Yet another 400ex smoking ?

[supertrooper90]

My friend bought this 400ex a few weeks ago and it was smoking when he bought it. As we have been working on it little by little I'm starting to find things that the seller wasnt exactly honest about. Like the ported and polished head and a few other odds and ends. We got it fired up today for the first time in the day light and it seems to run really strong and snappy. I'm thinking the piston is not stock. The oil we drained from it seemed much more slippery than the fresh rotella we were putting in.

Hes gonna bring a compression tester over tomorrow and we will check the compression. I'm leaning towards it needs a hone job and a new set of rings cause it will idle with very little smoke and a crack of the throttle and smoke bellows and doesn't really clear up. It runs really strong and sounds very healthy and starts up almost as soon as you hit the start button. Does anyone have any thoughts on this? If the motor was broken in on synthetic oil instead of regular oil could it smoke this way? Would it still have decent compression?
thanks in advance

[NMills]

Rotella? as in Diesel oil? really???

[trx400Rider]

Check the valve seals. Mine did the same. It was them. There cheap. Just replace them while u have it apart.

[supertrooper90]

i thought the valve seals would make it smoke upon start up and eventually clear up after running for a bit? How would I go about checking the valve seals? any suggestions?

[Thumpin440ex]

Does it continue to smoke after it is warmed up??? My bike with a fresh rebuild when it is super cold out will smoke if you blip the throttle, but as soon as it warms up it is gone, doesn't smoke a drop..


As for rotella it is fine to run it, I have been running it for a while now...


John

[NMills]

As for rotella it is fine to run it, I have been running it for a while now...


John [/B]


Hows the oil work with the clutch... i thought it had to have certain properties for the clutch...

[CJM]

Originally posted by NMills
Rotella? as in Diesel oil? really???

yes, alot of us use it. Why pay for honda oil-it aint that great.

[NMills]

Originally posted by CJM
yes, alot of us use it. Why pay for honda oil-it aint that great.


REALLY!>?!?!?!?!?!? crap i could get that stuff from work... i just thought we had to use honda oil as the clutch needed it... so i won't run into any problems running rotella? and drawbacks? what are the gains????

[supertrooper90]

there are a million threads about running rotella use GOOGLE. Im trying to get some ideas on the smoking issue Thanks

Thumpin440ex: yes it continues to smoke this way after it is fully warmed up

[crownandmonster]

I don't run rotella but I do use the chevron 15- 40 diesel oil we use in our fleet of trucks

[Thumpin440ex]

Then I will agree that it is prob valve seals, or even piston rings..

John

[CJM]

Smoke at startup and continues till it warms up like 15 mins is valve seals, smoke all the time-specially when you throttle up is bad rings.

A compression test will tell you if its rings, should be about 120psi or so give or take a few psi +/-

Also if its either of those you will be missing oil. If its not missing oil it could be to rich.

[tri5ron]

Originally posted by supertrooper90
My friend bought this 400ex a few weeks ago and it was smoking when he bought it. As we have been working on it little by little I'm starting to find things that the seller wasnt exactly honest about. Like the ported and polished head and a few other odds and ends. We got it fired up today for the first time in the day light and it seems to run really strong and snappy. I'm thinking the piston is not stock. The oil we drained from it seemed much more slippery than the fresh rotella we were putting in.

Hes gonna bring a compression tester over tomorrow and we will check the compression. I'm leaning towards it needs a hone job and a new set of rings cause it will idle with very little smoke and a crack of the throttle and smoke bellows and doesn't really clear up. It runs really strong and sounds very healthy and starts up almost as soon as you hit the start button. Does anyone have any thoughts on this? If the motor was broken in on synthetic oil instead of regular oil could it smoke this way? Would it still have decent compression?
thanks in advance
Proper break-in procedures have been argued and debated since the invention of the internal combustion engine.
Then, with the advent of synthetic oils, the controversy has only become more heated and disputed.

The contention against synthetics, in a new or newly rebuilt engine, is that the synthetics are SO slippery, they do not allow for the rings to properly seat in with he newly honed cylinder walls, and end up becoming Glazed, before they "Seat" properly, and ultimately allow for blow-by gasses to escape the combustion chamber, thus resulting in a loss of power.

Some people hold strond to that line of reasoning, while others will equally defend the use of the synthetics in a freshly built engine.

if you Google "Synthetic oil Break in" you can read on it for days on end.


Personally, I lean towards the older school of thought, which is, break in's are best done on non-synthetic oils, rpms are constantly varied, and fairly high, and the oil is changed the first couple of times very frequently.

[crownandmonster]

Originally posted by tri5ron
Proper break-in procedures have been argued and debated since the invention of the internal combustion engine.
Then, with the advent of synthetic oils, the controversy has only become more heated and disputed.

The contention against synthetics, in a new or newly rebuilt engine, is that the synthetics are SO slippery, they do not allow for the rings to properly seat in with he newly honed cylinder walls, and end up becoming Glazed, before they "Seat" properly, and ultimately allow for blow-by gasses to escape the combustion chamber, thus resulting in a loss of power.

Some people hold strond to that line of reasoning, while others will equally defend the use of the synthetics in a freshly built engine.

if you Google "Synthetic oil Break in" you can read on it for days on end.


Personally, I lean towards the older school of thought, which is, break in's are best done on non-synthetic oils, rpms are constantly varied, and fairly high, and the oil is changed the first couple of times very frequently.



In my opinion this is 99% correct. The only thing I would change is that in our experience with engine building is that the rings require very little "break in time" (seating the rings). My father recommends to everyone he builds a motor, be it a small block v-8 or a quad motor, to vary the rpms for about the first 5 minutes of ride time. Making sure to avoid lugging the motor down in the rpm range and full throttle runs for extended periods. After that 5 minutes let it completely cool down to room temperature and then hop on and ride it like you stole it for another 20-30 minutes, change the oil and filter and you're good to go. Now as for breaking in a Cam, that is a different story.....

[supertrooper90]

I know for sure its not too rich its definitely burning oil.
When I did my 416 over the summer I finished it the night before we left for a long weekend to an mx track in pa. A couple laps around to get to know the track and then rode it like i normally would and I have no regrets as far as that goes.

I'll post up my findings tomoro night after we check the compression.

So just to recap if its got good compression I should lean towards valve seals? and if not rings?

[CJM]

Yes, good comp means it is the valve seals.

generally if its valve seals it will burn much less oil than rings.

[supertrooper90]

we havent had a chance to get it out so I am not sure how much oil it really burns yet. But it puff quite a lot of smoke. we are still kinda puttin it back together and fixing a number of abortions before he rides it.

[trx400Rider]

Mine drank oil when the seals wore out. Id deff check them. But if your going to end up putting a piston it, go with new seals just to be safe :)