noises when going fast ?

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erikvilla

Guest
Hi I have a 80cc engine on a mountain bike. the engine works very good but when i am going top speed or close to top speed i hear a loud rattling sound coming from the engine.. when i first installed the engine i dont remember it making this noise. The motor seems to work just fine but i dont no what can be making this noise my other new 80cc engine on my cruiser bike doesnt make this noise at all. can any one help me out?
 


S

sideshowsideswipe

Guest
when I hit what I think may be close to me top speed my engine starts to whine, then a quick rattle and then an even hum crescendo... I don't like the rattle it makes before it gets to the hum though...

I am on about mile 250 and I still haven't taken my engine to the max...
 
M

Minnesota Hyena

Guest
I think i had same problem about brake in period.
I was worried about it but then it dissappeared by itself after few days.
 
E

erikvilla

Guest
Minnesota Hyena said:
I think i had same problem about brake in period.
I was worried about it but then it dissappeared by itself after few days.
Well the rattling is really loud and it rattles when i have the clutch disengaged and then i reve it up high.. also if i am going fast and i coast with out giving it gas i hear the noise. I didnt really follow the break in rules and im wondering if this is related to this ive only been riding it for about a week now.. do you think it may be something that will go away?
 
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erikvilla

Guest
srdavo said:
I'd make sure everything is tight. look the frame over too.
I have checked everythign for tightness.. the sound is coming from the engine because when i reve it up when i have the clutch disengaged ( pedal mode) i could hear it coming from there.
 
E

erikvilla

Guest
Today i took the engine apart and found my problem. the piston was slopy on the conection rod so i removed the piston from the rod and found that my connection rod bushing was broken, which was caushing the piston to move around the cylinder head sloply causing the noises.
Does anyone know where can order a new connection rod bushing for a 80cc chinease engine? please help me out if you know of anywheres
thanks Erik
 
G

Guest

Guest
Bushing on connecting rod instead of a nice bearing is reason why lubrication is SO critical in these engines.
 
G

gone_fishin

Guest
DrewD said:
Bushing on connecting rod instead of a nice bearing is reason why lubrication is SO critical in these engines.
ok, DrewD...as you've proven yourself to be quite knowledgeble on these engines, what permanent pre-mix ratio would you suggest?
 
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