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Discussion Starter · #1 ·
Yesterday I purchased a 2000 Honda 400ex from PA. I ride predominantly trails and hill climbs. All stock engine except for a replaced timing chain. Has some aftermarket bolt-on's and a white brothers E-series slip on. Has a fairly new rear carrier with a grommet installed for greasing. Overall I thought it was in pretty good shape for most 400's i found on craigslist. The bike has supposedly sat for about two years and could use a fresh tank of gas which I will be draining today and running 93 from here on out. I noticed a slight amount of smoke on occasion after a high rev in the garage and then also when i was using 2nd to keep my speed down(obviously at a decently high rev) while riding down a decently steep hill. I changed the oil before this to the pn4 10w40 but on the next oil change I think I will switch to mobil 1 15w50 to see if that helps. I feel like my valves may need adjusted but I'm not totally sure, If anyone has any wisdom to share or be able to direct me to helpful links I would very much appreciate it.
 

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Welcome to the forum!

Sounds like you got a pretty decent machine. A little smoke after a high rev is somewhat normal. I think I would stay with the GN 10W40 unless you run the engine extremely hot. The Mobil 1 (like all synthetic oil) is slicker than petroleum oil and can get by the rings easier. Most engines running synthetic oil uses about twice as much as an engine running petroleum. Check to see what the oil consumption is before switching. If the engine is hard to start, then the valves need adjusted. Since you don't know what the valve clearance is, check it anyway. .004 intake and .005 exhaust is usually sufficient. Too much clearance is better than not enough.
 

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In my opinion the engine seems to get fairly hot quickly which I would attribute to the oil and 80 degree temps( my thought). I plan on riding this weekend and then changing the oil again to help clean out the previous owners oil which was black and fairly broken down. I drained the gas however and removed the filter box to spray carb cleaner into the carb to try and help clean the carb a little without tearing it apart. I also put some Lucas fuel treatment in the gas to also help with cleaning the fuel system. When I test rode the bike I didn't tighten the air intake to the carb or put the air box lid on but did put the air filter on. When trying to go up the driveway it bogged down multiple time in multiple gears, would the filter box lid not being on cause that? It may have also had the fuel petcock on reserve. I can't recall though.
 

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For an air cooled engine, when the oil temp gets over 300 degrees, then it might be prudent to switch to a synthetic. My 97 250 would heat the oil to 350 degrees during a race. Petroleum oils can start to break down at 350 degrees, so I switched to a synthetic 15W50 which didn't start to break down till it reached about 400 degrees. Typical play riding will not heat oil above about 250 degrees, but getting bogged down, lugging the engine and extended idling will raise oil temps quickly. One of the worst things you can do to an air cooled engine is let it idle for more than 5 minutes after the engine is completely warmed up. Typically, 15 minutes of riding followed by 5 minutes of idling = an over heated engine (even at 32 degrees air temp)

In my opinion - spraying cleaner into a carb is like pouring water over a rock. It washes of some surface dirt, but it is not cleaning the parts that need to be cleaned. The fuel additive is a better approach, if you have the patience to let it work. I can't speak for the Lucas treatment, but the product I use (that actually works) takes about 3 tanks of fuel to do a good job.

Not tightening the intake probably didn't make a difference as long as you don't have backfiring out the intake (indicates a lean condition). Not having the air box lid on would definitely lean the mixture some, depending on what kind of air filter was in it and how the carb is jetted. You won't know about the jetting unless the previous owner can tell you how it's jetted or you take it apart and check the jet sizes.

Having the petcock on reserve is a good thing if you don't know how much fuel is in it, but's a bad thing if the fuel had alcohol in it. When alcohol blended fuel sets (as little as 30 days), the alcohol will absorb moisture out of the air and will fall out of the fuel (phase separation). When you switch to reserve, you get a pure alcohol/water mix going to the carb. It might run on it, but it is typically hard to start, low on power, runs hot and bogs horribly. I recommend you drain the fuel tank and try some fresh 92/93 (no higher then 95) octane fuel (alcohol free if you can get it).

Good luck and have patience
 
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