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Discussion Starter · #1 ·
Been busy riding and learning jumps as of late. fun stuff, aside from the kid who busted his leg and foot last week out at our trails (odd story). I'll have to get some pics up in the "places to ride" section.

Quick question. I have a burn problem (smoke form exhaust). Not 100% if it's oil getting into the mix, or just rich (it's a whiter smoke at idle and after letting off a rev, but darker when hitting it hard while the oil is over half way up my stick). But it's been forever since she had new rings. I had planed on doing a ring job (That just sounds wrong), but someone had made mention of a "main seal" or "rear main seal" that could be too.

I've looked through my service manual, and google'd WTH a "rear main seal" even is. There was no mention of it in my service manual and a quick google tells me it is the seal between the engine and the transmission. Since a quad has both of those components in the same "compartment" so-to-speak and according to the oil flow diagram that they are both feed by the oil circulation system in a uniform fashion; would I be safe in assuming I don't have a seal such as this and just concentrate my efforts on the piston rings?
 

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Good luck finding a rear main seal when they motor and tranny are in one case. Could be valve seals, could be valves. You could be extremely rich(mixture that is). Start easy. Don't rip into the piston until you check the stuff above it.

Whoever told you that it could be the rear main seal, ask them how the smoke would work it's way into the exhaust pipe. (if it had a rear main, you would be leaking oil onto the cases.)
 

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Discussion Starter · #3 · (Edited)
It's a standard 400ex motor, so it's kinda "all in one" type of setup. the Transmission being housed under the piston inside the crankcase. The service manual doesn't give me any info on how the two are separated. Maybe their not, have to read more.

I'll hit the valves and valve seals first then. I just keep checking the oil in her and making sure it's half way between low-high on the stick. I've got another growing list of maintenance items, but that's what happens with an old quad that was raced her whole life.

I had just found out the guy had not even been using it for 2 years before I bought it. Probably worn/old seals, old gas varnish washed through her, etc etc.

Thanks for the info!
 

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You are correct, they are both in one unit. No seal between the two.
 

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I would run a compression check for starters wet and dry. a wet test will determine if the rings are shot. I would remove the exhaust pipe from the head and check for signs of oil in the exhaust chambers if there is I would say you just need to freshen up the head. If you remove the spark plug what color is the electrode?
 

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Red is correct. The crank and transmission are one unit. You have no rear seal like in an automobile and the engine don't unbolt from the transmission. That's why you only have one oil for the engine and transmission. Red is also correct about the fact that if you did have a rear seal it would just be leaking oil and not getting into your cylinder to be burned.

Is it using any oil? Have you had to add oil? If it's using oil, then I would consider replacing the rings and the valve stem seals.
 

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Discussion Starter · #7 ·
Red is correct. The crank and transmission are one unit. You have no rear seal like in an automobile and the engine don't unbolt from the transmission. That's why you only have one oil for the engine and transmission. Red is also correct about the fact that if you did have a rear seal it would just be leaking oil and not getting into your cylinder to be burned.

Is it using any oil? Have you had to add oil? If it's using oil, then I would consider replacing the rings and the valve stem seals.
:(

:(

:(

:icon_ cry:


Well, she started dumping smoke today, and I was hardly riding her at all. Whitish type of smoke. I was eating through oil and every time I'd fill it it would smoke WORSE. But I didn't hear any knocking though. So I parked it in the Barn and am getting up the nerve for a top end rebuild.

I know I need new cylinder rings and possibly new valve steam seals. I want to get all the things that I possibly can in one shot done since I'll have the top end off her. Anything else I should attack while I have the piston head out and the top end apart?

Check the cylinder walls for damage of any type, check the cylinder shaft, the valve seats and steams. I imagine the service manual would outline what should need inspection and replacement, so just follow it then? I'm real nervous about doing a whole top myself....
 

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Change the timing chain and guide while you have it apart aswell!
Agree^^^^^ and with the exception of the boring cost you can step up to a 416 kit and that will really wake it up.
 

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Discussion Starter · #11 ·
If memory serves, it is a 426. I have to take the head in to verify, but the previous owner was that racer and I believe he said it was bored to a 426.

Now, I do have a Digital Caliper Measuring Tool. I guess I could verify with that after I take the top end off and see what the bore and piston sizes are.


Thanks for the tip Tom, I'll look into the timing chain and guard while I'm in there.



Wish me luck.... The other fixes were child's play.... but motor work is not my specialty.
 

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Discussion Starter · #14 · (Edited)
Well, I'm kinda sick but I'm gonna keep trucking this week to get the damn thing done!

Quick update. I pushed her into the garage and started removing plastics. Once I got everything down, I sat for abit staring at it, wondering how the hell I would be able to do this. My father was around, and noticed I wasn't too confident about it so he went to the junk pile out back and retrieved his old Suzuki 350 from his bike he was to do a rebuild on so long ago. gave it to me in pieces, and told me to put that back together first. It was missing most of the bolt, but had the cam, lifters with holders, spark plugs, cylinders, and some screws. While it is by NO MEANS in a put together state, I learned about how the cam works and how things would fit together and what to kinda expect with my own.

yay for a "not really" put together old motor!


