First Post Here Please Educate Me

[redstroke]

I would like to say hello, this is my first post on this forum, I am usually over on www.alldieselmotorsports.com/forum/index.php forum talking about diesel performance topics. I need some advice in the atv world, my ride is a 98 450 foreman, with 27" mudlites. I like the size of the 450 and I can usually get it out by myself, if stuck which we ride in some good stuff here in MI. All my buds are going to the biggger quads and I have rough time keeping up on the trail, we mostly run in the swamps though. I dont really like the bigger quads because when my buddys get stuck it is a big hassle getting them out. Yes we have winches but I would rather not use one. My quad can just about go all the place the bigger quads go and they are running 28" tires. I really lack power wise on the hills and I would like to hold 2nd gear in some situations in the mud and sadly I cannot. I was thinking of performance mods, or going to a Kodiak or something in the 450 size range with the highest power to weight ratio. Please educate me. Also is this site a unbiased site, I was posting on highlifters, but from what I was seeing over there, their parts can be over priced, and maybe pushed more than others?
Thanks Adam

[Jake]

You're right. The Highlifter site is a buisness tool for them. It would be pretty rude to walk into Burger King, and put up a sign that said there's a sale on cheeseburgers across the road at McDonalds.
There is a wealth of good information there. What you can get from that is experienced opinions on different items. (Few people there rides a stock bike, and most have loads of stuff done, lots of serious mud riders who wouldn't recognize their own four wheeler if you washed it when they weren't looking). If a pipe that Highlifter sells will give you the kind of extra power you're looking for, then it'll do the same if you get it elsewhere.

The Kodiak will have more top speed, but given the goals you're setting, I would think that a pipe and jets would do you a some good. Perhaps a spring kit for the centrifugal clutch.

[TechForeman]

a pipe and a jet kit would liven up the foreman. If you put a clutch kit in then you could put bigger tires on. to me, the big bores are like a puppy. they fun to look at and play with, but you dont like taking care of them.

[redstroke]

Thats one good analogy TechForeman. I think I have enough info from the forums to make the decision to keep the foreman, I really like it, but want to keep up a little more. Also it is just too dang easy to work on. My buddy just sank his AC 650 and what a pain to deal with working on it.

O.k. from what I am seeing I dont need to buy a jet kit, just factory main jetting in the 135 range will do (any good procedures for jetting adjustments?). Exhaust, should I spend the money and buy a good muffler or do the tractor mufflers work just as well? K&N air filter and pre-filter given. I am thinking about that nice snorkel form traingle, looks real nice, and I will not have to deal with building a insuperior snorkel (affects jetting?) Now cam questions, my decompressor is clicking all the time at idle, so the cam needs replaced, is a HL cam or equal worth the extra $60 over a stock one? Can it be installed with the jug left on? My clutch has been better, do I replace the clutch plates in the basket or the fingers on the engament clutch? Clutch kit only delays engament on the engament clutch correct? If I am slipping than I am assuming the secondary (if called that needs new clutch discs). Sorry for all the questions, point me in the right direction please.

[Jake]

Not to add confusion to your decision, as it sounds like you are leaning the right way, but here's what I think about the reliability of the big bore kit: The top end (the BBK its self) is just as reliable as stock. Below that will obviously be suffering a serious extra workload, though it's usually fine, and the carniage is limited to differentials and axles. The "unreliability" comes from the fact that most BBK owners A) got the kit to turn big tires (which puts them deep in the mud and water), and B) they installed the kits only AFTER something happened to the factory top end, which don't wear out easily unless there is mud or water involved, being sucked into the carburetor, crankcase vent, and leaky rear crankshaft seals. Of those people, not many take the engine and transmission down piece by piece to clean it properly, and still fewer replace the oil cooler, or are able to adequately flush the mud out of it. I've seen BBK motors do a whole lot of miles (over 15K on one in particular), so long as they never get dirt on the inside of the engine.

So now that I've said that, I will say that anything inside the engine is a big decision. If you're not sure, you probably don't want it. External stuff is a lot safer, a lot easier, offers good return for the investment, and is easily reversable if you don't care for it.

If your clutch is slipping, you have issues. The primary (centrifugal) clutch slips (too much) when there's too many miracle in a bottle things poured in the engine, or when it's worn beyond it's limits, but speed (RPM) usually helps it hook up. The more you hammer, the less it slips. The change clutch (Secondary, basket and disk type) is the opposite. It's all good when you're gentle, but slips under load, more RPMs leads to less pull at the wheels. That one is adjustable externally on the front of the motor. Try that first. Loosen the lock nut, unscrew the screw until you feel slight resistance (it may be crusty, but you'll feel it "hit"). Then screw the screw back in an eighth of a turn or a bit more, and lock the locknut.
If that doesn't fix it, you'll be going in to survery the damage. It's been my experience that if one is shot, the other isn't far behind.

