Dragon 700 engine rattle?

[Fanatic]

I have some kind of rattle/noise in my engine and i don't know whats wrong.

i can hear it on low rews, if i rew up it fades away and if i put in revers (electric) then the rattle disappears
i have removed the clutch and the noise is still there

any suggestions?

the local dealer think it's the crankshaft, but i don't agree because when i put in revers it stops rattle..

it has done 3500km

 

[MORSNO]

Could it as simple as the exhaust heat shield or the pipe/can? You should be able to open the hood and listen if it is coming from the engine, up front by the exhaust, or back by the gas tank and handlebar areas.

 

[Pownar]

Is it a buzzing rattle or more of a knock? If it's a knock, it could be piston slap. It is usually heard at low rpms and not in reverse as much.

 

[Fanatic]

it sounds like a piston slap now when you say it:/

is it dangerous? what can i do to make it stop?
change pistons?
or rod?
or both?

 

[CoyoteGirl]

it sounds like a piston slap now when you say it:/

is it dangerous? what can i do to make it stop?
change pistons?
or rod?
or both?

At 3500 K it wouldn't be unwise to replace pistons.

 

[Pownar]

Measure your cylinders. If they're to specs, just diamond hone and throw a new set of pistons in them. If scratched or off, get them re-nikasiled. People have been having better luck with the two ring pistons.

It's dangerous for your bottom end! Piston skirt can brake off.

 

[2006m7]

Could it as simple as the exhaust heat shield or the pipe/can? You should be able to open the hood and listen if it is coming from the engine, up front by the exhaust, or back by the gas tank and handlebar areas.

i agree with him considering i just had this problem it was an exhaust spring from the pipe to the can they weren't tight enough...hope this helps

 

[Super Dave3]

Something that hasn't been mentioned is exhaust valves. They get worn over time and will rattle in the cyl untill you pick up the throttle. Try taking the caps off and pull the EV out and try it.

 

[Fanatic]

Thanks for all the ideas, and i can't find anything loose like exhaust springs or heat shield
i have cleaned the exhaust valves but i haven't open them up, i will do that tomorrow.

if i listen with the top of a screwdriver the knocking sound sounds loudest in the bottom of the engine

the strangest thing is that the sound disappears when i put in revers, it feels like if it were the piston/rods/crankshaft/vavles then the sound would't disappear.. nothing changes in the engine when i put in revers.. right?

i'm going to the mountains over christmas and new year so i don't have the time to replace the piston.

//Lars

 

[Fanatic]

removed and cleaned inside the exhaust valve just now and i did't see anything wrong except for a lot of oil, but the sound is still there

 

[gotthefever]

I am pretty sure it is your pistons. I just picked up an 08 with 3500 miles and it did the same thing. Pretty loud piston slap. This is a common issue with the 700's when they start to get a few miles on them. Not sure why though. When I took mine apart, the cylinders were still in spec. So I just had them honed and put in new pistons. Problem solved!

 

[the_dougdangerak]

Check the spider nut on your primary clutch. Mine came loose a couple weeks ago, did the same thing you described. Just something to check.

 

[hogracer]

My Brother in law has a 2008 700 that had the same sound. He decided to ride it anyway, and 4 miles in he opened it up on a hill and a piston skirt broke breaking a cylinder both cases and the crank. Your best bet is to throw some new pistons in at the least, its alot cheaper the messing up your bottom end. We decided his was probably from running cheap oil, at least thats what we would hope seeing that this is one of polaris's best engines.