250-500cc wr300 issues....

Is that what the plug looks like after a wide open throttle run under load? Like Kelley said, do a top end plug chop.

The plug is after a day of riding. I'll have to do a plug chop sometime this week

I bought a used WR250 last season. Did a few short get-to-know-the-bike rides and all seemed fine. Keihin carb on bike and Rekluse.

Then, went on about a 60 mile ride. After super-tight single track of about six miles and chugging around not on the pipe we finally got out into open road.

I hit the gas in every gear and the bike practically didn't move. I changed the plug at lunch and no change. Adjusted carb and only a minor change.

Got home and checked lots of things. Power valve a little dirty but not bad. Bike was spooging pretty bad too.

Pilot jet had a spec of something inside so I cleaned it up.

I decided to take the silencer off and try to repack it. The thing seemed like it weighed 100 lbs.

The previous owner changed the stock pipe to a Leo Vince spark arrestor type. It was saturated with oil and the spark arrestor screen was almost plugged solid with carbon.

I ran the bike with no silencer and it ran great.

Moral of the story: check your spark arrestor if you have one.

I replaced the silencer with a new FMF with a non-screen spark arrestor.

Mike

my dynoport has the spiral turbine deal and this seems the way to go..
everything sounds like it checks out, reading throught the first posts i was wondering if the clutch is causing this, higher revs without actually gaining speed. no slippage on bottom but a top speed issue. my friends banshee was doing this with sacked clutch springs. hard to believe tho on a fairly new bike. i cant really comment on your gearing as my 95 is a 6 speed and my other huskies are swedes, and those are known to have true off road enduro trans that will burn down the road as well as the tight woods..the earlier italian 6 speed does swap into the later italian bikes easily, lots of info here about it.
unrelated to your top end problem but from the sound of it i would lean your rod a quarter turn, i bet its perfect then. your plug looks good to me, altho you say it stutters a tad at small steady throttle openings. the lectron should be very clean at this area. i run the same oil and ratio as you with great success, have for about 15 years now., altho i dont do super technical stuff for hours on end. my riding is varied with tight stuff for maybe a half hour then a chance run a gear or two in a field or longer trail. no spooge issues for me at all.

It seems like we have the same riding style, some tight stuff then a little time to open it up. I have alot of spoogle coming out of my pipe, to the point where it drips onto my swingarm. I'm going to get the jetting right and go from there and maybe throw heavy duty springs in if I can find them. I really appreceiate everyone's input

My wr300 ran fine and seemed normal but had pretty much no power from mid to top end when I lost compression. Just sayin....

Is this a leftover Italian or a KTM? Spooge is caused mostly by low combustion temp and WRs seem to have weak spark. There are plenty of threads where various prob's were solved by replacing the CDI, so something to consider maybe. Check your plug wire and the rest under the tank.
And I agree a clogged SA screen would do it.
My 300 with Lectron and Rekluse and 13/46 gears absolutely rages on top. No speedo yet, but pretty sure I'm hitting @60mph about 5-6000rpm in 5th gear. Guessing it should top out @ 70mph.
If 1 CS tooth = 3 RS teeth, 15/48 = 13/42, so you should be flying on top.

any one know how high rpm the 300's make? its gotta be around in the 10'000 no? always surpised me that my old 125 allegidly topped out at 12-13000 rpm its crazy to think a piston can change direction that quickly and not end up taking your face off as it has had enough.

300? IM SAYIN AROUND 9K

I think its a leftover italian 300. The spark issue brings up a good point since those ignitions are notorious for having issues

I was thinking @ 10K too. And I think I'd need to roll onto at least a 1/2 mile straight in 4th to get there.

If it's red it's Italian.
Just looking at the spark will give you an idea of it, I could barely see mine in bright daylight. On my XR, with nearly the same NGK Iridium plug, the spark is fat and bright. I'm sorting the suspension right now, but the ignition, electronics and a front light are next. I've been searching here to see what the options are/were, probably a call to Bill's or Hall's would be good.

So stock spark arrestor? If your bike has been spooging heavily for 40 hrs I'm interested in whether the SA is full or clogged.

I had a speedo on my 09 WR250 and in stock form with a mt43 trials tire with Tubliss @ 5psi (which grows taller at high speed acting like a 6th speed) it would do 80mph with 13:50 and 82mph with 13:48 the reason it was so similar in mph is because the engine could rev higher with the 13:50 and didn't quite have the power to rev as high with the 13:48. The 13:50 was ideal because it made 1st a bail out gear and trials like tasks were easily done with less clutch work. The 300 may not rev as high as the 250 but has more mid torque so unless you over do it and put a high gear in it that it can't pull in 5th gear it should be capable of higher speeds then my 250. I now am running a knobby with Tubliss and 13:48 gearing, the tire doesn't grow at all but top speed is similar because the FMF Gnarly and the Lectron let it rev out higher. I still prefer 13:50 but I had a new 48t sprocket that needed wearing out.

The spark problems on the Ducati ignition aren't causing a limiting factor when they fail but rather no start or completely cutting out under a load. I've only read of a few with these issues... probably no more percentage wise then the KTM or GasGas Kokusan digital ignitions.

Maybe I'll take the silencer off and take it for a quick spin. I don't know any more...

try taking the silencer apart and repacking to knock out a variable perhaps. at least that will be a maintenance item done...

How heavys the silencer if when you take itoff its like its full of lead yup repack, spark arresters are they removable? Can you not seestraight through the silencer? Strange laws in them there states.

A clutch can get "messed up" in a lot less than 40 hours. Not to mention the the Husky clutch set up isn't the greatest. Also, how did you verify 50 mph? Speedo or butt meter?

2007 WR 250 with 14-47 gearing will do 80mph for me, i hate to say it but i think you have to rip it apart and look at the transmission something is not right.

After I told my story somebody told me that I could have jammed a screwdriver through the screen to get the exhaust flowing better.

I beat the hell out of the pipe and couldn't get it apart. I saw maybe 2" of packing when I was done with it. Just threw it away.

sometimes on stubborn silencers (almost all are) i use a propane torch, heating around where the screws were and continue heating till its gets very hot to touch. using a soft dead blow mallet the silencer will start budging faster and faster with everything softened up