Double check the camshaft diagnosis. I replied to your other post regarding that. The decompressor is a centrifugal thing that just hangs loose, there isn't any spring. I've never seen or heard of one failing, but the only way it could is to actually break. I'm pretty sure at that point that it would just fall and sit harmlessly at the bottom of the engine case, as there's really nothing it could get into on the way there.

redstroke said:

point me in the right direction please.

Pipe, Jet kit (or "wing it" to the same effect with OEM jets, good advice from MM above to start, buy you may need to fine tune depending on variables), snorkle if you have a need (even "no-jetting" ones will require needle adjustment, and jetting adjustment if the rest of the bike isn't stock), a foam performance air filter if you trust them (stock foam isn't too bad really), and a factory Honda service manual. I can't say enough good about them. I've worked on everything from having pistons the size of your fingernail, to cylinders that I could climb in, and Honda makes a fairly complete, but unbelievably user friendly service manual. They're not cheap, $60.00 or a bit less, but if you're going in, they're money well spent.

[TechForeman]

im waitn on my manual to come in. everyso often, you can find one on ebay. i think they had 2 for sell here not too long ago. i would spend a little more money and get an hmf exhaust. i cant really say anything about the tractor muffler bc i dont know much about them.

[1badrancher]

i would go for the kodiak.. i almost bought one a few months ago.. i was planning on gettin the auto irs version.. my friend bought the 450 kodiak last week and he has 27 inch outlaws on it and it does just fine.. he says it pulls better than his old rancher or foreman ever did.. but if you want to keep the foreman add a clutch kit if you need help pulling the lites, or if your looking for speed then add a high performance cam or piston, maybe a pipe.. if you dont add a pipe dont jet it.. if you add a snorkel that has to be jetted then go a head and rejet.. a k and n air filter just lets in more dirt than stock filters.. i know alot of you are gonna shit bricks when you read this, buts its a fact.. i put it to the test

[TechForeman]

im just shittin a brick b/c your back.

[redstroke]

Thanks for all the info, and if I come off arrogent in any way here do not take it that way I am typing fast and trying to explain best I can. I dont agree with you on the cam issue though. I had a 400 Foreman and split the case to replace a final drive shaft that broke, and the decompressor on the cam had a spring. I have a manual (Clymer I believe great refrence) for a 400 so I assumed a 450 cam shaft was the same. I guess one question I have is what is the diference between a 400 and 450. I am open for any sugestions you have for the sound I get at idle from my quad? I know what all the different sounds are and this is the exact same sound my buddies brand new quad made but only for a few seconds on initial start up, mine pretty much does it all the time at idle. So that is what I diagnosted it as the decompressor, whyis its bad I dont know? My though was when I bought it the temp sending wire was pulled off, so the quad could have been overheated and fatigued the spring on the cam enough so that the decompressor stays on all the time on my quad. If I increase the idle it goes away. I you could explain to me how it works (the cam portion I understand the rest) that would also help, I believe it is a centrifical force issue. I also thought if that wasnt working properly then it would be holding the exhaust valve open during engine braking and make it backfire? (mine does with this problem) Thanks for all the great advice. Adam

[Jake]

Here's another way of looking at it:

The decompressor holds open the exhaust valve longer than it normally would be.
If the decompressor were stuck on for more than a day's riding, your exhaust valve would be burned up, just as they do if you adjusted the tappet too tightly which in turn holds it open too long. the engine would start but would not run strong at all, as the valve would be held open for additonal degrees all the time, and not just on decel, and you'd get massive backfires while you were driving along as well as decelerating. Another thought - Centrifugal force will be stronger at speed, thus meaning weaker at idle speeds, where a spring could overcome it. Given those parameters, I think if it had a spring, a spring would have to apply the decompressor, not release it, and thereby a weak spring would lead to hard cranking, from it not getting applied, and not poor running from it staying on.

