I went out for a little ride. Bike felt a little sluggish.No smoke from exhaust. Pull in the shop check oil. EMPTY. Not my bike, not a chance. I’m vigilant about checking everything all the time! Air box is coated with oil. I pull carb boot and it’s loaded as well. Upon further inspection I find the motor has retained all the oil. I think its a bad oil pump but I never heard of this issue on a 400 ex. Any input?

Okay, this issue is fixed, but i would like to know a little more about what was wrong just to further my knowledge on these things…
So I was working on a bike and it was having an issue after a top-end rebuild(previously skipped time and bent valves) That once it would hit High rpms like on a long stretch it would bog down and die. but if You were not pushing it or if it was idling it would be perfectly fine. it was popping a bit too when you’d go up high acceleration and let off. so He ended up taking it to another guy to look at it and he said it was the valve adjustment? he also rejetted the carb I think. And now it runs perfect.
So how would the valves being out cause it to die when going up on higher rpms? if they we’re too loose would they not open up enough to let enough gas in at high rpms where it uses more?

Okay, this issue is fixed, but i would like to know a little more about what was wrong just to further my knowledge on these things…
So I was working on a bike and it was having an issue after a top-end rebuild(previously skipped time and bent valves) That once it would hit High rpms like on a long stretch it would bog down and die. but if You were not pushing it or if it was idling it would be perfectly fine. it was popping a bit too when you’d go up high acceleration and let off. so He ended up taking it to another guy to look at it and he said it was the valve adjustment? he also rejetted the carb I think. And now it runs perfect.
So how would the valves being out cause it to die when going up on higher rpms? if they we’re too loose would they not open up enough to let enough gas in at high rpms where it uses more?

Hello I just bought a 400ex with a slip on exhaust and a k&n air filter the quad will only run up till 3/4th throttle so i’m going to change the jets out! I am currently in Port orange florida according to wiki its 3ft elevation or .9m im thinking off going with a 165 main jet and a 45 pilot jet any thoughts?

Hello I just bought a 400ex with a slip on exhaust and a k&n air filter the quad will only run up till 3/4th throttle so i’m going to change the jets out! I am currently in Port orange florida according to wiki its 3ft elevation or .9m im thinking off going with a 165 main jet and a 45 pilot jet any thoughts?

My uncle got my grandpa’s 300 back from the mechanic i don’t know how long ago it was I’m thinking a year ago hasn’t been up here since 2013. But anyway an issue that he told me about that I think everybody with a 300 4wd should know about is, that the guy had to pull off the head said timing chain and seals were shot and valve adjusters and lifters from what he told me where on the verge of needing replacing. He said the issue was from thick oil, then he said something about the transfer case was over filled and it blew that seal and oil leaked into the engine. The clutch plates were swelled up, axle bearing gone in the rear, the CV axles were shot and u joints.

But back to the oil issue if the oil leaked out of the transfer case and in the engine you got 10W-40 in the transfer case and 15W-40 in the engine, now can somebody please tell me how it would get so thick that it almost wouldnt pump good enough, I kept the oil changed regular and checked everything monthly, unless the oil in the transfer had more of something that thickened it up, idk but the oil on my finger was fine. The end total was 1,000.00 all together, I don’t neglect anything I take care of it, but the subject here is check ur fluids and if you have a 4wd atv with aftermarket foot boards that make it hard to get the your transfer case fill plug find a way to get to it

I have a 1995 300 fourtrax. Today I was riding it and I heard a loud pop, so I stopped and inspected it and started rolling it back and forth. The sound was coming from my rear diff. When I opened the oil cap there was broken peices of the gears coming out. I had oil in there. If you know what could have caused it, let me know. Thanks

I have a 1995 300 fourtrax. Today I was riding it and I heard a loud pop, so I stopped and inspected it and started rolling it back and forth. The sound was coming from my rear diff. When I opened the oil cap there was broken peices of the gears coming out. I had oil in there. If you know what could have caused it, let me know. Thanks

Hello,

I was using a friends ATV recently and didn’t do anything that I thought to be overly harsh however it is now broken.

I need to take responsibility and get it repaired and I was just wondering if the experts here could give me a feel for what I’m in for at the repair shop.

My friend climbed this rock before me and he stopped on it as he got nervous about the incline. He tottered but then slowly climbed over the rock.

I said you shouldn’t have stopped and he agreed but said he got nervous. Well I think I went to the other extreme and punched it too much.

See his is an automatic and mine manual so when I punched it I may have exceeded what first gear could handle?

Anyway when you watch the video below you’ll hear a breaking sound after I climbed the rock. From that point on ONLY the left front tire seemed to have power.

I say this purely because when on soft ground the left front tire would just bury itself and it *seemed* none of the other tires would propel.

Video of break

TIA

Working on fixing up 2002 rancher trx350fm. Old owner just told me he stopped using rancher about 4 -5 years ago. Ran it low on oil them it wouldn’t run right.

He had oil on spark plug. I’m pretty mechanical .
Where could that be coming from?
Valves or piston rings or both??? Trying to diag before i order part so i can order all at same time