt bog/stutter down low but will definitly be paying more attention to jetting when i finally get it back together & ride it(cmon xmas!). could maybe be crisper off the bottom. temperature & altitude dont change much here and never knew the mikuni was so shat upon, but the keihin seems to be the mod of choice on this site, might look into it. reckon its worth it? want a hydro clutch first tho! run me nail over them scratches and it doesnt catch but they do look a bit average. they start 10mm under the lower ring & are about 30-40mm long. gonna do a compression test and see what that reveals(ill let u know). shocks getting a service & was gonna go up on the spring, 5.4kg stock. im 100kgs reckon something around the 6kg mark-hard terrain generally-thorts?

Ok, yes, the PWK is really a good mod and worth the money. More linear powercurve and more easy to jet. Just look here at our jetting threads=). Everyone (almost)who has changed carb really like the PWK. With the PWK, high comp head, right jetting and Leo Vince silencer my bike delivers close to 50 bhp. My Mikuni has found it,s place on my sons WR 125 2008 instead=)! I personally have no problems with the cable clutch. I don,t think it,s that heavy actually. One thing that bothers me a bit is the clutch drag. That gives me some issues when the bike dies and when i,m standing still. it,s hard sometimes to get it in neutral. I will look at some other transmission oil. I think it,s a good idea to go up in springs for you, especially at front. i would like mine stiffer too, and i weigh arond 87-88kg,s.

+1 on Johnny's comments, the PWK is awesome, my mikuni was different day to day in Adelaide and the weather here is pretty consistant. I got 44.3hp with the same mods Johnny mentioned, plus a fmf expansion chamber(bottom to mid biased) but the dyno I used is known as the lowest reading in SA(best tuner though), and my engine is silky smooth and pulls from any revs everywhere.
I have an attachment for my clutch that came with my donor 360 bottom end(for the 6 speed) but I haven't bothered fitting it yet, as once I re-routed my clutch cable I didn't feel I needed it, have a play with what you've got before going the hydro route, it could be a waste of money...
I'm over 100kg, and saving for fork springs, the spacers I have in there now are just a band-aid mesure...

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hey twatty howd you re-route your clutch cable? got an EZ pull lever im gonna try too! be nice if manufacturers gave you options on spring rates when you buy a bike instead of one size fits all, couldnt be that hard & expensive surely