The decompressor on the Foreman... Boy, a picture would be worth a thousand words right here. I could almost picture somebody counting them to see how close I come. I hope I understand your question right.
The decompressor is a little narrow "cam lobe", right next to the exhaust cam lobe.
When the cam turns slowly, and the exhaust lobe points down, and the decompressor drops downward, towards the tip of the exhaust lobe. The decompressor profile is now the same is the exhaust cam lobe profile.
When the cam progresses 90 degrees, the decompressorwill move sideways, and catch on a mechanical "catch" or lip. So the previously matching profile is now held in a slightly later position.
The "catch" keeps it from falling down for the next 90 degrees, until the maximum cam lift, then just a bit beyond that, the decompressor lobe continues to hold the exhaust valve open, past the 90 degree mark, but it remains pinched between the lifter and the "catch". Another few degrees will fully release the pressure and gravity will drop the decompressor to it's normal position. As the cam continues around, if it's still slow, it'll drop down again, and catch on the catch, and decompress again. If the engine speed picks up at all, it's weighted very precicely, so centrifugal force will hold it up, never allowing it to drop down, and therefore never allow it to catch on the "catch", in which case it remains alligned with and recessed from the exhaust cam lobe, having no effect at all on the valve.


I don't mean to tell you that I have seen everything there is to see, and I can't say your decompressor isn't failed, but I have seen the inside of a lot if these 450 engines, (and been wasting idle time on these fourms for many years) and I really have never seen nor have I heard of any decompressor failing, and my instinct says that the symptoms are wrong. (but I've never seen it, so I don't know what they'd be for sure either). The backfire is a common thing for ATV's as pipes wear, and with the Foremans (400 and 450) it's an absolute classic complaint. If it didn't do it after bit, you'd want to to find out what is wrong. And like I say, and barring the backfire, which is a partial match at best, you make no complaint of drivability issues that would correspond to exhaust valve issues, and the basic design principal of this decompressor is to mock an exhaust valve failure.
you could have incorrect valve adjustment, incorrect idle speed adjustment, or you could have a connecting rod or wrist pin issue. Verify what you can, check for the correct weight of oil, and fresh enough not to have chunks in it, and if you don't find a solution among those items, you may have to go in to see what wiggles. You could be the first one I've heard of. (If you are, MuddnMason is never going to let me hear the end of it). If you've ever had a 400 engine out, then you know how (relatively) easy it is to take out a 450 engine for sure, and depending on where and what conditions you are working, it may well be worth it to get at the cam. Or if you don't want to haul it all out, it can be done in the bike as well.

How many miles does this critter have on it? How many hours? How long have you had it, and if you havn't had it since new, do you have any idea of any history? icidents of injesting water? Incidents of mud leaking through the rear crank seal? Incidents of running out of oil? any other incidents that may have been traumatic to any internal engine parts?

[redstroke]

First off that was a real good job describing the operation of the decompressor, by the way 810 words. Going off your description which is correct, the operation on how it works might be flawed. (Here we go)
So at starter cranking speeds the decompressor is on (low rpm centrifugal force), as rpms increase (more centrifugal force) the decompressor turns off. Therefore the spring would hold the decompressor off at a idle which is real close to cranking speeds (low centrifugal force). My quad exhibits this exact behavior. The only problem with this is the spring would then hold off the decompressor at starter cranking speeds too and not allow it to work at all.
The question is what exactly is the spring doing? If I turn up my idle the sound goes away, if someone else with a 450 turns there idle down enough the decompressor will make the sound. What has changed in my motor to make the rpms needed to keep the decompressor sound off? The only thing that could be fatigued or faulty is the spring, everything else is a steel component? All the other symptoms you mention have been addressed and found good. Another question, because we hear the clicking from the decompressor does that really mean it is on? I would have to say no, because the motor would not run like you are saying with the exhaust valve open, no compression. Therefore we are talking about two things, the operation of the decompressor, and a sound that it makes (spring?). I think that last sentence is the question, the rest I will leave due to my thought process. Thanks Adam

[Jake]

810 words... out of a thousand... I'll settle for a B-

My apologies for the "hacked" quoting, but I think it'll work out OK.

So at starter cranking speeds the decompressor is on (low rpm centrifugal force), as rpms increase (more centrifugal force) the decompressor turns off.

Yes.

Therefore the spring would hold the decompressor off at a idle

No. If it were a spring type (and I'm still sitting on the belief that it isn't a spring type), but if it were, the spring would push it out at cranking speed, but the spring would not be strong enough to overcome the centrifugal force to push it out at a higher speed like at idle. A weak spring would retract (deactivate) the decompressor at a slower RPM, not a higher one.

A loose reference as to the "factory" hold-off point: The decompressor decompresses during "push button" starting, however when you haul out the rope starter, you will easily turn the engine fast enough so that the decompressor will not activate. Both the electric and the manual "cranking speeds" are well short of the perscribed 1400 to 1500 rpm idle speed.

