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Discussion Starter #1
Hey guys I just bought a 2004 Vforce 700 a few days ago. I got a steal on it for $500. The guy had many atvs and did not want to deal with this one. The bike starts, runs and drives fine and just had the valves adjusted but the guy told me there is a wrist pin underneath the front cylinders piston that has a loose connection and play with the rod that connects to the crankshaft so its making a really loud knocking sound. Has anyone ever heard of this problem or could it be something else? How much will it cost to get fixed? Thanks alot and this is my first atv purchase so im really excited to get it out and cruising.
 

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Does the knocking sound only occur at idle and goes away as you rev the motor up? If so, you probably just need to rebuild the primary clutch (worn bearing in the cover plate). If the knocking sound continues as you rev up the motor, the motor may need to be torn down & rebuilt (replace worn rod bearings, etc.)
 

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Discussion Starter #3
Thanks for the reply. The sound does occur while its idling and when I rev the motor the knocking increases so its got to be a connection within there. The guy I bought it from had it checked out by a mechanic but he took it to him with the engine torn apart so he adjusted the valves and put it back together thinking that would be the problem and the guy didn't wanna put any more money into it so he just sold it to me. The mechanic said that the knocking was coming from the front cylinder though so that narrows it down.
 

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More times than not its the crankshaft bearings that go on these motors, in my experience.

Sounds like its coming from the cylinder but its actually the crank
 

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Discussion Starter #5
ok if it would be a crankshaft bearing would that mean I have to replace the whole crank?
 

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Yep. If it's knocking, your crank is gone too. There's alot of threads here pertaining to knocks and bad cranks.
 

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they are right. it's easy to toast a crank on these if you run it low on oil.

you will need 1 new crank. 2 new rods, 4 new journal bearings.

good time to put new cam chains in it too. figure you'd be in it for about 1000 in parts and small stuff to do it right.

just don't buy a used crank :lol: you'll get what you got already.

John
 

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Discussion Starter #8
The atv will still drive... If the crank was bad would it still be able to? A local mechanic also says its the connection between the rod and the piston... so its somewhere maybe where the wrist pin is. I desperatly hope I don't have to replace the whole crankshaft.:mad:
 

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I've never seen a wrist pin go bad. EVER. crank. YES. it's very common.

Yes it will still run and drive. until you put the rod thru the engine case when it seizes and snaps off.

the sound you may hear top end could be the piston hitting the head from the crank journal allowing more upward travel.

regardless. pull it apart and guaranteed, you'll be installing a crankshaft.

why do you think you got it for 500.00?? they absolutely knew what they sold and what it would take to fix it.

John
 

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Don't start it anymore
Like he said if you break the case or the head it just keeps getting more expensive


Sent from my iPhone on the toilet.
 

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Discussion Starter #11
Thanks for your imputs and replies. Ill be taking it into a local kawi dealership because im not very familiar with four stroke engines. One more question can you remove the connecting rods off of the crankshaft so maybe I could salvage them if they are in good condition?
 

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Be cautious where you take it. Do some research first. Just because they are a dealership doesnt always mean they have the best of mechanics in the surrounding area. Check out your other resources. You might have to pay just a tad more for a specialist to do it but would you rather pay a little more or start from scratch......again
 

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yeah mine as well tear it apart.My buddy had same noise kept riding an slam piston in head. take john advice he knows his stuff
 

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If it does need a new crank/bearings, you should consider buying a good used motor and installing it yourself. You might have to spend $1,000 or so to buy a used motor, but then you will have a total investment of about $1500 (assuming you install the motor yourself)...which is still very cheap!
 

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Discussion Starter #16
yeah i probaly wont buy a whole motor. Ill just buy all the parts I need to get it running again once someone diagnoses the problem by looking at it. If its not worth fixing its worth a whole lot more than $500 dollars in parts. Its got hmf dual exhausts which new run for like $500 alone and much more. I didn't buy this bike to part though. I honestly don't care if I spend a 1000 in parts to make it run.
 

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yeah i probaly wont buy a whole motor. Ill just buy all the parts I need to get it running again once someone diagnoses the problem by looking at it. If its not worth fixing its worth a whole lot more than $500 dollars in parts. Its got hmf dual exhausts which new run for like $500 alone and much more. I didn't buy this bike to part though. I honestly don't care if I spend a 1000 in parts to make it run.

I was just suggesting that if you have to tear down the motor/split the cases to rebuild the bottom-end (at a cost of say $1k) versus just buy a good used motor and install it yourself (at a cost of say $1k), then you are probably better off buying a used motor and installing it (meaning it will be faster/less effort to just buy a used motor and install it). Of course, some folks might prefer to tear down the motor/split the cases b/c they want to learn how to do all that work. Whatever you decide is fine with me, I was just trying to give you another option.
 

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^^^ Plus with another motor if something breaks (heaven forbid) at least you'd have a spare to swap parts
 

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Discussion Starter #20
Yeah it would be good to have a spare motor. The only two I can find for sale are on ebay for 1600 and 1700. I don't know what the rocker mod even is?
 
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