300ex Top End ????

[jgray]

I am installing a new exhaust. I have noticed some smoke from the exhaust the last couple times I have ridden it. After I tore the exhaust off, I noticed it was pretty black with the exhaust pipe. Then I peeked into the exhaust port, same thing, BLACK.
I am going to attach a couple pics (I hope). the intake looks good. I'll attach the intake first, then 3 exhaust. Sorry for the poor quality. I need the bed..

[jgray]

INTAKE

[jgray]

EXHAUST #1

[jgray]

EXHAUST #2

[jgray]

EXHAUST #3

[duke416ex]

Can't tell much from the pic, if it is just a powder like black, then it is fine it is just sought. Unless it is smoking enough to repel bugs. Everything will get that build up just from the remains of the combustion process. If it is an oily build up you need a rebuild. Since it's not a 2 stroke you don't want the oil build up.

[jgray]

Thanks for the reply, Its a dry black build up. I gues I am fine then. Thanks again..

Repel bugs !!!! interesting, I will try that tonight after dark, I'll update tomorrow.. lol

It does blow more then I woul like, its the blueish whiteish smoke !!! Not sure if its the valves or the rings ???

[bwamos]

Aye, as long as it's a thin coating it is normal. If you're getting heavy deposits in a short amount of time, you probably just need to lean up the carb jets a size or two.

[jgray]

it appears to be a thin coating, but I didn't want to chip it away and in far back into the engine. I am rejetting, so hopefully I will lean it out while doing so.

should I tear the head apart to clean that all out. or will it slowly break apart and clean itself up a little

[bwamos]

If it's just a thin coating, jsut leave it..

Thick is pretty obvious, as it gets a real fuzzy appearance to it.

The pics are blurry, but it looks fine. Doesn't appear to be any abnormal buildup.

[jgray]

I am not a expert, but it looked ok to me also. It was late last night, but I will take another look at it and make sure of the build up !!

As you can see I am not a expert with a camera either.

[bwamos]

Just noticed in your origional post.. that you were getting some black smoke form your exhaust? Black right?

If so you are a tad rich. Try dropping your main jet down a size or two and see how she feels. You can always put it back if she runs like crap ;)

[jgray]

I don't think I ever had BLACK smoke. It was more of a blueish/whiteish. If that makes sense. The black I was referring too was the biuldup inside the exhaust pipe and inside the exhaust port.
I do hope to lean it out a little though !!

[duke416ex]

Do you have to add oil to it often, that would be a sign to me. I mean some quads, I wasn't around but a few 300ex, but those and most 400ex that I was around would use a very small amount of oil . Not even enough to think about, maybe a 1/4 quart in between oil changes, if that much(I don't change after every ride just every so many hours of riding) If you are having to add oil then think about it, the other stuff looked fine don't worry bout it.

[jgray]

I am definitly burning oil I assume. I due add oil, not sure exactly how much, but I due loose it somewhere. But I am not sure if it the rings or the valves. Anyway to tell before tearing into it. Whats a estimated cost of having this procedure done. I am a DIYer. but just have any machining, porting, grinding, polishing done professionaly, unless I could do it myself with some guidance from you guys.. I was tol dby a friend, that his grandfather use to say "oil is cheap, just add it" lol.. not the greatest advice i have gotten, but has gotten me this far !!

[bwamos]

Probably just need new valve guides, or piston rings. Being that your 300 is a 95 (10 yrs old) it's probably just leaking around the valves or rings a little. Does it smoke more at startup or mainly after it warms up and is running hard?

Startup is valve guides/seal. (cheap fix)
Warm high rpm is most likley worn piston rings. Then you just need a hone and new rings. (cheap fix)

Your jetting is probably ok if your not getting the black smoke. It rund good, correct?

300's are simple.. really the only 2 places you'd get burnt oil from. ;)

[jgray]

It is 10 yrs old.. So probably ready for the mentioned repairs.. There is more "white" smoke at startup, the the "blueish/whiteish" smoke during normal riding. Sounds like a liitle bit of both then huh.. Guess i will look into valve guides/seals and a hone and rings.

When you hone, is that inlarging the bore, do I just by stock size rings?

[duke416ex]

Originally posted by jgray
[B]"oil is cheap, just add it" B]


:D That's a good one, honing doesn't enlarge your bore any, it just cleans the walls up and wil take out some very small markings if there is any. I mean very small, if you have any serious scratches that you can see very plainly or feel, get it bored. I learned a while back not to order parts before you have it apart if you aren't sure of the prob.

Price: valve seals around 10 bucks or so, top end gasket kit, 30, rings, 30, you doing labor, free, other doing labor, probably 200 or so.