That should be a post for the website www.thereifixedit.com

Anyway, I get to the top of the motor and notice something.....



See the bottom right? THE F--KING MOTOR IS MISSING A BOLT! I hope the god it's not an important one.

And with Lectron carb's they have an issue with stock throttles. The travel distance on the thumb throttle doesn't move far enough to lift the slide. Most of the time, you shortened the spring inside or something else.

I did mentioned that my quad was owned by ******* racers, right?
TO HELL WITH ALL THAT FANCY-SMANCY CITY BOY BULLS--T!



THERE, FIXED IT!

Seriously, there needs to be a sub forum entitled "There, fixed it"

My quad can be the fricken logo.....

More to come, I'll stop rambling now.
 

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The most important thing about working on something is to understand how it works. If you truly understand how something works, then it is usually pretty simple to fix.
 

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Discussion Starter · #16 ·
I'm starting to get discouraged...

So far the top end is all off and the damage isn't HORRIBLE, but it ain't good either.

The cylinder head looks great, the valves had a lot of carbon buildup that I took off with repeated cleanings of oven cleaner and a soft brass wire brush. they leak a little, but my dad mentioned a compound that you put on the seats and the valve and then spin the valves. It's slightly grinds both the valve and the seat down perfect.

The cylinder wall is bad though. There is what looks to be a crack that goes up one to about 3mm from the top, goes around the top about 3/4 of the way, then back down into the cylinder wall. It's scorched on that entire line too. The 1/4 of the rim of the wall that isn't cracked has no scorch. I'll get some pics up later on, but I guess I need a new cylinder wall pressed in there

I've destroyed other gaskets as well in the process. The bottom gasket between crankcase and cylinder housing, and right crank case cover gasket (was trying to replace the shifter dust seal and had to pull it). The triple metal gasket between the cylinder housing and the cylinder head seems ok, as does the metal gasket between the cylinder head and the cylinder head cover.

Here is the problem. The cylinder head measures 88mm. The service manual states it should be a 85mm. So it's a big bore kit. Took it to our local atv/motorcycle shop and got the head measurements verified. They can get me the cylinder rings ok, but the gasket kits for the 400ex come in 87mm and 89mm. No 88mm. They are gonna call their suppliers and find out who/how/what/and where about the 88mm kits. There are 88mm kits for the fortrax foreman 400's, but not for the 400EX's.

And now I need a new cylinder sleeve put in as well... Anyone got ANY kinda ideas on what the cost for a new sleeve plus the removal/install would be? or hell, where to even FIND one?

Oh, I know why she burned out the rings and scorched the cylinder walls. The exhaust that was on there? Yea, it wasn't. They had placed a supertrapp on there, one of the pre-1983 types that are made either for closed circuit races or pre-1983 motorcycles only. There is no baffle, no spark arrester, hell it's a damn straight pipe form the heads on out. No back pressure. Great for racing if you got sponsors to pay for your rebuilds.

I know when I get it all back together it will run like it never ever has before. But It's just discouraging. I guess that happens a lot on big projects half way through. For the 2000$ I spent on her, I'd much rather have been riding it. But alas, shit happens.

I'll throw some pics up later tonight on some of the issues I'm talking about.
 

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Discussion Starter · #17 ·
UPDATE:

Now THERE'S your problem!



Yes, that is the wall you see THROUGH my cylinder sleeve. Shot. 100%. If I would have pushed it, I'd have torn that off and bye bye entire top end.

Ouchie.

Drew the damage on this second pic for a better view.





Ok, so new Cylider Sleeve, new rings, new gaskets, Mod'd the 4in Fan for the oil cooler, fix some plastics damage. DONE. Man, it sounds great too!

So I've decided to tackle a few of my other problems. Got a bad wobble in the left rear tire. The rear disk brake is bent all to hell. Getting new disk soon, but I need to know


Is this axle good? Wondering if it is causing my tire wobble.

YouTube - MVI_1726.MOV

The left side seems perfect. But the right side has a distinct "wobble" to it. Not crazy, but not perfect either. The REALLY wierd part? It's the LEFT side with the tire problem (tire wobble).
 

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The axle looks to be bent a tad...
 

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Discussion Starter · #19 ·
I put the tires back on, and that specific rim looks like it has the "Wobble". I'd put that tire on either side of the axle and it would wobble regardless, while the other tire would be somewhat ok. Damnit, I was hoping not to have to spend a bundle more.

The axle has a tweak, that's true. But the tire is real bad. Looks like I'll need new back tires and rims.

It never ends, does it?
 

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I have a set of ITP T9 rims, black. They are used, some dings and the powder coat is chipping a little but they work perfect. Let me know if you are interested.
 
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