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Bad rattling coming from bike?

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Hi, i took the bike out today and it started rattling pretty bad when riding it sounds horrible, i cant pinpoint it exactly but i think its coming from the top end, the bikes recently had a new piston about a month ago but not too sure if that's the reason? 

 

ive uploaded a quick video can anyone tell me what the problem might be?

 

http://www.youtube.com/watch?v=ETO2Yr7l8a0&feature=youtu.be

 

 

 

also when i start the bike and give it some gas it seems to hold the acceleration up for 3-4 seconds after ive checked the pin inside the carb to see if its getting stuck but it isn't anyone have any ideas?

 

thanks in advance

 

 

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Look at the easy stuff first? Pipe springs loose, or rattling? Is the kick starter rattling against the pipe or something else? Stand next to your bike and rev it while carefully looking around the engine, watching/ listening. You may find the issue..Loose parts/ bolts...never know! Unfortunately the video is not much help.

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Look at the easy stuff first? Pipe springs loose, or rattling? Is the kick starter rattling against the pipe or something else? Stand next to your bike and rev it while carefully looking around the engine, watching/ listening. You may find the issue..Loose parts/ bolts...never know! Unfortunately the video is not much help.

thanks, ive checked all the loose parts bolts etc.. it seems to be coming from the engine - really does sound like top end, would it be worth stripping it down?

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Honestly from what I could hear in the video it sounds like its just running to rich. I couldn't hear any rattling, of course I'm at work though. If there is legitimate rattling in there, I have no clue what it could be.... Off topic, what type of fuel are you using and what's you're fuel to oil mix ratio?

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Also when you pull the spark plug out what color is it? It SHOULD be a nice gold brown.... Make sure it's not black and oily. As far as the rattling is concerned like the other guy said it could be something external... My KX 125 back in the day rattled real bad and it was the springs that hold the pipe on by the cylinder. Hope that helps.... Sorry I couldn't hear much from the video

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does it rattle when the bike is sitting still or does it only rattle when you are riding it?

 

If it rattles only when you are riding it, the #1 rattle that freaks people out is the chain slapping the top of the chain slider (near the shock). This is usually due to the chain being a little too loose and at lower rpm, the chain develops a vibration where it moves up and down and slaps the chain slider.

 

It sounds like you have a different rattle but this is worth mentioning any time someone talks about a scary rattle.

 

From the video, it sounds like it is sputtering at low rpm which is a result of rich jetting. When you rev it out, it seems to clear up and run smooth. Its hard to hear any mechanical rattle noises from that video, just the exhaust note.  I would look at your jetting, refer to multiple jetting charts for that bike (factory, pro circuit, FMF etc) and see if you are in the ball park for your temperature and elevation. It definitely sounds like it is running rich at low rpm/partial throttle...

Edited by Ilove2strokes

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Thanks for all your comments, i think iv'e found the 50% of the problem i think its something inside the expansion chamber because when i pull it up with my hand it seems to ease the noise i was told its nothing to worry about but i think personally doesn't sound good so i think i am going to replace then see what i get from there has anyone had anything similar? sorry for the lack of detail in the video which i do apologize for it was the best i could get as the noise is quite low when the bike is just idling so couldn't really get a clear sound of it

 

also for the revs i have another video which i will post which is more self explanatory which i will post once again thanks for everyone help

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does it rattle when the bike is sitting still or does it only rattle when you are riding it?

 

If it rattles only when you are riding it, the #1 rattle that freaks people out is the chain slapping the top of the chain slider (near the shock). This is usually due to the chain being a little too loose and at lower rpm, the chain develops a vibration where it moves up and down and slaps the chain slider.

 

It sounds like you have a different rattle but this is worth mentioning any time someone talks about a scary rattle.

 

From the video, it sounds like it is sputtering at low rpm which is a result of rich jetting. When you rev it out, it seems to clear up and run smooth. Its hard to hear any mechanical rattle noises from that video, just the exhaust note.  I would look at your jetting, refer to multiple jetting charts for that bike (factory, pro circuit, FMF etc) and see if you are in the ball park for your temperature and elevation. It definitely sounds like it is running rich at low rpm/partial throttle...

thanks for the reply i double checked the chain but its not the chain, i just posted a quick update of the problem if you would like to read it, thanks for all the help tho

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http://www.youtube.com/watch?v=XqHcbB93EnM

 

this is my revving issue in this video the bike is NOT being revved its held all the way open about 3 quarters and its doing this could it be an air leak? i think it is running rich as a few people said up the this forum due to the huge amount of smoke,

 

this bike has gave me nothing but problems

 

 

thanks again

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Also when you pull the spark plug out what color is it? It SHOULD be a nice gold brown.... Make sure it's not black and oily. As far as the rattling is concerned like the other guy said it could be something external... My KX 125 back in the day rattled real bad and it was the springs that hold the pipe on by the cylinder. Hope that helps.... Sorry I couldn't hear much from the video

i just had a quick look at the plug and it seems it is black and has some form of oil on it what does this mean the bike is over fueling?

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sorry for your troubles..... 

 

I see 2 problems.... one, the bike is obviously not running correctly due to the surging/rough running in the latest video you posted. Two, there is a rattle somewhere around the engine.  What is causing the bike to run poorly, the rattle or something else? Could the rattle and rough running be 2 different problems that do not affect each other?- maybe...

 

In a situation like this, it is really best to go over the whole bike and make sure each component is functioning properly, starting with the easiest stuff to check and then working towards the harder more involved stuff.

