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Yz85 losing power in powerband

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Hey guys im having issues with my yz85, runs great except when it hits poweband it cuts out/boggs, seems like a fuel/spark problem but i cant figure it out, air screw is 1/2 turn out, tried putting i to 1 1/2 but wouldn't start, theres also quite a bit of oil seeping of the spot when the 'header' connects to the silencer, the rubber boot is shredded, where could i buy a new one or could i use something else? Not too much spooge coming out of the silencer, just from that joint. My spark plug was fouled, was running a bpr9es but. Replaced it with a ngk br8es, is idling a bit better, haven't been riding it too much just because of how much oil is coming out of that joint, could it be a jetting issue? Haven't had a chance to take the carb apart yet to check the jetting, any help is appreciated, just need to get my bike running properly again. 

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Sounds to me like that bike needs a good going over.  Maintenance is important, you can't just ride it and put gas and oil in it. 

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1 hour ago, cjjeepercreeper said:

Sounds to me like that bike needs a good going over.  Maintenance is important, you can't just ride it and put gas and oil in it. 

Yeah i know that, i just recently bought it probably only put 2 hours on it, im just not sure what needs to be checked etc, i just put a new plug in it and its running a bit better, not trying to sound like a "noob" but i dont much about 2 strokes, ridden 4 strokes all my life. Would yiu happen to know what that rubber piece is called that connects the exhaust to the silencer? Cant find it anywhere. 

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Black spooge should not come out the exhaust anywhere. Sealing the pipe is like mopping the floor while the bath tube is overflowing. Fix the source.

Needs a clean air filter?

Jetting too rich for the warmer air temps?

Exhaust clogged with oily sludge making the motor run even richer?

Top end caked with carbon, making the problems worse?

I've never seen a stock YZ85 with correct jetting for moderate temps at sea level. Always too rich.

What jetting is in it now?  Pilot, main, needle part# and needle clip?

Edited by numroe

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2 hours ago, numroe said:

Black spooge should not come out the exhaust anywhere. Sealing the pipe is like mopping the floor while the bath tube is overflowing. Fix the source.

Needs a clean air filter?

Jetting too rich for the warmer air temps?

Exhaust clogged with oily sludge making the motor run even richer?

Top end caked with carbon, making the problems worse?

I've never seen a stock YZ85 with correct jetting for moderate temps at sea level. Always too rich.

What jetting is in it now?  Pilot, main, needle part# and needle clip?

Air filter is almost new, not perfect but pretty clean

As far as i know jetting is stock but i haven't taken the carb apart yet as i am very busy with school/work right now, but will look as soon as i have time. 

Exhaust might be clogged but i replaced the spark plug and its running quite a bit better now, still some spooge but not near as bad as before, boggs down a bit in 2nd when it hits powerband but thats it

I took the spark plug out and shined a flashlight into the hole and there quite alot of black sludge or carbon built up on the piston, should i just wipe that off? Or is that a result of running rich i assume. 

Yeah i live in Midwestern Ontario Canada, gets pretty hot and humid in the summer, about 20-35 Celsius up to 40 with humidity sometimes. 

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Some spooge is OK. Its a 2-stroke and there will always be some unburned fuel/oil going out the exhaust at least until we get direct injection. You will want to replace the exhaust joint, but it is not the cause of your problems. 

In your case, you should start with the basics: fresh piston and rings, reeds in good condition, clean air filter good spark plug and fresh gas with the correct oil ratio. Once you are sure those are all good, you can move on to the jetting, which may be rich now that the hot weather has come.

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I should have added to repack your silencer. 

You should also take the top end apart and replace the piston and rings, check the cylinder for wear and check the rod and crankshaft bearings. There is likely no point in trying to clean the carbon off the piston. This may sound intimidating if you have never done it, but it is fairly simple and can be done with basic tools. 

 

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25 minutes ago, Woodzi said:

Some spooge is OK. Its a 2-stroke and there will always be some unburned fuel/oil going out the exhaust at least until we get direct injection. You will want to replace the exhaust joint, but it is not the cause of your problems. 

