2005 CR85R struggles

[Tekime]

Adopted this bike for a while and it rips. But it also doesn't want to stay running. Starts up OK when cold with choke, but after a couple minutes of warming up just feels like it wants to die. Pretty sure the exhaust is aftermarket/shorty and apparently the "carbs were done" but who knows what. It's leaking a little black oil from the exhaust header and pipe, lots of white smoke, makes me think it's running super rich.

I don't know much about 2 strokes, is that normal? What's typical for warming up - I've heard you shouldn't idle for long. Haven't tinkered with it much yet but any tips on where to start would be cool.

[Imbeek]

Turn the choke knob clockwise to increase idle. Two strokes should stall after a second or two at idle, at least for motocross. Most people I know who ride two stroke dirt bikes shut off the choke the instant the bike starts and rarely if ever let the bike idle...otherwise, plugs can foul quickly. Regarding the spooge, try some Avgas from the airport and 50/1 premix or if you wanna spend some more money, race gas. The whole gas choice thing is highly debatable and Avgas probably isn't ideal, but I tried some because all my buddies run it and it definitely stopped black goo from appearing at the end of my silencer, and the bike runs better and cleaner for less than 5 bucks a gallon.

So, adjust idle, fresh plug, don't let it run with choke on or expect it to idle long, clean up your fuel choice, and if it still isn't running right, clean the carb and/or get it jetted right.

[Tekime]

Great thanks man. I definitely kept the choke open for a good few minutes and probably drowned it. Will see how things go later today and look into Avgas.

[breakdirt916]

imbeek hit it...adjust/clean/jet...*sometimes* replace carb, but that's less common

I'd also add - check the reeds (and sometimes exhaust valve if stuck open)

white smoke could be coolant or condensation though...hoping it's not the former

but otherwise, they're pretty smokey

And be careful...small in size but packs quite the punch... probably the bike I have gotten most hurt on!!!

[typeone]

if the previous owner told you that the "carbs were done" ... i'd tear the whole thing down

but as a basic start: drain/dispose of gas in tank unless you have done the premixed fill at the proper ratio, remove/drain/clean carb (all of it + note jetting and air screw position), inspect/replace reeds, remove/inspect expansion pipe and silencer, repack silencer, clean filter, fresh plug. sounds like a lot but it's all easy and important if the bike has been run since ~'05 without any of this.

like breakdirt said, white smoke is interesting. since you're not familiar with 2-strokes, watch the coolant level. could just be rich and gummy though. once tuned and hot, you don't see much smoke but lots of factors there.

sweet score! 80's are a blast.

[Tekime]

Gave her a quick start again, fired right up, got off the choke fast, kept it revved and it died/bogged in about 10 seconds. Dripping black goo again after that short run. Doesn't want to start again. So I'm starting to think maybe it's not user error (entirely).

Gonna follow all this awesome advice, start with the gas, plug, pop the carbs off, clean/inspect, check the reeds, check the pipes, probably fit a new gasket/check the header bolts it looks like a tiny leak up front.

I wanna fuggin ride this thing!!! It's like a hundred chainsaws singing in unison

[number9]

My KTM needs the choke to start but I turn it off as soon as the bike actually runs. This usually means some time holding the throttle open enough to prevent it stalling..

[aldend123]

See if you can use some throttle to keep it running and let it warm up a bit. If you can get it running, then see how the throttle feels. Now make your assessment. Difficult to start is different (and better) from difficult to run. If it died right after start up, you're probably starting to accumulate unburned gas and oil in the chamber. Don't be surprised if it takes you quite a few kicks after it sputters out.

In my limited experience, most small engines seem to have a routine they prefer that you have to learn. My WR's manual says not to twist the throttle when starting 'because it has a pumper carb'. Recently, I was struggling to start it in the cold and a yamaha rider twists his wrist at me. Two pumps followed by thump-thump-thump.

[Imbeek]

Don't forget to turn on the petcock and make sure there's gas in the tank (LOL)

[b0xmonkey]

I had the same bike, same year for my kid a few years back. Had the same exact symptoms you listed too. Spent a lot of time trying to figure it out, ended up grabbing a newish carb on ebay and my problems were solved forever. The previous owner had also done some "mods" like altering the air box so my best guess is something was drilled out in the carb that I couldn't see. So if you can't get past it, give this a shot.