If you bore it I would guess at around 50 or so for the bore and 90 for the piston and rings. Hope this helps, oh these are all close estimates on honda parts, I have a 300ex tore apart in my shop right now.

[jgray]

"oil is cheap, just add it"

I kinda liked it too.

Sounds like I have a weekend project.. Though I have a weekend ride Sept. 25th I do not want to miss. Also long as there is oil in the engine, its not gonna hurt anything that is not hurt already, RIGHT??? Its not a big ride, but a guys weekend away with a little poker run on sunday !!!!

Thanks for all your replys and help on this.. I love this site and am amazed at the help myself and others get from the members. Thanks again,
Jason

[bwamos]

Originally posted by jgray
When you hone, is that inlarging the bore, do I just by stock size rings?

A hone doesn't require a larger bore.. it just cleans the walls back up so your new rings can re-seat.

But sometimes the walls are worn enough that you need to go 0.020 overbore. If you do end up needing a bore due to wear.. you might look into going with a true 300 @ 11:1. ;)

[jgray]

So a hone just cleans to walls and keeps it stock. What size piston would I buy to take it to a true 300. .080" over?? Would I have to run high octane gas or race gas @11:1. I prefer the cheap regular gas. Expecially in todays market..

[bwamos]

11:1 will run on premium pump gas.

yea 76mm bore will give you ~296cc. 2mm overbore; 0.080" overbore.

It will keep it sport class legal, if you do any occasional XC.

[jgray]

My only hesitation to bore it .080" over, would be what if something happened in the future and I would have to bore it even larger.. What would I have to do. I guess it has made it 10 years with stock, could do another 10 with .080" over ??

[bwamos]

Could get quite a few years out of the 300. The 11:1 adds a tiny bit more wear.. but not much. I've got 5 years on my 330cc, and I race it in the MHSC several times a year, as well as the normal weekend riding.

You can keep increasing the bore by 0.020" all the way up to an 0.240" overbore (330ex), which I run w/o issue.

The 300ex has an aluminum cylinder with a steel sleeve. No special coatings like the 450r. You just keep boring her out.

But the 330 requires a resleeve.. so at a point of overbore a little smaller than the 330, you'd just replace the sleeve with a new one. They are pretty cheap.

[Konaracing]

When going to a 330 would you have to do a new cam right away? I know it will help a lot but don't have the $$$ to do it all right now. I was hoping to do the 330 kit in the next few months and then a new cam next year possibly. Thanks for all the info.

[Cody_300ex]

Originally posted by Konaracing
When going to a 330 would you have to do a new cam right away? I know it will help a lot but don't have the $$$ to do it all right now. I was hoping to do the 330 kit in the next few months and then a new cam next year possibly. Thanks for all the info.

No you dont need a cam but it will help a lot. The highest bore you can go out to on a stock 300ex sleeve is a .120 overbore, which is a 305cc. After that you need a re-sleeve.

[jgray]

wow, .120" over, never heard that before.. Thats make the decision a little easier. I will go .080" over if I need to bore it out !!! I didn't amke much progress over the weekend, actually no progress. I'll try to keep everyone posted.. Though cash is none existant right now in the household, so probally nothing real soon !! Thanks
for all the info.. greatly appriciated !!!

Jason

[jgray]

I have the exhaust on eand i have ran it once so far. During warm up, there is a little white smoke after letting of the gas... Then almost goes away. Then once warmed up, its seem to be the same. Alot when you let off the gas. Thouh its hard to watch yourself while driving and looking backwards. I will have a friend drive it tomorrow and see what it does..
Is this jetting. I have a 128 main with needle on 4th notch down. I have a 125 main. Should the needle go back up to the 3rd notch. It seems to run real strong thru all gears. Nothing seems to be off, but the smoke might be a signal for something?? What is it though ??

Thanks
Jason

[Trevor]

Your jetting is likely fine you just need to throw a set of rings in her sometime. As long as you keep it full of oil burning a little won't hurt anything. If you start to burn alot of oil you will start to foul the plug and it may start to fun like crap. Chuck a new plug in her and your good to go. When it starts to smoke alot then you will likely have some $ set aside for the work.

[hondajoe05]

when you rev it up does more whiteish/blue smoke come out? cuz thats your rings if it does

ive had that problem twice aready:(

and a local guy said it woudl be about $180 for him to do the rings and gasket last time i had to get it bored which was arond 500$ all together

[jgray]

I kinda thought the jetting was ok. From What I can tell, while it idles there is a slight smoke. then when I hit the gas, there is a little more smoke. then when I let off the gas, that when there is a lot of smoke. I assume its the rings and valve seals. I will put that on my todo list. I am sure my wofe will put that at the bottom though !!!