In your case, you should start with the basics: fresh piston and rings, reeds in good condition, clean air filter good spark plug and fresh gas with the correct oil ratio. Once you are sure those are all good, you can move on to the jetting, which may be rich now that the hot weather has come.

Yeah ive already ordered the joint now

Im not sure piston and rings is necessary, the previous owner had proof of rebuild and only 6 hours on it (top end) and i have only put 2-3 hours on it but ill look into it. 

Air filter and plug are good, will check reeds/jetting soon, thanks alot for your help! 

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3 hours ago, Woodzi said:

I should have added to repack your silencer. 

You should also take the top end apart and replace the piston and rings, check the cylinder for wear and check the rod and crankshaft bearings. There is likely no point in trying to clean the carbon off the piston. This may sound intimidating if you have never done it, but it is fairly simple and can be done with basic tools. 

 

Ok yeah i repacked it once already but am sure i need to again, cylinder and piston look fine, took carb off and exhaust and look into the cylinder, rings looked fine aswell, one reed had some scratches but nothing major, couldn't check jetting as screws on the carb are stripped and couldn't open it up. 

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2 hours ago, S.O.A.N.Z said:

you probably need to get into the carby to check for peace of mind

I will see if i can grind the screws so a flathead would work, not sure why all the screws are Philips, strip too easy.. I will update when i open up the carb? 

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Brace the carby in a vice and use a center punch on the edge of the screw just enough to budge them to get the screwdriver in there

 

29430.jpg

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On 6/11/2017 at 8:08 PM, S.O.A.N.Z said:

you probably need to get into the carby to check for peace of mind

Alright so i got into the carb, was suprisingly very clean, here are some pictures of the jets, not sure what they are called, also noticed a hole/chip under my water pump, coolant is slowly leaking out when it warm, someone said just to cover it with high heat jb weld, not sure what i think about that though, and the bike is running a bit better, but plug comes out wet every time and getting a little spooge

2017-06-21 18.47.03.jpg

2017-06-21 18.46.35.jpg

20170621_152310.jpg

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On 11/06/2017 at 1:10 PM, Braapstustu said:

Air filter is almost new, not perfect but pretty clean

As far as i know jetting is stock but i haven't taken the carb apart yet as i am very busy with school/work right now, but will look as soon as i have time. 

Exhaust might be clogged but i replaced the spark plug and its running quite a bit better now, still some spooge but not near as bad as before, boggs down a bit in 2nd when it hits powerband but thats it

I took the spark plug out and shined a flashlight into the hole and there quite alot of black sludge or carbon built up on the piston, should i just wipe that off? Or is that a result of running rich i assume. 

Yeah i live in Midwestern Ontario Canada, gets pretty hot and humid in the summer, about 20-35 Celsius up to 40 with humidity sometimes. 

I'll guess that the problem is as I wrote last time. Rich stock jetting. Clogged up top end and exhaust. Conditions get warmer and more humid making the problem worse.  So I think you should change the jetting.

Interesting you have a 140 main. I thought stock YZ85 is a 138. Check your owner's manual. That could be your problem right there.

It'll be safe to try a smaller 42 pilot jet. Most YZ85s are rich below 1/4 throttle.

Check your needle clip position vs your owner's manual. Ensure that clip is stock and try that (with the smaller jets).  If you motor still feel rich at 1/2 throttle (with the 138 main and 42 pilot) then try going one clip position leaner on the needle (clip higher so needle sits lower).

Be sure to clean and repack your muffler.

If you still have problems then put a new piston in it. I guess it's pretty easy on your bike:  Remove tank+shrouds. Remove the pipe. Drain the coolant. Remove spark plug cap and coolant top hose. Then unbolt the base of the cylinder and take the cylinder off. When the cylinder is removed be sure to clean the exhaust port. If the head dome of carboned up, then rempve head from the cyl and head the head too.  When putting the new piston on, put a clean white rag around the conrod to catch anything from dropping into the crank case.

It's also possible that your intake reeds are damaged.