[Tekime]

Lol, yes fuel & petcock in order

Even getting right off the choke and keeping it alive with the throttle, still died fairly quick and then doesn't want to start. My gut says the chamber is filling up, maybe weak spark or dirty carb? Not enough air? But my gut likes to mess with me..

Top end was blown up last year, entire case was split and top/bottom end done, I see new gaskets everywhere. Think she's been sitting for a while this year though.

Oh, and when I got it in my truck a mouse jumped out from... somewhere. Which I totally forgot about until now, there's probably a frigging nest in the airbox.

Got a few things to check I guess

[Tekime]

I had the same bike, same year for my kid a few years back. Had the same exact symptoms you listed too. Spent a lot of time trying to figure it out, ended up grabbing a newish carb on ebay and my problems were solved forever. The previous owner had also done some "mods" like altering the air box so my best guess is something was drilled out in the carb that I couldn't see. So if you can't get past it, give this a shot.

Same thing with a little 50cc China 2 stroke I picked up last month - rebuilt the carbs three times, ultrasonic cleaning, made new gaskets.. finally bought a $35 carb for an LT80 and she runs mint now.

Lucky kid BTW

[GearHd6]

Sometimes you can chase this stuff for days when it's as simple as installing a new plug.

[Imbeek]

I'd definitely try a new plug and there are very few places mice like to live in dirtbikes. Get the acorns, insulation, and other stuff out of the airbox/carb...

[carsick]

Just to confuse things, a lean misfire will dump unburned fuel into the exhaust and blue smoke and spooge, just like a rich mixture. Also, regardless of jetting, a plugged air bleed circuit will richen the shit out of otherwise good jetting (think choke plate on a car carb). Two strokes are sensitive creatures, but when you get the mixture right they rip! Crisp is a perfect adjective. My KDX likes a little Italian tune up, it'll sputter and foul the plug unless I run the piss outta it.

[Tekime]

That looks clean right?

I'd definitely try a new plug and there are very few places mice like to live in dirtbikes. Get the acorns, insulation, and other stuff out of the airbox/carb...

Damn it now where am I gonna keep my acorns?

Just to confuse things, a lean misfire will dump unburned fuel into the exhaust and blue smoke and spooge, just like a rich mixture. Also, regardless of jetting, a plugged air bleed circuit will richen the shit out of otherwise good jetting (think choke plate on a car carb). Two strokes are sensitive creatures, but when you get the mixture right they rip! Crisp is a perfect adjective. My KDX likes a little Italian tune up, it'll sputter and foul the plug unless I run the piss outta it.

Confusion is the moment before epiphany right? Makes sense though, either way it isn't getting burnt up?

"sensitive creatures" sounds about right.. so far I'm reminded of a few ex-girlfriends.

[aldend123]

Is that one of your steaks wrapped in hay?

[Tekime]

Is that one of your steaks wrapped in hay?

LOL it really brings out the flavor

[typeone]

oh man, hahaa, see my first comment... tear that bish down. those squatters built a sweet pad

[Imbeek]

Nice!

[carsick]

"sensitive creatures" sounds about right.. so far I'm reminded of a few ex-girlfriends.

Ah, but when you get the tune right, they're a lovely thing. As long as they didn't have a mouse nest in the box.

[Tekime]

oh man, hahaa, see my first comment... tear that bish down. those squatters built a sweet pad

Yep yep, pretty sure the bastard came home in the truck, he's probably migrated to one of my other bikes already. Time to build a wall!

Ah, but when you get the tune right, they're a lovely thing. As long as they didn't have a mouse nest in the box.

I'm starting to see the strange attraction to these things.

Dirty box is never good though

[typeone]

nothing strange about it, just wait until you can actually rip on that thing mini powerbands > sex.

[cdovego]

I suggest selling it, you'll never get that going. (I can be by Sunday)

[Larry]

I may have skipped past it but if no one said it yet, check the exhaust for a nice too. Expansion chambers make for a cozy mouse house