The question is what exactly is the spring doing?

I'm still not convinced that it's a spring operated device. The 400 and the 450 use a different part number, however they do interchange without any noticable driveability changes... Maybe that's the difference?

because we hear the clicking from the decompressor does that really mean it is on? I would have to say no, because the motor would not run like you are saying with the exhaust valve open, no compression. Therefore we are talking about two things, the operation of the decompressor, and a sound that it makes (spring?). .

Absolutely. You are right. The clicking, by the fact that there is clicking, would mean that centrifugal force hadn't pulled it completely tight against the "other side" of the cam.

If I turn up my idle the sound goes away,

Do you have a way to measure the actual speed? If so, I'd be interrested in where the rattle stops, and I could dig some stuff out of the shed and compare some notes with what mine does, as that's just had it's internal condition pretty thoroughly brought up to par after a recent incident.

[Jake]

I noticed you discussing in the other forum about "unswamping" a bike. Usually when we ride, we have to spoil at least two or three good engines before anybody will concede that something's undoable. Is there any chance that your Foreman has seen water down the intake system?

[redstroke]

Quote:
No. If it were a spring type (and I'm still sitting on the belief that it isn't a spring type), but if it were, the spring would push it out at cranking speed, but the spring would not be strong enough to overcome the centrifugal force to push it out at a higher speed like at idle. A weak spring would retract (deactivate) the decompressor at a slower RPM, not a higher one.

Is this what you ment to say? Anyways, the quad has around 2500 miles on it and I have never had milky oil in it but I have no previous history on the quad. It was bought with the click, thought it was just the valves, adjusted them, and it still clicked. Runs fine operates same as any other quad just clicks at idle only, when rpms are incresed the click goes away. I also have did my share off sinking quads, and that was a 400 and it is sold now, I have heard crank bearing noise, rod pin bearing noise, piston rattle, spark knocks, exhaust leaks, whatever. This has none of these just the little piston rattle under higher rpm loads that all the new 450s have. I think it is really hard to diagnose like this, I am sure it is cam decompressor related, the exact cause I dont know. If I replace I am sure it will solve the problem.

Jake thank you for all the help. Next question for you what do I replace it with?
HL cam, stock, anybody else's?
While I am in there I am planning on replacing both clutch components that wear (dont know exact name)and a spring kit to engage at higher rpms.
Here are my clutch symptoms example if, I drive the quad up to a tree and try to say push it over and I am getting real good traction in first gear the clutch will slip and allow the motor to increase in rpms and the tires will not spin. Also happens in the real bad virgin swamps, when your getting towed out by a winch sometimes has a hard time turning the tires. Basically any time with real good tire contact clutch will slip. Which part do I need to replace, I have no problem doing all of it when I am in there?

[Jake]

Yes. I reread, and that describes any comperable decompression mechanism that I've seen.

What to replace it with... New OEM, OEM remanufactured into performance, or all new performance parts (Big $$$). Are you on a budget? Think on this a second. If the cam it's self is not shot? They got the decompressor in there somehow, and it's a loose piece, there's bound to be a way to get it out. I think it's hardened steel, but it <may> be cast, but either way I'd bet it would crack before it bent with a hammer and a cold chisel... Free stock cam with no decompressor. Don't knick the lobe though. (Read on before you form a final opinion on this).
Performance cams are OEM cams that are built up with a weld bead (specially done on special equipment, not just a guy with a welder), then the oversized area is reground to a new profile. This new profile will no longer coinside with the original decompressor, thus it no longer has a purpose, thus they leave it off of the cam. This tells me two things:
First, from an internal part compatability perspective, there isn't any harm in not having it.
Second, from an external perspective, the electric starter won't roll the engine over so easily, but it starts up the performance cam equipped engines, so I'm sure it'll still start a stock one without the decompressor, even if it "grunts" a little more.

Do you need a performance cam? I've put one in for a friend who does his own "tinkering" which includes jetting, but he won't "dig in". I drove it from my bay at work into the back of his pickup. All I can say is it sounded like it might do something, but I never gave it more than a quick smack as I crossed the speedi-dri pile. Probably a decent improvement, but it didn't blow my mind by any means. And like most internal stuff, I really recommend that you be out of other options before you go in.

It's hard to believe that either clutch is bad with that few miles, and I don't want to say that I'm positive on this, since I can't feel it myself, but it sounds like the change clutch to me. I've said before, but I can't remember if it was in one of your posts, that typically if one clutch is shot, unless something specific happened to it, then they both will be well worn.