Screen Shot 2017-06-22 at 9.15.25 am.png

Edited by numroe
reeds

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On 6/21/2017 at 7:18 PM, numroe said:

I'll guess that the problem is as I wrote last time. Rich stock jetting. Clogged up top end and exhaust. Conditions get warmer and more humid making the problem worse.  So I think you should change the jetting.

Interesting you have a 140 main. I thought stock YZ85 is a 138. Check your owner's manual. That could be your problem right there.

It'll be safe to try a smaller 42 pilot jet. Most YZ85s are rich below 1/4 throttle.

Check your needle clip position vs your owner's manual. Ensure that clip is stock and try that (with the smaller jets).  If you motor still feel rich at 1/2 throttle (with the 138 main and 42 pilot) then try going one clip position leaner on the needle (clip higher so needle sits lower).

Be sure to clean and repack your muffler.

If you still have problems then put a new piston in it. I guess it's pretty easy on your bike:  Remove tank+shrouds. Remove the pipe. Drain the coolant. Remove spark plug cap and coolant top hose. Then unbolt the base of the cylinder and take the cylinder off. When the cylinder is removed be sure to clean the exhaust port. If the head dome of carboned up, then rempve head from the cyl and head the head too.  When putting the new piston on, put a clean white rag around the conrod to catch anything from dropping into the crank case.

It's also possible that your intake reeds are damaged.

Screen Shot 2017-06-22 at 9.15.25 am.png

Exhaust and top end are perfectly fine, took it apart and checked already. 

Reeds are also in good condition, ill look more into the jetting/needle  postion  sometime soon

What do you know about that little hole on the bottom of my water pump? Can i just cover it with jb weld or do i have to replace the pump, which id rather not do. 

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Great. Next fix the jetting. Main jet, pilot jet and maybe also the needle clip.

That drain hole is probably there for the same purpose as on the 250. So that a leaky coolant or oil seal means coolant or oil can get out but the two fluids cannot mix inside your motor. So try a new coolant seal. Don't block a weep hole which has a great purpose.

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15 hours ago, numroe said:

Great. Next fix the jetting. Main jet, pilot jet and maybe also the needle clip.

That drain hole is probably there for the same purpose as on the 250. So that a leaky coolant or oil seal means coolant or oil can get out but the two fluids cannot mix inside your motor. So try a new coolant seal. Don't block a weep hole which has a great purpose.

Yeah i covered it then an hour later found out it had a purpose, looked like a chip from a rock at first, not much coolant comes out, theres a small wet spot around it after riding for a while but thats it, ive heard you have to split the cases to fix it, is that true? 

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7 hours ago, Braapstustu said:

ive heard you have to split the cases to fix it, is that true?

No. You never need to split the cases to replace water pump seals.

Looking at this YZ85 parts diagram it looks the same as in the YZ250. Remove the pump cover, then unscrew the impeller (anti-clockwise), take out the washer, then you can pull the old seal out (part 5) using a pick. Then push in a new seal and put it back together.  Just tighten the impeller gently, since it self tightens due to water resistance when you rev the motor.

If my some rare chance your pump shaft is damaged, then you replace it my removing the right side cover, but don't split the cases or remove the motor.

 

Screen Shot 2017-06-27 at 5.00.57 pm.png

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On 6/27/2017 at 3:06 AM, numroe said:

No. You never need to split the cases to replace water pump seals.

Looking at this YZ85 parts diagram it looks the same as in the YZ250. Remove the pump cover, then unscrew the impeller (anti-clockwise), take out the washer, then you can pull the old seal out (part 5) using a pick. Then push in a new seal and put it back together.  Just tighten the impeller gently, since it self tightens due to water resistance when you rev the motor.

If my some rare chance your pump shaft is damaged, then you replace it my removing the right side cover, but don't split the cases or remove the motor.

 

Screen Shot 2017-06-27 at 5.00.57 pm.png

Ok thanks for your help! Can i still ride the bike like this? Just make sure my coolant is topped up.. Will it do any damage to the engine/pump if i dont change it out right away? Will probably be a few weeks before i can get the part i need. Or would it be best to just wait it out. 

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