It sounds as if the leaness in the jetting is causing high operating temperatures resulting in oil breakdown and pre-mature ring wear.

That blue smoke is blow by; caused by oil getting past the rings and into the combustion chamber.

 

no doubt rings..but honda made major changes to the motor from the XR..I cant rember the specs but it has more torque cam, larger clutch and grear's and differnt head gasket material... sounds like a honda prob because i have friends who run havline 30W for years with no problem in there bikes and quads
Joe

 

Thanks Guys. I'll try the thicker oil and like you say, "hope it's not too late". I'll try some synthetic oils and if that doesn't do it, take it into the shop and see what damage I've caused. Wish they would have told me that when I bought it. But, I'm sure they don't want to admit to their "Honda" 4 stoke oil not to be good enough for that machine.
www.geocities.com/hulioni

 

Duster,

Your analysis that the 400ex engine "still needs refinement" is, I feel, a bit bogus. I have ridden the absolute hell out of mine for the last 12 months while racing hare scrambles and GNCC's and have seen absolutely no smoking (or any other) problems to date. I think there is a reason that so many people are having smoking problems - they aren't taking care of their engines. I too have seen a few 400's with bad cases of smoke, but in every case the person had either been running the dang thing WAY too lean, running with a K&N type filter in dusty conditions, or wasn't changing their oil enough.

Too many folks throw a new pipe on their EX or take off the air box lid (or both) with out properly re-jetting. My dumb-*** cousin put on a pipe and filter and actually jetted his DOWN (despite my protests) because he said it felt more responsive and because some other idiot had told him that the 400 was jetted way too rich from the factory. Even though he changed the oil every weekend, not four months after getting the thing he has just put in a new piston, rings, and valve seals. If anything, I think it’s a testament to the quality of the engine that it is able to take such abuse.

Dennis

 

400EXtric8,

I definitely think that running the proper weight oil is important but I would also recommend that you double-check your jetting AND consider switching to a foam filter if you ever ride in even slightly dusty conditions. The K&N filters have been the silent assassin of more engines around here than I can count (including one of mine). While they are great free-flowing filters, they just can't filter out the finer dust particles.

If your want to see for yourself, after riding in dusty conditions, remove your carb from the air boots and run your finger inside the mouth of the carb and the intake boot. If you can feel the slightest bit of grit between your fingers, you can be sure that your engine is being trashed by dust. I’d recommend that you switch over to a foam filter like a UNI or even the stocker to prevent further damage. Just remember to keep it well oiled.

Regards,

Dennis

 

oh yeah, ditch the K&N.. they dont work, My friend is getting his 99' ford F-350 powerstroke rebuild because of a K&N filtercharger letting dust in..his engine repair bill is $8,000.00
Buy a UNI fliter !

 

Doesn't the 400EX have a temperature light that goes on if the engine gets too hot (prior to oil burning and the onset of motor destruction)? If it doesn't, in addition to resolving the issue with the type of oil and jetting, I would install some type of oil temperature sensor that you can monitor during hard riding to make sure you don't exceed a certain oil temperature. This way you can turn the engine off BEFORE the oil burning and onset of motor destruction begins. Can you mount & wire up a free running fan to blow air on the fins to help with the cooling?

 

I run 20w50 in my ex, when I first got it it smoked (breaking it in) but as soon as I put the 20w50 oil in it,it hasn't smoked a bit. I see a lot of people wanting to put synthetics in their ATV's, I'm not sure if this is the right thing to do, Wiseco says not to use it,&Web Cam will void the warranty if you use it! Synthetics will hold up longer but they don't lubricate as well. I suggest changing oil more often.

 

Wive's tales and folklore. How can they last longer but not lubricate as well? I also understand that they can ONLY use synthetic oils in jet engines (take it for what it's worth). I have personally stripped down my 350X that was run for years on synthetic, it had an abnormal lack of wear. I am now running my 400EX on synthetic.

I have personally run just about every engine I have ever owned (that didn't leak profusely) on synthetic, never had any of the horror story problems (eg. leaks, trashed cams, bearing troubles). For some reason some people treat oil like a religion and have trouble accepting something "new" and will make up myths to explain what they don't understand.

Heck on page 96 of your owners manual Honda themselves recommend HP4 oil, about as synthetic as it gets.

Also contrary to popular belief, synthetics will not cause your clutch to slip, they are not more slippery than conventional oil, they just lack some of the nasty traits of conventional oils, such as gelling in cold temps, premature breakdown, etc...

I do agree with the 20w50 though. The 400EX generates much too high oil temps to trust the engine with anything less.

 

hmm, how'd this happen?