300ex Blow up??

[wboy62417]

The past 2 months my 300ex has been making a loud taping sound. Me and my cuzin were trying to figure out what it was we thought at first it was a brokin clutch plate and later thought it was the piston skirts slaping a little or something. I was hoping and praying it would make it through the winter and i was gonna rebuild it in the spring. I was pulling the sled with my 300 on the first snow we had in Illinois and i decided to take the sled off about a half hour afterwards to play around on my own in the snow. after i took it off i got back on and put it in gear(running while taking the sled off) i took off and then went to shift into second gear and it died.(all of a sudden) and when you hit the start button it acts like there is nothing like holding the starter back at all like the starter isnt turning over anything but when you put it in gear and hit the start button(without the clutch pulled) it wants to take off but still doesnt act like there is much holding it back. Help i need some ideas on where to start my rebuild:confused: Did my atv blow up?

[Cody_300ex]

Sounds like you dropped a valve...

[h400exrydr]

ya valves i would say

[bwamos]

Originally posted by wboy62417
but when you put it in gear and hit the start button(without the clutch pulled) it wants to take off but still doesnt act like there is much holding it back. Help i need some ideas on where to start my rebuild:confused: Did my atv blow up?

Did the motor actually turn over at all when you did this in gear? (Not fire, but turn over)

If it did, you didn't drop a valve.

I would reccomend a complete teardown from the head down to the piston & cylinder, for a full inspection. I'm sure you need a hone and new rings anyway. Inspect the head, etc.. for proper valve lash before removing the head cover. Dont have to adjust at that point, just see if it was too loose while the rockers are still in place.

You'll need to inspect the head, cam, rockers, timing chain, sleeve, piston & rings, and the clutch assembly. While you have the clutch exposed.. give the crankshaft a good move around to see if the bearings have gotten sloppy.

Basically, just grab a service maual and work your way from the top down, and side in. Splitting the cases should be a last resort. ;)

[bwamos]

Re reading that post.. are you saying that the starter is spinning free in neutral and barely grabbing when in gear?

If you sou probably have broken teeth on your starter or starter gear. That could make ticking noises when riding too.

[wboy62417]

The motor will not even attempt to start it acts like the starter isnt turning anything but when in gear it turns over and wants to take off without the clutch pulled(kinda like it doesnt have any compression AT ALL) i just rebuilt the 4 wheeler about 6 months ago bored and honed wiseco piston and rings and 230 dollars worte of electrical work and a new back break caliper (just to let you all know)

[wboy62417]

o yea and a new starter forgot that part.

[wboy62417]

sorry about all the posts without waiting for replys but i keep forgeting stuff..........The ticking was more like a chattering i guess you could say and it was coming from the top end

[CDCHONDAS]

I'd do what the guy above said and tear it down but the cam chains can do some pretty good noise making but other than that it could be a couple things, if the cam chain broke and somehow landed on top and not jammed in the bottom it would have compression, sometimes if a rod bearing goes and things happen right you can bend valves, just have it torn down.

[wboy62417]

Thanks i am planing the teardown for this weekend i will let you guys know how it goes if anyone else has any suggestions please post it I am going to go through this motor completely thanks for the help guys

[wboy62417]

Found the problem the cam broke in half the taping noise was the cam gear it came loose (somehow) and broke the came so when we put it together i am gonna use some thread lock on it thanks for the help guys i didnt have to get very far into the moter to figure this one out

[bwamos]

Wow, that's an odd one.

Glad you found it. Make sure you flush out the tranny. Don't want metal bits in your bearings.

Yea, you want to use a drop or two of loc-tite on the bolts holding on the cam sprocket so they dont back out under vibration. (I use blue loc-tite. Never had a problem with them backing off)

Remember, to set the cam timing with the front side of the chain tight (non-slider side). Common mistake. Figured I'd give you a heads up before you have to take the head cover off again.

How'd you like getting that cover off. That orange gasket material grabs hard doesn't it? ;)

[wboy62417]

Thanks for the tip i will be using the blue lock tight stuff like you said right now i am stuck i am trying to find a aftermarket cam for it to go with my high compression piston and the only thing i can find is web cams so i will probly have to get that one i have everything ordered but the cam and the springs i had to get the gasket set and rocker arms and stuff so i ordered all of that any suggestions on a cam??