 

If this was my bike and it was behaving like that, this is what I would do.

 

1) Get a copy of the factory Honda service manual for it because you should have one anyway.....

 

2) Replace the spark plug and clean the airfilter and check the operation of the engine. If this does not fix it, go to step 3.

 

3) Do a compression check. This doesnt tell you a lot but it is worth checking. Make sure the pressure is "up there" :), do a search for a rough idea of correct engine compression on a CR85. We want to make sure the rings are sealing.

 

4) Remove the carburetor and reed cage.

 

5) Inspect the reeds. They should be tight and flush with the cage they are bolted to. You should not see ANY gaps or holes in the reeds. They need to seal 100%.

 

6) Inspect the carburetor. Determine what jets are installed, check the float height, and the height of the needle. Look at the factory manual for elevation and temperature and see if your jets, needle clip, and air screw match the 'recommended' specs in the book. While the carb is apart, clean it out with carb cleaner making sure all passages and jets are CLEAN.

 

7) Look at the rubber boot between the carburetor and cylinder head and see if there is any trash or debris that is preventing it from making a good seal on both ends.

 

8) Once the first 7 steps are completed, reassemble the engine and see how it runs.

 

9) If it still runs poorly, you may have a problem in the bottom end of the engine; like crank seal that is leaking. If the carburetor and top end are in good shape, a poor running bike and LOTS of smoke from the exhaust are usually a sign of the clutch side crank seal leaking. This causes transmission fluid to enter the engine which throws the air/fuel mixture off and the trans fluid burns off as excess smoke. Does the exhaust smoke smell like gas/oil premix or does it have another smell like burning transmission fluid? Does the exhaust pipe blow black specs all over the rear fender? Replace both left and right side crankshaft seals and recheck the engine. Now, on a side note, if you find a bad crank seal, and you have a rattle, it could be a bad crankshaft bearing which causes the crank to move up and down a small bit, which makes causes your rattle and wears out the crank seal right next to it..... That would mean its time for a bottom end rebuild.

 

That is where I would start.....

Edited by Ilove2strokes

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i just had a quick look at the plug and it seems it is black and has some form of oil on it what does this mean the bike is over fueling?

It could mean one of several things.... Gas mixture is too rich... Take it from 32:1 to 40:1 which is what I mix.... Or it's not getting enough air... I'm sure there's plenty of other causes but that's what pops up in my head.... Hope this helps

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going from 32:1 to 40:1 causes the fuel mixture to be RICHER which will make his situation even worse if its simply a jetting problem.  40:1 means less oil and MORE fuel per gallon than 32:1. Less gas and more oil leans the bike out. 

 

Keep your fuel mixture at 32:1, and then start troubleshooting the engine.

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sorry for your troubles..... 

 

I see 2 problems.... one, the bike is obviously not running correctly due to the surging/rough running in the latest video you posted. Two, there is a rattle somewhere around the engine.  What is causing the bike to run poorly, the rattle or something else? Could the rattle and rough running be 2 different problems that do not affect each other?- maybe...

 

In a situation like this, it is really best to go over the whole bike and make sure each component is functioning properly, starting with the easiest stuff to check and then working towards the harder more involved stuff.

 

If this was my bike and it was behaving like that, this is what I would do.

 

1) Get a copy of the factory Honda service manual for it because you should have one anyway.....

 

2) Replace the spark plug and clean the airfilter and check the operation of the engine. If this does not fix it, go to step 3.

 

3) Do a compression check. This doesnt tell you a lot but it is worth checking. Make sure the pressure is "up there" :), do a search for a rough idea of correct engine compression on a CR85. We want to make sure the rings are sealing.

 

4) Remove the carburetor and reed cage.

 

5) Inspect the reeds. They should be tight and flush with the cage they are bolted to. You should not see ANY gaps or holes in the reeds. They need to seal 100%.

 

6) Inspect the carburetor. Determine what jets are installed, check the float height, and the height of the needle. Look at the factory manual for elevation and temperature and see if your jets, needle clip, and air screw match the 'recommended' specs in the book. While the carb is apart, clean it out with carb cleaner making sure all passages and jets are CLEAN.

 

7) Look at the rubber boot between the carburetor and cylinder head and see if there is any trash or debris that is preventing it from making a good seal on both ends.

 

8) Once the first 7 steps are completed, reassemble the engine and see how it runs.

 

9) If it still runs poorly, you may have a problem in the bottom end of the engine; like crank seal that is leaking. If the carburetor and top end are in good shape, a poor running bike and LOTS of smoke from the exhaust are usually a sign of the clutch side crank seal leaking. This causes transmission fluid to enter the engine which throws the air/fuel mixture off and the trans fluid burns off as excess smoke. Does the exhaust smoke smell like gas/oil premix or does it have another smell like burning transmission fluid? Does the exhaust pipe blow black specs all over the rear fender? Replace both left and right side crankshaft seals and recheck the engine. Now, on a side note, if you find a bad crank seal, and you have a rattle, it could be a bad crankshaft bearing which causes the crank to move up and down a small bit, which makes causes your rattle and wears out the crank seal right next to it..... That would mean its time for a bottom end rebuild.

 

That is where I would start.....

thank you very much for the detailed information, i will start to look at these asap, just a point you mentioned at the end about the exhaust it seems the exhaust is leaking some kind of fluid causing black specks to spread over the fender as you said and over the rear wheel & caliper its quite a lot if im honest...although it doesn't seem to smell any different it just smells like normal gas, i will go though each step thoroughly that you gave me to find the problem, once again thank you for the help 

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