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what the eff is wrong with my dirtbike :(

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i have an 85 bored to a 95. it runs. but not good. when you take off you have to play with the clutch and gas a little then it suddenly takes off. i took it out last week and when i was going up a hill that wasnt even that gnarly, it died out on me. lol. what could it be?

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Sounds like a dirty or lean pilot jet from what you described. Was the carb re jetted after it was punched out?? Does the engine run good at higher speeds?? Does it only bog out at low speeds, 0-1/4 throttle??

we did the main jet. not sure if the main and pilot are the same. hah. and it runs okay unless youre going up a hill or when you get up to 6th gear. its so annoying. it runs really rich too. and my bf has messed air and all that . and the carb is fine, we have had it apart probably around 20 times.

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Big bore kits almost always require leaner jetting to run correctly.

 

Have you checked the reeds to make sure they are sealing properly?

 

The YZ85 doesn't have a power valve, and as such doesn't have very good low-end torque, you have to  scream it to make any power. And if the tuner that did the big-bore install ported it for even more top-end that will only exacerbate the issue.

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Big bore kits almost always require leaner jetting to run correctly.

Have you checked the reeds to make sure they are sealing properly?

The YZ85 doesn't have a power valve, and as such doesn't have very good low-end torque, you have to scream it to make any power. And if the tuner that did the big-bore install ported it for even more top-end that will only exacerbate the issue.

i will have my bf check them. its a cr85 also, not sure if theyre pretty much the same. ... according to the manual, we need an 18 jet. the people had a 27 or 28. or something like that. but the shops here only had a 15 or 20. were running it with a 20 now cause were afraid to go too lean.

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Oops, don't know why I assumed YZ...:bonk:

 

Going too lean on the pilot won't damage anything, it will just make starting difficult and kill throttle response.

 

You probably need to be focusing mainly on the needle though.

 

Since it's a CR, I would ask in the Honda Two-Stroke forum, someone there may have previous experience on jetting a big-bore CR85.

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Write down how the bike was before you started messing with it, pilot # main # and needle # and position you will be scratching your head and chasing your tail in circles if you don't . That way you will have something to fall back on when it gets worse . 

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There is a 95cc kit? I thought the only option was 105cc  :confused:

 

Sounds like your jetting is pretty effed up. Get somebody who knows jetting to fix it. Or do some thorough reading on here. There are thousands of threads on how to read the plug and tell the signs of rich/lean and jet accordingly. But dont just blindly start throwing different jets in it. 

 

Also, I know I say this on just about every thread, but do a compression test. If it bogs out on you going up a hill then you may need a new set of rings. Just a thought.

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There is a 95cc kit? I thought the only option was 105cc :confused:

Sounds like your jetting is pretty effed up. Get somebody who knows jetting to fix it. Or do some thorough reading on here. There are thousands of threads on how to read the plug and tell the signs of rich/lean and jet accordingly. But dont just blindly start throwing different jets in it.

Also, I know I say this on just about every thread, but do a compression test. If it bogs out on you going up a hill then you may need a new set of rings. Just a thought.

its not really that we were "blindly" throwing jets in. we have the manual so we were doing it to spec . my bf isnt a tard, and if i feel he is acting like one, i tell him. lol. and the big bore kit.. i dunno. thats just what the guy told me. ... its okay for me to be a tard. sh.

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There is a 95cc kit? I thought the only option was 105cc :confused:

Sounds like your jetting is pretty effed up. Get somebody who knows jetting to fix it. Or do some thorough reading on here. There are thousands of threads on how to read the plug and tell the signs of rich/lean and jet accordingly. But dont just blindly start throwing different jets in it.

Also, I know I say this on just about every thread, but do a compression test. If it bogs out on you going up a hill then you may need a new set of rings. Just a thought.

and. how do you do a compression test on a two stroke

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According to RMATV, stock jetting for an 03 CR85 is a 50 Pilot and 125 Main... I'm not sure what manual you're looking at that says to use 18 or 20 sized pilot jets.

 

I'd first go thru the bike as said before to become familiar with everything... reeds, top end, silencer packing, carb, etc.

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According to RMATV, stock jetting for an 03 CR85 is a 50 Pilot and 125 Main... I'm not sure what manual you're looking at that says to use 18 or 20 sized pilot jets.

 

I'd first go thru the bike as said before to become familiar with everything... reeds, top end, silencer packing, carb, etc.

 

 

If it's a Keihin, I believe 45 is the smallest pilot they make.

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sorry. 118 main. .. but we have a 120 main. we called fmf to see what they would do and the said set from your specs 3 up for the main and 2 up for the pilot. we had a 50 pilot. so we got a 52. were putting it in right now.

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How does it idle? You said it runs really rich, so check the air screw and reeds for wear. If it's turned all the way in, you'd have to turn up the idle screw to keep it from dying out. That will make it run terribly. It's best to be between 1.5-2 turns out. After you put the 52 in, does it sound lazy barking the throttle off idle (not zippy) and spits smoke out the back?

 

I'd say you're close enough for now with the main, and if it idles smooth and crisp, do as Chokey said, work on the needle. Did you take a look at what it says on the needle? What clip position is it in, relative to the very top position?

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How does it idle? You said it runs really rich, so check the air screw and reeds for wear. If it's turned all the way in, you'd have to turn up the idle screw to keep it from dying out. That will make it run terribly. It's best to be between 1.5-2 turns out. After you put the 52 in, does it sound lazy barking the throttle off idle (not zippy) and spits smoke out the back?

I'd say you're close enough for now with the main, and if it idles smooth and crisp, do as Chokey said, work on the needle. Did you take a look at what it says on the needle? What clip position is it in, relative to the very top position?

it idles like crap i think. its reeeeeeally hard to start without the choke. it used to not idle, but my bf messed with it, i think its around 2 turns out. .. and the needle is in position 2 of 5. ... as for the way it sounds and stuff.. i will have to wait for my bf to wake up cause it just sounds like a dirt bike to me. ..

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The bike should need the choke to start cold, or else you know you're just too rich on the pilot.

 

Once it's warm, it should start easily without choke. If it's hard to start warm without choke, you're rich on the pilot and need more air on the air screw. If it's more than 2.5 turns out, go down a size on the pilot and start back at 1.5 turns out.

 

Also try dropping the needle down to 3rd from the top and see if that helps or hurts the mid range.

 

This all makes me wonder...did the bike run well before? Or did you just buy it and you're trying to get it all sorted out?

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